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.

Jerry, AC5JM is the IARU Region 2 HF Beacon Coordinator and over the last few weeks has been updating all of the HF beacons that are in North and South America. The vast majority of these are on the 28 MHz (10m) band.

The old list had become badly out of date with some beacons that hadn't been heard in years. AC5JM has put a lot of work into seeing what beacons have been heard of late and trying to contact other beacon owners to find out the current status.

On the 18th of March 2024, Jerry reported the following... "As of today, and to my knowledge there are officially 310 beacons on the active list in Region 2 but about 49 of them are temporarily down due to equipment failures and QTH moves and another 11 have been inactive for more than 1 year.  

I used RBN (Reverse Beacon Network), emails from beacon owners, and reception reports from others to determine if a beacon is active or not.  Some that I have have moved to the inactive list may in fact be active.  Please let me know if any corrections need to be made."

The list can be viewed from the following link... https://www.iaru-r2.org/en/on-the-air/beacon-network/

Bernie, ZS4TX reports that a new 144 MHz beacon has started in South Africa to investigate the possibility of Trans-Equatorial Propagation (TEP) to the Mediterranean and Europe.

Bernie, ZS4TX writes... "New ZS Beacon for 2M TEP tests in April from KG33XU. ZS6RVC has started a 25W beacon on 2M with a 14 element yagi 20M high on a mountain site with a clear shot to EU.

Analysis... As the 144 MHz signals are likely to cross the Geomagnetic Equator at right angles (90 deg), the most likely area for reception of this beacon is probably going to be the eastern half of the Mediterranean.

Back in 1981, there was a TEP opening on 144 MHz from this part of South Africa to the Athens area in Greece so it may be possible again.

Dave AA7EE alerted us to this attack.  Please follow-up by posting reception reports (and triangulations!) in the comments below.  Dave writes:  

Recently, an unlicensed beacon (for which read pirate) has turned up on 3579 KHz. It seems to be located somewhere in the Western US, in the tradition of unlicensed HF beacons dating back to the late 80's that were solar-powered, and located in remote areas of the Southwestern deserts. The very first ones were a cluster of beacons around 4096 KHz (a frequency for which crystals were cheaply and easily available).

Here’s a little project I put together on a whim about 18 months ago. It was my tribute to the unlicensed (i.e. pirate) beacon cluster around 4096 KHz. There were several of them operating in full force, with powers ranging from around 100mW to a watt or so a few years ago. Their heyday was about 20 years ago. They were located somewhere in the southwestern deserts of the US, and were powered by batteries and solar panels. The feller who placed and maintained them has stopped their upkeep and, as a result, most, if not all of them, are no longer operational. (There was a small group who also placed these beacons, and I believe they too stopped doing so years ago).

This little beacon, using a commonly available crystal, put out around 30 or 40mW, if I remember correctly, into a 51 ohm resistor as a dummy load. If it were to be connected to an antenna, which will not happen at this frequency, it would need a low pass filter. I haven’t posted the schematic here, for two reasons –

1. I don’t want to encourage unlicensed operation and
2. This particular circuit is a bit of a kludgy design, and not one I’d use anyway.

I’m posting the photos as a reminder that if you don’t have Manhatttan pads, or don’t want to make your own, then so-called “ugly construction” is a very viable way of putting circuits together. If you do it well, your circuits can be quite robust and long-lasting. One of Rex’s MePADS was used for the IC, but everything else was built ugly-style.

In the next overhead picture, you can see the ATTiny85 that keys the transmitter. Above and to the right of it, is a 78L05 that supplies 5V to the chip. Directly below the crystal is the oscillator transistor, which is keyed by the transistor to the left of it. On the right is the PA transistor. All 3 transistors are 2N3904’s.

Before ending this post, there is a key part of ugly construction that is worth mentioning. High value resistors (1MΩ and above) can be used as standoffs. To circuit components, they look like insulators. In this circuit, there are two 1MΩ resistors used for this purpose. I later bought 200 x 10MΩ resistors from Mouser, and will be using them as standoffs in the future. They won’t increase your current draw by any significant amount either. A 1MΩ resistor to ground from a point at 12V potential will only cause an increase in current consumption of 0.012mA. A 10MΩ resistor will have even less of an effect, incurring an increase of just 0.0012mA. That’s 120µA. I can live with that!

