Some Thoughts on 2200 and 630 Meter DX

I came to these bands with a long history of being a 160 meter DX hound. Some of my perceptions and expectations were influenced by that history. Clearly propagation is more challenging at the lower frequencies and being limited to very low EIRP doesn’t help. Nevertheless I was expecting to find a hard core group of low frequency DXers clawing away every night in search of those elusive long distance QSOs. Reality has proven to be very different.

On 160 meters we have a good amount of nightly activity. No matter how late the hour one can find avid DXers CQing away, putting in chair time because with propagation being so variable that is what it takes for success. You have to be there consistently. On 630 Meters that isn’t the case. There is a good amount of nightly WSPR beacon activity which clearly demonstrates the potential for DX QSOs, but very rarely are there human operators behind radios running QSO modes at the times when propagation is there. It seems possible to motivate small numbers to get on and make an effort once in a while, particularly after a very good run of nights on WSPR. This is prone to failure since propagation is so unpredictable. On 2200 meters there is very little activity of any kind, including beacons!

It is, of course, very difficult for most people to be on the air late at night, which is when most of the DX potential exists at lower frequencies. If it isn’t late night at one end of a DX path, chances are it is at the other. The question I keep asking is why do we have a core group of ever present DXers on 160 but not on 630 or 2200 meters? Part of the answer undoubtedly lies in numbers alone. Let’s face it, there are many more stations with 160 meter capability than there are stations with 630 and/or 2200 meter capability. There are a number of immediately evident reasons for the lower number of capable stations. It becomes increasingly challenging to build a capable transmitting antenna system on the lower frequencies. Man made noise tends to be more of a problem and some people live in locations which are hopelessly  noisy. There is a lack of commercial equipment available, so these bands are, for the most part, occupied only by those who build their own. All of these factors contribute to keeping the number of active stations down. Fewer active stations means fewer who have the drive and ability to be on late at night. Numbers clearly play a role in DXing activity. It is actually a rather small percentage of 160 meter operators who are there night after night seeking DX QSOs. Similarly it will be a small percentage on the lower bands but with far lower numbers overall this tends to keep the number of avid DXers below critical mass.

But it probably goes deeper than that. To explain the lack of DXing activity we probably need to consider other factors. What are the motivations and rewards for working DX? For some it is simply the thrill of making that rare contact. For others it is the pursuit of long term achievements, collecting operating awards. There are many awards available to the 160 meter operator: DXCC, WAS, WAC, and many more. This isn’t true for the lower bands. For one thing, most awards are not even offered for these bands. If they were, most of the traditional major awards would not be attainable down here. DXCC is probably not possible for the vast majority of stations on 630 meters and probably not for anyone on 2200 meters. Propagation and the EIRP limits simply put it out of reach. WAS may be possible someday for those in North America (when we have active stations in all 50 states, which hasn’t happened yet) but is probably not possible for those in other parts of the world for the same reasons DXCC is impractical. WAC? Good luck, same problems. Are there in fact any available and reachable operating achievement awards for these bands? Not that I am aware of. So there is one motivation missing. If a well established and recognized organization offered attainable operating achievement awards for these bands, it might help to spur activity, perhaps even attracting more people to these bands in the first place.

Do these bands tend to attract a different group of people? Probably to some extent, yes. With lack of off affordable off the shelf equipment and no awards program, these bands may tend to attract mainly experimenters and those with special interests in low frequency radio. It may be that a large percentage are more interested in experimenting than in making QSOs. The results of the latest antenna change or transmitter upgrade can be easily and effectively assessed through beaconing, primarily using WSPR mode. One doesn’t need to be up late  sitting behind a radio for this. Clearly some of the operators who are on these bands are recognizable as DXers on higher bands — 160 meters, HF, even VHF and UHF. But they are a small minority.

I have given this a good deal of thought and continue to do so. What I have arrived at so far is a sense that we simply haven’t reached critical mass for DXing activity on either of these bands. It takes a certain amount of activity in in place to motivate most people to stay up late and get on the air. Even the most motivated operator may struggle to convince himself to be there night after night knowing there very likely is no one there to work. When activity is so low that there is very little chance of working anyone, the motivation is missing or insufficient. I am struggling with this myself. I am a very avid DXer  and I am very interested in trying to work as many stations and states as possible on 630 meters. But, looking at my unattended JT9 decodes each morning clearly shows the chances of working anyone out west on any given night are extremely low. So low, in fact, that I am usually unable to convince myself to stay up and try. Of course this works both ways as having few here in the east to look for probably keeps some in the west from being on every night. With the overall low number of capable stations, DX minded operators and fewer incentives driving the desire for QSOs, it is my opinion that we haven’t reached critical mass. There is not enough consistent activity to get the ball rolling and keep it rolling.

So how do we change this? Can it be changed? Would it help if there were a small group of extremely hard core DXers committed to CQing during key times every night? Perhaps this starts with those at the end of a DX path presenting more convenient hours. If those who would need to be up very late at night to make these QSOs had assurance that there were stations making noise, would this increase the likelihood that they would try? I am currently trying a limited run experiment along these lines, as I have committed to calling CQ every night this week for at least two hours during a time that is convenient for me and frequently offers propagation to Europe. The hours are not so convenient on the European end of the path! Unfortunately this experiment comes to an end when I finish repairs to the 2200 meter loading coil and return to that band. My one other thought on the subject is that those who do succeed in making DX QSOs on these bands should do everything possible to publicize this far and wide – both within and outside the LF/MF community. We need to show the world that long distance QSOs can be made on these bands! We need to promote them as QSO bands, as I believe the outside world still largely sees them as experimenter and beacon territory.

