Confirming Ham Radio Contacts: The Art of QSLing

This is one of a series of “Notes” I published on Facebook. Since Facebook has discontinued the Notes feature, I am publishing that series here on my blog.

QSLing, or exchanging of QSL cards goes back to the earliest days of ham radio. It is often said “a QSL is the final courtesy of a QSO”, which hints at the importance that has always been placed on this aspect of ham radio as a hobby. Traditionally a QSL is a postcard which confirms that radio communication was carried out between two stations. QSL cards have the callsign of the station issuing the card, information about the station location and owner, and possibly other information printed on the card. The callsign of the station contacted, along with date, time, band, mode and signal report is handwritten or otherwise filled into areas of the card reserved for this before being sent out. The front and back of my N1BUG QSL card can be seen in the cover photo. Why do hams exchange QSL cards? Some do it because they like to get and collect QSLs to commemorate memorable QSOs (contacts, conversations). Some QSL cards are truly works of art. Others feature breathtaking photos of exotic places. Others collect QSL cards for contact verification when applying for operating achievement awards such as Worked All States (WAS), Worked All Zones (WAZ), or DX Century Club (DXCC). These awards are not issued on the honor system. One must show some evidence that they did in fact establish radio contact with the locations they are claiming. QSL cards are the traditional means of verification.

How does this work? Suppose I make radio contact with a station in Iceland, and that for whatever reason I want a QSL card from that station to confirm or commemorate the contact. I will fill in his callsign and the contact details – date, time, band, mode, signal report and perhaps a personal comment on one of my station QSL cards. I will check a box on my card which says “Please QSL” to indicate I want a card in return. I will then mail my card to the other operator along with some means of paying for the cost of return postage. Why do we send return postage? Suppose the ham in Iceland makes several hundred or even several thousand contacts in a year and many of the stations contacted want his QSL card. If the Icelandic ham had to pay for postage to send each of those cards it could easily cost the equivalent of hundreds or even thousands of dollars. This could easily put the cost of ham radio out of the reach of many or force them to not respond to QSL requests! Chances are he doesn’t need my card for anything (he probably has a huge collection already), but I do need his. So, as a courtesy I will cover the cost of postage for the return card. When the other operator gets my card he will fill in the QSO details on one of his QSL cards (probably checking the “Thanks for QSL” box), then mail it to me. I may display it in my shack or file it away for later use in applying for awards, depending on my goals and interests.

When sending cards within the U.S. it is customary to send a self addressed, stamped envelope (SASE) to cover return postage costs and to save the other operator the time of writing my address on an envelope. Remember, most active stations get many such requests and most people don’t have unlimited time for this hobby. When sending QSLs to other countries there are a few options on how to pay for return postage. In the past the International Reply Coupon (IRC) was a popular choice. An IRC could be sent with the QSL and in most countries that IRC could be exchanged for the correct amount of postage to return one piece of first class mail to the country of origin. The IRC has diminished greatly in popularity (some would say it has become all but unusable), because the USPS no longer sells them and because many countries no longer accept them. The most popular method today is to send US one dollar bills to pay for return postage. In ham radio QSL parlance we call them green stamps. They can be exchanged for local currency in most countries, but do your homework before sending them! In a few countries, one can get into a lot of trouble for the mere possession of US currency! I do not know where to find a comprehensive list of such places, but keep reading for tips how to know what to send or not send. Be aware that $1 is not enough to cover the cost of returning a card from most countries, just as it now costs over $1 to buy a stamp to mail something out of the US. $2 may still be enough in some countries but many require $3 and I believe some are now $4. Obviously this gets expensive – at current rates, $1.20 for the stamp to mail something out, $3 to cover the cost of getting a reply. Another method that is gaining in popularity is to send stamps from the DX operator’s own country along with your QSL. There is at least one service (William Plum DX Supplies) making such stamps available to hams.

Recognizing the high cost of exchanging QSLs, many countries participate in a network of QSL bureaus. Here is how this works. If I contact many DX stations whose QSLs I want, I can fill out all of the QSLs, sort them by country of destination, and along with a modest fee send them to the American Radio Relay League (ARRL) Outgoing QSL Bureau. The bureau will then combine my outgoing cards with those of many other US hams and send them in batches to QSL bureaus in other countries for distribution to hams in each country. Incoming QSLs through the system are handled by a number of regional bureaus across the country. In order to receive incoming QSLs through the bureau system, I periodically send money to the W1 QSL Bureau. They receive thousands of QSLs destined for US hams in the first call area (W1), which comprises the six New England states. They get these cards from bureaus around the world. The incoming QSLs are sorted by destination station, and when they have accumulated a reasonable number that are going to my station or a certain amount of time has passed since their last mailing to me, they mail them to me (using some of the postage credit on my account). Exchanging QSLs through the bureau system is much cheaper than going direct, but it takes more time. The amount of time required to get a QSL card this way can be months or even years. Bear in mind not all countries have a QSL bureau, and not all hams in any given country use the bureau if it has one. Many hams use the bureau to obtain QSLs they would like to have, but are in no hurry for. Note that the ARRL bureau is for sending cards to other countries and cannot be used for sending cards to other US stations.

Some hams, particularly those in rare or semi-rare countries, have a QSL manager. This is a person who handles the chore of responding to QSL requests f0r the ham, who may not have enough time to do it. In some cases, hams have QSL managers because delivery of mail in their country is not entirely reliable. The QSL manager may or may not live in the same country as the ham using his services. Sometimes you get lucky and the ham you just worked in that rare country has a QSL manager in the US! This is great, as it costs you less and you usually get your wanted QSL card in less time.

So how you do you know where to send your QSL for that DX station you just worked? You need to look it up. I usually start with QRZ.com. If the DX station has a listing there, it will likely tell you how to QSL that station, be it direct, via bureau or via a manager. Often it will tell you what methods are accepted for return postage and what not to send. Not all stations are listed on QRZ.com. For those you need to look further. There are DX newsletters to which you can subscribe which often give QSL information for rare stations and DXpeditions. Some of them have back issues available online. Sites such as DXNews.com and DXcoffee.com can be valuable resources for finding QSL information. A good source for DXpedition QSL info is ng3k.com, particulary his ADXO (Announced DX Operations) pages. In short, the avid DXer with an interest in QSL cards needs to have a variety of resources from which to gather information.

When sending cards to other countries, there are a few things to keep in mind. Mail isn’t as safe in many places as it is in the US. Putting callsigns on the envelope suggests that it may contain a QSL and some US $1 bills – which may then get stolen! The best advice is don’t put callsigns on the envelope, just names and addresses (that of the station you are sending it to and your return address, of course). Try to hide what is inside so it can’t be clearly seen if the envelope is held up to a bright light. You may want to use security envelopes or wrap a couple sheets of paper around your QSL and funds for return postage before placing it in the envelope. Whatever you do, write clearly and legibly when filling out your QSL card and addressing the envelope. Remember this may be going to, or through, places where English is not the primary language and even to places that use a totally different alphabet! Don’t expect them to decipher a scribbled address. Sending a self addressed envelope for the return QSL may save the other operator some time in replying, but US sized envelopes are not acceptable in all countries. William Plum DX Supplies sells envelopes specifically for this purpose.

With postage costs escalating and in view of the fact many only want QSL cards for contact verification in applying for awards (as opposed to collecting the cards themselves), modern technology has provided an alternative: electronic QSLing. There are two major services in operation today: eQSL and ARRL’s Logbook of The World (LoTW). Each has its advantages and disadvantages, which should be considered in selecting which service(s) to use.

LoTW confirmations are currently good for ARRL awards (WAS, DXCC, VUCC) and the CQ WPX award – but not for others. There is no cost to sign up and participate in LoTW but there is a nominal fee of 12 cents per QSL for any you decide to use for awards applications. The LoTW sign up process has drawn heavy criticism on grounds that it is too difficult. Paperwork is often challenging for me but I didn’t find anything difficult about the LoTW sign up process, and the documentation leads you through it step by step. The registration process is designed to avoid fraud so that some integrity may remain in the awards system. It is not an “instant gratification” process. It takes about a week since it does involve a postcard through the US mail for one part of it. You only have to go through this process once. Once you are signed up, using LoTW is usually very easy. Most hams today log all of the contacts they make using one of several different logging programs that are available. Major logging programs automate the process of uploading contacts to LoTW. With the one I use (DXKeeper) it is as easy as a click or two. There is no printable “QSL card” with a LoTW contact verification. It is strictly an electronic acknowledgement that the contact is confirmed.

The other major online QSL system, eQSL, has a somewhat easier registration process. Confirmations through eQSL count for CQ awards and perhaps others, but cannot be used to apply for ARRL awards. eQSL allows each station to design their own electronic QSL “card”, and receiving stations can print out and keep a copy for each contact confirmed through the system. Most major logging programs automate the process of uploading contacts to eQSL.

It is important to choose which service(s) best meet your objectives. My main awards focus is DXCC and I like contesting. I use LoTW because confirmations there can be used for the DXCC awards and because uploading all of my QSOs there greatly reduces the number of QSL card requests I get through the mail. Otherwise I would be overwhelmed due to the number of contacts I make while contesting. By the way, award application fees are often less for electronic applications than for paper ones which require more processing on the part of the organization issuing the award. I send for paper QSL cards when I work stations needed for DXCC who do not use LoTW. I also like to get paper QSLs for major DXpeditions even if they use LoTW (most do), because often those QSLs are something extra special with pictures of the rare and exotic places and once in a lifetime adventures. Some are multi-sided fold-out cards or even small booklets with pictures and story of a great DX adventure.