Anyway, that’s it. I hope this inspires you to get the soldering iron out and build a little circuit. A simple receiver or transmitter, a novelty circuit, or anything really. Building these little things and getting them to work is fun. Incidentally, if you’re interested in listening out for these unlicensed HF beacons, the best source of information is the forums at HF Underground. The forum you’ll want is the one called “HF Beacons” though there are many other great sub-forums there as well.

Chris, N3IZN near San Diego in California reports reception of the Irish EI1CAB beacon on 40.016 MHz on Friday 9th of February 2024. Chris was able to decode the PI4 signal from the 8m beacon and as it shows in the graphic above, the signal level was down at -22dB which is well below what is audible to the human ear.

The EI1CAH beacon is located on the west of Ireland and it's 25-watt signal is often heard across the Atlantic in the eastern part of the United States. This isn't all that unusual now that we're near the peak of the sunspot cycle. 

The more northern path to California is much more difficult and it's interesting to see a signal at 40 MHz complete the 8,124km path.

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.

I haven’t been building much at all, for quite a long time now. However, the urge occasionally returns. When it does, it’s wonderful to have a small stash of parts on hand, so I can pull the soldering iron out and start building before the desire dissipates. I’ve been interested in beacons for a while, and this interest has followed a logical progression. I first noticed that my interest in talking with other hams over the air using phone (i.e. SSB) was waning. During this time, I would still check in daily with the Noontime Net on 40M (now on 7284 KHz). A quick check-in to a net was fine, and it was good to hear the other stations, many of whom were regulars, also check-in, and have the occasional quick conversation. In addition I noticed that my inclination towards CW QSO’s was also diminishing. I’m not exactly sure why. I enjoy talking with close friends, acquaintances, and neighbors in person, but my enthusiasm for chatting with relative strangers who I can’t see, and don’t know that well, all but disappeared. Too many QSO’s seem very cookie cuttter. Either that, or the conversation is about subjects that don’t interest me.

My main interest in amateur radio was fast becoming the medium of radio communication and the science behind it, rather than the content. I enjoyed quick contest exchanges, as it was a way of seeing where my signal was getting to. Some folk dislike contests, preferring to ragchew, but I find the average ragchew on the bands rather dull. Mike Rainey AA1TJ referred to brief QSO’s as being akin to high-fiving someone when you’re walking down the street. It’s an acknowledgement – a quick, “Hi! It’s good to see you. Talk later!” If you just built something, it’s good to know that it works, and a way to marvel in the mechanism of propagation that made it all possible.

This is why I like beacons. The ones I listen to send CW at regular speeds. I tend not to look for QRSS beacons, or data signals. I like CW that I can listen to and decode in my head, even if it’s just a few letters that are constantly repeated. I can put in the work to decode a very weak signal from a QRP (and often QRPp) beacon, figure out roughly where it is in some cases, and feel the satisfaction of having received a very weak signal, without listening to some chap talking about the model number of his transceiver, his latest medication, his political/social opinions, or whether he mowed the lawn and watered his plants today.

I’ve probably explained this before, but there are two main types of beacon I like to listen out for. The first are the so-called “unlicensed HF beacons” (for which read pirate). They tend to operate in the lower half of the HF spectrum. The lowest frequency one I know of is on 2097.3 KHz, is located somewhere in the southwest (many of them are in the SW deserts), and is relatively high power – probably in the range of 5-15W. It sends the letter A once every 10 seconds (approximately). There are a number clustered around 4096 KHz (a popular crystal frequency), quite a few around 8000 KHz, and others up to about 8500 KHz. A good one to listen out for, is the fairly new Desert Whooper, on 4095.65 KHz. It must be relatively high power, as I have heard it regularly in 6 Western states, on a recent campervan trip, with a portable receiver and set-top whip. It sends a whooping sound for a few minutes then, in CW, it sends the battery voltage, the outside temperature, the inside temperature, and a number that is related to the solar panel voltage. Then, if I remember correctly, it sends it’s ID a few times (DW, for Desert Whooper), and goes back to whooping for the next few minutes. The current list of known active unlicensed HF beacons is here, on the very excellent HF Underground forums –