Update 10 January: Over the past several days an experiment was carried out. I announced that over a several night period I would be calling CQ on JT9 mode for at least two hours during the early part of the Europe to North America window (which tends to be the least inconvenient time for the Europeans). This attracted the attention of a few who indicated they would be looking for me. I promoted this as an activity period on both the European and North American email lists. I was joined on the North American side by NO3M and more casually by others. After a slow first night or two, I became the second in the U.S. to complete a trans-Atlantic QSO on 630 meters when I worked G3KEV (the first was AA1A working G0MRF several weeks earlier). Shortly thereafter, NO3M worked G3KEV. I had a partial QSO with PA0A. News of this success brought increasing interest. The following night both myself and NO3M worked G3KEV again. There were partial QSOs between N1BUG and OR7T, N1BUG and DK7FC, NO3M and DK7FC and possibly others but none of these were completed due to QSB or other factors. During this several night activity, hours of operation increased from two to four or more. That is a lot of chair time and CQing for very few QSOs. Clearly we have proven that many QSOs are possible but it will take dedication and effort. Frankly I do not have the stamina to sit there CQing four hours every night. If there were a large enough pool or interested operators to provide reasonable assurance that someone would be there every night, this might become self sustaining. As it is, we simply don’t have that level of activity.

Having more DX-minded operators on the bands would help. But getting on these bands can seem intimidating. There are some web sites that make it all sound so technical and complicated as to scare people away. It doesn’t have to be complicated. Probably the most challenging aspect is knowing what your EIRP is. If you can make basic measurements such as antenna system resistance and antenna current there are online calculators that take the work out of this. Chances are most hams have access to someone with the equipment to make such measurements if they don’t have it themselves.

Home built equipment can be very cost effective but one can buy a transmit converter for $80, a power meter for $40 and throw some wire in the air. If you don’t already have a receiver that works on these bands, there are inexpensive converters and simple SDRs that don’t cost an arm and a leg. There are some pricey equipment options out there. I don’t claim the cost is entirely unwarranted for those who can afford it. But it is not necessary to spend a fortune to get started or even to build a very capable close-to-high-end station. If you’re looking for intercontinental DX you will want to take the time to get up near the legal limit on EIRP but it can still be done on a budget.

For the time being, I suggest the most likely means of working DX is to organize and promote occasional “activity periods” where several stations at both ends of a DX path commit to calling CQ during a certain window for one or more nights. In the long term we need more DX-minded, motivated operators on the bands. Active promotion of the fun and challenge of DX QSOs on these bands is needed. A sensible awards program might be helpful.

A Low Drive 630 Meter Amplifier

My first attempt at amplifier building for the new low bands was a disaster. Being low on funds and patience at the time, I tried building a dual band “linear” amplifier that was said to be capable of 25 to 50 watts on both bands. It turned out to be a design plagued by problems which I won’t get into here. I was fretting about what to do next, as there was no budget at all, when Ken K5DNL came to the rescue. He kindly helped with parts and schematic for a modified, low drive version of the popular GW3UEP amplifier. Credit for the design goes to GW3UEP and K5DNL. Where I have made minor changes I will note that in this post.

Schematic of the low drive amplifier

Referring to the schematic, the 2N2222 provides additional gain to fulfill the low drive objective. This amplifier can be driven to full output with 0 dBm (one milliwatt) input. Mine actually produced full power down to -2 dBm but don’t count on every build being exactly the same. The BC550/BC560 pair forms a squarer to ensure we have a nice clean square wave to drive the FET. The FET in the original GW3UEP was a IRF540. Ken sent a couple of 30NF20 FETs which is what I used in mine. C2 and C4 were not on the schematic I received from Ken. After building it I found the gain and power output peak was around 505 kHz. Looking at the original design on GW3UEP’s web site I noted the the originally specified capacitor values were for that frequency, with a notation to add capacitors for 472-479 kHz operation. After I added C2 and C4, my amplifier peaked at 475 kHz. All capacitors in the FET output circuit should be good quality pulse rated film or silver mica. C1, C3, and C5 in my amplifier are WIMA FKP1. C2 and C4 are CM06 size silver mica with a 500 volt rating. The 1 uF DC blocking capacitor is a WIMA MKS4. Watch the capacitor voltage ratings. Theoretically, 100 volt capacitors should be good enough, though marginal if you intend to run on 24 volts. Some digging into spec sheets on the WIMA capacitors reveals voltage ratings are reduced as frequency increases and we are well down the slope on most of them at 475 kHz. If you are going to buy capacitors I suggest going with the highest voltage rating available. The other change I made was to relocate the blocking capacitor to the location shown. It was at the amplifier output on the schematic I received (and yes, if you are eagle-eyed you will see I have it at the output in the photo below. I relocated it later).

The completed amplifier. IMPORTANT NOTE: The 50 ohm shunt input resistor shown on the schematic is brown in color and mostly hidden under the input coax, just to the left of the 0.1 uF input coupling capacitor. The six blue resistors seen in the photo are not on the schematic. They form an input attenuator, needed because I am driving this amplifier with 250 milliwatts. The input attenuator takes that down to 1-2 milliwatts which is a perfect input level for the amplifier as shown in the schematic.

It should be noted that one need not use exactly the parallel combinations of capacitors specified. The important thing is that by whatever method, be it a single capacitor or several in parallel, we arrive at the required total capacitance at each point in the circuit. You will notice my capacitor combination at C3/C4 quite different from the original GW3UEP.