QSL cards from rare locations and DXpeditions. Top left: a bi-fold QSL card from a base in Antarctica. Top right: front of a QSL from 3Y0X Peter I Island DXpedition. Second row: middle of fold-out 3Y0X QSL. Third row: Bi-fold card from BS7H Scarborough Reef DXpedition. Bottom: middle of a 32 page QSL card “booklet” telling the story of the VP6DX Ducie Island Dxpedition.

One other method deserves mention. A system called Online QSL Request System (OQRS) is becoming quite popular, especially for DXpeditions. A DXpedition is by definition a temporary ham radio operation from some rare and often remote place. The person or people who went on a DXpedition does not need your QSL card, but very likely you need theirs. Many of them now post their logs online and offer OQRS through various systems. The way this works is you go to their onling log site, enter your callsign and it will show you all contacts you made with that DXpedition. It will then offer you a chance to “order” QSLs for some or all of those contacts. You may have to fill in the details such as date and time for each QSO. Usually there is a nominal fee involved. It may seem high but bear in mind this is one way of helping to pay for a trip that was done for your benefit and likely cost in the hundreds of thousands of dollars! The advantage for you is that you usually get your card(s) much quicker than any other method. Many DXpeditions now use Club Log for their online log and OQRS. Any station can upload logs to Clug Log. If you participate, this makes OQRS even easier. Since Club Log has both the DXpedition log and your log, it already knows all details of the matching QSOs! All you have to do is select the ones you want QSLs for and complete the transaction by making payment. For those like me who hate paperwork, this is the ultimate in simplicity and convenience on getting those rare DXpdition QSLs. I used Club Log OQRS for my recent contacts with K5P (Palmyra), VP8STI (South Sandwich), and VP8SGI (South Georgia).

You have a number of choices when having QSL cards printed for your station. Many printing services offer generic card designs customized with your callsign, name, and location. Others will design a card from your photo or artwork, or you can do all the design work yourself and just have them print a batch of cards. I designed my QSL card myself and submitted it to UX5UO Print. For less than $100 I got 1,000 full color double sided cards featuring photos from a hiking trip to Mount Katahdin. Cards can be ordered from many printers in smaller quantity, and generic designs are cheaper than color photo cards. Of course you can design and print your own if you want. QSL cards don’t have to be fancy. In fact, some are very basic but still do the job of confirming QSOs. Because the people you contact will be wanting your card for a variety of purposes, I suggest you put the following on your card as a minimum: your callsign, name, and mailing address; state and country (if not obvious from the address), county, CQ zone, ITU zone, and grid square. Additional information may apply in some cases. If you live on an island which counts for Islands on the Air (IOTA), for example, you might want to put its IOTA number on your card.

Examples of basic QSL cards. Top: Single color, two sided card (reverse not shown). Bottom left: Single color single sided card. Bottom right: two color single sided card.

Ham Radio Contesting: Not Just About Winning

This is one of a series of “Notes” I published on Facebook. Since Facebook has discontinued the Notes feature, I am publishing that series here on my blog.

Some hams complain about contests clogging up the bands, others love them. These days it seems there is a contest of some sort just about every weekend: some big, some small; some very fast paced and competitive, others more relaxed and friendly. Generally speaking, the object of a contest is to work (contact) as many stations as possible in a given amount of time. Most who participate in contests have little to no chance of winning the contest and they know it. In most contests, the big stations with the most experienced operators are always going to win. With present day proliferation of superstations, that doesn’t leave the average ham much of a chance to win, per se. So why would one participate in a contest if winning isn’t possible? There are many reasons! Let’s explore that. Even if you don’t win the contest and get a nice plaque for your wall, that’s not to say you don’t “win” something of value to you!

Whether you’re out to compete or not, contesting should be fun. There are many ways to have fun in a contest without pushing yourself to get a high score. Some like contests as a means of improving operator skill. Contests are about short, snappy exchanges, usually with a good amount of QRM (interference) just to make things more interesting. The more you do it, the better you will become at copying through QRM or just digging out and understanding weaker signals. Your operator skills will be enhanced in other ways as you learn to be quick and brief while maintaining accuracy. These skills carry over into many other aspects of ham radio, including public service. For the CW (Morse code) contester, improving sending and receiving speed is another major benefit.

Contests are a great way to find stations in states, countries or other subdivisions needed for operating achievement awards. Contests concentrate many stations on the bands during a short time period and often bring out DX (long distance contacts) in semi-rare countries that aren’t on very often. Perhaps you’re interested in making contacts with a part of the world that is difficult for you, or places you have a particular interest in. Maybe you just want to test your station to find out what you can work, or test yourself! You may be pleasantly surprised. You may learn things about propagation that you didn’t know.

Some “contesters” just want to test and evaluate themselves. It can be fun to set a personal goal, such as working all 50 states or some number of countries in a contest. Or perhaps you just want to compete against yourself and see if you can do better in a particular contest than last time. The beauty of this is that you can set a goal that is attainable and yet challenging enough to keep you motivated! In one recent contest I set a goal of working a certain number of countries. When that goal was completed less than a third of the way through the contest much to my surprise, I changed my emphasis for the remainder. I spent some time looking for Asia, since I am always interested in working that part of the world. I looked for and worked old friends. I practiced my skill at tuning the band and moving as quickly as possible from one QSO (contact) to the next. Since I wasn’t competing against others, I could spend as much or as little time operating as I wanted, consistent with trying to meet my self assigned goal. I took more break time than operating time.

Whatever your interest, be prepared. Know the rules of the contest you will be participating in. For example, what information is to be exchanged for a valid contact? A signal report is usually part of the exchange and is almost always 59 on phone or 599 on CW or RTTY. Most contests require exchange of state, CQ or ITU zone, grid square, or some other information in addition to signal report. Can you work stations anywhere, just DX, or just your own country? When does the contest start and end? What bands and modes are allowed? Can you work a station just one time, or can you work the same station on each band? If you will be competing you will also want to know about other rules, such as required off time, scoring, how to submit a log, entry classes, and so on. There are many resources for contest listings. To see what is happening this week, I use This Week’s Contests at contesting.com for a listing and a short summary of the most basic rules for each contest. If I want to see what contests are coming up weeks or months from now, WA7BNM Content Calendar is a great resource.

Whatever your reason for contesting, knowledge of propagation can help. If you are out to win the contest, you need to know how to take advantage of propagation to get the most contacts and the most multipliers. A multiplier is usually a state, country, zone or other subdivision that can really boost your score. If you are looking for contacts in a particular area, knowing propagation can help with that too. I often use contests to look for eastern Asia, the most challenging part of the world to work from my home in Maine. Not only have I learned when the various bands will most likely be open to Asia (which varies with solar activity and season), but I know there is a characteristic flutter or warble to signals coming over the poles, whether short or long path. I can easily identify signals from that region even without hearing a callsign, and can select them quickly while tuning. While it is true that signals from other areas (notably South America in the late afternoon/evening and sometimes Europe/Africa) can have similar effects, a trained ear will soon recognize the difference on any given day, allowing quick and easy selection of signals from deep Asia. But don’t worry! If you don’t already know a lot about propagation, active participation in contests will help you learn.

Remember, in a contest time is a precious commodity. If you aren’t competing yourself, many of those you work probably are, either in the contest itself or to meet some personal goal. Try to keep it brief and snappy. This is often one of the biggest challenges for new contesters who may be unsure of themselves and/or more accustomed to other types of operating. Many newcomers feel they are being impolite if they don’t include greetings and friendly phrases as part of an exchange. Actually, it is polite to keep it as brief as possible since many of the stations you work are competing and time is precious to them. Before delving into this further, you should know there are two basic paradigms of contest operating: one is search and pounce, the other is known as running. In search and pounce, you tune the band to find a station you want to work, then pounce (call the station). Running is when you call CQ and let stations come to you. Both are fun, but running can be far more challenging. Most contesters start with search and pounce until they gain confidence.

Let’s look at a typical contest QSO between WW0TST (who is running) and N1BUG (doing search and pounce) in a phone (voice) contest where the exchange is signal report and state. The shortest and most desirable form under good copy conditions goes like so:

“Whiskey Whiskey Zero Tango Sierra Tango, Contest”
“November One Bravo Uniform Golf”
“November One Bravo Uniform Golf, Five Nine Colorado”
“Five Nine Maine”
“Thanks, Whiskey Whiskey Zero Tango Sierra Tango”

There are no extraneous words. This is the most efficient contact flow possible. Many operators will preface “Five Nine Maine” with “Thanks” or “Thank you” but the most experienced contest operators usually don’t. This may need to be modified under certain circumstances. For example, if WW0TST didn’t copy my full call at the beginning, he might just say the portion of it he got, which is a request for me to repeat it. The flow then becomes this:

“Whiskey Whiskey Zero Tango Sierra Tango, Contest”
“November One Bravo Uniform Golf”
“Uniform Golf”
“November One Bravo Uniform Golf”
“November One Bravo Uniform Golf, Five Nine Colorado”
“Five Nine Maine”
“Thanks, Whiskey Whiskey Zero Tango Sierra Tango”

Sometimes an operator might simply say “Again” which means repeat whatever you last said. There are many possible variations and you will get the hang of it with practice! What you don’t want to do is include a lot of extra verbiage such as “WW0TST, this is November One Bravo Uniform Golf” or “good morning, you are five nine here in Maine”. The exception might be in a small, relaxed contest where the point of the event itself is to have fun as opposed to the more typical rabid competition, or when working an operator who shows an obvious preference for such relaxed exchanges. Although there is no hard and fast rule, you will often find the most experienced, dyed-in-the-wool contesters toward the bottom of the band, less experienced part-time contesters higher up. Sometimes you may get and wish to send something extra when working an operator you know personally or from other ham radio activities. But in general, short is good. Don’t worry if you find yourself adding more to the exchanges at first. Contesting is very different from normal QSOs and it does take some getting used to. Just keep reminding yourself to be brief and try to mimic the way the experienced operators do it.