https://www.hfunderground.com/board/index.php/topic,9478.0.html

I’m a bit too chicken to deploy one of these types of beacons, partly because I’m a licensed amateur. Also, how do you really know that your HF beacon is not operating on, or close to, some frequency that is used for critical communications? Certainly, there are published bandplans, but I’m not sure how much detail they really go into. On top of that, I just cannot bring myself to leave something that emits RF in a remote location such that I would have trouble getting back there quickly, were the beacon to malfunction. It’s a control thing, I suppose. I’m responsible for my stuff, and I like to be able to switch it on and off, and service it, at will. I know that the likelihood of a 100mW HF beacon interfering with critical communications is pretty unlikely but even so. Besides, as an amateur, there is a wide swath of spectrum I am allowed to use legally (though not for unmanned beacons below 28MHz).

The other type of beacons that I find quite fascinating to listen for, are the HiFERs. These are also unlicensed, though if you keep your power low enough, they are legal (in the US, at least). The FCC, for the 13553 – 13567 KHz ISM band, regulate the power level allowed in terms of the field strength a certain distance from the antenna. For those of us without a professional calibrated field strength meter (most of us, because they are expensive!) a couple of helpful gentlemen have expressed this in terms of power to various antennas. According to W1TAG’s calculations, you should be within, or close to, the allowed field strength with 4.6mW into a half-wave dipole, or 2.3mW into a quarter-wave groundplane. K6STI uses several different antenna installations over varying degrees of ground conductivity. Under certain conditions, he calculates that up to 473mW would be allowed. His calculations are at –

http://ham-radio.com/k6sti/hifer.htm

I’ll leave it up to you to decide what power level to use, but it sounds to me as if you’re pretty safe if you keep it under about 5mW. What? you think. Is it possible to even hear beacons at distance at those sorts of power levels? It certainly is. If you, like me, either have a poor antenna installation, or none at all, you can still hear some of these HiFERs by utilizing online SDR’s. One of my favorites is the KFS SDR, that uses several large antennas on a 150 foot cliff overlooking the Pacific Ocean, 6 miles south of Half Moon Bay, CA. This SDR has good ears! In the last few days, on this SDR, I have heard TON in Tonopah, Arizona, PCO in Pine, Colorado, and TSN in Tucson, Arizona.

Which brings me to this project. I wanted to build a HiFER beacon that would operate from a LiPoly battery charged by a small solar panel, for a compact installation that could be located outside on a hilltop, or in some desert area. These batteries are 4.2V at full charge, so I built up my beacon with a LP2950 5V regulator on board, figuring that if it worked at 5V, it would probably work at 4.2V. The regulator and it’s bypass capacitors are not shown in the following schematic, but there is a 100uF and a 0.047uF bypass cap on the input of the regulator. The bypassing on the output is shown in the schematic, and consists of a 0.047uF on pin 8 of the ATTiny85, and another 0.047uF on the +ve supply line side of the 8.2uH choke that feeds the collector of the PA transistor. A molded choke was used in this position.

13.56MHz crystals are easily available from many suppliers of electronic parts. I bought a bag of 20 on eBay. The RF chain is very straightforward, and is the same one seen in the transmit section of the Pixie transceiver. The output filtering is more than is necessary for this application. 2 poles of filtering would have sufficed, but it doesn’t hurt to add an extra pole. The 47pF capacitor across the center toroid forms a parallel tuned circuit with that inductor to increase rejection at the second harmonic. It’s a design by W3NQN. I took the values from the 20M LPF –

https://www.gqrp.com/technical2.htm

The ATTiny85 keys the oscillator. There is no chirp or instability caused by doing this. I like this approach, rather than keeping the oscillator running and keying the PA. I build most of these beacons for use around the house, and am usually in close proximity to them. If the oscillator is keyed, I don’t hear the constant backwave from the oscillator transistor. The code for keying, as in my Boris Beacon, was courtesy of Nick SV1DJG. I use pin 2 of the chip as the keying line, and had to change that in Nick’s sketch. The line –

