Category Archives: MF & LF

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!

2200m Reboot: The Receiver

The SSR-2200E, my second generation LF receiver based on the SoftRock Lite II

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 first in a series of posts about new equipment for our lowest frequency amateur radio allocation.

After using the original modified SoftRock Lite II receiver for three years, it was time to move on. That first receiver served me very well. With it I was able to make three trans-Atlantic QSOs, and heard a lot of DX on various modes. In the end, however, I wasn’t satisfied with the frequency stability of the crystal oscillator, which was about 1 ppm, or a little less than 0.15 Hz drift on 2200 meters. That may seem completely insignificant to the HF, VHF or microwave operator but for the most serious DX pursuits on LF it not sufficient. With the one watt EIRP legal power limit, propagation and high noise levels at 137 kHz we need very slow modes to succeed over great distances. As a general concept, the slower the mode the greater the frequency stability needed. Legacy modes include QRSS (extremely slow CW meant to be read visually from a waterfall) and its derivatives like DFCW. Readers may recall my first DX QSO with 2E0ILY used DFCW60, meaning that each “dit” or “dah” takes 60 seconds to send! Drift of 0.15 Hz is clearly visible at that speed and can lead to difficulty “reading” signals at even slower speeds. Today we have various slow digital modes for beaconing and QSOs. At the extreme, EbNaut requires transmitter and receiver drift be no more than a few tens of microHertz! Others are more tolerant but current evolution suggests one should strive to stay within 0.01 Hz or better during any 30 minute period if DX is of prime interest.

During those first three years I had tried various receiver, filter and preamp configurations. I now know what is needed with the SoftRock and my available antennas. I wanted to combine the filter, preamp and receiver into one box but I wanted to use a GPS referenced local oscillator for stability. In the end I settled on a design which puts all but the local oscillator into one box. The LO is a separate Leo Bodnar GPS Clock which supplies 408 kHz for the receiver (divided by four in the SoftRock quadrature LO generator) and 136 kHz for a 2200m phasing exciter.

The major building block for the receiver is a SoftRock Lite II kit from Five Dash. A few modifications need to be made for 2200m operation. The schematic shows the values for parts that need to change for operation on this band (C3, C4, C10, C11, C12, L1, T1, R5, R6, R16), as well as the removal of the crystal and external LO connections in its former place. The capacitors can be ceramic. I recommend mounting the SoftRock Lite II board with the insulating hardware that comes with it. Ideally one wants everything isolated from the metal box except for the shield of the audio cable connector. To maintain that one ground point I run the receiver either on a battery or an isolated wall wart.

Schematic of the modified SoftRock Lite II

For the front end stages I have married a filter design by YU1LM and a preamp design by W1VD. The filter provides a bandpass response to keep out of band signals from overwhelming the receiver, while the preamp provides about 20 dB gain which is needed with many small receiving antennas on LF. You want enough gain in the front end and receiver so that the noise floor comes up at least 10 dB when you connect the antenna. If this seems a little different from conventional advice, consider that we are dealing with extremely weak signals where even fractions of a dB can make a difference. If we want to keep the signal to noise ratio from being degraded a meaningful amount, we need that much gain to be sure the SoftRock and sound card noise floor don’t degrade S/N of the system. With the exception of the 10 uF electrolytic, all capacitors are ceramic types.

Schematic of the front end filter and preamp

Next I needed a suitably stable local oscillator. We need a final LO frequency that is close enough to the 2200 meter band to allow tuning it with whatever sound card will be used. If the sound card sample rate is 96 kHz, we need to be within 48 kHz of the receiving frequency. I recommend staying a few kHz less than that due to the way anti-aliasing filters in sound cards work. This means we want our LO to be between about 96 kHz and 178 kHz in practice, preferably avoiding putting it “in band”. The LO frequency is divided by four in the SoftRock quadrature generator circuit. This means we need to inject a frequency four times higher into the receiver. Anything between 384 and 712 kHz will work. I was already using one of the two outputs from the GPS Clock to provide 136000 Hz LO to my phasing exciter. Available frequencies for the second output are somewhat limited and tied to the first frequency but in this case 408000 Hz is one of the options, and it is perfect. That puts our final LO at 102 kHz, comfortably within range, yet far enough removed from the band of interest to put the image frequency around 67 kHz, well down the slope of the receiver front end bandpass filter. Perfect!

