Introduction... QRSS is a beacon mode where callsigns are sent at very slow speeds in morse code and it's a useful mode for investigating radio propagation. The signal can usually be found on the main HF bands just below the WSPR signals.

For example, the 10m WSPR frequency is 28.1246 MHz USB and the WSPR signals are in the audio range of 1400 to 1600 Hz. Using the same dial frequency, the QRSS signals are about 400 Hz lower in frequency around 1100 Hz.

This has the advantage of using programmes like WSJT-X to decode the WSPR signals while at the same time, you can see the QRSS signals with programmes like SpectrumLab which displays the audio spectrum.

Some people operate 'grabbers' which take screen grabs of the QRSS band from their receiver and these are them put up on a website. They usually update every 10 minutes.

28 MHz tests... At about 12:00 UTC on the 29th of May 2024, I noticed that there was a Sporadic-E opening between Sweden and Ireland. The image above shows how my callsign was successfully received by the SA6BSS grabber in Sweden at a distance of about 1554kms.

How to send QRSS signals... If you are already using FT8 with programmes like WSJT-X then you are all set up for sending QRSS signals. For my tests, I was just using my HF radio and a PC.

The first thing I did was to go to the PA2OHH website and using the SPACE, DOT & DASH tabs, I generated my callsign in morse code. The audio can be adjusted from 1500 to 1900 Hz. The QRSS mode can be adjusted for length as well as whether it is on/off or uses Frequency Shift Keying (FSK).

After pressing 'Start QRSS', it's just a case of waiting for the sequence to start which happens at 10-minute intervals past the hour e.g. 12:00, 12:10, 12:20 and so on. In my case, it was really as simple as holding the microphone next to the PC speaker and pressing the PTT once the QRSS sequence started.

In terms of frequencies, I used the default 1600 Hz option. I tuned the radio down about 300 Hz from the WSPR frequency to about 28.1243 MHz USB. This made sure that my transmit signal was below the WSPR band and above the other QRSS signals.

If we look at my signal above in more detail, the bright part at the start was when the audio from the PC speaker was too loud and I had to turn it down. The rest of the QRSS audio resulted in an output power of about 5-10 watts from my radio.

There is also a very obvious upward drift in the signal! My callsign was sent over the space of just over 5-minutes and in that time, my signal drifted upwards by about 10 Hz.

My HF radio is quite old and for modes like CW or SSB, 10 Hz is really nothing. If you were to listen to CW or SSB signals from my HF rig then you'd hear nothing wrong. It's just that with QRSS, tiny changes like 10Hz become very obvious.

Nearly all QRSS signals on the bands are from dedicated transmit modules which are GPS stabilised. You can see these is the top image as nice straight signals. In my case, there is probably some crystal oscillator in the transmit chain in my HF radio that is being turned on and is drifting slowly as it warms up. 

Aurora... Back on the 10th of May 2024, I tried this QRSS test as well during the big aurora.

Using the same grabber in Sweden, the signals from the SE of England are there and are of course distorted by the aurora. I'm almost certain the signal above is me and it even has that little telltale upward drift.

In hindsight, I probably should have used on/off keying rather than frequency shift keying and the signal would have been a lot more obvious. It's still pretty cool to see your own signal coming back from the auroral region.

In conclusion... What I have outlined above is basically just putting the microphone from your radio up to the speaker of a PC and checking a website to see if your signal was heard, it's really that simple. It would be nice to see others giving it a try.

Links... Here are some useful sources...

1) https://groups.io/g/qrssknights - This email group is the place to go for all things QRSS related.

2) https://www.qsl.net/pa2ohh/21htmlqrss01.htm - PA2OHH website for generating QRSS signals.

3) https://www.qsl.net/sa6bss/ - SA6BSS grabber in Sweden.

4) https://www.qsl.net/pa2ohh/grabber.htm - PA2OHH grabber in the SE of Spain.

5) https://qsl.net/g4iog/ - G4IOG grabber in SE England

6) https://www.qsl.net/g0ftd/grabber.htm - G0FTD operates a grabber from various online receivers.

7) https://qsl.net/wa5djj/ - WA5DJJ operates several grabbers from New Mexico in the United States.

8) https://swharden.com/qrss/plus/ - AJ4VD has links to a lot of grabbers

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 14th of May, I got a screengrab of the QRSS signal 'SP' which was sent by the IZKXQ/B beacon in the north of Italy.

Usually, nearly all of the QRSS signals on the 10m band are on 28.1246 MHz and the audio of the signals is about 400-500Hz below the WSPR signals. In this case, the IZ1KXQ beacon was on 28.3215 MHz.

In the image above, the fuzzy part of the signal is when it was sending the callsign of the beacon in normal morse code. The QRSS 'SP' part is sent after this.

The beacon runs 0.1-watts or 100-milliwatts into an inverted V-dipole antenna.