#define ledPort 1

was changed to

#define ledPort 3

The feedback capacitors C1 and C2, as well as forming part of the feedback loop to maintain oscillation, help to pull the crystal, to determine the frequency of operation. Initially, C2 was 100pF, and there was no capacitor in the C1 position. The oscillator ran reliably, but it was on around 13561, which is too close to the center of the band where all the RF from the various ISM and RFID devices is. Take a look at 13560 ± 1 or 2 KHz on a waterfall display – on your own receiver if you have a good antenna, or a good online SDR. You’ll see why you wouldn’t want to run a QRPp beacon there. Too much RFI! However, above about 13562, and below around 13559.5, the band is quite clear. It’s a gift for very low power beacon enthusiasts. Where else in the HF spectrum can we legally operate an unmanned beacon that stands a chance of being heard? (Well apart from 10 meters, that is.)

I wanted to avoid frequencies that established and known beacons are operating on, as well as the 3 other devices in this band that I use at my house. I ended up with a 100pF cap for C2, and a 150pF one for C1, which gave me an operating frequency of 13557.49 KHz ± a few tens of Hz, depending on the ambient temperature.

With the above setup powered by the 5V regulator, I measured 0.913V across the 51 ohm resistor with the N5ESE RF probe and an EEVBlog Brymen BM235 DMM. The voltage drop across the diode in the probe was 0.234V, so this translates to a power of about 25mW. I removed the 51 ohm resistor and measured the power with a freshly calibrated WM-2 QRP Wattmeter. The reading was about 6 or 7mW. I am not sure why the discrepancy between the two readings, but if I’m able to get my hands on a DSO in the near future, I’ll be interested to see which of the two readings is the more accurate. I suspect it’s the wattmeter reading. If the power is closer to 25mW, it can easily be dropped with an attenuating pad, or a lower supply voltage from either a LiPoly battery, or a 3.3V regulator.

A successful project, I think. I may even press it into service one day!

Aviation LF/MF beacons provide the opportunity to admire electrically-small antenna design on a macroscopic scale.

The post Anatomy of a low frequency aviation radio beacon appeared first on Ham Radio . Magnum Experimentum.

In this post from May of last year, I detailed the construction of a 1mW solar-powered HiFER beacon. I named it the Boris Beacon, in tribute to my neighbor’s cat. The beacon was never mounted permanently outside. I kept it indoors, powered from a small solar panel in the window, and feeding an “antenna” of sorts, consisting of the original dipole wires folded up into two small bundles. Obviously, I had no serious intention of it being heard by anyone; I just liked having it come on every day when the sun came up, and transmitting until later in the day, when the light was too low to sustain operation.

Recently, another location became available in my house that seemed like a good place to install a beacon outside. The Boris Beacon was still in operation from inside my apartment. Moving it outside onto this first floor balcony and spreading the dipole legs would be a straightforward task. You’ll notice from the original post on this beacon that, in attempting to seal the holes where the leads entered the enclosure, I used Plastidip. It’s a rubbery solution that sprays on. It’s great for some applications, but not for this one, as I ended up getting the rubbery liquid all over the enclosure. I do like my projects not to look too messy, so for this new iteration of the Boris Beacon, I moved the circuit board into a new enclosure –

Here it is, close to it’s final installed position, on a first floor balcony (Edit – I just noticed, after a year, that I should have called it a second floor balcony. In the UK, where I haven’t lived since I was in my early 20’s, we call the second floor the first floor, and the first floor the ground floor. I guess old habits die hard!) –

In it’s final installed position. The solar panel is fixed to the top of the wooden railing with 2 wood screws, as is the beacon enclosure. The dipole is stretched out behind the wooden  fence at the top, and then trails down onto the balcony floor in one direction. In the other direction, it is attached at the other end to the wall of the house, so is partially elevated –

A close-up view, showing the silicone caulk around the entrance/exit holes. The underside of the lid has a foam weather sealing strip embedded in it, which can be seen in the original post, linked to at the beginning of this post –

I was unsure how impervious the little solar panel would be to the elements, so I caulked around the edges. If it fails, these kinds of low wattage panels are cheap and easily available anyway –