On CW, the most efficient form is:

“WW0TST TEST”
“N1BUG”
“N1BUG 5NN CO”
“5NN ME”
“TU WW0TST”

Again, repeats may be needed. If, after my initial call, WW0TST didn’t get all of it, he might send “1B”; I would then send my full call once again. A more generic form is “?” meaning repeat whatever you last sent. This can also be “AGN”. On CW, many search and pounce operators will preface the exchange with the callsign of the running station, for example “WW0TST 5NN ME”. I can see the logic of this, to avoid possible confusion when QRM is high. There might be some uncertainty as to whether I am working WW0TST or his very close neighbor on the band. Sending his callsign alleviates any doubt. However it comes at the cost of additional time. I generally don’t do it. Notice there is no “BK” (over, or I’m done, now you go ahead) at the end of a transmission. Believe it or not, it just isn’t necessary! Even the least experienced novice contesters don’t need to hear this to recognize it’s their turn.

Of course there are many variations. Things don’t always go by the book and sometimes multiple repeats may be required for the callsign and/or exchange. This is one way contests help to improve skills. The more you do it, the better you will become at responding quickly and accurately to varying situations. It is good mental exercise. The best way to learn is to get on the air and contest! Sometimes, repeating a piece of information more than once in a single transmission can be useful. If I’m calling a station and he has asked for a repeat on my call more than twice I will usually give it twice in one go. This is always a judgement call and practice will be your best teacher once again.

Conventional wisdom (and it is wise) says never send the exchange until the other station has your callsign correct. For example if he had it as N1BUZ I would simply repeat my callsign again, and not send 5NN ME until he has it right. Failure to follow this rule may result in a what we call a “busted” QSO where he never gets it right and logs the wrong call. Trying to correct your callsign and send the exchange in one go is risky. Personally, I will sometimes break this rule of thumb and give a call correction along with the exchange, for example “N1BUG BUG 5NN ME”. It is a judgement call, but understand the risk before you make it. I do this only when signals are strong, never in what seem to be difficult conditions. I never take this risk if I need the contact for a new country!

One other thing you will hear in CW contesting is “NR” after you have sent your exchange. This means the operator needs that part of your exchange after the signal report again, be it a serial number, state, zone, or what have you. In a contest where state is the exchange he might use “ST” instead of “NR”; where ARRL section is part of the exchange it might be “SEC”. There are a few others specific to particular contests, but most will be self explanatory if you are familiar with the contest rules and exchange. If asked to repeat a specific thing it is best to repeat only that piece and not the whole exchange. On phone, the full word will be used instead of abbreviations” “Number”, “State”, “Section”, etc.

You may notice the 5NN replacing 599 in the CW example. It is common to abbreviate, or “cut” numbers to save time. This is true in DXing as well as contesting, but to a lesser degree. Usually only 9 is cut in DXing. In contesting other numbers may be cut. The number 9 is almost always cut to N. Often the number 0 (zero) to T; the number 1 to A; and occasionally the number 5 to E. You only do this for the exchange, never when a number is part of a callsign! In a recent CW contest where the exchange was signal report and power I often got “ENN ATT” which means “599 100”. Why? Because in Morse code, ENN ATT take much less time to send than does 599 100. It may look strange now, but you’ll get used to it!

In RTTY contesting the flow tends to be a little different, for reasons I won’t fully delve into here. Suffice to say it has to do with error rates and the operator having to rely on the RTTY decoder which can’t make a confidence assessment as the human brain does in other modes. This makes a certain amount of redundancy desirable in all but very strong signal conditions. A typical RTTY contest exchange would be:

“WW0TST TEST”
“N1BUG N1BUG N1BUG”
“N1BUG 599 CO CO N1BUG”.
“WW0TST 599 ME ME N1BUG”
“N1BUG TU WW0TST”

Different skill sets are needed for running vs. search and pounce. If you’re not feeling highly confident in search and pounce you can always listen for a minute before calling a station. You will already know his callsign and probably the exchange he will give you. All you have to do then is recognize your callsign when he responds. You can also take your time logging the QSO before moving on to the next station.

Running is very different and more challenging. You will have to copy the callsigns of stations calling, and often there may be more than one calling at the same time. Often you won’t know the exchange in advance and will need to copy that too. Unless you have super powers, you will find that logging operations slow you down and create awkward pauses while learning to run. You’re not alone. If you tune the bands you will find other contesters who are learning to run having the same difficulty. It gets easier the more you do it! Eventually you will learn to perform logging operations while receiving and sending. Then you’ll be able to run stations as quickly as if you weren’t logging at all. Good contest logging software can help.

You may wish to consider a few additional factors when getting into contesting. If using VOX (voice operated transmit) on phone or semi-QSK (semi break-in) on CW, make sure your end-of-transmission delay is short. If it takes your transceiver (and any accessories) too long to switch from transmit to receive you will undoubtedly miss part of the other station’s transmissions. Experienced contesters are very quick on the turn-around! Your station layout should be comfortable and ergonomic, having all controls within easy reach. Consider the advantages of contesting software such as N3FJP or my favorite, N1MM Logger. Good contest software not only logs your QSOs, but can send CW, RTTY, and voice recordings automatically and error free. These packages will also score a contest for you, flag dupes (duplicates; stations you’ve already worked and cannot work again for contest credit), tell you where to find multipliers (assuming this is allowed in your entry category if competing) and many other things. I love getting a good run going with N1MM Logger where I can crank up the CW speed and go for it! It does wonders for my overall prowess as a radio operator and it’s fun! You may also want to consider whether your transmitter can handle the rigors of contesting. Virtually any modern transceiver should be fine, but if you have an amplifier you should give this some thought. Some amplifiers may overheat with prolonged contesting, and many are not be rated for full power on high duty cycle modes like RTTY.

Contesting can be a lot of fun even if you only make a few contacts. Set some goals and give it a try! Start simple. Maybe a goal of ten contacts is enough for your first attempt. Or you might try for the WAC (Worked All Continents) award. That one is easy because you only need six (North America, South America, Europe, Africa, Asia, Oceania). But be forewarned: for many people, contesting is addictive. If you are a very competitive person or you get a thrill from realizing you are performing at a new peak level, watch out: for you, the danger of contest addiction may be great.

My First Foray into RTTY Contesting

This is one of a series of “Notes” I published on Facebook. Since Facebook has discontinued the Notes feature, I am publishing that series here on my blog.

If you ask anyone who knows me, they will probably tell you I’m not into digital modes. It’s not that I am anti-digital. I have tried several of the newer modes, but found them uninteresting. I left EME after having put nearly all my eggs in that basket for 18 years because the digital mode that replaced CW made it anything but fun or interesting to me personally. But, I recently began to experiment with RTTY for purposes of working DXpeditions on another mode. To my surprise, I’m finding it moderately fun. I would say RTTY is the only “mainstream” digital mode in DX and contesting. Perhaps that is because it was the original digital mode, aside from Morse code of course. The mode itself has been around and in use by amateurs for a very long time, originally using teletype machines – noisy, clacking mechanical behemoths that allowed the sending station to enter text on a typewriter style keyboard, and printed the text on paper at the receiving station. RTTY is short for Radio Teletype”. Today, RTTY is easily achieved using a computer and sound card. Nearly every major DXpedition operates RTTY in addition to SSB and CW. A few do a limited amount of PSK, but most don’t. Hence if you want to work the rare DX on digital, you’re probably going to want to be on RTTY. There are quite a few RTTY contests, including a few major ones.

On Friday afternoon, just prior to the start of the CQ WW WPX RTTY Contest (a big one!) I got the notion into my head that this might be a good opportunity to work a few more countries on the mode and get a little more experience with it. I assumed, this being a digital mode, that I would just be making a few contacts, picking and choosing those stations that would be a “new one” on RTTY or on a particular band. It was a perfectly good theory, but I should have known better!

I didn’t really know the format for exchanges in RTTY contesting. I knew the required exchange for this contest was signal report (always 599 in a contest) and serial number starting with 001 if it is your first QSO in the contest. What I didn’t know was whether to include callsigns in every transmission or omit them after the other station has correctly copied that information. I didn’t know whether the serial number should be repeated more than once. In some respects this is very different from CW or SSB contesting. In those modes, the operator is the decoder. You hear the information, you decide what was said and can easily assess your confidence in having heard it correctly or not based on signal strength, interference, and so on. With RTTY the software and/or hardware is doing the decoding. Even if you are monitoring the receive audio (annoying, since it is a high pitched warbling sound) you may not know for sure whether a burst of noise or signal flutter may have caused a number to decode incorrectly. It can be totally wrong! A common one I see time and time again under marginal conditions is “599” decoding as “TOO”. That’s not even close! Because of these uncertainties, I decided to wait until the start of the contest to program macros – short sequences to automate the sending of contest exchanges. I would see what others were doing first, then set up mine accordingly.

Hastily tuning around in the first few minutes of the contest and just listening (watching?) I was able to come up with some guidelines. As with contesting in other modes there are many variations, but I discovered the most common QSO format looks something like this, where DX1TST is the station calling CQ and the bold italic lines are sent by the answering station:

CQ DX1TST DX1TST
CQ DX1TST DX1TST
N1BUG N1BUG N1BUG
N1BUG 599 123 123 N1BUG

N1BUG 599 123 123 N1BUG
DX1TST 599 001 001 N1BUG
N1BUG TU DX1TST

These exchanges contain much which would be considered extraneous in a CW or SSB contest, but they help to assure confidence in the decoded information and to be sure the correct station is being copied since they all sound exactly alike. I set up my macros accordingly and proceeded to look for stations I wanted to work.