The map above shows the path and the distance was about 1600kms. The signal was almost certainly via Sporadic-E and it's pretty much the ideal distance for that mode of propagation.

In summary... That brings the QRSS tally so far for 2024 up to 21-callsigns & 10 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 8th of May, I got a screengrab of the QRSS signal 'HK' which was sent by the IW0HK/B beacon near Rome in Italy.

Usually, nearly all of the QRSS signals on the 10m band are on 28.1246 MHz and the audio of the signals is about 400-500Hz below the WSPR signals. In this case, the IW0HK beacon was on 28.322 MHz.

In the image above, the fuzzy part of the signal is when it was sending the callsign and locator of the beacon in normal morse code. The QRSS 'HK' part is sent after this.

The beacon runs 1-watt into a vertical five-eight wave antenna.

The map above shows the path and the distance was about 1800kms. The signal was almost certainly via Sporadic-E and it's pretty much the ideal distance for that mode of propagation.

In summary... That brings the QRSS tally so far for 2024 up to 20-callsigns & 10 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 30th of April, I got a screengrab of the 'Flying M' from Mauro, IK1WVQ in the NW of Italy.

I received this signal during the afternoon on the QRSS frequency of 28.1246 MHz USB. This is the same as the WSPR frequency and the only difference is that the audio frequency of the QRSS signals is about 400-500 Hz lower than the WSPR ones.

The signal is a little unusual in that it uses steps to generate the letter 'M rather than the usual morse identification. I think that Mauro was using 1-watt into a dipole antenna.

The map above shows the path and the distance was about 1500kms. The signal was almost certainly via Sporadic-E and it's pretty much the ideal distance for that mode of propagation.

Now that the Sporadic-E season has started, I should be able to receive more signals in the 500-1500km distance from my location. These are normally too close for the F2 layer propagation that has been there since the start of the year.

In summary... That brings the QRSS tally so far for 2024 up to 19-callsigns & 10 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 5th of March, I got a screengrab of FR1GZ/B on the island of Reunion in the Indian Ocean.

Yvon, FR1GZ has been making adjustments to the speed and spacing over the last few days above the QRSS band and just below the WSPR segment. On the 5th, he moved his transmitter down about 280 Hz to where the other QRSS signals on 28.1246 MHz are.

The full sequence can be seen above from Yvon and he is sending his beacon callsign FR1GZ/B as well as his locator / grid square LG79RC. As you can see, Yvon is using ON/OFF keying as opposed to Frequency Shift Keying (FSK) for his transmitter.

The signal in more detail can be seen below...

I took this screengrab at about 11:15 UTC and conditions at the time were quite poor. At the moment, we're near the peak of the sunspot cycle and I usually decode my first WSPR spots on 28 MHz at about 06:30 UTC which is about 35 minutes before my sunrise.

On the 5th of March, I didn't get me first decode until 09:38 UTC which is about two and a half hours after sunrise. The recent solar flares and aurora seem to be having an impact on conditions for the last two days at least.

The 28 MHz from my location on the south coast of Ireland to Reunion Island is about 10,170kms. The propagation mode is multiple F2 layer hops and the signal from FR1GZ/B should be pretty consistent in Europe considering the roughly north-south path.

In summary... That brings the QRSS tally so far for 2024 up to 18-callsigns & 10 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 2nd of March, I got a screengrab of WA1EDJ in the state of Georgia in the south-east of the United States.

The distance was in the region of 6170kms and was probably two F2 layer hops. 

Even though the south-eastern part of the USA is one of the easier paths for me, it took quite a while to get this screengrab. It was often be very weak or I'd miss parts in fading but I got a complete call eventually.

In summary... That brings the QRSS tally so far for 2024 up to 17-callsigns & 9 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 28th of February, I noticed VK4BAP Queensland, Australia.

For my first attempt above, I managed to get a positive ID on the signal. However, a very strong OH station from Finland just above using WSPR was playing havoc with my audio levels. I tried to adjust the volume as best as I could and managed some sort of screen grab.

Finland is just one F2 layer hop from my location on the south coast of Ireland and signals are usually very strong. The QRSS signal from Australia by contrast is just about visible in the noise.

It's a bit like waiting on the bank of a river and waiting for a fish to bite. I'd start to get a reasonable QRSS signal from VK4BAP only for the OH station to then clobber it! :o)

Eventually, the timing got to a stage so that the VK station started just after the OH station had finished transmitting and I managed to get a reasonable if somewhat weak screengrab.

My target at the end of the day is to get a full screengrab of a signal which can be positively identified regardless of how weak it is.

The distance was about 16,070 kms and the propagation mode was via multiple F2 layer hops. There may have been some chordal hop in there as well. The time for the reception reports was about 09:00 UTC.

In summary... That brings the QRSS tally so far for 2024 up to 16-callsigns & 9 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 27th of February, I managed to get a good capture of NM5ER in New Mexico.