The panel I’m using is a small 1.8W one, intended for use as a 12V battery maintainer –

It is probably overkill, but I popped a silica gel packet in the enclosure, to mop up any excess humidity that might find it’s way inside. The dessicant turns pink when saturated, and is blue when dehydrated and ready for action –

Another view, with the gel packet flipped –

The beacon sends the letters “BRS” at 10wpm, with a break of 3 or 4 seconds between the end of one transmission and the beginning of the next, with a mighty power to the dipole of about 1mW. The frequency is a nominal 13556.9KHz (13.5569MHz), which varies either way by a few tens of Hz, depending on the outside ambient temperature. I will be overjoyed if anyone, anywhere hears it! There is no battery, so it transmits during daylight hours only. It comes on about half an hour after local sunrise, and goes off about half an hour before local sunset. I’ll update this with more accurate information, as I observe the on and off times over the next few days.

The Boris Beacon is definitely a successful project. I just need someone to hear it. Even one person will do! If we were allowed to run 100mW on this band then getting spots would be much easier. In fact, if the dipole were situated more up and in the clear, that would help too. As it is, 1mW into a compromise dipole will make this little beacon a super DX catch. I don’t know how long it will remain in operation, as the long-term future of my current living situation is in doubt. I suspect that it will be up and running for much of 2019 though. I will update this page if and when it goes off the air.

Reception reports greatly appreciated!

EDIT –

Almost a week later, and it seems to be faring well in the rain, although it’s early days –

Rain was pooling on top of the panel and although it’s supposed to be weatherproof, I’m not too sure how waterproof this panel really is –

I raised one end slightly, to help a bit –

Still no reports!

EDIT – As of Aug 2019, the BRS beacon is off the air, probably permanently. The space from which I was operating it from is no longer available. It was put to sleep, having received not one report. I put it down to two things. Firstly, it was active during a period of particularly poor HF propagation. Secondly, the power was around 1mW. Even so, I was hoping for at least one report. I think it would have been worthwhile to have reprogrammed the chip to send QRSS.

My build of the K7TMG HF Morse Code Thermometer was fun, and it inspired me to use the same circuit to create a new HiFER beacon to honor my neighbor’s cat Boris. With some of my indoor cat-owning neighbors in the past, I have acted as caretaker when their parents are out of town or at work. I don’t have that kind of relationship with Boris though, so she and I stare longingly at each other through the window when she is out. (Edit – I’ve looked after Boris a few times since first writing this post, so kitty-human relations have definitely progressed!) We are two beings sharing a mutual admiration, but separated by a sheet of glass –

When there’s a kitty who you want to hang out with but can’t, the obvious thing, of course, is to build a little HF beacon to transmit their name in Morse code. It’s the thing to do and so, I found myself building another K7TMG HF thermometer, but without the temperature-sensing circuitry. I also added a 2-section LPF to attenuate harmonics. I used the capacitance and inductance values that Chris Smolinski uses in his HiFER beacon kit, but recalculated the number of turns on the toroids so that I could use T37-6 cores instead of the larger T50-2 ones he uses. I think that the tuned tank circuit in the collector of the oscillator transistor must also help reduce the harmonic output of this stage as the level of the 2nd harmonic at the antenna is further down on the fundamental than I would normally expect from a 2-stage low pass filter like this –

For the firmware, I found a very versatile and useful piece of AVR beacon freeware written by Nick SV1DJG. If you use the circuit above, in which pin 2 of the ATtiny85 keys the oscillator, you’ll need to change the line

#define ledPort 1

in Nick’s code, to

#define ledPort 3

If you leave the output port as port 1, you’ll need to make pin 6 of the ATtiny85 the keying line instead of pin 2. If you want to make pin 3 the keying line, just specify “ledPort 4″Also, in the code, you can specify the message (or callsign/ID) you want to send, the keying speed, and the length of pause before it repeats. My beacon sends the letters BRS at a speed of ~5wpm, with a pause of 2 seconds. If you want to send QRSS with this program, there is also an option to specify the dot length in milliseconds. It is currently set at 1200. The dash length is derived from that, being specified as 3 times the dot length. Inter-character and inter-word spaces are also defined in terms of the dot length, so when you change the dot length, everything else follows.

