(Disclaimer)

I do not claim to be knowledgeable in Space Weather (forecasting).

 I consider myself a Space Weather enthusiast.

The sun shines bright in my old Kentucky home as it does over most of the earth during Solar Cycle 25. 

For several weeks now it seems no matter what region of the Sun is facing Earth, the Sun is having a hissy fit with solar flares, solar storms, CMEs and radio blackouts.  How has Solar Cycle 25 affected, if any your Amateur Radio operating?

In anticipation of Solar Cycle25, during the Pandemic shutdown I delved  into areas of Amateur Radio that I was familiar with but wanted to expand my knowledge.  One area is Space Weather and the effects the sun has on Amateur Radio operating.   

During the shutdown, I  probed the far reaches of the internet searching for any content, instructions, courses, papers, blogs, social media posts and videos for information on space weather.  I knew a little about how the sun effects radio propagation from my Amateur Radio exams over the years. One thin I did know from spending many hours in TV weather sets during my broadcasting career, that Space Weather is just as unpredictable as Terrestrial Weather. One thing I wasn't aware of,  Space Weather forecasting is basically in its infancy in comparison to Terrestrial Weather.   Especially in the area of Solar Cycles, since they come basically every 11 years.  Satellites and computer models data models have definitely aided in space weather forecasting.

My internet search turned up many people with vast knowledge in Space Weather and  Space Weather forecasting.  The person who caught my eye and provided ME with an easy understanding of Space Weather and Forecasting is "The Space Weather Woman:, Dr. Tamitha Skov. 

https://www.spaceweatherwoman.com/

https://www.facebook.com/spaceweatherwoman

https://x.com/tamithaskov

https://www.instagram.com/tamithaskov/

https://www.youtube.com/@TamithaSkov/featured

I don't have a hard fast RULE of whether I allow a Space Weather forecast determine if I am going to operate that day. Basically, I use Space Weather forecast data as a means to determine what antenna I may use, QRP or QRO rigs, what mode I may use (SSB, CW, or Data) or if I'm operating Parks on the Air, what park and what area of a park I'll operate from. I use this data just as I would a Terrestrial weather forecast that may forecast a 30% chance of rain.  Do I need to carry an umbrella

After several months of trying to determine what works for me. Here are  some of the places I visit almost daily.

National Oceanic and Atmospheric Administration  (NOAA)

Space Weather Prediction Center

https://www.swpc.noaa.gov/communities/radio-communications

https://www.facebook.com/NWSSWPC/

https://x.com/nwsswpc

Space Weather LIVE

https://www.spaceweatherlive.com/

https://www.facebook.com/SpaceWeatherLive

https://x.com/_SpaceWeather_

https://www.youtube.com/@Spaceweatherlive

Solar Ham

https://www.solarham.com/

https://www.facebook.com/SolarHam/

https://x.com/SolarHam

https://www.youtube.com/user/ve3en1

Sometimes I will check band conditions at the following sites.

https://pskreporter.info/pskmap.html

WSPR Net

I would love to hear from those who follow other sites. Leave message in comments.

I have been playing around with the weak-signal propagation mode WSPR for about a year now. Most of my WSPR initial work was in receiving and reporting Spots from WSPR transmitters. Now I wanted to do some HF antenna testing but it was in a rough RF reception environment. So instead of receiving and reporting WSPR packets, I decided to use a WSPR Transmitter and to analyze resulting Spots reported by monitoring Stations. That allows me to see how other stations are receiving my signal, as I change or modify antennas. I think using a single transmitter on my end, and many receivers is better than the alternative for me anyway. It gives me control of the most important signal factors.