The QRSS signal of NM5ER can be seen above at the top of the screen and this was the best one of several that I saw today. It really was a marginal signal and it didn't take much fading for me to lose large parts of the signal.

By contrast, the other signals listed about were a lot more consistent.

The distance was about 7800kms and I suspect the propagation mode was either two long or three shorter F2 layer hops.

In summary... That brings the QRSS tally so far for 2024 up to 15-callsigns & 8 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 26th of February, I managed to get a good capture of VE6NGK in the city of Calgary in the province of Alberta, Canada.

As can be seen from the image above, there was quite a bit of frequency drift on the QRSS signal. In reality, the signal only drifted upwards about 5Hz over the space of about 8 minutes but in the world of QRSS, these small changes are easily visible.

About 20 minutes later, I got a second screen capture when the signal was stronger.

The distance from Calgary to my location on the south coast of Ireland is about 6620kms. The propagation mode was probably two F2 layer hops but what make this path more of a challenge is that it goes well to the north.

I also saw NM3ER in New Mexico but I was unable to get a good screen grab. Another day.

Addendum: Kam, VA6CA reports the following... "VE6NGK is my other call. I was running 5W at the time I believe. Was at 500mW at the beginning but not getting anywhere.

Below is the transmitting station.  It's a homebrew project using components from my junk box. The controller uses TTL logic chips. and the dual tone audio generator (the bottom board) uses two "tuning fork resonators" at frequencies 410 Hz. I physically trimmed one to get the audio tone frequency difference I need. The 410Hz was 4X up using PLL to get the output harmonics outside the FT817 SSB filter to minimize splattering."

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 21st of February, I managed to get a good capture of PY3FF in Brazil, South America.

The QRSS signal from PY3FF can be seen at the top of the screen grab above. Rafael reports running 700 milliwatts into a dipole from his location in the south of Brazil.

The path length was around 10,000kms and it's likely it was three F2 layer hops. The G0MBA/G0PKT duo also shown in the screen grab are from the east coast of England and are about 700kms from my location. I believe that I am getting those signals via F2 layer backscatter.

The VOACAP propagation map below shows that the path from my location to the south of Brazil is reasonably good.

In summary... That brings the QRSS tally so far for 2024 up to 13-callsigns & 8 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 16th of February, I managed to get screen captures of IK2JET in the north of Italy and N8NJ in Ohio in the US.

1) IK2JET... At 16:17 UTC, I managed to get a successful screen capture of the QRSS signal from Alberto, IK2JET.

As can be seen from the image above, the signal wasn't too strong but it was a positive ID all the same and a new DXCC for 2024.

You can note how the QRSS signal has a slight 'fuzz' to it and is slightly distorted. It's similar to the backscatter signals from G0PKT & G0MBA which are going across the centre of the screen.

2) N8NJ... At 16:24 UTC, I got another screen capture and this time, I got a nice QRSS signal from Larry, N8NJ in Ohio.

The signal from N8NJ can be seen above at the top of the screen and it looks cleaner with less 'fuzz' than some of the other signals.

These are the WSPR decodes that I got from N8NJ during that hour and it suggests that the QRSS signal might have been in the region of -10dB.

Propagation Modes???.... What were the propagation modes responsible for these signals? I generated this propagation map below with VOACAP and the stations are marked in black.

N8NJ at 5570kms seems to be about right for two F2 layer hops and that one is easily explained.

The signal from IK2JET at 1550kms is more difficult. If it was a few more hundred kms away, I'd be more certain of one F2 hop but it seems a bit close. 

It could be Sporadic-E but we're in the middle of February and not the Summer Sp-E season. I did note plenty of other of WSPR signals on the day from the white skip zone around my location.

The signal as noted had some 'fuzz' to it which is unlike a nice clean one hop signal and that might suggest a back scatter or multi-path quality about it.

Sometimes, you just look at the evidence and it's hard to come to any firm conclusion.

In summary... That brings the QRSS tally so far for 2024 up to 12-callsigns & 7 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 6th of February, I managed to get a good capture of VA3RYV in Ontario, Canada.

The QRSS signal of VA3RYV can be seen in the image above. It starts with a 'Slow Hell' image of the VA3RYV callsign followed by the signal in morse code. The whole sequence lasted about 6-minutes.

Wes, VA3RYV was using 100-milliwatts output power into a have-wave dipole about 15m above ground level. The path length was around 5,255kms and it's likely it was two F2 layer hops.

In summary... That brings the QRSS tally so far for 2024 up to 10-callsigns & 6 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year. On the 18th of January, I managed to get a good capture of TF3HZ in Iceland.

On the 17th of January, I had seen the QRSS signal of TF3HZ in between G0MBA and G0PKT so I knew where to look. on the 18th at 12:14 UTC, the signal appeared out of the noise.

This is a good example of how useful QRSS is in that you can 'see' the propagation changing. It shows how within the space of a minute, the path between Ireland and Iceland opened up.