First I tried injecting the 408 kHz square wave directly into the SoftRock. It worked but I didn’t have a good feeling about it. For one thing, that meant that the SoftRock and GPS clock grounds were connected, a situation which I was trying to avoid in case of ground loops and noise getting into the system. The GPS Clock also didn’t like the impedance, causing it to put out not only the harmonic rich square wave but also a significant amount of HF energy as ringing due to impedance mismatch. I tried using a transformer (for ground isolation) and low pass filter to clean up harmonics but this made the GPS Clock even less happy with a lot of ringing due to reflections. Since I had signal to spare I solved this, albeit somewhat crudely, but inserting a 10 dB attenuator between the GPS Clock and transformer. This gave a nice clean sine wave at sufficient level into the SoftRock LO circuit. I don’t claim this design to be elegant or perfect, but I do claim it works well for me. I used film capacitors in the filter because I had them on hand, but ceramic should be quite acceptable.

Schematic for the LO isolation and filter circuit

This new receiver has been in operation for several months. Sensitivity and gain is more than adequate for use with my LNV antenna. Frequency stability is now determined almost entirely by sound card sample rate drift and is on the order of 0.01 Hz over several hours. This is sufficient for all but EbNaut, where the sound card sample rate requires continuous monitoring and correction. I have not conquered that yet.

Internal view of competed receiver

2200m Variometer Failure

On the morning of January 15 I was nearing the end of a 72 hour test of the JT9 submodes (JT9-10, JT9-5, JT9-2, JT9-1) on 136.395 kHz. The transmitter had been running 87% duty cycle for two days and as far as I knew all had been well. On this morning I checked in on things when I got up just before sunrise. It was running as expected with the waveforms on the ScopeMatch looking normal. I went about some morning chores and came back about 20 minutes later to check again. The transmitter was still running but the antenna was far off resonance. Minor changes are common but this was more than a minor change. I knew something was very wrong.

Loading coil and variometer assembly. The outer coil is 2 mH. The inner coil is about 180 uH and is driven up and down by a motor and threaded nylon rod. The adjustment range is approximately 2.3 to 2.5 mH total. This is more than sufficient to resonate the antenna anywhere in the 2200 meter band and allow for changes in weather conditions.

I quickly shut down the transmitter, grabbed my binoculars and went to the window to inspect the antenna. All wires were up and intact. I then hastily bundled up and went outside to check the loading coil / variometer. It didn’t take long to realize where the trouble was. When I removed the cover from the assembly housing, acrid smoke came billowing out and I could feel heat radiating from somewhere inside. This was not good! Since the smoke was so thick and presumably toxic, I could not do a full inspection until things had aired out a while.

2200m (left) and 630m (right) variometer enclosures. The blue drum is not tall enough to fully enclose the 2200m unit, hence the upside down bucket which is part of the lid assembly.

Upon subsequent inspection I found the bottom of the moving inner coil badly damaged. I can only guess as to what happened. Careful inspection of the following pictures will reveal something of the construction. There was a wire (12 AWG solid, insulated) running down the length of the form on the inside. This provides connection from the bottom of the inner coil to a a terminal at the top of the coil form which is jumpered to the top of the large outer coil. At both ends, the method of feeding through the form was a 18-8 stainless machine screw with washers and nuts as needed. On the inside the ring lug on the wire was between the head of the machine screw and the coil form. Stainless hardware may not have been an optimal choice. It stays clean practically forever but it has poor electrical properties. I had assumed it would be fine with the expected 2 amps or so of low frequency RF current.

What I suspect happened is that over time, probably aided by thermal expansion and contraction cycles of the PVC form, the hardware became loose on that bottom connection. As it began to loosen slightly, resistance of the connections may have increased somewhat, leading to more heat being generated. This may in turn have led to some slight softening of the PVC, allowing pressure on the connections to relax even more. I believe eventually it became so loose there was arcing which produced extreme heat in a localized area, eventually leading to the damage.

Before disassembly, some damage can be seen at the lower end of the inner coil.
After removing the inner coil assembly, the extent of damage is more apparent.
With the coil removed from the base plate there is more evidence the machine screw was the source of the problem. All of the damage centers around it. The wire inside is badly heat damaged, and the PVC form has either been on fire or has suffered damage from arcing (or both).