This amplifier should produce 30 watts output at 13 volts, 100 watts on 24 volts. I am running mine on 19 volts and getting about 65 watts out into a 50 ohm load. I have been running this amp on WSPR at 33% duty cycle for several days and it has performed perfectly. One should strive to keep the antenna resonant and matched, but mine has at times wandered off a bit with no ill affect on the amplifier aside from power output variation as the load impedance changes.

Note: This amplifier has a built in low pass filter but it does not meet FCC requirements for spectral purity. If you are subject to FCC regulations, you should use additional low pass filtering after this amplifier.

Building a 630-Meter Transmit Converter

Inside view of completed 630m transmit converter

This is a companion to my earlier 2200-meter transmit converter. Refer to that post for more details. This one produces about 25 dBm output. Not much is different here except for component values in the low pass filter and the trimmer potentiometer. I didn’t have another of the same type and value. It isn’t critical since it is only being used as a voltage divider to set bias on the BS170 FET.

 

 

 

 

Schematic diagram and parts values for the 630m transmit converter

Building a 2200-Meter Transmit Converter

I recently began running a WSPR beacon on 2200 meters. Beaconing is fine, but I also want to be able to make QSOs on this new band. To that end I needed a very low cost transmit converter so that I could use my FT-2000, which is fully interfaced to the computer for digital modes. Dave, AA1A came to the rescue with an old Anzac MD-143 mixer. The rest I built from stock parts and the junk box. Stock parts are new, current production parts I keep on hand for projects. The junkbox is a collection of old, surplus, used, salvaged and anything else I happen to be able to get my hands on. I don’t need a linear converter or amplifier for this band, and the resulting converter is not linear. It can be used on CW and any mode which does not require linear amplification.

The converter post-mixer amplification and low pass filter are separate from the mixer

The MD-143 takes a nominal 7 dBm local oscillator signal in the 5 to 500 MHz range. For RF it likes about 0 dBm in the same range. Conversion loss is around 6 dB so we can expect about -6 dBm output at the IF port, which is rated DC to 500 MHz. I wanted to get that up to 24 dBm (250 milliwatts) so it provide the same amplifier drive level as my Ultimate 3S beacon transmitter. The fewer things I have to remember when switching modes, bands, activities or exciters the better! I knew I could use a BS170 FET and low pass filter to duplicate the amplifier section of the Ultimate 3S but I would need something on the order of 10 dBm drive to assure equal output. Wayde, K3MF, suggested using a venerable 2N3904 and kindly sent a long a copy of a schematic. This was good because I have a drawer full of 2N3904 transistors! Some quick and dirty breadboarding and testing showed that I could get 12 dBm out of it with -6 dBm input from the mixer. Perfect!

Inside view of the completed post-mixer amplifier and low pass filter

I set about throwing a circuit together. I was only going to be building the post-mixer amplification and low pass filter stages since I wanted to use the Anzac mixer with this and a similar unit for 630 meters. It’s really very simple: a 2N3904 which produces a nice square wave output followed by a BS170 and finally a low pass filter. There is a 5 volt regulator to power the BS170 in order to hold it to the 24 dBm output level, same as in the Ultimate 3S which runs on 5 volts. After throwing the thing together, it showed exactly 24 dBm output on the first try! Whoa… let me note this on my calendar. It’s a historic occasion!

I am temporarily using my trusty HP 3325B function generator as a 10 MHz local oscillator. When I can afford it I plan to get a dedicated 10 MHz LO for this converter, ore more appropriately one that can be shared between this and its soon-to-be-built 630 meter counterpart. My FT-2000 has been modified for general coverage transmit so I can use it on both bands (10.135.7 to 10.137.8 for 2200 meters and 10.472 to 10.479 for 630 meters.

There is not much else to say about this. I am including a schematic for those who may wish to borrow ideas from this simple gadget. Unfortunately I am reduced to posting photographs of schematics since my printer/scanner finally died after many years of faithful service.

Schematic diagram of the post-mixer amp and LPF stages of the converter

 

Finally QRV on 2200 Meters!

Results of my second night of WSPR transmissions. W3PM is 1909km from me.

I have been so busy with station building projects that I have failed to write about several of them. Those have resulted in my station being able to transmit on the 2200 meter band after nearly ten months of work toward that goal. In my first two nights running a WSPR beacon at 12 watts transmitter power I have been heard by more than a dozen stations at distances to 1909km (1186 miles). My effective isotropic radiated power (EIRP) is less than 0.1 watt, which is 10 dB down from the legal limit. I am confident my station can span the Atlantic on this band when I reach full legal limit.

My sincere thanks to NI7J/WH2XND for help getting QRV, also to K7PO/WH2XXP for help with an upcoming project to increase transmitter power.

My transmitting antenna is a Marconi in a T configuration with 27m vertical and a top hat consisting of three 30m parallel wires spaced 1.5m apart.

This is the loading coil / variometer for the antenna. Maximum inductance of this coil is 2500 uH. My antenna requires about 2250 uH to resonate at 137.5 kHz. I’m still thinking about a proper replacement for the spring clip.