Tuning in a RTTY signal takes a bit of practice and must be done quite precisely since the two tones are only 170 Hz apart and the software expects them to be almost exactly in a certain place. The software I am using (WinWarbler) includes a tuning indicator which attempts to reproduce the RTTY scope pattern of days gone by. It is a pair of rotating ellipses at right angles to each other (like a plus sign) with one ellipse representing each of the two tones. The tones are called mark and space just in case you’re wondering. When a station is properly tuned one ellipse should be vertical, the other horizontal. Any tilt indicates mistuning, and if you are off by more than a small amount, one or both ellipses will shrink in length or completely disappear as that tone falls outside the receiver or decoder filter. By default, my tuning indicator rotated clockwise for a counterclockwise rotation of the tuning knob and vice versa. Oh boy! This hadn’t been more than a minor annoyance in DXing, since I had plenty of time to tune the station properly. But in contesting it slowed me down as I had to keep reminding myself which way to turn the knob. Probably this would have improved in time, but WinWarbler has an option to reverse the tuning indicator direction of rotation. Having it rotate the same way as the tuning knob helps tremendously! If I need the indicator to rotate clockwise, I turn the knob clockwise. My mind can handle that.

At first I was very slow. I was reminded of my first steps in CW and SSB contesting years ago. As a rookie, you’re going to be somewhat tentative for a while. I had to stop and think about what key to hit or macro to click every time. Even though I was looking at a band map that contained spots and choosing the stations I wanted to work, I was tuning to them manually. I found myself using the mouse exclusively to position the cursor in the proper fields for entering log information, click on macros, and press the ‘Log’ button at the end of a QSO. This RTTY contesting was turning out to be a lot of work! At some point I realized that pressing <Ctrl>+<L> on the keyboard to log a QSO would save me some mouse work and was quite a bit more efficient. That might have been obvious under normal circumstances, but I was still rather nervous and uncertain about this whole RTTY contesting thing. Some time later I realized that WinWarbler has a contest mode which, when selected, positions the cursor where needed most of the time, unless you somehow get out of sync, such as having an unusual situation in the flow of a QSO. Also, it automatically increments the sent serial number for each QSO. Hotkeys were a much better way of sending macros, the only trick being to remember which key sends what without looking at the list every time. Yes, I got it wrong a few times and got all flustered trying to recover. Mistakes are part of learning something new. Things were beginning to speed up and this was a lot less like work if I let the software help. Eventually it dawned on me that I didn’t have to manually tune to the stations I saw spotted. All I had to do was click the station’s callsign in the band map and presto, my rig was tuned to the spotted frequency, the station’s callsign entered in the appropriate box for logging, etc. Wow!

With those revelations and a few hours of intermittent operating behind me, it happened: contest fever took over and I started clicking on every callsign in the band map instead of being choosy. Oh, great. I was slipping into a contest mindset without realizing it. I found that I could go from QSO to QSO very quickly now, with little or no thought. The only trouble was I knew the spotted stations on the band map were but a few of the stations available. If I wanted to work the others I was going to have to learn how to “tune the band”, finding stations myself. Even with the tuning indicator and knob now rotating in the same direction, it took a while to get comfortable with this process. Trust me. On a crowded band it is necessary to use narrow filters in the receiver to keep QRM down. But, narrow filters means that sometimes only one of the two tones is within the filter, and you probably don’t know which one. Hence you don’t know which way to tune. It is entirely possible to have the mark tone from one station in the filter, but not his space tone or vice versa. Yet you see two tones because you have one tone from an adjacent station in the filter. Honestly, I can’t say that I liked this operating strategy much on RTTY, but perhaps if I do it enough it will become less challenging. Overall, my skills were improving by leaps and bounds and I was finding plenty of stations to work.

On Sunday, propagation to Europe on the higher bands (20,15, and 10 meters) was very good with many signals being 30 or more dB over S9, some pegging the meter. Under these conditions I found that stations I called were responding with “N1BUG 599 1234” instead of the longer, more cautious message. I hastily set up a new macro to respond in kind “TU 599 321”. Under those conditions I suppose one can expect perfect decoding (called print in RTTY) almost every time, so the shorter exchange makes sense. At the other extreme, fluttery signals coming over the north pole from deep Asia can be quite difficult to get good print even when the signal strength is excellent. The software does have several different decoding algorithms to choose from, including one or two for fluttered signals. They help, but error rates are still high and more repeats are often required.

I never did feel comfortable enough to try “running” – that is, being the CQing station and letting people come to me. All my operating was search and pounce (find a CQing station and work them).

On Sunday afternoon it occurred to me that I had worked over 70 DXCC entities in this contest. Knowing that, I had an irresistible urge to see if I could work RTTY DXCC (100 entities) in a single weekend. Suddenly I was back to my original modus operandi for the most part – seeking stations that would give me a “new one” in DXCC terms. I ended up with 89. This is not just bad, it is downright ugly! Oh, not because I failed to reach 100 this time. It is ugly because I got close enough that next time RTTY DXCC in a weekend is likely to be my goal from the outset. Next time!? Oh boy. Another monster has escaped captivity. Sadly, no one has yet found a cure for this DX and contesting affliction, so I’m stuck with it.

I had fun messing with people who know me and my usual avoidance of digital modes. I got several “N1BUG?! 599 …” responses, which, while ambiguous, tended to come only from those I am acquainted with. “N1BUG ON DIGI!!!” was seen a couple of times, and “N1BUG ON DIGI, WOW!!!!!” once. There was no ambiguity of meaning there.

I made 333 QSOs in the contest. That’s not bad for a first attempt with quite limited operating time doing all search and pounce. There was a moment of panic five minutes from the end when it looked like I might end up with 332. An even number? No, no, no, no, no! I may have been trying something new and unexpected, but I was still me after all! I never said I was without idiosyncrasies. Fortunately I was able to find and work one more before it ended. Whew!

I am much more comfortable with the software and RTTY operating now. This will no doubt serve me well in day to day pursuit of DXpedition QSOs. Whatever your interest in ham radio, even if it is mostly public service, there is nothing like contesting to improve operator skill. Those of us who are prone to being highly competitive probably get the most out of it, but even casual contest operation does more than one might think.

Amateur Radio Public Image

This is one of a series of “Notes” I published on Facebook. Since Facebook has discontinued the Notes feature, I am publishing that series here on my blog.

Thirty-something years ago when I got into ham radio I recall my parents discussing my new hobby with people they knew and visitors to my dad’s shop. My antennas weren’t exactly inconspicuous even in those early days so the subject had a way of coming up. It was a long time ago but I would estimate about half had heard of ham/amateur radio. Most of those believed it was a radio hobby of some sort that provided opportunity to communicate around the world. A smaller percentage seemed to be aware of its public service and emergency communications aspects.

Has that changed? Three years ago I ran across a lot of curious people while I was out hunting power line noise. The vast majority had either not heard of ham/amateur radio or thought it was the same as CB radio. Of the ones who were aware of ham radio as something other than another name for CB, most were under the impression it was only used in emergencies or for public service. More than a few were shocked when I mentioned other facets of it. Since that time I have been making a point of bringing up the subject with people I meet. It’s true I don’t meet a lot of people. But the trend in what people know or don’t know about ham radio seems to span the community as far as I have been able to discern. The contrast between then and now stands out.

I find it somewhat curious that fewer people seem aware of ham radio today despite a much larger number of hams in the community, greater visibility, and more publicity in local media. Perhaps it just doesn’t make an impression in today’s world of cell phones and internet. Perhaps people are too busy to notice. Maybe it is just information overload. We are bombarded by so much these days. I know I tend to ignore a lot of it.  I’m not surprised that among those who are aware of us, public service is the image they have. This makes sense to me since over the last twenty years, much of the increased public exposure and publicity has been in that vein.

Public service is, of course, a vital part of ham radio. It is not my intent to dismiss or devalue that in any way. But I have seen ham radio be so much more. I have seen ham radio as a hobby change and enrich lives. I have seen what it can do to enhance international goodwill and bring people together. It has been suggested that I place too much value on ham radio and too much emphasis on it being a hobby. Well, yes… I am very passionate about ham radio as a hobby. If that is a crime I proudly plead guilty! I could write a book on what ham radio has done for me, about the positive influence it has had on my life. Maybe someday I will write that book. Point is, I’m not the only one. Beyond any doubt whatsoever I am certain others could enjoy and benefit from it as I and many have. But first they have to be exposed to it and develop an interest.

Some say ham radio as a hobby is dying out because it just isn’t as relevant or interesting as it once was. Surely there is an element of truth to that. With the proliferation of cell phones and the internet, radio has taken a back seat as a means of communication. Yet around the world we still see a percentage (albeit smaller) of people getting involved in the personal, recreational, and educational aspects of ham radio. But before they can do that, people need to be aware of it. They need to be aware of the many aspects of it. Are we simply not doing enough to promote the broader sense of ham radio? If we’re not doing enough to promote it, how do we change that? Seriously. Please comment!

Since I started the publicity campaign for a recently completed amateur radio licensing class back in February I have been giving this a great deal of thought. Were I not so “constrained” by personal circumstance I would be seeking opportunities to demonstrate ham radio in public places, at local community events. While I have the passion and am more than willing to make the time, this remains beyond my personal reach without assistance.