In hindsight, there may have been two warning signs that something was not right. If these were signs of failure in progress, things had been going south for some time. About two or three weeks prior to this incident I had noticed that when I was transmitting I would sometimes see “fuzz” appearing on both sides of my signal when viewed on the waterfall of my SDR receiver. It usually lasted only for several seconds, then cleared up. I did wonder about arcing, but the ScopeMatch looked perfectly normal. I put it down to just another artifact of severe receiver overload. It’s not as though my signal ever looked clean in the local receiver! There was always plenty of junk, no doubt worsened by the use of back to back diodes across the receiver front end to prevent damage from my own transmissions. But this particular “fuzz” phenomenon was something I hadn’t recalled seeing previously.

The second possible warning sign came 24 hours prior to discovery of the failure. On that morning resonance suddenly “jumped” higher in frequency. It wasn’t a big change, but was something I hadn’t seen before in benign weather conditions. Re-resonating took care of it but about an hour later it “jumped” back to the original resonance condition and needed to be adjusted again. This unexplained behavior should have been a warning that something was not right.

Much of what I think I know about this failure is speculation based on inspection after the fact. My theory seems further supported by the fact that the other stainless machine screws passing through this form had all loosened considerably. I know they were tight when it was built, but I was able to remove them using just my fingers. I will never know for sure exactly what happened, but the new inner coil will be designed to avoid the suspected failure scenario. If it fails again, I will have to reexamine my theories!

Mowable Temporary Cables

What? Mowable cables? That doesn’t make any sense! Let me explain. Throughout my nearly four decades exploring radio, I have often had occasion to run a “temporary” cable to some antenna. Usually these end up laying on the ground where they quickly become a nuisance, having to be moved every time the grass needs to be cut. This often continues for some time. After all, in a ham radio sense the definition of temporary is “anything expected to be in service for less than the life expectancy of the operator”. About year ago I had a sudden explosion of “temporary” cables. I needed to run coax and a variometer control cable to my new 2200 and 630 meter transmitting antenna, as well as coax to a receiving antenna for those bands in another location. These were put down just after the last lawn mowing of the season, but were at risk of damage from the snowblower as I kept a path cleared to the transmitting antenna during the winter. This summer they have been a constant source of irritation as I had to move them every time I mowed the grass.

Since I still can’t afford good coax and conduit to do this job in a permanent (meaning less irritating) fashion, something had to be done. One obvious solution is to dig a shallow trench and lay the cable in it — with our without burying afterward. This tends to be a lot of work and it’s messy, disturbing the grass (uh, I mean the weeds) and leaving dirt strewn all over. I was looking for a cleaner and, hopefully, easier method. One morning about 2 AM it came to me. I sat bolt upright in bed, sending Boo (the cat, who had been asleep on my chest) fleeing for cover. Who said you had to dig a trench? I have soft, sandy soil. Surely one could press a trench into the ground without the mess. It just might be easier, too. The following series of pictures depict the process, which worked very well.

Step One: Mark a line. Drive in stakes at each end and at any locations along the run where a bend is required. Run string (or small wire) from end to end, then spray paint a line on the ground along it.

Details of the string (wire) and painted line at a bend point.

Step Two: Hammer a slot into the ground. I used an 8″ x 8″ dirt tamper and a 10″ length of 1.6″ OD steel pipe. Lay the pipe on the painted line and hammer it in until its top is flush with the surface of the soil. In my soil this takes two to three blows, and the flat plate of the tamper makes it easy to know when you’ve reached the correct depth. This photo shows the pipe in place before being driven into the soil.

Here is a photo showing results after the pipe has been driven flush with the soil. To continue I simply pull out the pipe and move it forward 9 inches (just a bit less than the length of the pipe), then drive it into the soil again. The process moves along quite quickly.

Step Three: Lay the cable into the trench. I make 15 to 20 feet of trench at a time, then lay cable into it, then do another section of trench.

The completed job. There is no messy strewing of dirt, the paint line has virtually vanished, and the cable can barely be seen if one is not standing very close to it or directly in line with it. The top o of the cable is 3/4″ to 1″ below grade, so it is out of danger from the mower. Of course it is still subject to damage from any number of things, but with temporary cable runs that is usually a fact of life.