In the next cycle, I got a nice strong QRSS signal and screengrab for TF3HZ.

The path distance was 1576kms so it's hard to know for certain what the propagation mode was. Was it F2 layer? Was it some mid-Winter Sporadic-E? The sudden appearance of the signal is very similar to a lot of the QRSS signals I have seen during the Sporadic-E season but it's not conclusive evidence. I think it's just one of those cases where no-one can be certain which of the propagation modes it was.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year.

QRSS are very slow morse code transmissions where the dots and dashes are several seconds long and the signals are decoded by looking at a waterfall display on a screen rather than listening to the signal.

The QRSS signals are usually just below the WSPR signals on the amateur radio bands. This means it's possible to have your PC decoding WSPR signals up around 1500 Hz while you look at the QRSS signals about 500 Hz or so lower in the audio spectrum at the same time.

2024 #8 - OH5KUY... The 8th QRSS signal that I managed to capture this year was Ari, OH5KUY in Finland. Ari reports that he is running 1.5-watts into a C610 vertical antenna. His locator square is KP41DB.

The distance is from OH5KUY to my location is about 2437kms, an ideal distance for F2 layer propagation when the 28 MHz opens up to these northern latitudes.

Ari's signal was actually very strong for a QRSS signal and I had to adjust the volume settings on the radio because it was too strong compared to the rest. Most QRSS signals are buried in the noise and you get to see them only on a screen. Ari's signal by contrast was up to S4 here and it was a loud clear signal.

That's the beauty of QRSS, you can actually 'see' the signal. You can see the frequency drift , you can see how the strength of the signal changes over time and you can see any unusual propagation effects.

With digital modes like FT8 and WSPR, you either get a decode or you didn't and if there isn't a decode, you're often not sure why. With SSB or CW, you're listening to an audio signal but it's what's happening here and now. You're missing those visual clues of QRSS which add so much more information.

The one that got away... It looks as if there was Sporadic-E on the band as well on the 17th. TF3HZ in Iceland popped out of the noise and I was all ready to get a nice screengrab but I lost it when I changed some settings on the SpectrumLab software. Lesson... screengrab first, adjustments later. Another day...

In summary... That brings the QRSS tally so far for 2024 up to 8-callsigns & 5 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year.

QRSS are very slow morse code transmissions where the dots and dashes are several seconds long and the signals are decoded by looking at a waterfall display on a screen rather than listening to the signal.

The QRSS signals are usually just below the WSPR signals on the amateur radio bands. This means it's possible to have your PC decoding WSPR signals up around 1500 Hz while you look at the QRSS signals about 500 Hz or so lower in the audio spectrum at the same time.

2024 #6 - RD4HU... Most QRSS signals take the form of very slow morse code transmissions but sometimes, other modes are used. The screen capture above shows the slow-Hellschreiber mode which is more often referred to as "slow Hell".

RD4HU is located in the city of Samara on the Volga River in European Russia and was using 5-watts as far as I know. His signal was strong as can be seen by the clear trace.

The distance to my location on the south coast of Ireland is about 3855 kms which is ideal for one F2 layer hop, hence the strong signal.

2024 #7 - W1BW... Another method of sending a signal is as a symbol or character. This is where some degree of artistic flair comes into play.

Bruce, W1BW in Boston has a flying 'W' that he uses for QRSS. W1BW is running 200mW from a Hermes Lite 2 and the antenna is a random dipole about 25m long on the rooftop of a condominium building in the city of Boston, about 25m AGL and 2m above roof level..

W1BW is located just over 4700kms from my location and the mode of propagation was probably two hops from the F2 layer of the ionosphere.

In summary... That brings the QRSS tally so far for 2024 up to 7-callsigns & 4 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year.

QRSS are very slow morse code transmissions where the dots and dashes are several seconds long and the signals are decoded by looking at a waterfall display on a screen rather than listening to the signal.

The QRSS signals are usually just below the WSPR signals on the amateur radio bands. This means it's possible to have your PC decoding WSPR signals up around 1500 Hz while you look at the QRSS signals about 500 Hz or so lower in the audio spectrum at the same time.

2024 #3 & #4 - G0MBA & G0PKT... The QRSS signals shown above were captured at about 10:40 UTC and it shows the QRSS trace from G0MBA and G0PKT who are 650kms to the east of my location in Essex, England. From what I know, I think both are running 0.2-watts into vertical antennas.

You'll notice that the signals have a slight 'fuzz' as opposed to a clean tone. I hear/see these two stations practically every day and I think the signals are F2 layer backscatter. If I was to try again during the Sporadic-E season during the summer, both signals would be nice and clean.

At 650kms, both signals from G0MBA & G0PKT are way too far for ground wave and too close for normal F2. The signals are probably being propagated off the F2 layer, being reflected in some distant region and then returning to my location.

2024 #5 - AE0V...In the afternoon, I got a capture of the QRSS signal of AE0V in Minnesota (EN34FU) in the USA who is about 6,000kms from my location.