The build went smoothly, and there’s not too much to say about it. As always, Rex’s MeSQUARES and MePADS did a sterling job of making the process of building Manhattan-style a lot easier. I cut the board to fit into a specific enclosure, and it worked straight off the bat. The trimcap had very little effect on the amplitude of the output signal, and the oscillator started perfectly at all settings. A fixed capacitor of around 47pF probably would have worked as well. There is also room for experimentation with the values of the 2 feedback capacitors, which are 470pF and 330pF in my circuit. Lowering those values will shift the oscillator up in frequency. Two 100pF capacitors should work. You may even be able to go lower in the value of these capacitors. My oscillator came up on a nominal 13556.9KHz. It was a good frequency for me, and didn’t seem to conflict with any of the HiFER beacons listed over at the LWCA website page of MedFER, BeFER and HiFER beacons. Great – no need to change any components!

Unfortunately, a different enclosure was sent from the one I ordered. The one I wanted had 2 external lugs for fixing it to a wall, post etc. The lack of these meant that I had to drill holes and fix it with screws protruding from the inside of the enclosure. It wasn’t ideal, as it meant more holes needed to be sealed to prevent moisture ingress. At this point though, it was the enclosure that I had, so it was the one that I used. It’s a nice weatherproof enclosure, available from China for as little as $3.41 inc shipping, or just a couple dollars more if you want it quicker from a supplier within the US. There are versions with external mounting lugs and clear tops too, if you like that sort of thing. An eBay search for “85x58x33mm waterproof plastic box”, or similar, should show plenty of options –

I wanted to mount this little beacon outdoors and power it exclusively from a small solar panel with no battery. This meant that it would only operate during daylight hours, of course, but I’m thinking that some grey-line action should still be possible, as the beacon will still be operating when locations just to the east are entering their grey-line phase. Living in a rented multi-unit building means that I need to be cognizant of the wishes and sensibilities of others, and I didn’t want to take the chance of a battery exploding inside a very hot enclosure in the summer heat. It’s probably unlikely, but with little previous experience in this area, I didn’t want to take the chance. Besides, the idea of a little circuit that is entirely dependent on the sun in a very direct fashion appeals to me. The panel I used was an old one that I bought cheaply as a lot of two, from a fellow on eBay who decided he didn’t want it, immediately after purchasing it. When drilling and filing the hole in the enclosure for the cable from the solar panel, I was careful to keep it as small as possible, so that sealing it against the elements would be straightforward –

Boris seemed to like it –

The plan was to install it on top of a fence on the property line of the building I live in. Sitting on top of the fence, the solar panel would receive light until fairly close to sundown with little obstruction from nearby buildings. My tube of silicone marine grade sealant had dried up, so I decided to try using a product called Plastidip, a can of which I had on hand. It’s a black rubbery solution that comes in an aerosol can. You spray it on, and it forms a weatherproof seal. I’ve used it successfully in the past for sealing the ends of coax at dipole center-feed insulators, so figured it should be usable in this application too, though perhaps not quite as easy to keep to a small area as squeezing silicone sealant out of a tube. Here’s a close-up of the beacon just below the top of the fence –

I sprayed the the screws that fixed the enclosure to the fence with Plastidip, and at this point began to wish that I had either held out for the enclosure with the external lugs, or at least used silicone sealant. I had forgotten how very liquid Plastidip is before it sets. Much of it dribbled down to the bottom of the enclosure and pooled. You can see it oozing out from the bottom of the board in the next shot. I’m not sure whether it conducts when in the liquid state, but I didn’t much like this. Plus, it just looked messy –

All this time, I had been monitoring the beacon signal with my K2 on a battery, to make sure that I didn’t break any connections during installation. Strangely, at this point, the beacon had stopped, and was just emitting the occasional dit or dah. I guesssed (incorrectly, it later turned out) that perhaps the liquid Plastidip was conductive, and was the cause –