First USA to Europe Amateur Radio 2200 Meter QSO

It was early morning on the 28th day of March, 2018. Most people were sound asleep but not me. I was in my ham shack, hands trembling, heart pounding as I typed a few letters and numbers into my logging program. I could barely breathe. I had just completed one of the most exciting QSOs of my nearly four decades chasing DX. This single QSO cost more money and time than any other I had ever made. It was a QSO with England. You may wonder what is so exciting about that when any ham with five watts and a piece of wire can contact England from Maine. Well, this was special because we did it on the 2200 meter band. It was the first amateur radio USA to Europe QSO on what is, for us, a new band. This was no easy feat. It required months of station building and four nights just to complete the QSO. Some would call it a ridiculous folly and see no sense at all in it. But to me this is the true spirit of amateur radio, finding a way to communicate against the odds, adapting equipment and technique to accomplish the desired result. It is man and his machine against nature, determined to succeed under the most difficult circumstances.

The 2200 meter band allocation is 135.7 to 137.8 kilohertz in the long wave part of the radio spectrum known as LF or low frequency. In some ways this goes back to amateur radio’s early roots on 1750 meters, but it had been more than 100 years since U.S. amateurs were allowed to transmit in this part of the radio spectrum. These frequencies are not easy! Normal size antennas would be huge. A half wave dipole would be 3400 feet long; a quarter wave vertical towering to a height of 1700 feet. Natural and man made noise tend to be very high in this part of the radio spectrum and ionospheric propagation is feeble compared to the short waves. On top of that, we are only permitted to run one watt effective isotropic radiated power (EIRP). That is flea power compared to what we can use on most any of our higher frequency allocations! By comparison, when I was doing EME (moonbounce) on the two meter band I was legally running about 450,000 watts EIRP. But ham radio DXers who like a good challenge can be a very determined lot. The greater the challenge, the greater the reward.

I became interested in 2200 meters in late 2016 after the local club asked me to prepare a report on this and the 630 meter band, which were expected to soon be opened for amateur radio use in the U.S. At that time the only way to legally transmit on either band was to get a Part 5 FCC license under the experimental radio service. One could almost write one’s own ticket on power limits and frequency allocations but this wasn’t amateur radio. I did apply for and was granted a Part 5 license but never used it since FCC opened these new bands to amateurs just as I was getting a station put together. I found receiving on 630 meters to be relatively easy, if somewhat plagued by noise and available antennas. But 2200 meters was a very different thing. It took weeks of experimentation and testing to detect the first trace of signal on this band. Many weeks later after more trial and error I was rewarded with my first reception of a ham radio signal from Europe on the band when DC0DX appeared in my WSPR decodes. I confess it was then that I first started to dream of someday making a two way QSO across the Atlantic on long wave.

I thought I had plenty of time to build a station, since the FCC process on opening these bands had been dragging on for years. But in the Spring of 2017 the announcement came that we would get these new bands in a few months! Now the race was on. I frantically began building transmitting apparatus. I didn’t quite make it for opening day in October but I was on the band a few weeks later. Early amplifiers were plagued by budget shortfalls and poor performance. By mid February, 2018 I had managed to achieve 0.5 watt EIRP, just three decibels below the legal limit. The flood gates opened and to my amazement I started receiving numerous WSPR decodes from European stations. Wow!

I believed a two way trans-Atlantic QSO was in my future but was not sure when. I was eager for an attempt but still very much struggling with equipment and budget. I was hearing stations from Europe. Stations from Europe were hearing me. But for the most part, those who heard me did not have transmitting capability or not sufficient to reach across the Atlantic. The best bet would seem to be 2E0ILY. We had conducted tests earlier in the season and I could often copy his JT9 beacon. Chris could occasionally copy my WSPR signal but not at sufficient strength for JT9 to be viable. I knew there were ways to get it done, but this would take several nights. I was hesitant to ask anyone to commit such effort and time to a QSO.