Antenna Testing with WSPR

It seems like WSPR is a natural for HF antenna testing and evaluation/comparison. I have heard some say that it is NOT a good vehicle for antenna testing because of the way HF propagation changes and varies over time. It IS true that you could not perform evaluation of a single antenna over many weeks or months without considering this variable. There are some things to keep in mind when using WSPR for testing of antennas:

1. HF Propagation changes, so you must run tests over relatively short periods of time and watch for significant events (like Solar Storms) that could change signal propagation on a Band or Bands.
2. Remember that you do NOT know what is on the receiving end of the link, unless you coordinate with the receiving Station. But there are many stations that are monitoring consistently with fixed antenna configurations.
3. If running tests over several days, test at the same time of day or as close as possible for each run.
4. For best results, find some Stations that appear to always be monitoring, and seem to be able to pickup your signals on a daily basis. There are may out there.
5. If you are using a particular Receive Station and you want to make sure they are using a consistent antenna on some Band, just ask them. Most people using WSPR would be thrilled to hear that you are using their WSPR reports to improve your Station/antennas

Selecting a WSPR Transmitter

You can use most modern HF radios with WSJT-X software as your WSPR transmitter. There are some drawbacks. Many HF Transceivers only go down to 5 watts. While this is acceptable, it is overkill. Most testing on WSPR is done with 10s or hundreds of milliwatts. If you do not use GPS for timing, some other means of time synchronization will be required. For my field testing, I selected a nice portable WSPR Transmitter from Zachtek. There are many transmitters out there to choose from. The one I am using can be found here. A picture is provided below. Help is also readily available on the Zachtek forum, if you run into any trouble.

This unit uses just 5V DC which you can provide from any USB charger. It does REQUIRE GPS and an antenna is provided. GPS is used for both timing ad location calculation, so it is not optional. I have found that placing the included GPS antenna on a ground plane (mine is about 10 X 10 inches) gives me adequate signal, even inside my house with metal-backed roof insulation. The Zachtek Desktop unit can transmit on any HF Band or a combination of Bands. For my current testing, I transmit on 15, 20, and 80 meters during each 10 minute time period.

Observing WSPR reports for your Transmissions

All stations that receive WSPR packets can report their signal reports to a universal database. You can find this database online and have permanent access to all WSPR Spots ever reported. There is also an incredible WSPR front-end by VK7JJ which can be found at WSPR.ROCKS This provides an interface for extracting and sorting of WSPR Spots from the universal database. Here is a screenshot of my WSPR reports after a few hours. I was using 200 mW from the Zachtek Transmitter and the antenna was an 80 meter broadband dipole. Here is a screenshot of the map vies for my transmissions at the WSPR.Rocks Site:

Table-oriented lists are also available at WSPR.ROCKS and they can be easily imported into any spreadsheet or data analysis software.

Initial Results

When I start a WSPR session, I am always shocked at the locations where my low-power WSPR transmissions are being received. This transmitter is well designed for protection even from poorly-matched antennas. Antenna tuners are not really needed unless there is some terribly high-SWR case that is being used.

I have now found several WSPR monitoring stations that can receive my signals on a daily basis. I am just in the process of creating some test scenarios for evaluation. If you like working with HF antennas and you aren’t using WSPR, why not? It takes little of no investment if you already have HF radio equipment. If you give this a try, please let me know how it works out for you. There is much to be learned here!

73,

Tom, KG3V

WITH

using

James Watt

As some of you know I do some QRPp Parks on the Air activations using the QRP Labs QCX Mini. For the past couple of years I've had GREAT results using my 40 and 20 meter QCX Mini with what I call, "My Smoke Detector Battery" setup

QRP Labs QCXX Mini 20 Meters

 

A few days later on May 1, 2024; I decided to give it another try but this time on 40 meters when conditions were not quite optimal. And again, I was amazed with the number of stations picking up my signal with "My Smoke Detector Battery"

QRP Labs QCX Mini 40 Meters

As most of you may know, during the month of June 2024, the sun has presented several Earth facing regions which have been quite active with solar storms, solar flares, large sunspot regions, CME's and HF radio blackouts. These conditions have not been favorable for QRPp communications. Living in Kentucky, USA this time of year also represents days and weeks of hot, humid weather with potential for almost daily thunderstorms. So far in June 2024; we've seen record low morning temperatures of 82 degrees and several days of temperatures exceeding 95 degrees with heat indices well over 100 degrees.