What else can we do? Would informational displays in libraries or other public places be of any use? Would it be possible to do presentations in local schools? What other ideas do you have? I hope this note will stimulate discussion. Furthermore I hope to get from this discussion some direction, ideas and hopefully find a practical way for me to become involved with educating the public about the broad spectrum of interests which comprise amateur radio. If anyone in the local area would like to partner with me to promote our hobby, please contact me.

Amateur Radio Practice: Honesty in Signal Reports?

This is one of a series of “Notes” I published on Facebook. Since Facebook has discontinued the Notes feature, I am publishing the that series here on my blog.

This may seem like a rant, but I don’t mean it that way.  My hope is to stimulate thought and discussion.

When I was getting into amateur radio, my elmer (one who teaches, guides, advises) taught me to give accurate and honest signal reports to the stations I work (make contact with). He said this was a time honored tradition and that most hams (amateur radio operators) would want to know if their signal quality wasn’t the best so they could strive to improve it. It made sense to me. For the most part on the HF (high frequency: good for long distance communication) bands, strangers still today give each other honest signal quality evaluations.

But what about on VHF and repeaters, where we are often communicating among friends and it is more or less local in nature? I have observed that many of us, myself included, seem hesitant to be honest with each other. Why is that? Are we so afraid of upsetting someone that we hide the truth from them? Is that really doing them a favor? For that matter, are we being a good friend to them?

Consider the case where someone buys a new radio, gets on the air to try it out and see how it is working. In reality the audio is distorted, harsh and fatiguing to listen to. Some words are even hard to understand. Yet everyone tells him/her the new radio sounds good. Why? If I just bought a new radio I would want to hear honest reports, even nit-picky ones. Most new radios purchased through reputable dealers can be returned if they aren’t right. I would certainly want to know so that I could return a defective radio (or microphone or whatever). Yet I have heard this scenario play out more than once, with seasoned hams giving the not-entirely-accurate reports. What is happening to us?

Low audio seems to be reaching epidemic proportions on VHF/UHF FM, at least in this area. As a repeater owner, this subject is of prime interest to me. There are two schools of thought on how to set up audio handling on a repeater. I have always believed a repeater should faithfully reproduce the signal it hears, not changing the quality in any way. For one thing, this makes it possible for hams to give each other honest signal evaluations when talking through a repeater. Were the repeater to change the signal in some way, signal quality reports would become less meaningful and prone to errors. Can this be one reason people often refrain from being critical of audio? Since some repeaters do change the audio significantly, it may be that people have become wary of judging user audio when it has been repeated. For almost twenty years I have set up my repeaters to faithfully reproduce user audio (what comes in goes out unchanged). I believe this is one reason I have received so much positive feedback on how natural they sound. The problem with this approach is that so many radios on the amateur market today have low transmit audio, often exacerbated by other factors such as talking too far away from the microphone. At least 20% of users on local repeaters have audio that is low enough to be a serious problem. Probably no more than 60% have audio that would be considered in the “good practice” range for narrow-band FM. One shouldn’t have to turn the volume up on a receiver to hear those with weak audio and then be blasted by those whose audio is in the normal range. If there is any noise to contend with, low audio makes it that much harder to be heard through it.

The other school of thought is that repeaters should process user audio. In its usual implementation, this can significantly boost low user audio while clipping or limiting more robust user audio. Boosting low audio can help in some situations. If noise is a factor on the receiving user side of the communications circuit, a repeater that boosts low audio can certainly enhance communication reliability. If noise is a factor at the repeater receive site, the boost won’t help. The flip side is that signals with robust audio must be limited in some way. This is most often implemented by taking advantage of built-in audio clipping or compression in the repeater transmitter. Unfortunately this “colors” the audio of users with normal (read: communications industry standard) audio, making them sound less natural, somewhat harsh, and even muffled in some cases. Virtually all user radios have already clipped or compressed audio in the transmitter. If the repeater does the same, the audio has now been processed twice. The result can be less than pleasant. I have been thinking about this a lot and have experimented with it to some degree on my newest repeater. It does help those with low audio, but it hurts those who had good audio to start with. To be honest, I’m having trouble with the concept of hurting those with good sounding radios in order to help those with not-so-good ones. Is this fair? Is it good practice?

What if we all gave truly honest signal evaluations to those we talk to on the air? What if we let them know when their audio is low or distorted, and encourage them to find out why? Perhaps they just need to hold the microphone differently. Perhaps they are using an aftermarket microphone that isn’t a good pairing with their radio. Or perhaps it is the radio itself, in which case it may or may not have an internal adjustment to compensate for the problem. I will wager that the majority of those in my local area whose VHF or UHF FM audio is chronically low don’t even realize it – because it hasn’t been brought to their attention. Sometimes we try to soft peddle the truth, as in “Your audio is a little low but I can understand you.” While that may be accurate, I suggest it falls a bit short of good amateur operating practice. This may leave the other operator feeling as though it’s nothing to be concerned about, when in reality his/her audio could be low enough to cause real problems under different circumstances. Perhaps this would be better: “Your audio is low. I can understand you, but it could cause copy to be difficult or impossible in some situations. I would encourage you to look into it.” If it is a new ham or one who might not have the resources to investigate, perhaps add an offer to assist with it. This may be a bit more verbose, but it conveys a message that the signal is not what it should be and encourages them to strive for improvement.

I am taking a long, hard look at the way I give reports and whether I am doing my fellow hams any favors in this respect. I encourage others to give this some thought.

Update on ‘A Low Drive 2200 Meter Amplifier’

The amplifier. This was a “junkbox special”, so yes it’s a bit ugly!

This is an update to an earlier blog post describing a moderate power 2200m class E amplifier with very low drive requirement. The design had been evolving for some time but is now in a finished state as far as I am concerned. In its current configuration I have many hours on this little amplifier running 250 to 275 watts RF output, including numerous nights running 80% or higher duty cycle for hours at a time. It has proven to be very reliable. The basic design requires just 0 dBm drive (one milliwatt), but I have included a built in 20 dB attenuator in mine to accommodate the +20 to +24 dBm drive provided by my various exciters.

Amplifier schematic. The 20 dB input attenuator I included in my unit is not shown.

Use caution when selecting capacitors for the output circuit, namely C1 through C4. It may be very tempting to use a single capacitor of the specified value, but doing so will likely mean operating the capacitor beyond its voltage ratings if it is a film capacitor. Film capacitors must have their voltage derated as frequency increases. Capacitor data sheets usually have curves for this derating. I had capacitors in a 630 meter amplifier fail because I had not taken that into account. Generally smaller value capacitors can handle more voltage at a given frequency than higher value ones, which is why I use several low value capacitors in parallel to reach the desired capacitance.

When selecting a FET, choose something rated 200 volts or more if you plan to run this amplifier at full power. Voltage peaks at the FET drain are about 3.5 times the applied DC voltage. So with 40 VDC on it, the FET is going to see a peak voltage around 140 volts on every RF cycle.

The FET requires good heat sinking. I prefer either directly mounting the FET with a bit of thermal grease to a heat sink isolated from ground (note the heatsink will have drain voltage and RF on it, so be careful what might come into contact with it) or a mica insulator with thermal grease for a normal grounded heat sink. I do not recommend using greaseless Sil-pad thermal pads as they may be unable to provide adequate cooling efficiency. The heat sink on my amplifier is about 5 x 3 x 1.5 inches. A fan on the heatsink is not required for low duty cycle such as two minute WSPR transmissions at 33% or lower duty cycle. For long T/R period modes or frequent transmission resulting in high duty cycle, you will need either a larger heatsink or a fan. I also have a fan on the bottom pushing air into the amplifier and air exhaust vents on the other end. Again, this is not needed for short transmissions of low duty cycle but if you are going to run 15 or 30 minute modes or very frequent transmissions, it will be necessary to supply cooling air to L1 and L2. I also have an internal fan assuring high volume air flow across those inductors, though that is probably not needed. It was there to move air across the inductors before I added the bottom cover and intake fan, and I didn’t bother removing it.

Bottom view of the amplifier showing the fan and air exhaust

As noted in the previous post, this amplifier was constructed by making “islands” in a solid copper plated PC board using a Dremel rotary tool. Other methods will surely work as well.

Internal view of the amplifier

The only future change I might make is to replace the little TO-220 size 34N20 FET with a FDA59N30 in the larger TO-3P package. I have not experienced any FET failures with the present configuration but I like the larger FETs for better cooling efficiency.

A High Power 2200m Amplifier Saga

Kilowatt class-D 2200 meter amplifier

The story of this amplifier starts back in 2017 when I held a FCC Part 5 experimental license (WI2XTC). This was prior to FCC granting amateur privileges on 2200 and 630 meters. I was looking for a kilowatt-class amplifier that seemed reasonably easy and inexpensive to reproduce. I settled on the W1VD kilowatt class D design.

After building the amplifier I had a lot of problems with blown FETs. After many months of testing, troubleshooting and trying various things, I got that problem under control for the most part. It turns out this was not a problem with the design or my construction, but simply that modern modes and operating practices are not consistent with the intent of the design. The amplifier was designed for a steady RF signal at its input, with transmission to start and stop by using one of the keying inputs to enable and disable the FET driver IC. That just isn’t how modern computer generated modes work. The software usually provides for PTT (amplifier keying), but it is the opposite of what would be needed to keep the amplifier happy. PTT is asserted before RF generation starts and held until after RF stops. The amplifier needed the opposite to be safe: PTT asserted after the start of RF generation and released before RF stops.