As the relatively quiet season was drawing to an end I realized another season is never guaranteed for any number of reasons. I had given the matter considerable thought. There were no practical digital modes which would work with the low signal levels involved. Two old school modes came to mind: QRSS and DFCW. Both are very slow, trading time for weak signal detection capability. QRSS is extremely slow CW, so slow in fact that it can only be copied by reading it off a computer screen. In this case, a speed of QRSS60 would be best, meaning that each dot would be 60 seconds in duration. A dash is three times as long, just as in normal CW. This mode requires nothing special for equipment, as it uses on/off keying of a carrier and is fairly tolerant of frequency drift. But, the shortest element, the dot, sets the achievable signal to noise ratio. There is no advantage gained from the dashes being three times as long, so it is essentially time wasted. Time is valuable, as signal fading means you have a limited amount of time to copy the message. DFCW, or dual frequency CW is an offshoot of QRSS in which dots and dashes are the same length but sent on slightly different frequencies so that one may be differentiated from the other. This saves considerable time with no reduction in signal to noise ratio but requires more complex transmitter keying and reasonably tight frequency stability. In a typical DFCW60 transmission, the dot to dash frequency shift is a small fraction of a hertz. Transmitter and receiver drift must be held to less than this in order to avoid dot-dash ambiguity at the receiving end. It would take about an hour to send two call signs at DFCW60 speed. It was now late March. Clearly there would not be enough common darkness between Maine and any part of Europe to allow a QSO to be completed in a single night at this speed.

It may be useful to consider what is a QSO. These days the term means different things to different people. I came up through the DXing ranks with what is now a somewhat old school definition for a minimum acceptable information exchange to claim a QSO under very weak signal conditions. I still firmly believe in the old way, as we are after all supposed to be communicators. That definition is that each station must receive from the other both call signs, signal report or other piece of information, and acknowledgment. This requires that two transmissions be copied in each direction. Anything less than that does not seem like communication to me, and leaves me with no sense of accomplishment.

It seemed the best way to go about it would be to borrow operating and reporting techniques from EME, modifying procedure slightly to account for the much longer period of time required to send a message on the long waves. In this procedure, the letter O would be used as a signal report to indicate full call signs had been copied; R and O would be used to indicate full call signs plus signal report had been copied; R by itself to indicate call signs, report, and R (as part of R and O) had been copied. As for timing, it seemed sensible to use night by night sequencing. That meant the two stations would take turns transmitting, one going the first night the other the second, alternating back and forth throughout the QSO. It would take a minimum of four nights to complete a QSO, assuming the full message could be copied each night. If it wasn’t, additional nights would be required for repeats. That’s really slow! But it did offer some advantages with the equipment available. In order to achieve the required frequency stability I would have to use my QRP Labs Ultimate 3S beacon transmitter. The U3S is a great piece of gear, but editing messages is tedious. Night by night sequencing would give me all day to change the message for the next night’s transmission! A complete QSO would look like this, where bold indicates my transmissions, italics indicate transmissions from the other station:

2E0ILY N1BUG
N1BUG 2E0ILY O
RO
R

Meaning of the first line is obvious. I am transmitting both call signs. In the second line my QSO partner adds the signal report, O, to let me know he had copied both call signs fully. In the third line I send RO which means I have copied call signs and my report, your report is O. In the last line my QSO partner sends R, meaning I have copied all on my end. When I copy the R the QSO is complete. If a message is not copied, or not enough information is copied, then one continues to transmit the previous message until getting something back which advances the QSO.

I had worked out a viable technique. Now I just needed a QSO partner. Just in time I worked up the courage to ask Chris, 2E0ILY if he would be willing to give it a try. I was very happy when he said he’d have a go at it.

We had decided I would transmit the first night, so I set the U3S to send ‘2E0ILY N1BUG’ over and over during the hours of common darkness between our respective locations. It turned out to be an ugly night in terms of weather. I was getting heavy wet snow squalls. Nothing causes a 2200 meter Marconi antenna (vertical) to go out of resonance any quicker than wet snow! These antennas are electrically short and require huge loading coils to resonate them. They are high impedance antennas and the bandwidth is very narrow. These antennas are prone to changing characteristics on a whim. Every time the snow started, stopped, changed intensity or the amount of snow clinging to the antenna changed, the thing went wandering up or down the band and required retuning for resonance on the operating frequency. Fortunately the variometer at the antenna base was motorized and I could adjust it from the comfort of my transmitter room. But I had to keep a constant vigil, watching antenna resonance and adjusting as needed. I had my finger on the switch for variometer adjustment far more than not. After a while my fingers were getting sore from constantly manipulating the tuning switch. Perhaps I shouldn’t have used a miniature toggle switch there. If you think this was an automated QSO without operator involvement, think again! My presence and diligence at the controls was absolutely vital that night!