Ned, AE0V reports using a solar powered transmitter with no battery storage running 100mW into a 1/4 wave stainless whip about 8m above the ground.

The signal from the USA is easily explained as it's via multi-hop F2 layer propagation. 

In summary... That brings the QRSS tally so far for 2024 up to 5-callsigns & 3 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year.

QRSS are very slow morse code transmissions where the dots and dashes are several seconds long and the signals are decoded by looking at a waterfall display on a screen rather than listening to the signal.

The QRSS signals are usually just below the WSPR signals on the amateur radio bands. This means it's possible to have your PC decoding WSPR signals up around 1500 Hz while you look at the QRSS signals about 500 Hz or so lower in the audio spectrum at the same time.

2024 #2 - VA1VM... The first signal I captured in 2024 was from Vernon, VE1VDM in Nova Scotia, Canada back on the 8th of January. This is outlined in this previous post.

Conditions on the 28 MHz band were better on the 10th of January and the 'VDM' QRSS signal was in again but stronger as can be seen above. For this beacon, Vernon was using a QrpLabs U3S with low pass-filter into a QrpLabs power amplifier delivering 1-watt on 10m. The antenna was ground mounted Hustler 6BTV vertical.

In the last 24-hours, Vernon has put a second QRSS transmitter on the air with the callsign VA1VM. You can see this as a weaker signal in the image above.

The VA1VM signal is from a 150 milliwatt transmitter into a  Hustler 10m 1/4 wave resonator mounted on a 1.37-metre long Hustler mast extender. It really is amazing that a 0.15 watt signal can make it across the Atlantic.

Both beacons are located in the town of Truro in Nova Scotia and are just a few kms apart. The antenna on my side was a simple CB type half-wave vertical.

The map above shows the location of the transmitter and receiver. The distance is about 4000kms which is ideal for 1-hop of F2 layer propagation.

Even though it's the same person, it's a second QRSS signal. That brings the QRSS tally so far for 2024 up to 2-callsigns & 1 DXCC.

As part of a challenge for 2024, I've decided to see how many QRSS signals I could capture on the 28 MHz band during the year.

QRSS are very slow morse code transmissions where the dots and dashes are several seconds long and the signals are decoded by looking at a waterfall display on a screen rather than listening to the signal.

The QRSS signals are usually just below the WSPR signals on the amateur radio bands. This means it's possible to have your PC decoding WSPR signals up around 1500 Hz while you look at the QRSS signals about 500 Hz or so lower in the audio spectrum at the same time.

2024 #1 - VE1VDM... The first signal I captured in 2024 was from Vernon, VE1VDM in Nova Scotia, Canada.

Vernon was using a QrpLabs U3S with low pass-filter into a QrpLabs power amplifier delivering 1-watt on 10m. The antenna was ground mounted Hustler 6BTV vertical.

The antenna on my side was a simple CB type half-wave vertical.

The map above shows the location of the transmitter and receiver. The distance is about 4000kms which is ideal for 1-hop of F2 layer propagation.

So that's the QRSS tally so far for 2024... 1-callsign & 1 DXCC.

I first tried WSPR out in 2009, with a Signalink USB interface attached to my FT-817 and PC. For anyone interested in QRP and QRPp, the process of being able to decode a signal that is up to about 34dB below the noise level is quite fascinating. Morse code, sent by way of CW, engages and tickles my brain in ways that other modes don’t. WSPR though (and other weak signal modes), has it handily beat in terms of it’s sheer ability to extract data from a signal that the human ear cannot even detect. A few years later, in 2018, I assembled an Ultimate 3S QRSS/WSPR beacon transmitter from QRP Labs for a ham friend. This project opened me to the appeal of a standalone WSPR beacon that, unlike my earlier foray into WSPR, didn’t require tying up my main station gear. The addition of a GPS unit, as well as setting the timing of the transmissions, could also automatically insert the Maidenhead grid locator – no need to manually program that, making it ideal for travel.

Fast forward to the current day. I’ve recently become a bit more active on the bands, and decided that I wanted to “stop the rot” of my CW skills, which were slightly degrading due to lack of use. I signed up for an online CW course with the CW Academy, offered by CW Ops. I just completed their intermediate course, and enjoyed it immensely. The Intermediate course is designed to take ops from 10-20 wpm. I was already comfortably having conversational QSO’s at about 16-18 wpm. At CW Academy, the emphasis is on head-copying, so that you can converse without needing to write anything down other than the occasional piece of essential info (name, rig, etc.) This, they explain, is an important skill, if you are to increase your speed. I, along with most of the other students, found it surprisingly challenging to listen to short stories in code, and extract meaning from them without writing anything down. It helped that we had a fantastic advisor, in the form of Randy N1SP. Practice sessions in between our online Zoom sessions could be challenging, but the prospect of classes led by Randy were a great incentive. He made learning fun.