Initially I was experiencing frequent FET failures with any exciter I used, but they were far more common, in fact almost guaranteed using an exciter capable of amplitude shaping the start and/or end of the RF envelope. I don’t have a storage oscilloscope, but after seeing some FET drain waveforms provided by other users of the same amplifier it was apparent there were (or could be) voltage spikes exceeding the 200 volt rating of the FQP34N20 FETs at the start and especially end of a transmission. Additionally there appeared to be extended times of zero voltage on one pair of FETs or the other, possibly indicating a longer than normal on time. One might wonder if there were current surges occurring at those times. After a lengthy search for replacement FETs rated for higher voltage and current but otherwise having similar ratings to the FQP34N20, I tried the FDA59N30. That eliminated any blowing of FETs with exciters or modes that are not capable of RF envelope shaping, such as the QRP Labs Ultimate 3S which I use extensively. I had just one FET failure in more than a year of operation. It appeared that may have been due to overheating. I found the mounting screw on the failed FET was not tight. Both the mounting surface of the FET and the Sil-Pad underneath were discolored in a way that suggested excessive heating. The FDA59N30 is a current production part while the FQP34N20 is long discontinued and becoming very hard to find except from some overseas sources which are selling counterfeit devices.

During the summer of 2020 I was invited to join the early testing team for the new FST4 and FST4W modes being developed for use at LF and MF. It was one of the better things to happen in 2020! Initially I was able to run these modes using the phasing exciter but I noticed some peculiar glitches on the scopematch (sophisticated RF power and SWR monitor using an oscilloscope) at the start and particularly at the end of transmissions. I also had some intermittent problems with amplitude and phase fluctuations during FST4/W transmissions. Eventually while looking for the source of that problem, I discovered the IR2110 FET driver was not entirely healthy. One side was OK but the other was providing only weak gate drive to the FETs. I replaced the driver and that was the end of being able to transmit using the new modes! FETs were constantly meeting their demise with the new modes, while other modes were OK. My pile of dead FETs was again growing rapidly! At about the same time I learned something about the new modes that I had not previously known. They were intentionally using envelope shaping at the beginning and end of transmissions! (Note: with the general availability release of WSJT-X 2.3.0, the FST4/W envelope shaping can be disabled.) Sure enough, when I tried manually enabling the FET driver after the envelope shaping at the start and disabling it before RF shaping commenced at the end of transmissions, FETs did not fail.

It has never been clear to me exactly where in the amplifier problems start with non-constant amplitude drive, but clearly bad things were happening somewhere. Was it strictly in the output circuit, or was something going wrong in the driver or the pre-driver logic? It would be fair to say I was never entirely happy with the configuration of the amplifier anyway. Since it used a flip-flop to clock the IR2110 FET driver, it required the RF input signal to be at twice the operating frequency. For 137.5 kHz operation, it needed RF drive at 275 kHz. In order to achieve that with common exciters and relatively minimum hassle, I used a frequency doubler circuit before the driver. That always seemed like unnecessary complexity to me, but at the time of construction there were few, if any alternate driver designs for class D amplifiers that didn’t use a flip-flop, therefore requiring drive at twice the operating frequency. The doubler also caused some problems running EbNaut, which uses 180 degree phase shift keying.

While struggling to think of a solution to the FST4/W envelope shaping killing FETs en masse, it came to my attention that others were now using drivers for class D amplifiers that did not use the flip-flop and worked with “normal” drive at the operating frequency. I decided to try an experiment. Melding elements from three different designs, I came up with a driver that provided all of the control inputs of the original, required no doubler and allowed for some adjustment of the duty cycle. The circuit uses a 1:9 impedance step up transformer driving a pair of LM311 comparators. The comparator outputs control the IR2110 FET driver. One obvious advantage is that this does not require drive at twice the operating frequency. Another is that, unlike the original driver configuration this one allows for some adjustment of the length of the drive pulses to the FETs. This made it possible to get cleaner drain waveforms with less high frequency ringing.

New driver circuit for kilowatt class D amplifier

With the original driver there was always some high frequency drain ringing. With this driver it can be almost entirely eliminated by adjusting the 20 ohm trimmer to vary the duty cycle or length of drive pulses. There is a tradeoff between the circuits. The original amplifier input consisted of a frequency doubler and the flip-flop preceding the IR2110. With that configuration there was little to no change in drain waveforms over a 15 dB drive power range. With the new circuit, drain waveforms change with drive level. The change is minimal over about a 6 dB range but increases outside those limits. The range of acceptable input can be pushed to 15 dB before things start looking really alarming. This worked fine for all but FST4/W modes (prior to the 2.3.0 GA release with envelope shaping disabled). With FST4/W slowly rising from zero to full power at the start of a transmission and slowly decreasing from full power to zero at the end, the drain waveforms went through some ugly periods. I was still occasionally losing FETs.

I wondered if an RF sensing circuit could solve that problem. It should be possible to sample the incoming RF drive, rectify it and use the resulting DC voltage to control a comparator which would enable the IR2110 only after drive had reached a safe amplitude. The question I had was would it be fast enough to disable the FET driver at the end while the envelope was decaying. If it was too slow, it might not disable the driver before the amplitude reached a low enough level to cause problems. Never blindly trust my math or circuit design skills but by my reasoning it looked possible. The envelope shaping occurs over approximately 2.5 seconds for a FST4/W 1800 second transmission. I believe it scales linearly with the T/R period, so for the 15 second transmission it should be about .02 second. There should be plenty of time to shut things down if I used an RC time constant of about .0002 second. Instead of rambling though all of my rough calculations let me just say I tested the circuit as built with several hours of FST4-15 transmissions, which would require the fastest timing. There were no glitches evident and no FETs were harmed during the test.

RF sensing and comparator circuit. The driver enable output is internally connected to + Key on the above driver circuit.

I built the new driver circuit on a board which was the same size as the original and used the same connectors, so it was a drop in replacement for the amplifier. Similarly the RF sensing and control circuit is a drop in replacement for the no longer needed frequency doubler.

RF sensing (mounted vertically on chassis end wall) and driver (foreground) boards mounted in the amplifier. Blue and green twisted pairs go to the FET gate resistor/diode networks.
Overall internal bottom view of the amplifier with new input boards installed. The bottom cover has a fan that blows air directly onto the output transformer and an air exhaust which is directly under the driver board. Two inch legs raise the amplifier sufficiently to allow good airflow.

The remainder of the amplifier remains mostly unchanged from the W1VD circuit except for the substitution of FETs as discussed earlier. It should be noted that for power levels above 400 to 500 watts at high duty cycle, a small fan cooling the output transformer is a good idea.

Schematic of the rest of the amplifier

The power supply is about as simple (and efficient) as you can get, a few luxuries notwithstanding. It is unregulated, consisting of a variac, transformer, two bridge rectifiers and two large filter capacitors. It can provide 0 to 50 volts for the FET drains. The power transformer has two secondaries. Each has its own rectifier and filter capacitor. The two are combined at the output terminals of the supply. A small fan is used to blow air across the bridge rectifiers to aid in cooling. Because the filter capacitors are large and the transformer resistance is low, a soft start circuit is used to prevent inrush current problems. There is a separate transformer with a similar configuration to supply 12 volts to the amplifier driver circuits. The 12 volt supply also controls the soft start by means of a comparator which closes a relay to short out a resistor in the AC input to the variac after a short (adjustable) delay.

Schematic of the power supply
Internal view of the power supply. Space is limited and the variac would not fit on the front panel. It is accessed through a hole cut in the top cover of the supply.
The power supply with top cover in place

Experimenting with a K9AY loop on LF

50 foot mast supporting LF/MF K9AY loop

During the late summer and autumn of 2020 I built a K9AY loop, hoping it would help me hear DX on 2200 meters. Computer modeling suggested the minimum size for good front to back ratio and overall pattern would be twice the size of the original 160/80 meter K9AY loop design. This required a 50 foot mast. I chose to use a fiberglass mast to ensure there would be no interaction with the antenna. Since the “gain” of this antenna at 137 kHz is -55 dB, I was worried about common mode noise ingress. In an effort to minimize any such problems, transformer coupling was used at both ends of the coaxial cable feeding the antenna.

Having limited space I was not sure how successful this project would be. The K9AY would have to be located within 50 feet of my 2200 meter transmitting antenna, over the 160/630/2200 meter radial field, no more than 50 feet from one of the towers and just a bit over 100 feet from the other. That is not an ideal environment for a small directional receiving antenna!

The best location, considering other antennas, seemed to be atop a small mound in the back yard. I immediately had misgivings about that, since I knew the origin of that mound. It was what was left after the lawn area was flattened with a bulldozer about 45 years ago. At the time there was an automobile junk yard next door, spilling over onto this property which was owned by the same party. I had no idea what I might find when I tried to dig a hole to put in concrete for the mast footing! In the first several inches, I encountered several strands of old barbed wire. Lovely! Next was a power steering pump and a water pump. At about the two foot level the real challenge presented itself: a buried concrete slab several inches thick, obscuring about two thirds of my hole area, and tilted at a 30 degree angle with respect to horizontal. Oh, great! It took hours of beating on that slab with a heavy steel bar to break it up and continue excavation. Digging a four foot deep hole 18 inches in diameter with nothing more than a spade is always fun, but I got the job done. It has been suggested on several occasions that I am “determined”. I think that is a nice way of calling me stubborn! But it fits.

Base of the K9AY loop mast (coax and control cable not yet installed)

When the antenna became operational, front to back was no better than 3 to 6 dB. Some quick experimentation showed that de-resonating the 2200 meter transmitting antenna improved the situation greatly. With that change I could often see 15 dB front to back but not always. Several methods for de-resonating were tried, but it turns out simply disconnecting the bottom of the loading coil/variometer from the secondary of the toroidal impedance matching transformer is as effective as any other method. I modified my station so that I could do that from the operating position and even have the antenna automatically resonated while transmitting and de-resonated while receiving.