Low Noise Vertical for LF and MF Receiving

The LNV antenna with my southwest tower (which is the transmitting vertical for 160 meters) behind it

Note 12 May 2018: I moved this antenna to a new location and made a discovery. It had been working in part due to mutual coupling with my transmitting antenna. I should have known this because when I resonated the transmitting antenna on 2200m the LNV noise floor and signal levels came up about 20 dB on that band. Similarly when I resonated the transmitting antenna on 630 meters, output of the LNV came up nearly 10 dB on that band. When I moved it away from the transmitting antenna, output on both bands dropped to within 3 dB of my receiver noise floor even with the preamp (my simple SDRs are not ultra sensitive). Another factor may have been that the new location was surrounded by trees. The antenna has been moved back to its original location. Subsequently, a new receiver allows noise from the LNV to be about 12 dB above the receiver noise floor.

During the initial phase of experimentation I had found that some of my 160 meter Beverage antennas worked reasonably well for receiving on 2200 and 630 meters. I was hearing plenty of Europeans on both bands. Obviously at these frequencies they didn’t work as Beverages. What the actual operating mode was I don’t know. There were a few problems with this arrangement, primarily that I couldn’t run LF and MF receive operations concurrently with 160 (or 80) meter DXing. That was not good!

After reading a number of blog posts and web articles about the “low noise vertical” or LNV, I decided to give it a try. VE7SL has an article on his blog with links to additional information. As is often the case I pulled ideas from several sources, then mixed and matched (and even went off on my own a bit) for my version. My LNV is a 30 foot self supporting vertical made from scrap aluminum tubing I had on hand. It starts out with 1.5 inch OD at the base and tapers to 1/2 inch at the top. The bottom foot of the vertical is slid inside a two foot piece of 1.5 inch schedule 40 PVC pipe and secured in place with set screws (bottom) and a worm clamp (top). Looking at the photo that may be confusing. The set screws (three 1/4-20 stainless tap bolts)  go through the worm clamp and PVC just above the transformer box. You can see that in the photo. What is not visible is the other worm clamp securing the aluminum tubing to the top of the short PVC section. These details are unimportant. Just make sure your vertical is insulated at the base! A piece of wire hanging from a tree would no doubt work just as well, but I wanted to do mine this way.

The base of the LNV antenna with transformer inside the plastic mini box

A couple of words about the overview photo at the top of this post. First, in the thumbnail you may not be able to make out the LNV in the foreground just to the right of the tower behind it. Second, usually the yagi antennas on that tower are lined up with each other! We had a recent storm with wind gusts to 70 mph which skewed things and I haven’t been up to fix it yet. The LNV is only 40 feet from that tower which is my 160 meter transmitting vertical (shunt fed). Thanks to good band pass filters, my 2200 and 630 meter receivers don’t react at all when I transmit with 1500 watts on 160.

In some write ups about the LNV it is said one needs more than one ground rod for best performance. Surprisingly I am using just one four foot “ground rod” which is a section of a stainless steel mobile antenna whip which I pushed into the sandy soil by hand! I plan to try adding real ground rods later but the antenna is working with the minimal ground. As of this writing it has heard 2E0ILY nine consecutive nights on 2200 meters.

LNV base transformer primary winding

My LNV is fed with about 250 feet of WD1A twisted pair wire which is laying on the ground. This is ex military field phone wire and is practically indestructible as long as you keep water out of the ends. It has three steel and four tinned copper strands in each conductor along with incredibly tough insulation that takes a lot of abuse. Any twisted pair wire should work fine in this application.

LNV base transformer secondary

The transformer at the antenna base is wound on a FT-114-JC core, 80 turns primary, 8 turns secondary. First, the 80 turn primary is wound directly on the core using 20 AWG enameled wire. If a non-coated core is used, it would probably be wise to wrap the core with some kind of tape before winding the primary. One end of the primary winding connects to the base of the LNV, the other end to the ground rod.

The primary was wrapped with teflon thread seal tape, then the secondary was wound over the cold (ground) end of the primary using 20 AWG solid plastic coated wire. Another layer of teflon tape keeps everything nice and tight. The secondary winding connects to the twisted pair feed line.

LNV base transformer in its protective box

The finished transformer is mounted in a small plastic mini box of the type that has a rubber gasket to keep out water. The ground and antenna connections are #8-32 stainless machine screws at opposite ends of the box, while the connections for the twisted pair feed line are together on one side of the box.

Twisted pair to coax transformer for the shack end of the feed line. The RCA connector has subsequently been replaced by a BNC

At the shack end of the feed line I use another FT-114-JC core with 8 turn primary (twisted pair from the antenna), 6 turn secondary for 50 ohm coax to the receiver (or in my case two receivers via a splitter).

After using this antenna for 10 days, initial results are very promising, especially on the lower band. I am not able to listen with this and the old antenna at the same time, but I am hearing 2E0ILY on 2200 meters much more often and with stronger signals than I ever did with the short Beverage. To the west it seems about on par with the Beverage. On 630 meters I don’t think it is quite as good, but I am hearing a number of Europeans.

Diagram of the LNV antenna

Automating HF/VHF/UHF Band Switching – Part 1

Last  year I acquired some transverters with the idea of getting back on the VHF and UHF bands. I only have one station transceiver so everything has to work from that. The transceiver’s ANT 1 connection normally goes to the input of my 160-10m amplifier, ANT 2 to the input of my 6m amplifier, and RX ANT IN to a low band receive antenna switching and control unit. For use with a transverter, I need ANT 1 to go to a transverter drive attenuator, the output of which goes to the transverter IF input (transmit), RX ANT IN to the transverter IF output (receive). This requires me to remember to change two switches, and forgetting one during a quick band change can be disastrous. I proved that last year when I forgot a switch and accidentally dumped 1500 watts of RF into the makeshift drive attenuator I was using at the time. Poof! Szzzt! There went the magic smoke, costing me $40 for another hybrid attenuator. The situation gets even more complicated when more than one transverter is involved and the correct one must be selected. Since I have several amplifiers sharing a common high voltage supply it is also important that the correct one (and only the correct one) be enabled for transmitting while all the others be locked into standby. This was a nightmare!