Message copied from 2E0ILY on the second night of the QSO (annotated). Note dots on the lower frequency, dashes shifted 0.187 Hz higher. When the signal is this strong, elements tend to bleed together a little but since they are of fixed length it is still very readable.

The next night it was my turn to listen. Due to the extremely slow speed DFCW is copied visually  using software designed for this purpose. Anxiously I stared at the screen. When I wasn’t nervously pacing, that is! I began to see traces of signal, then an odd letter here and there. There was a B, a 2, a Y and I even thought I saw an O but couldn’t be sure. Eventually conditions stabilized and I began to get steady print on the screen. Waiting 60 seconds for a dot or dash to fully paint on the screen can be agonizing. Slowly the elements accumulate and become characters. If you are lucky, propagation holds up long enough to copy the full message. Fortunately, after somewhat of a slow start copy remained solid and I eventually had N1BUG, 2E0ILY and a very nice O painted on my screen! I had copied full call signs and a signal report indicating Chris had got full call signs from me the previous night! We were half way there!

The third night I was transmitting again. Since I knew Chris had already copied full call signs from me, it was not necessary to transmit them at this stage of the QSO. Technically I could have just sent RO repeating throughout the night, but being of the cautious type I decided to include call sign suffixes to provide positive evidence the correct station was being copied. Thus the message I transmitted was ‘ILY BUG RO’. This was a risk as it takes far longer to send than simply ‘RO’ and signal fading can be a huge factor. At least the weather was better and I didn’t have to ride the variometer all night.

Soon it was night four, back to pacing and staring hopefully at the screen. I was especially nervous that night, as I had some strong, drifting interference right on top of Chris! Finally it moved just enough that I could make out ‘BUG ILY R’. There was rapid fading and the dash in the R was much fainter than the rest. Fainter but unmistakably there. I was positive about the R but being the cautious type and realizing this QSO would be an amateur radio first I really wanted to see it more clearly before declaring the QSO complete. The signal faded and nothing was seen for hours. Sunrise at 2E0ILY was fast approaching and I had to make a decision. Was I going to log the QSO or retransmit my RO message the following night in hope of getting better copy of the R on night six? Just before dawn the signal reappeared, very weak. I could barely make out ‘BUG IL’, then the ‘Y’ was quite strong. Given the proximity to sunrise every minute felt like an eternity. Ticking of the clock became offensively loud. It was going to take another four minutes to get an R! Would it hold up that long? Slowly, as the clock ticked and my heart raced, a crystal clear ‘R’ painted on the screen. There were traces of signal for some time after that but nothing  I would call readable, save a stray ‘Y’ that somehow came through well past dawn. So it came to be that shortly after 0600 UTC (1:00 AM local time) on this, the 28th day of March, 2018 I entered this QSO into my station log. We had done it!

QSL card received for this very memorable QSO!

This was an amateur radio first from the U.S. but nothing new in terms of distance on the 2200 meter band. Canadian stations, operating under amateur call signs but otherwise a program similar to our Part 5 licenses, had worked Europe years earlier. Much longer distances had been covered. But for me this was one of the most exciting QSOs of my nearly 40 years as a DXer. It ranks right up there with my first EME QSO, the QSO that put me on the DXCC Honor Roll and several other notable events such as being credited with the first North American two meter auroral E QSO back in 1989. My thanks to Chris, 2E0ILY for his time and patience to make this happen – not to mention the kilowatt hours of electricity expended.

DFCW may be old school but it gets the job done under extremely difficult conditions. DFCW ‘decoding’ is done by the human operator. Deciding what has been copied is not left to computer software which may use assumption or non amateur radio means to fill in things it couldn’t positively make out over the air. DFCW is painfully slow but here we had a very positive over the air exchange of full call signs, reports and acknowledgement without any shortcuts or fudging. I was very pleased with that!