Along with my renewed interest in CW came interest in weak signal modes generally, as well as a slight stirring in the desire to build radio things again. Over the last 3 years, I’ve been putting time and effort into working on my camper van, which took energy and money away from amateur radio. Well, I’m gradually angling towards selling the campervan, which will free up some mojo for other pursuits. Anyone want to buy a 1993 Airstream B190, with 67K miles, 200w of solar on the roof, and a 2″ lift?

Back to radio. The Autumn 2022 issue of SPRAT contained an article by Paul VK3HN, detailing the WSPR beacon he had built using modified open source code from Harry at ZachTek and, of course, the JTEncode and Si5351 libraries from Jason NT7S (Jason’s libraries pop up everywhere). If you don’t have access to SPRAT, and even if you do, Paul describes his beacon on his blog here.

As long as you know how to upload a program to an Arduino, or flash firmware to a microprocessor (same thing), the barrier to entry to building a WSPR beacon is now quite low – even lower if you don’t build a PA stage, and take the ~10mW output from the Si5351 clock output directly to the LPF and the antenna. Here’s what I built –

The output is taken from the CLK 0 output of the Si5351 and feeds directly into the PA stage that Hans Summers uses in the QRP Labs Ultimate 3S QRSS/WSPR transmitter. I’ve built both the Ultimate 3S and QCX rigs, and liked the class E PA’s he used in both designs. Simple in design – and I also like the fact that, because the BS170 is a MOSFET that doesn’t suffer from thermal runaway, you can simply parallel them up for greater power, without the need for balancing. Details of how to wind the bifilar transformer can be found in the assembly manual for the Ultimate 3S on the QRP Labs website.

In his beacon, Paul runs the Si5351 at it’s default of 2mW output, and follows it with a W7ZOI-designed 2 stage PA from the pages of EMRFD . Due, I suppose, to sheer laziness, I wanted to keep the PA stage as simple as possible, so opted for higher output from the Si5351, and a single MOSFET, with very few supporting components, for the PA. Paul mentioned that in the earlier days of the Si5351 being available to experimenters, he heard some talk of higher phase noise and jitter from the Si5351 at higher output levels. Perhaps running it at a lower output level, and making up for that later, is a worthy strategy? To run the Si5351 at it’s maximum power of about 10mW out into 50 ohms, I found the following line in Paul’s modified code –

si5351.init(SI5351_CRYSTAL_LOAD_8PF, 0, 0);

and inserted the following line after it –

si5351.drive_strength(SI5351_CLK0, SI5351_DRIVE_8MA);

This sets the chip to produce the maximum power at the CLK0 output.

The very first iteration of this project used a passive patch antenna, as I didn’t realize that the GPS module supported active antennas. The patch antenna, with it’s very short piece of coax, was quite difficult to implement in the diecast enclosure I had chosen for the project. I mounted it on top of the lid, with the main board mounted on the inside of the lid, and the coax passing through a hole in the top. When I took the lid off to work on the circuit, the antenna was shielded from satellites by the lid, which was inconvenient. Once I discovered that the GPS module supported active antennas, I installed one. I have no photos of the implementation with the passive antenna.

Here’s a view of the next version of the board, with the clock generator and Nano boards unplugged, to allow viewing of the wiring underneath. As usual, I have used Rex’s wonderful MePADS and MeSQUARES for the Manhattan pads, and strips of header to plug the Si5351 board, Nano, and LPF boards into. Operating on a different band just requires changing the output filter, and reprogramming the Nano via it’s ICSP header –

The first version of this build used a single 7805 voltage regulator, bolted straight onto the board for heatsinking. I had forgotten how very hot these 1 amp regulators get. The IC itself got very hot, as did much of the ground plane on the board to which it was bolted. Although not my best idea, it turned out to be dwarfed by a particularly poorly thought-out aspect of the layout –

It’s perhaps not immediately obvious from the above photo, but might become more apparent from this image –

That is the BS170 PA transistor mounted directly underneath the frequency synthesizer board. The problem, is that the PA transistor gets very warm. Warm air rises – and what is directly above? Yes indeed – the most frequency sensitive part of the whole circuit. What a fool, an oaf, a bumpkin, a buffoon, and a rube! When laying out the build, I was mainly concerned with fitting everything in, and not having a long wire between the output of the Si5351 and the PA. I’m not sure why, as a short length of RG-174 would have worked just fine. Nevertheless, slightly disheartened at my mistake, I forged on, and proceeded to attempt to calibrate the unit using Jason NT7S’ calibration script. I’ll spare you the long, dull version, and just say that I couldn’t get Jason’s script to work. My suspicions lay with either the cheap Nano board, or the cheap Si5351 board that I had bought from Amazon. Not pictured here, the first Si5351 board I tried was a direct clone of the Adafruit board, with a purple board instead of the Adafruit blue color, and without the Adafruit branding on it. I ditched Jason’s script, and went for a rough calibration by beating the output of the board against WWV, and making adjustments to the correction factor, until I was within a Hz or two of zero-beat.