The original K9AY feed box with fixed terminating resistor (before installing coax and control cable)

Over several weeks it became apparent the antenna’s performance was not stable. The pattern seemed to improve and worsen with environmental factors such as temperature and snow cover. Several other K9AY loop users suggested improving my ground system might help stabilize it but with snow already on the ground I decided that would not be practical until spring. I decided to modify the K9AY to use a vactrol instead of a fixed resistor for the termination. A vactrol is essentially a voltage variable resistor consisting of a LED and a photocell in a small four lead package. I obtained a VTL5C4 vactrol made by Xvive and installed it on the K9AY. Additional control conductors were run to the antenna so I could control the termination resistance remotely from the operating position. This change has thus far allowed achieving at least 17 dB front to back using sky wave signals as a reference on any given night. There have been times when I see more than 30 dB front to back on DX signals. I have no explanation for that, since the computer model suggested a maximum of 17.5 dB. Front to back often undergoes short term changes which I suspect are due to changing vertical arrival angle of signals, possibly with some contribution from skew path signals if that phenomenon exists on 2200 meters. Skew path is common on 160 meters. Termination resistance typically requires adjustment with major temperature changes and after significant snowfall events.

Modified K9AY loop box with vactrol for variable termination resistance

So, with those changes made, how does it work? Better than expected! I have been comparing antennas by listening simultaneously on both using identical receivers feeding identical sound interfaces on the same computer. I am using six instances of WSJT-X monitoring three modes: WSPR2, FST4W-120, and FST4W-1800. SNR as reported by WSJT-X is recorded for every signal received and each antenna it is received with. From that data, the following results have been extracted and calculated. The method is not perfect as there is uncertainty in the reported SNR, especially with weak signals near the decoding threshold. However it is the most practical method to get a reasonable comparison.

Before getting into the results, I should point out that having the new directional antenna has confirmed something I already suspected: I have more man made noise to the southwest/west than to the northeast/east. This means I get a bigger advantage from the K9AY loop when listening to signals from the northeast, which puts many of my local noise sources off the back. Any advantage when listening southwest is largely nullified by the fact that my local noise mostly comes from that direction. During the day, when atmospheric noise is not a factor, my noise floor increases between 2 and 5 dB in the southwest direction compared to northeast. In addition to this increase in the overall noise floor, a number of “interference lines” and some narrow smears can be seen.

The WSPR/FST4W band segment. Northeast prior to 0930Z, southwest thereafter. Note more interference lines and squiggles southwest and the appearance of WB5MMB (1550 Hz) and WH2XND (1575 Hz) WSPR signals.
The WSPR/FST4W band segment, Northeast prior to 0930Z, southwest thereafter. Note the huge increase in WH2XND’s WSPR signal at 1575 Hz.

Results from the night of 22/23 January, 2021: With the K9AY loop listening northeast, a total of 35 transmissions from European stations were received. Of those, 21 were decoded only on the K9AY loop, while 14 were decoded both on the K9AY and the LNV. Of the latter 14, signal to noise ratio was always better on the K9AY, the improvement ranging between 3 and 7 dB for an average of 4.3 dB. While listening southwest, a total of 47 transmissions from stations in that general direction were received. Of those, 45 were decoded on both antennas with an average advantage of 0.3 dB to the K9AY. One transmission was decoded only using the LNV and one using only the K9AY.

Results from the night of 23/24 January, 2021: Listening northeast, a total of 56 transmissions from European stations were decoded; 25 only on the K9AY and 31 on both antennas. Of the 31, S/N ranged from 2 to 7 dB better on the K9AY for an average of 4.0 dB. Listening southwest, a total of 66 transmissions were received from stations in that direction; 62 on both antennas with an average advantage of 0.2 dB to the K9AY, 3 only on the LNV and 1 only on the K9AY.

Results from the night of 24/25 January, 2021: Listening northeast, a total of 89 transmissions from European stations were decoded, 45 only on the K9AY and 44 on both antennas. Of the 44, S/N ranged from 1 to 11 dB better on the K9AY for an average of 5.5 dB. The k9AY gained greater advantage later in the period. This may have been due in part to increasing static from storms over the central U.S. Listening southwest, a total of 12 transmissions were received from stations in that direction. All were decoded on both antennas with an average advantage of 0.3 dB to the K9AY.

Results from the night of 25/26 January, 2021: Listening northeast, a total of 17 transmissions from European stations were decoded; 7 only on the K9AY and 10 on both antennas. Of the 10, S/N ranged from 2 to 6 dB better on the K9AY for an average of 4.0 dB. Listening southwest, just one transmission was decoded, and only on the K9AY. However, it was a good one, AX4YB (VK4YB with a special prefix for Australia Day).

Results from the night of 26/27 January, 2021: Listening northeast, a total of 6 transmissions from European stations were decoded; 1 only on the K9AY and 5 on both antennas. Of the 5, S/N ranged from 1 to 5 dB better on the K9AY for an average of 3.6 dB. Listening southwest, a total of 18 transmissions were received from stations in that direction; all were received with both antennas with an average advantage of 0.3 dB to the LNV.

Results from the night of 27/28 January, 2021: Listening northeast, a total of 27 transmissions from European stations were decoded; 6 only on the K9AY and 21 on both antennas. Of the 21, S/N ranged from 2 to 6 dB better on the K9AY for an average of 2.8 dB. Listening southwest, a total of 49 transmissions were received from stations in that direction; 45 on both antennas with an average advantage of 0.4 dB to the K9AY, 1 only on the LNV and 3 only on the K9AY.

Results from the night of 28/29 January, 2021: On this night my local noise was somewhat lower than in previous nights, which may have contributed to slightly different results. Listening northeast, a total of 24 transmissions from European stations were decoded; 7 only on the K9AY, 1 only on the LNV and 16 on both antennas. Of the 16, S/N ranged from 0 to 4 dB better on the K9AY for an average of 2.3 dB. Listening southwest, a total of 47 transmissions were received from stations in that direction; 44 on both antennas with an average advantage of 0.6 dB to the K9AY, 3 only on the K9AY. VK4YB was received twice on each antenna, the first time with a 2 dB advantage to the K9AY and the second time equal on both antennas.

Results from the night of 29/30 January, 2021: Northeast there were a total of 21 transmissions from Europe decoded. Of the 10 captured on both antennas, S/N ranged from 2 to 4 dB better on the K9AY for an average of 2.7 dB. Southwest had a total of 38. 37 were received on both antennas with an average advantage of 0.1 dB to the K9AY. One was decoded only with the LNV.

Results from the night of 30/31 January: Northeast had a total of 8, four being heard with both antennas with S/N favoring the K9AY between 2 and 3 dB with an average of 2.7 dB. Southwest there were 40 in total, 36 being heard on both antennas with an average advantage of 0.4 dB to the K9AY. Two were heard only with the LNV and two only with the K9AY.

These results should be considered in the context of “what can I receive with one antenna that I cannot with the other” rather than “how many dB better is one antenna than the other”. Why? Because of the noise blanker settings I am using for the FST4W modes in WSJT-X. The way I have it set, it will first try to decode without any noise blanking. If that succeeds it will stop there. If not it will next try with a noise blanker setting of 5%. If that succeeds it will stop there. If not it will in turn try 10, 15, and 20% but it will stop at any point if a successful decode is obtained. What this means is that if on a given antenna it is able to decode a signal without using the noise blanker or with a low noise blanker level, it makes no attempt to see if it could get a better signal to noise ratio using more noise blanking. But when decoding on the “weaker” antenna it might get one or more levels deeper into noise blanking before obtaining a decode. This can have the effect of reducing the reported difference in S/N between the two antennas. During these tests I saw many cases where it decoded almost immediately on the K9AY but took longer on the LNV. This suggests on the LNV it was requiring more noise blanking to succeed, and that some of the decodes on that antenna might not have happened at all if I used no noise blanking or only one fixed setting. So if anything, the advantage of the K9AY is likely understated in these tests.

While not formally summarized in the above results, I have been paying attention to apparent front to back when receiving signals off the back of the K9AY. I say apparent because I am not switching the K9AY to the other direction but instead comparing the S/N ratio on the LNV to that of the K9AY. One some nights, apparent front to back is typically 10 to 15 dB with some values in the single digits. Other nights it ranges from single or low double digits to 24 dB or more. I suspect at times it is even more. For example I received a transmission from WH2XND at 0 dB S/N on the LNV but it did not decode at all off the back of the K9AY and could not be seen on any of my waterfalls, fast or slow! That would suggest something on the order of 30 dB difference between the two antennas.

The bottom line is that I am receiving a lot more European DX thanks to the K9AY loop. This antenna is well worth the work and expense that went into it.

Intermittent listening on 630 meters prior to the vactrol modification suggested an even bigger improvement northeast over the LNV on that band, though no formal comparison was made to to lack of a second receiver. On this band there may have been more advantage to the K9AY in the southwest direction but it was hard to tell with just one receiver.