Although this single QSO cost more than any other, this was a low budget operation. Most of the LF station consists of low cost kits and home built gear. Equipment used at my station for this QSO was the QRP Labs Ultimate 3S driving a home built amplifier to 175 watts output. The transmitting antenna was a 90 foot Marconi (vertical) with a top hat consisting of three wires each 100 feet long, spaced five feet apart. Three one inch diameter aluminum spreaders plus triangular wire sections at each end are electrically part of the top loading. This is resonated at the base with an inductance of approximately 2.3 millihenries. Loss resistance at the time was near 100 ohms, resulting in EIRP of 0.5 watt. For receive I used a 30 foot low noise vertical, band pass filter, W1VD preamp, and a modified Softrock Lite II SDR receiver. The amplifier and most of the receive system has been described on my blog and/or web site. There are photos of the antenna and variometer on my web site.

A Low Drive 2200 Meter Amplifier

Note 25 January 2019: The drain waveform has been corrected and this amp has run many hours at 250W output including some rather high duty cycle mixed WSR-15 / WSPR-2. It seems very reliable at that level. I will revise this post further when I have more time.

Note 12 May 2018: I have discovered this amplifier does not operate with a nominal Class E drain waveform. However that does not change the fact it has performed very well as described in this post. I intend to publish and updated version with corrected waveform at a later date.

While still planning and collecting parts for a high power 2200 meter amplifier I began to wonder if the design I use on 630 meters could be converted and made to work at 2200 meters – and if so, would I have the right parts to build it? Some quick math, assuming linear scaling of component values with frequency, showed that I just might be able to hit the correct values using parts salvaged from a problem ridden dual band amplifier I had given up on. So I set out to build and test a prototype. It took some fine tuning of inductor and capacitor values in the output circuit to get best efficiency and power peak at 137 kHz.

Schematic of the completed amplifier

Initially I used T106-2 cores for the inductors but in order to fit the required number of turns I had to use 24 AWG wire. Heating of the wire was excessive but otherwise the amplifier was showing a lot of promise. I decided to bite the bullet and order some T157-2 cores which would allow using 20 AWG wire. Note: heating of the wire in these inductors was not a surprise. My 630 meter unit does the same, as do several built by others. In the final design, it is possible to run high duty cycle at 100 watts output without a problem. For higher power I recommend a small fan blowing air across L1 and L2. It would probably be OK without the fan but I prefer to err on the side of caution. Capacitors C1 through C4 are made by connecting smaller values in parallel. I had a bunch of .01 uF 630 volt WIMA FKP2 capacitors and some 2000 pf 500 volt silver mica capacitors. These were the only two values needed when using the proper combination in parallel. The DC blocking capacitor is 2 uF, comprised of two 1 uF WIMA MKS4 capacitors in parallel. Initially I used a single 1 uF as in the 630 meter version but I found it was heating up slightly. Going to two of them in parallel resulted in no detectable heating.

The 22200 meter “junk box” amplifier

Construction is similar to the 630 meter amplifier discussed in an earlier post. “islands” were made by grinding away some foil from double sided FR4 material with a rotary tool and diamond bit. The finished amplifier can be driven with one milliwatt (0 dBm), like its 630 meter counterpart. Power output is similar. I measured in excess of 30 watts with a 13 volt supply, 110 watts with 24 volts, and 155 watts with 28 volts. In all cases, efficiency is 87 to 88 per cent. These figures hold over a range of 134 to 140 kHz. Outside that range it beings to roll off rapidly. I have been running mine for the past couple of nights at 28 volts and it seems fine. In the interest of disclosure I did have one FET die during testing but I had not been watching the antenna matching closely enough. Temperatures plummeted from the mid forties to the high single digits during that night of operation, causing the antenna resistance to drop sharply. This caused power output to soar above 200 watts before the FET finally gave up at 3:30 in the morning. I do not consider this a fault of the amplifier. Knowing how 2200 meter antennas are, the operator should have been watching more closely!

Update March 7, 2018: The amplifier has been running perfectly with no additional FET deaths. For more than a week I have been transmitting a combination of WSPR-15 (a good test for any amplifier) and WSPR-2 at 150+ watts output.

Update March 10, 2018: I cranked the voltage up to 30V and have been running the amp at 175 watts output for three nights with high duty cycle WSPR-15 and WSPR-2.

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