Clearly I needed a better system. What I needed was automation of the process. A band decoder connected to the transceiver band data socket would do no good since that would only support bands that are native to the radio – 160 through 6 meters. Since I always have CAT software running (DXLab Commander) while operating there was another option. I could add a parallel port to my PC and configure it so that Commander would make one of the data pins go high for HF, another for 6 meters, another for 2 meters and so on. I could then build a control unit and add relays to do all the band switching tasks.

Concept drawing

The first thing I did was sketch a basic concept diagram so I could better visualize what I needed. I was going to need two regular SPDT coaxial relays; one to route the transceiver’s ANT 1 connection to either the input of the 160-10m amplifier (for HF) or to the transverter drive attenuator (for VHF/UHF), the other to route the transceiver’s RX ANT IN to the low band antenna switch box (for HF) or to one or more transverters (for VHF/UHF). To select the proper transverter I was either going to need a lot of relays in a complex matrix or I was going to need two single input, multiple output matrix relays ready made. I found two of the latter on eBay. Specifications were not available and I have no idea what they were made for, so I took some measurements. At 28 MHz, worst case port to port isolation is 90 dB. That’s good enough! Although I don’t fully trust the accuracy of my return loss measurement, it is at least in the ballpark. The relays measured 29 dB (1.07 VSWR), again plenty good enough). They obviously aren’t designed to handle much power but they don’t need to in this application. There will only be 10 milliwatts (+10 dBm) on the transmit relay.

One of the two transverter IF switching relays

Relay isolation test

Relay return loss test

The next step was to start thinking about control circuit configuration. For HF and 6

meters, the only action to be performed would be to enable one

Concept for switching circuit, HF or 6m amp enable

of the amplifiers. Except for the enable relay which would be added to each amplifier, all other system relays would be de-energized for these bands, thus needed no switching. Out came the pen and paper for a little more design concept drawing. It would be elegant to use opto-isolators to interface the parallel port data lines from the relays to be switched, but that would involve buying a lot of parts. I wanted to use what I had, and I had drawers full of small transistors that could be used as switches in this application. I selected the venerable PN2222 transistor for this task. A look at the data sheet was promising but I wanted to verify that its actual DC current gain (hFE) was adequate for a good hard switching action in this application. The first thing I needed to know was how much current I could safely

Testing PN2222 DC current gain ‘in circuit’

draw from the data lines on my PC’s newly added parallel port – a Rosewill RC-302E PCI-e adaptor. I measured open circuit voltage at 3.30 volts. With a 1k ohm resistor to ground that dropped to 3.18 volts at 3.2 milliamps of current. The minimal voltage drop indicated this should be safe enough and would not damage the RC-302E. Allowing for 0.6 volt drop across the PN2222 base-emitter junction, this would leave me with about 2.6 mA base current (3.18-0.6 equals 2.58 volts across the 1k resistor). Cobbling together a quick and dirty test circuit I found that at 250 mA through the collector-emitter circuit, voltage drop across the PN2222 was less than 0.6 volt. In reality I only need to draw about 40 mA with the relays I plan to use, so this was more than good enough.

To be continued…

Update on 2200 Meter Trans-Atlantic Reception

On the better nights I continue to receive WSPR2 signals from across the Atlantic on 137 kHz. Like my early EME days decades ago, the thrill remains high. I get excited beyond reason every time I see one of these pop up in my list of decodes. When I can predict which periods a station will be transmitting, I find myself intently watching the waterfall during those periods to see if I can visually detect anything. There are a large number of periods when the signal can be seen but does not decode. Factors that can prevent a decode on an otherwise OK signal include fading, atmospheric static (which is becoming ever more a factor as Spring approaches), and local interference.

I am convinced that much more frequent Atlantic crossings are possible. There are many nights when no capable stations are transmitting during the peak hours (or at any hour).

Below is an updated list of all 2200 Meter trans-Atlantic decodes to date.

2017-01-29 01:20 DC0DX    0.137469 -27 JO31lk 0.2  N1BUG FN55mf 5399
2017-01-29 02:18 DC0DX    0.137469 -24 JO31lk 0.2  N1BUG FN55mf 5399
2017-01-29 04:14 DC0DX    0.137469 -27 JO31lk 0.2  N1BUG FN55mf 5399
2017-01-29 07:08 DC0DX    0.137468 -27 JO31lk 0.2  N1BUG FN55mf 5399

2017-01-30 06:12 DC0DX    0.137468 -25 JO31lk 0.2  N1BUG FN55mf 5399

2017-01-31 07:20 G8HUH    0.137425 -28 IO81mg 0.1  N1BUG FN55mf 4766

2017-02-01 07:10 DC0DX    0.137469 -27 JO31lk 0.2  N1BUG FN55mf 5399

2017-02-02 05:36 DC0DX    0.137469 -23 JO31lk 0.2  N1BUG FN55mf 5399
2017-02-02 05:58 DC0DX    0.137469 -24 JO31lk 0.2  N1BUG FN55mf 5399
2017-02-02 06:20 DC0DX    0.137469 -25 JO31lk 0.2  N1BUG FN55mf 5399