I pulled the board out, cleaned up the oozing mess with Q-Tips, then reinstalled it in the enclosure. Poking around the micro-controller with my fingers, the beacon sprang back to life. I wasn’t able to determine exactly what had caused the problems, which concerned me. Unfortunately, I was pushed for time, as I was trying to complete the installation before one of my neighbors returned, a woman with whom, sadly, relations have completely broken down. It’s a long and uninteresting tale but at this point, nothing I can do or say will help things. It seems that I have been identified as a mortal enemy.  The fact that she doesn’t like cats doesn’t help either   At this point, I decided to press on with the installation as swiftly as possible. I stapled the dipole antenna just underneath the top of the fence in both directions, and mounted the solar panel on top with two short screws –

This is the type of install I was aiming for – unobtrusive. My neighbor on the other side might see the solar panel, but I was hoping that they wouldn’t mind. You never really know with folk what will bother them and what won’t. It’s at times like this that I can see the advantage of owning my own place with a big plot of land in a lesser populated area. The dipole is horizontal and only about 8 feet above ground level, so it’s probably a bit of a cloud-warmer. Definitely a compromise installation –

I went back inside and, monitoring from indoors, was happy to hear a good signal coming from the beacon. The letters “BRS” were being sent at 10wpm (my initial setting) with a 2 second pause before repeating, and absolutely no chirp on the signal. Monitoring the signal on and off throughout the rest of the day, I was happy to note that it stayed on the air for about 2 1/2 hours longer than it had when located indoors with the solar panel mounted in the window. It continued to transmit until about 48 minutes before local sunset. Exposure to direct sunlight makes a huge difference to solar panels. If I had been able to angle the panel toward the sinking sun, no doubt I could have eked out a bit more time on the air. All was good. I was happy, and fell asleep that night with the K2 on, expecting to wake up to the next morning to the sweet sound of the letters “BRS” singing from my K2.

Instead, I awoke to the sound of a minute or two of dits, with the occasional pause, a few meaningless dits and dahs, then another minute or so of dits. Perhaps as the sun rose higher in the sky, the situation would correct itself, I thought. It didn’t however, and at 10:30, with the sun fairly high in the sky, and more than enough light to power the beacon, it was still sending out long series’ of dits, punctuated by occasional pauses, a few dits and dahs, and then the next long series of dits. Not a BRS to be heard anywhere. This was disappointing, and not what I expected. I decided to dismantle the installation, so that I could take my time trouble-shooting inside, as opposed to at the top of a step ladder. Bringing the beacon inside, I put the solar panel in the window and – lo and behold, the beacon started up perfectly, sending out it’s BRS callsign exactly the way it was supposed to.

So – why wasn’t the micro-controller starting up properly in the morning? At this point, I did what any modern 21st century renaissance man would do, and Googled it. A few others had experienced this exact same issue, of an ATtiny not starting correctly when powered just by a solar panel with no battery. One explanation offered in a forum seemed very likely – that when the solar panel is beginning to receive light, as the voltage gets to the point that the micro-controller wakes up, a small panel still isn’t capable of supplying much current. Anything else in the circuit that draws current, such as the crystal oscillator, will cause the voltage to drop below the point at which the micro-controller can operate properly. At this point, I was using a 78L05 regulator, which was drawing ~4mA of quiescent current. It’s not a lot, but when light is low, and the panel is only supplying a few volts, that extra current draw was most likely enough to cause the voltage to sag when the oscillator kicked in. Listening to the beacon, it seemed very likely that this is what was happening. The ATtiny, in the low light, had enough current to operate, so it turned the keying pin high, at which point, the oscillator began drawing current. However, that extra current draw caused the voltage to sag below the point at which the ATtiny could operate. As a result, the ATtiny turned off, the keying pin went low, the oscillator turned off, the voltage went back up, and the whole process started over. This gave way to the transmission of a constant series of dits, instead of the beacon callsign. Unfortunately, as the sun rose higher, and the light level also rose, the ATtiny was not recovering.  What was needed was to set the BOD (Brown-Out Detection) to a voltage level such that when the voltage from the panel equals or exceeds this voltage, it is also capable of supplying enough current to the entire circuit without the voltage dropping below the BOD voltage. I reset the BOD to either 2.7V or 4.3V (I forget), from it’s previous level of 1.8V and this seemed to solve the problem. However, with the beacon in it’s new (temporary) position indoors, with the solar panel in the window, the higher BOD meant that the beacon often didn’t come on until late in the morning, due to the fact that a) it was a small panel and b) panels in windows tend to generate much less power than panels outdoors.