Diagram of the LF/MF K9AY Loop

Multiple WSJT-X Instances on the Windows Desktop

With the recent 2.3.0-rc1 release of WSJT-X providing a first opportunity for everyone to try the new FST4 and FST4W modes designed for LF and MF, I have been getting questions about how I set up and manage multiple instances of the program. With these new modes it is very desirable to be able to run several instances of the program at a time, each with its own unique configuration and files area. This does not require installing the program multiple times. The program has a built in method to run multiple copies of itself from a single installation. The manual mentions starting multiple instances from the command line, but that is awkward when you need to start several instances for every operating session. Fortunately, desktop shortcuts can be used to start multiple instances of WSJT-X, and those shortcuts can also be pinned to the taskbar where they are always in view for starting instances even if the desktop is already completely covered over by various running programs. Here is a screen shot showing part of my desktop with five shortcuts, each of which starts a unique instance of WSJT-X:

Shortcuts for starting several instances of WSJT-X on my desktop

The shortcut named WSJT-X FST4W-120A starts an instance of the program specifically configured for the FST4W-120 submode. Likewise the others are for starting instances for FST4W-300, FST4W-900, FST4W-1800, and FST4. The latter is a more generic instance that I use for QSOs using FST4 mode. Each of the four FST4W instances has its own configuration, including a unique ‘My Call’ in the settings that adds a suffix to my call sign. That way, the spots I upload to WSPRnet identify which mode and T/R period the stations I decode are operating on. The FST4W-120 instance uses N1BUG/120. Likewise the others use N1BUG/300, N1BUG/900, and N1BUG/1800. I run all four of those every night that I am active, and usually have anywhere from one to three additional instances of WSJT-X running too.

So how did I create all those shortcuts? First I will describe the basic idea, then I will go into specifics of setting them up on Windows 10. The basics are:

  • Create a desktop shortcut to the WSJT-X executable
  • Rename the shortcut in a way that clearly indicates to you its intended use
  • In the shortcut properties, add a parameter to uniquely identify this instance to the operating system and the program

The latter is done by adding a parameter in the shortcut properties. This has the form of -r or –rig-name followed by a unique identifier of your choice. Here is what that looks like for the FST4W-120A shortcut:

The shortcut command for starting the FST4W-120A instance

Notice the –rig-name parameter followed by FST4W120A. I’ve got in the habit of using that instead of just -r which would be simpler. Please note that if you use –rig-name, that is two hyphens at the start. You need a space after .exe, then –rig-name, another space, and your chosen name for this instance. I know alphanumeric characters work for the name itself. I have not tried any non-alphanumeric characters. In this example, FST4W120A is the unique identifier that allows WSJT-X and Windows to differentiate this particular copy of the program from any other when it is started.

It is very important that every WSJT-X shortcut have its own unique –rig-name parameter! Do not try to run one instance without a –rig-name identifier along with one that does not. It won’t work!

After creating a shortcut for a new instance, don’t forget to start that instance and configure it. You need to add your call sign, locator, basic options, configure your sound card and rig, etc. All of these can be the same or different from other instances you may have.

Let’s look at how I create each shortcut. There are several ways to do it. Many people recommend making a copy of an existing desktop shortcut and reconfiguring the copy. That works but there are pitfalls if you make a minor mistake. I have gotten myself into a mess doing that a couple of times, so I no longer use that method. I will now describe in detail how I do it. A word of caution is in order here. Windows 10 can be configured in many ways which change the look and feel of this process. If you have Windows configured differently than I do, you may not see exactly what I see. I can’t discuss all of the various possibilities here.

First you want to open Windows File Explorer. You probably have a desktop shortcut or taskbar shortcut for that already. It’s the little yellow and blue folder icon. If you don’t have that shortcut, there are multiple ways to start File Explorer. A web search will turn up at least seven ways, but here is one way:

  • Click the Windows ‘Start’ button
  • Type ‘file’

You should see this:

You should see this after clicking the Start button (extreme lower left of this screen shot) and typing ‘file’

From there you can start File Explorer by clicking in the blue highlighted area at the upper left or just by pressing the Enter key on your keyboard.

Next you need to navigate to the folder where you installed WSJT-X. The default is C:\wsjtx but I have mine installed in C:\Radio\wsjtx.

  • You should see the name of your hard drive or SSD, usually C: on the left of File Explorer. A single click there should get you on your way, or
  • You may see your C: drive only on the right. It will probably take a double-click on that to get to C:
My File Explorer with my C: drive highlighted on the left

Once you’ve gotten to drive C: (or whatever drive you have WSJT-X installed on if you have more than one hard drive or SSD), you need to navigate to the folder where WSJT-X is installed using the list on the right. Here is what mine looks like after I’ve gotten to the proper folder:

One final step is to navigate into the bin folder. Now you should see a list of files. Here I have scrolled down that list to find the one called wsjtx.exe. Depending on how you have Windows configured you might not see the .exe part, but the name should be wsjtx and it should be identified as an Application:

Hover the mouse over that file to highlight it (as shown above) and press the right mouse button. You should see this pop-up menu:

Now move the mouse pointer over Send To > on that menu and click on Desktop (create shortcut) in the additional menu that pops up on the right:

Somewhere on your desktop a new shortcut should have just appeared. Mine looks like this:

I don’t like where it is, so the next thing I will do is left click on the new wsjt-x shortcut and drag it to some convenient spot on my desktop. Next, I will hover the mouse over it and click the right button. From the pop up menu I will choose Properties to get this:

I’m going to be making this one for starting an instance of WSJT-X which I will use for transmitting FST4W with my standard call sign, so that I don’t have to use one of my receive only instances with suffixes after my call sign. First I need to add a unique name to identify this instance to Windows. I’ll use FST4WTX. I carefully left click on the Target box, being careful not to delete any text that is already there. To the end of that I want to add a space character, then –rig-name, another space, and finally FST4TX. It must be typed exactly like that including required spaces. When I finish typing that I will click the Apply button and it will look like this:

Now on the tabs at the top I will click on General to get here:

Now I want to replace the shortcut’s default name, wsjtx.exe – Shortcut with something more user friendly that I can recognize as being my shortcut for starting an instance I will use for transmitting FST4W. I’ll choose something very similar to the parameter added in the last step, but making it a little more eye friendly, like WSJT-X FST4WTx. I will click into the box, delete the text that is there and type what I want. Now it looks like this:

All that remains now is to click the OK button. Now the new shortcut is ready for use on my desktop:

The first time I run the program from the new shortcut I will go trough all the settings in File > Settings, configuring it with my call sign, grid square and all other needed options. Once I have it all set the way I want it, I will use this particular instance only for transmitting FST4W. Since I have receive instances which I want to upload to WSPRnet with the unique call sign suffixes indicating submode, I will remove the check from ‘Upload spots’ on this one’s main window.

These same steps can be used to create as many different shortcuts as you need for starting different instances of WSJT-X. Just remember to give each of them a unique –rig-name parameter in the shortcut properties, and finally name it something convenient.

If you often have a lot of windows open, covering the desktop you may find it helpful to pin desktop shortcuts to the taskbar. Just right click on a desktop shortcut and choose pin to taskbar from the popup menu.

2200m Reboot: Phasing Exciter

External view of the phasing exciter

In early 2020 I began phasing out much of the first generation LF equipment and building replacements. My LF operating interests focus largely on DX. As I have learned more about all of this, it became obvious I needed some upgrades. This is the second in a series of posts about new equipment for our lowest frequency amateur radio allocation.

Like the first generation receiver, the transmitting downconverter did not have adequate frequency stability for slow modes on LF. I also wanted something that didn’t tie up my only HF rig when operating on 2200 meters. After reviewing several designs for phasing exciters I settled on a design by W1VD. I built mine Manhattan style using MEPads and MESquares from QRPme.

The MPS6650 and MPS6652 transistors used by W1VD are no longer available. I successfully substituted BC33716BU and BC32716BU devices but I have not been able to achieve the stated +20 dBm output. Mine will only make +16 dBm before the output waveform becomes distorted. This works OK with my amplifier but is a subject I would like to revisit at a later date.

Initially I encountered some difficulty getting good carrier and opposite sideband suppression. I traced the problem to the LO signal to the two mixers not being 90 degrees out of phase. I built several variants of the quadrature hybrid but I could not get accurate 90 degree phase shift or equal amplitude. Trying some alternate approaches, I achieved success using a Wilkinson divider and phase shift network. Some cut and try adjustment of two capacitor values was needed but in the end I achieved accurate 90 degree phase shift with similar amplitude on both ports. I used 6 dB resistive attenuators on the two LO signals before feeding the mixers. The two outputs from this circuit go directly to pin 8 on the two SBL-3 mixers in the exciter. The 6 dB pad, C1, C2, T1, C3, C4 and the associated 49.9 ohm resistor shown in the W1VD exciter schematic were omitted. With this arrangement I was able to achieve better than 55 dB carrier and opposite sideband rejection after careful adjustment of the level and phase balance trimmers in the exciter. If you build this and find it is operating on the wrong sideband, reverse the LO inputs to the mixers. If you look closely at the blue and orange wires coming off the LO divider and phase shift board, you will see they cross over each other on the way to the mixers on the main board below. Mine had ended up being on lower sideband the first time around! One other change should be made to the phasing exciter if you will be operating it into a 50 ohm load: omit the 49.9 ohm resistor in series with the output. The 1 uF capacitor should connect directly to the junction of the two 5.1 ohm resistors.

LO filter and Wilkinson divider with phase shift network

I am using the same Leo Bodnar GPS Clock that supplies 408000 Hz to the new receiver. It supplies 136000 Hz square wave to the exciter, which I low pass filter before the divider.

Internal view of the completed phasing exciter. Originally mounted to the side of a rack in my main shack, I had placed the power switch and LED on the side opposite the connectors. When I subsequently relocated LF operations to the workshop, that was not convenient so I added another switch and LED near the DC power connector.

I have many hours of operation with this exciter in various modes. It has performed well. One thing this exciter does not like is magnetic fields which can couple 60 Hz energy to the audio circuits. Don’t put it too close to a linear power supply!