I then uploaded VK3HN’s script to the Nano. The unit was indeed WSPR’ing but, despite the fact that I had calibrated it fairly accurately, quite a few of the WSPR transmissions were out of band by anything up to 100Hz. This didn’t seem right, so I tried calibrating the board again, only to find that each time I calibrated the board, I came up with a significantly different correction factor. Replacing it with a genuine Adafruit board solved the problems. Suddenly, Jason’s calibration routine worked beautifully, and the board began producing consistent, repeatable frequencies. All subsequent WSPR transmissions were in-band. The Si5351 board that I had purchased from HiLetgo was only about $3 less than the genuine article from Adafruit. In retrospect, it was not worth the trouble just to save a few bucks. Lesson learned. In contrast, their Nano boards are significantly cheaper than the “real” thing, and seem to work just fine.

My first foray into WSPR with this mini concoction was on 10M. Drift figures were nearly all -4’s, and I wasn’t getting anywhere near as many spots as I would have expected to get. Because nearly all the drift figures were -4’s, that indicated to me that many spots were very possibly being missed, due to a drift figure of higher than -4. Placing the board in a diecast enclosure with the top on helped. I was then getting more spots, but still all with drift figures of -3 and -4, with more -4’s than -3’s. I went down to 20M, where the drift figures were a little better, but still not good enough. From cold, the first few transmissions produced no spots. After an initial warm-up period of about 30 minutes, I was getting more -3’s, and even a few -2’s. Still not good enough.

One obvious change would be to relocate the PA to the opposite side of the board, away from the clock generator board. If I did that, it would be in another build completely so, for the time being, I concentrated on other ways to bring the drift down. Here’s what I did –

1. Mounted the 7805 regulator on the side of the diecast enclosure, to which it was bolted. I also added a 7808 regulator, thinking that it wouldn’t hurt to spread the heat generation between two devices, even though these parts are designed to run very warm.
   
2. Added a 1N4001 diode in series with the 12V DC input. As well as providing reverse polarity protection, the forward voltage drop of about 0.7V should help to spread the heat dissipation from the regulators out just a little more.
   
3. Secured the clock generator board with 2 nylon screws and a threaded nylon spacer. I had been waiting for the parts to arrive from Adafruit, so hadn’t done this earlier. (This kit of nylon screws and spacers should last a while!)
   
4. Although not a modification, one thing I did differently this time before testing out the beacon, was to screw down the top of the enclosure tightly, instead of just placing the top on.
   
   

After these changes, the difference was dramatic. No spots were picked up on the first transmission. On the second transmission (on a 50% transmission duty cycle), several spots were received, all with drifts of -4. Things improved with every cycle until, after about 45 minutes, all spots were -1’s and 0’s, with the very occasional -2. Much better, and very encouraging.

Some more shots of the board with the regulator removed, and replaced with 2 regulators in series (a 7808 and 7805), both bolted to the side of the enclosure. The enclosure is a bigger mass of metal that provides more effective dissipation of heat from the devices –

Here’s a view of the board with the Si5351 breakout board and Nano board unplugged, to show the wiring underneath –

Looking dead sexy in it’s diecast enclosure from Tayda –

In attempt to further improve the drift figures, I made a heatsink from a piece of brass strip, and epoxied the BS170 PA transistor to it with JB Weld. A clamp held the mighty little MOSFET in place while the epoxy set –

A pair of round-nose pliers were used to bend the leads. The leads on some of these parts are quite delicate, so I prefer to coax them round the bend, rather than foisting an abrupt 90 degree angle on them –

I am unsure of the dielectric properties of JB Weld so, to avoid any problems, made sure to keep the area around the leads free of epoxy –

I think this heatsink looks mighty spiffy. Brass is such an attractive alloy –

A close-up of the heatsink –

Unfortunately, with the heatsink fitted, the drift figures were worse. After about a 90 minute warm-up period, I was getting drift figures of mainly -2’s and -1’s. Removing the heatsink got me back to drift figures of mainly -1’s and 0’s, with the occasional 2, after warm-up. After 2 hours, the drift figures are equally split between -1’s and 0’s. All of the figures I have quoted are from 20M operation, by the way. A quite satisfactory result, I think, from a frequency generator board that is not temperature compensated.