I wanted to make this little setup as efficient as possible before putting it back outside, so swapped out the voltage regulator for the one shown in the schematic – a 5V LP2950. This series of regulators has a much lower dropout voltage than the 78L series – between about 0.04V and 0.38V, depending on current draw. They also have much lower quiescent current, at less than 0.1mA, compared to around 4mA for the 78L series. My final version of the Boris Beacon had an LP2950, and the BOD on the ATtiny85 set to 1.8V. You can do this with the 10PU version. By contrast, he lowest BOD on the 20PU version is 2.7V. It worked like a charm! I’ve had the beacon in the shack, powered just by the small 1.8W solar panel sitting in an east-facing window. It starts running early in the morning, even on overcast days, and stays on until fairly late in the afternoon. It would run for even longer hours if the panel was mounted outside. This was a very encouraging result.

You’ll notice that the capacitor on the input side of the voltage regulator is shown as a 100uF part. Normally, I’d use something in the range of 1 – 10uF, and I did start with a 1uF cap in that position. A larger value capacitor in that place helped to smooth out the voltage swings when the light level was marginal. When the ATTiny was beginning to send a semi-random series of dits, due to the sagging voltage issue previously described, a larger value capacitor helped to mitigate that somewhat. A 330uF, 470uF or larger part could help a little more but ultimately, when the light level falls, it falls. At most, I doubt that a large cap here would buy you more than an extra few minutes of operation at the very beginning and end of the day. Another idea for experimentation would be to try a different transistor. I’m wondering if, say, a 2N2222A would provide a little more power?

At this point, I feel that the experiment is complete, and am not feeling the need to mount it outside again. It would be interesting to see if the mighty 1mW RF output could earn me any spots, but that was really not the main purpose of doing this. My primary motivation was an interest in the circuit – building it, and optimizing it. I did order another enclosure, with lugs, which would be perfect for outside mounting. Alternatively, this case could, as well as housing the circuit board, effectively act as the center part of a dipole, with the lugs acting as strain reliefs. The wire carrying the power could hang down from the center of the enclosure –

The above case was bought on eBay, from a US seller, for $4.83 including shipping. I saw what looked like the same case from a Chinese seller, for the lower price of $1.56 + $2 shipping, so bought that as well, to compare the two.  Interestingly, the cheaper one directly from China looked like exactly the same case, but of inferior quality. It looked like it had been cast from essentially the same mold, but wasn’t as nicely finished. One imperfection almost made for a bad seal with the lid.  I intend to purchase a few more of this case, for future use, but will make sure to get them from the US seller. For sealing the holes where the wires enter, a silicone sealant should be more practical than the rubbery Plastidip that I had used earlier. This stuff should do the job nicely –

Another idea for an outdoor beacon enclosure would be an electrical junction box. I found this in my local hardware store. It’s 4″ x 4″ by a little over 2″ high. It has a rubbery seal around the lid, and is certified for burial, so should certainly withstand the weather above ground. It also has 4 lugs on the outside for fixing the enclosure to a wall, fence, or post. For securing the circuit board, the adhesive standoffs pictured should work well, so that you don’t have to drill holes in the enclosure. They are available for a 5/16″ hole, and in several different lengths. The ones pictured hold the board 3/8″ away from the box, and were part # 91443A130 from McMaster Carr. Someone in one of my discussion groups, when talking about outdoor enclosures for transmitters, suggested that if you have a completely sealed box, with no ventilation, it might be an idea to add a silica gel packet or two, to prevent condensation from forming inside the enclosure. I haven’t had any issues with the completely sealed non-metallic enclosure that houses my outdoor Part 15 AM transmitter, but it’s a good idea, and definitely worthy of consideration –

This little beacon has been greeting me in the mornings for the last few days, with the letters “BRS” sent at 5wpm. I rather like the fact that it comes on every day with the light, and goes to sleep at night – the way that we all did before gas and, especially, electric lighting came on the scene.

UPDATE – The Boris Beacon is now on the air. Details here!