2017-02-06 04:26 DC0DX    0.137470 -24 JO31lk 0.2  N1BUG FN55mf 5399
2017-02-06 04:48 DC0DX    0.137470 -25 JO31lk 0.2  N1BUG FN55mf 5399
2017-02-06 05:54 DC0DX    0.137469 -26 JO31lk 0.2  N1BUG FN55mf 5399

2017-02-07 02:36 DC0DX    0.137470 -27 JO31lk 0.2  N1BUG FN55mf 5399

2017-02-14 22:32 2E0ILY   0.137551 -29 IO82qv 0.1  N1BUG FN55mf 4731
2017-02-14 23:28 2E0ILY   0.137551 -29 IO82qv 0.1  N1BUG FN55mf 4731
2017-02-15 04:40 G8HUH    0.137422 -24 IO81mg 0.1  N1BUG FN55mf 4766

2017-02-22 04:20 G8HUH    0.137424 -28 IO81mg 0.1  N1BUG FN55mf 4766
2017-02-22 04:30 G8HUH    0.137424 -25 IO81mg 0.1  N1BUG FN55mf 4766
2017-02-22 05:50 G8HUH    0.137424 -28 IO81mg 0.1  N1BUG FN55mf 4766

2017-02-23 05:06 G8HUH    0.137424 -26 IO81mg 0.1  N1BUG FN55mf 4766
2017-02-23 05:10 G8HUH    0.137424 -25 IO81mg 0.1  N1BUG FN55mf 4766
2017-02-23 05:14 G8HUH    0.137424 -24 IO81mg 0.1  N1BUG FN55mf 4766
2017-02-23 05:18 G8HUH    0.137424 -26 IO81mg 0.1  N1BUG FN55mf 4766
2017-02-23 05:22 G8HUH    0.137424 -27 IO81mg 0.1  N1BUG FN55mf 4766

2017-02-23 23:08 2E0ILY   0.137552 -29 IO82qv 0.02 N1BUG FN55mf 4731
2017-02-23 23:56 2E0ILY   0.137552 -27 IO82qv 0.02 N1BUG FN55mf 4731

2017-02-26 00:06 2E0ILY   0.137551 -28 IO82qv 0.02 N1BUG FN55mf 4731
2017-02-26 00:44 2E0ILY   0.137551 -28 IO82qv 0.02 N1BUG FN55mf 4731
2017-02-26 00:54 2E0ILY   0.137552 -28 IO82qv 0.02 N1BUG FN55mf 4731
2017-02-26 00:56 2E0ILY   0.137552 -28 IO82qv 0.02 N1BUG FN55mf 4731

2017-02-26 23:30 2E0ILY   0.137549 -28 IO82qv 0.02 N1BUG FN55mf 4731

2017-03-05 05:08 2E0ILY   0.137550 -28 IO82qv 0.2  N1BUG FN55mf 4731

2017-03-13 23:54 2E0ILY   0.137550 -27 IO82qv 0.2  N1BUG FN55mf 4731
2017-03-14 00:12 2E0ILY   0.137550 -27 IO82qv 0.2  N1BUG FN55mf 4731
2017-03-14 02:16 2E0ILY   0.137550 -28 IO82qv 0.2  N1BUG FN55mf 4731

2017-03-15 00:32 2E0ILY   0.137550 -28 IO82qv 0.2  N1BUG FN55mf 4731
2017-03-15 02:48 2E0ILY   0.137550 -29 IO82qv 0.2  N1BUG FN55mf 4731
2017-03-15 03:00 2E0ILY   0.137550 -27 IO82qv 0.2  N1BUG FN55mf 4731
2017-03-15 03:32 2E0ILY   0.137550 -27 IO82qv 0.2  N1BUG FN55mf 4731
2017-03-15 03:48 2E0ILY   0.137550 -25 IO82qv 0.2  N1BUG FN55mf 4731
2017-03-15 04:16 2E0ILY   0.137550 -27 IO82qv 0.2  N1BUG FN55mf 4731
2017-03-15 04:32 2E0ILY   0.137550 -27 IO82qv 0.2  N1BUG FN55mf 4731

Transverter Drive Attenuator

The completed attenuator and heat sink assembly

Edit: After writing this I devised a safe method to run the FT-2000 at 10 watts when on VHF/UHF. The entire band switching system is software-centric, controlled by DXLab Commander. Since the Yaesu CAT command set includes a method for setting power, I programmed each VHF/UHF band button to set the transceiver to 10 watts output. This is safe since there is no way to “bypass” software control in band switching where VHF/UHF is involved. The only possible glitch is in forgetting to reset power when going to HF, but this simply results in low power operation with no risk of equipment damage. In order to facilitate easy power resetting when going to HF I created an additional “HF” band button in Commander which disables the VHF/UHF system and resets power to 100 watts.

I needed an attenuator for driving VHF/UHF transverters. The goal was to take 100 watts of drive at 26 to 30 MHz down to +10 dBm (10 milliwatts) using whatever junk I could find. My 2 meter transverter uses a 26 MHz IF for 144 MHz, while my other transverters (222, 432, 1296 MHz) use a 28 MHz IF.

First, a few words about why. My Yaesu FT-2000 transceiver does have a low level transverter output. The level is -10 dBm, 20 dB below what I need. It could easily be amplified to reach the correct level, so why would I choose not to use it? The answer is both simple and complicated. I have just the one transceiver which I use from 1.8 to 144 MHz and hope to use for higher bands soon. Band switching all the stuff that needs to change going from HF to VHF or UHF with a transverter gets complex enough that I tend to forget things. I wanted to automate all the band switching tasks (RF routing to correct path, be it an HF amplifier or VHF transverter, enabling the correct amplifier while disabling all others, etc. I can easily do this using DXLab, which is my preferred multi function DXing software suite. DXlab understands transverters, so I can set it up to recognize what band I am on, be it 144, 222, 432 or even 1296 MHz, though the transceiver would be on 28 MHz for all of these. This would greatly simplify logging since the correct frequency would always be auto-filled in the logging software. The one stipulation in order to do all this is that band switching must be done through DXLab Commander in order for it to understand what band I am currently on when using transverters. If I set the band from the radio, Commander has no way of knowing that 28 MHz doesn’t mean I am operating on 10 meters!