I was already fairly satisfied with this result, but then things became better. The heat from the PA transistor was rising, and heating up the Si5351 board, forming a sort of crystal oven. Because of this, it occurred to me that if I were to adjust the bias on that BS170, it would affect the amount of heat the transistor gave off, and might also affect the drift figures reported by wsprnet.org. The transistor was currently providing about 200mW to the antenna. Although, by adjusting the bias, I could have coaxed some more power out of it – perhaps as much as 250mW, I didn’t want the transistor to run much hotter than it was already running. Likewise, I didn’t really want to run much less than 200mW. Fiddling around with the bias trimpot, I ended up with it in almost the same place as it was before. The transistor was probably putting out a mW or two more, but not much more. However, the difference in the drift was dramatic. Check out this wonderful result (still on 20M), achieved after a warm-up period of around 40 minutes or so –

These fantastic drift figures almost made me giddy! The only other thing I had changed, was to swap out the 4 oxide black panhead 4-40 machine screws on the sides of the diecast enclosure, for regular stainless steel machine screws. Perhaps they have slightly different thermal properties, but I think the main factor responsible for the improvement in drift, was the very slight change in the bias setting. I had haphazardly settled on a near-perfect bias setting, and created a very effective crystal oven! I did have a couple of other ideas I was going to try, namely placing foam over the Si5351 board, to insulate the Si5351 and crystal from air currents, and looking for a TCXO to replace the crystal in the Adafruit board. However, at this point, I don’t think it’s necessary. Running the beacon for another 6 hours, the results were much the same, though a single -2 and +4 drift figure did pop up. I think the +4 was an anomaly, probably caused by drift in the other station. This is a better result than I had hoped for. I’m ecstatic!

On 10M, it takes 3 hours to fully settle down, after which, drift figures are mainly -2’s and -1’s, with a few -3’s, the occasional 0, and the very occasional -4. However, I do notice that after running it all night, drift figures in the morning are a little worse, with a lot of -3’s and a few more 4’s. This suggests to me that the ambient temperature of the room might be playing a part.

Incidentally, changing bands only involves changing the band in the code, which requires simple changes to two lines in the sketch, plugging in a different LPF, and uploading the new sketch via the ICSP header on the Nano board in the WSPR beacon. As far as initial setup goes, before you upload Paul’s modified code, you will need to insert your callsign, and the power level in dBM. Mine puts out about 200mW, which is 23dBm. You can input your grid locator if you want, but the unit will calculate that from the GPS, once it has gotten a fix. Although I haven’t tested it yet, I assume that if the unit moves into a different grid square, it will report the new locator. (EDIT – Paul informs me that, although it would be easily possible to insert code that calculates the grid locator, his modified code doesn’t do that. I assumed it did, based on the fact that although I input my locator as CM87, wsprnet reports it as CM87ut. However, they are probably doing that based on their knowledge of my location. Looks as if I have something else to work on!)

By the way, when you’re changing bands, remember to also change the LPF. When assembling the LPF boards from QRP Labs, I always check the response curve on my NanoVNA. As an added testament to the fact that they do indeed work, I recently flashed the unit with firmware to change the operation from 80M to 20M and left it to run overnight. In the morning, there had been absolutely no spots. I was flummoxed, and even thought I might have fried the Nano board, until it dawned on me that I had not changed the LPF. The beacon was running on 20M, with an 80M LPF still plugged in. No wonder!

In the future, I may experiment with an Si5351 board that has a TCXO, in order to improve the drift figures on the higher HF bands. In the meantime though, I am deliriously happy with the performance on 20M (and presumably below). This project was inspired by VK3HN’s SPRAT article, and the realization that “throwing together” a few boards, and constructing a simple PA and LPF should be easy, and wouldn’t constitute a full-blown project. I have become somewhat shy of such lengthy endeavors these days. I wasn’t expecting it to turn into a cased-up and very serviceable WSPR beacon though. I tend to let it run in the evenings and overnight, when I’m not operating. That way, in the morning, I can check wsprnet to get an idea of what propagation is like. As many others have said, it’s a handy propagation tool. If you don’t want to build one, you can buy a ready-made WSPR beacon from Harry at Zachtek.

At the risk of posting too many pictures, here are a few more –

A cigar box from the local tobacconist, and some packing foam, makes a good storage box for my growing collection of QRP-Labs LPF’s and BPF’s. Only the LPF’s are used in this project. The BPF’s, in the front row, are for receivers (though they could be used in the early stages of transmitters, where only very low signal levels are involved) –

Definitely a successful project. Thank you Harry Zachrisson of ZachTek, Paul VK3HN, and Jason NT7S –

One last gloat. Look at these great drift figures. Pretty good for an Si5351 board without a TCXO! To date, this 200mW powerhouse has been spotted all over Europe, North, South, and Central America, Hawaii, Taiwan, Hong Kong, Australia, New Zealand, and several island clusters and nations in the middle of vast oceans. Exciting stuff!

Oh, and one last thing. Paul included an LCD display in his transmitter, which shows some extra useful information. The code will support it, and his blog shows how to connect the display. I think there is just enough space to fit a display into my unit. I didn’t chance it however, as I seem to have the thermal balance inside the case just right (for 20M and below, at least) and I don’t want to upset anything. My desire for a display isn’t strong enough to want to make any more changes. I’m fine with this, as I think of it as a set and forget kind of beacon. In the evenings, I plug it in, and forget about it until morning.