Here’s the catch. On the FT-2000, the only way to activate the low level transverter output port is to switch to a special band called ‘AU’. This band is 28 MHz, but behavior is different from 10 meters in that on AU band the PA is disabled and the transverter output enabled. There is no way to do that when the radio is set to the normal 10 meter band or when sending a band/frequency request via CAT command. There is no CAT command for this AU band! It must be selected from the front of the radio, and not by a particularly intuitive process like all the other bands. If I used the transverter output, all my automation for band switching ideas would be out the window. Furthermore there would be confusion as to what band I was operating and I would have to manually edit frequency for each logged QSO. Forget it. That’s not going to happen! Hence my desire to use the high level output on the transceiver. I didn’t want to have to remember to turn down the drive, say to 5 or 10 watts each time I went to VHF or UHF, because I would tend to forget that eventually and the results might be costly. So, I wanted a transverter drive attenuator that would take 100 watts down to 10 milliwatts. That is 40 dB of attenuation.

Before deciding on the attenuator approach, I considered applying a fixed negative voltage to the FT-2000 ALC input to reduce its output to a very low level. I asked about this in two forums frequented by VHFers and was warned that there can be pitfalls. Some radios put out an initial spike of full power even with fixed voltage on the ALC line, which would not be good. Even if that were not the case for my FT-2000, failure of the ALC bias circuit would surely result in ugly consequences. I decided to forget about it and go with the high power attenuator. As always, I am grateful for the advice and elmering I received!

Schematic diagram and parts list for the attenuator

I had some 250 watt, 50 ohm RF load resistors on hand. One of those would make a fine input resistor for a pi network attenuator. I had some 51 ohm, one watt metal film resistors. One of those would do fine for the output. But for 40 dB attenuation, the series resistor in the pi network would have to be 2500 ohms at around 2 watts. I didn’t have something like that and trying to make one out of a series-parallel combination of resistors might add considerable stray capacitance. Ordinarily that might not matter too much at 28 MHz, but when making a 40 dB attenuator, stray capacitance could tend to “bypass” the resistor and cause the attenuation to be too low. However, there is another trick that can be used. The series resistive element can be replaced by a capacitor having reactance equal to the required resistor value at the frequency of interest. That works out to about 2.3 pF in this case. That is not much, but I had some Johanson 5200 0.8 to 10 pF muti turn air trimmers around. If I could keep circuit strays low enough or shield input from output that should work. Using a variable element would allow me to “dial in” the proper amount of attenuation, compensating for circuit strays (as long as they weren’t too great). There is a caveat when using a capacitor for the series element in a pi network attenuator. Attenuation will not be constant over a wide frequency range, because the reactance of the capacitor is frequency dependent. That wasn’t a problem for my intended use, since only a narrow frequency range is involved.

I needed a heat sink that could handle 100 watts intermittent duty. I immediately remembered I had some old repeater parts that might do the trick. Some folks might shoot me for this, but I grabbed a NOS Motorala MICOR UHF base station antenna network. This is a circulator, relay, filter and some other bits on a nice heat sink! I stripped all the rubbish off and there was my heat sink, ready to go. It’s a bit of an irregular shaped thing and has some extraneous holes here and there, but who cares? I was going to hide it behind a rack of equipment anyway. The antenna network also provided a type N female bulkhead  connector with a short length of RG-400 coax already connected t it, as well as a BNC female bulkhead connector with a similar RG-400 lead. Wahoo! There were my input and output connections for the attenuator. I clipped them off before tossing the rest of the antenna network in my electronic refuse bin. RG-400 is nice stuff: Teflon dielectric, double silver plated braid, stranded silver plated center conductor. You can’t melt this stuff with soldering heat! All the better. A little more digging turned up a small cast aluminum box which I could use to house the attenuator components.

Inside view of attenuator with cover removed

I exercised some care in circuit layout and lead dress. I also left the shield on input and output coax as close to the end as possible in the hope that this might eliminate any need for a shield between input and output. After putting the circuit together I checked it on a spectrum analyzer / tracking generator. To my delight I found that using the trimmer I could vary the attenuation from 27 to 51 dB at 28 MHz. Wow! My circuit layout and construction was good enough. Flatness of attenuation over the 26 to 30 MHz range was within 1.5 dB. That is fine. In practice it will only be used over a 200-300 kHz range with any given transverter, and each transverter has its own built in adjustable input attenuator to fine tune its drive level. Attenuation slope over a 300 kHz range is too little for me to measure but probably about 0.1 dB. Return loss (input SWR) is better than my ability to measure, which is limited to about 30 dB RL (1.07 SWR). Plenty good enough.

One final note. I stripped the paint off the surface of the box that mates with the heat sink and from around the hole where the BNC connector is. Was this necessary? I don’t know but my standard operating procedure for RF circuits is to remove paint between mating surfaces in the enclosure or where connectors attach. I find it easier to do this in the first place than to disassemble something and strip paint after finding there was a problem!

2200m/630m Transatlantic Reception, January 26 to February 2

The past few nights have been very interesting on LF and MF. For starters, January 29 was the first time I heard Europe on 2200 meters. I have decoded at least one transmission from Europe on the band each of five nights since then. This may be in whole or in part due to a change I made to my receiving setup on January 29. However, a number of other curious things emerge when looking at the data.

For one thing, I did not decode any 630m transatlantic signals on the night of January 28/29, but I did decode DC0DX four times on 2200m.

The second thing of note is the decodes on the night of February 1/2. On 630 meters I only decoded EA5DOM, which is quite low latitude for a transatlantic path. The northern stations were completely missing, not only from Europe but also no transcontinental decodes from the VE7 or northern W7 areas. This would be a typical pattern given an upturn in geomagnetic activity from mostly quiet to active/minor storm. Yet this was the second best night for transatlantic on 2200m with three DC0DX decodes, including the best S/N yet observed.

The other thing of interest is that on 630m, excepting an early start by PA0A on the night of January 31/February 1, most of the decodes are about in the middle of common darkness; not near my sunset or near sunrise at the eastern end of the path. There is one late decode of EA5DOM on the night of January 30/31. On 2200 meters we find most of the decodes were late, not too long before sunrise at the eastern end. The only exception is three earlier decodes of DC0DX on the night of January 28/29.

Although not shown here, WH2XND on 2200m was notably weaker on the final night, February 1/2 than on the previous nights in this period.

There is insufficient data to draw any conclusions, but in the early days of hearing transatlantic signals on 2200m it does not seem to correlate well with what is happening on 630m. I wonder if any clear trends will emerge as more data is accumulated.

 

 

Transatlantic decodes, 630m, January 26 – February 2:

2017-01-30 02:36 EA5DOM  0.475610 -26 IM98xn N1BUG FN55mf 5578 301 
2017-01-30 02:48 EA5DOM  0.475610 -27 IM98xn N1BUG FN55mf 5578 301 

2017-01-31 00:12 EA5DOM  0.475610 -26 IM98xn N1BUG FN55mf 5578 301 
2017-01-31 01:12 G3KEV   0.475705 -23 IO94sh N1BUG FN55mf 4820 287 
2017-01-31 01:20 G3KEV   0.475705 -25 IO94sh N1BUG FN55mf 4820 287 
2017-01-31 03:16 ON5TA   0.475671 -27 JO20es N1BUG FN55mf 5264 293 
2017-01-31 06:24 EA5DOM  0.475609 -28 IM98xn N1BUG FN55mf 5578 301 

2017-01-31 21:48 PA0A    0.475730 -25 JO33de N1BUG FN55mf 5280 292 
2017-01-31 21:50 PA0A    0.475730 -27 JO33de N1BUG FN55mf 5280 292 
2017-01-31 23:50 PA0A    0.475730 -29 JO33de N1BUG FN55mf 5280 292 
2017-01-31 23:54 PA0A    0.475730 -27 JO33de N1BUG FN55mf 5280 292 
2017-02-01 00:24 G8HUH   0.475782 -26 IO81mg N1BUG FN55mf 4766 289 
2017-02-01 00:24 EA5DOM  0.475610 -27 IM98xn N1BUG FN55mf 5578 301 
2017-02-01 00:44 G8HUH   0.475782 -26 IO81mg N1BUG FN55mf 4766 289 
2017-02-01 00:48 EA5DOM  0.475610 -29 IM98xn N1BUG FN55mf 5578 301 
2017-02-01 00:54 G8HUH   0.475782 -22 IO81mg N1BUG FN55mf 4766 289 
2017-02-01 02:48 EA5DOM  0.475609 -27 IM98xn N1BUG FN55mf 5578 301 
2017-02-01 03:36 EA5DOM  0.475609 -28 IM98xn N1BUG FN55mf 5578 301 
2017-02-01 03:44 F1AFJ   0.475727 -28 JN06ht N1BUG FN55mf 5193 295 
2017-02-01 04:00 EA5DOM  0.475609 -30 IM98xn N1BUG FN55mf 5578 301 

2017-02-02 02:36 EA5DOM  0.475610 -28 IM98xn N1BUG FN55mf 5578 301 
2017-02-02 03:24 EA5DOM  0.475609 -25 IM98xn N1BUG FN55mf 5578 301

Transatlantic decodes, 2200m, January 26 – February 2:

2017-01-29 01:20 DC0DX 0.137469 -27 JO31lk N1BUG FN55mf 5399 294 
2017-01-29 02:18 DC0DX 0.137469 -24 JO31lk N1BUG FN55mf 5399 294 
2017-01-29 04:14 DC0DX 0.137469 -27 JO31lk N1BUG FN55mf 5399 294 
2017-01-29 07:08 DC0DX 0.137468 -27 JO31lk N1BUG FN55mf 5399 294 

2017-01-30 06:12 DC0DX 0.137468 -25 JO31lk N1BUG FN55mf 5399 294 

2017-01-31 07:20 G8HUH 0.137425 -28 IO81mg N1BUG FN55mf 4766 289 

2017-02-01 07:10 DC0DX 0.137469 -27 JO31lk N1BUG FN55mf 5399 294 

2017-02-02 05:36 DC0DX 0.137469 -23 JO31lk N1BUG FN55mf 5399 294 
2017-02-02 05:58 DC0DX 0.137469 -24 JO31lk N1BUG FN55mf 5399 294 
2017-02-02 06:20 DC0DX 0.137469 -25 JO31lk N1BUG FN55mf 5399 294