Finally the Solar Space Weather forecast for the first few days of July 2024 looked like an excellent opportunity to try some Parks on the Air CW activations using QRPp. However, terrestrial weather was another issue. Heat advisories were forecasted for the last few days of June 2024 and first few days of July 2024.  It was time to take advantage of this brief window to do some QRPp operating.

QRPp Equipment Set Up

The antenna I was going to use was the Tufteln 40 / 20 Linked EFHW. I made this antenna specifically for my QRP Labs 40 & 20 Meter QCX Minis.

Tufteln 40 / 20 Meter Linked EFHW

As for a keyer, I was going to use the American Morse Equipment Ultra Porta Paddle. 

American Morse Equipment Ultra Porta Paddle

Upon awaking before daybreak, I checked the NOAA Space Weather Predication Center's website for Space Weather conditions. It all looked favorable. Terrestrial weather had a Heat Advisory forecasted for July 2, 2024, so I decided to head out for a near sunrise Parks on the Air activation at Beargrass Creek State Nature Preserve US-7956 which is less than 4 miles from my QTH.

Not knowing who would be hunting at 1130 UTC, I arrived on site; throw up my arborist line about 45 feet into a tree and pulled up my antenna in a sloper configuration, set up my 40 meter QCX Mini and was ready to go.

At 1142 I started sending CQ and 'BEHOLD" within a minute or two the hunters responded top my calls and kept me busy for the next 50 minutes. Below are the results of what a QRPp CW Parks on the Air activation yielded me.

The highlight of this day's activation was a QSO with Greg / VE3GSS  Port Carling, ON, Canada. A little over 920 km from my Kentucky POTA site with less than 1 WATT.

At 1235 UTC the temperature had risen to 84 degrees. It made no sense in pushing it as I had already achieved more than I expected. To say I walked away with a HUGE grin on my face is an understatement. It was a GREAT Parks on the Air activation.

                                                         

On July 3, 2024 my internal clock woke me at 0900 UTC with basically the same Space and Terrestrial conditions that were in play as the day before.  So why not make this "Ground Hog Day in July.  Same time, same set up on July 3, 2024. One difference; today I would try 20 meters.

Within less than a minute after my CQ on 40 meters at 1143 UTC, my activation began with hunters eagerly wanting to be acknowledged.  I didn't disappoint and neither did they.  QSOs were rapid fire for almost an hour.

 At 1240, I switched over to my 20 meter QCX Mini to see what I could garner, knowing that at time time of morning in the U.S., the likelihood of getting any action on 20 meters was suspect.   I did manage one 20 meter QSO.  Here was my catch for a July "Ground Hog Day"

  

The highlight of this day was as try for a Park-to-Park QSO with a station in Japan. I tirelessly tried for several minutes to make a 40 meter contact with a Parks on the Air station JJVAS at JP- 0128. The QSB was pronounced and the strongest I could get was a 229.  The operator was kind enough to send AGN? a few times but I was just trilled for that reply with less than 1 WATT.

This day like many others brought greetings from people who have become familiar with my operations as they get in their daily walks, runs and cycling before the heat sets in.  Today though I met Dr. Tamekka Cornelius, Ph. D, who was out on her daily walk. She, like others are inquisitive about seeing a man sitting in a mostly open field connected to some wires, a bicycle close by and some weird equipment strapped to his legs.   Dr. Cornelius and I had a nice chat about Amateur Radio, brief history of my broadcast career and my bicycling activities.

 

Operating QRPp reminds me of the country music singer Kenny Rogers' song: 

"The Gambler"

You've got to know when to hold 'em

Know when to fold 'em

Know when to walk away

And know when to run

Once in your ham radio journey, try operating QRPp.

You might be surprised with YOUR results.

73

Jim

"Ham on a Bike"

]

 

    

Thank you to Ihar Yatsevich for writing in and sharing with us his open-source WSPR beacon project. The WSPR beacon consists of a custom PCB with ATMega328 microcontroller, GPS module, single transistor amplifier, and Si5351 with TCXO.

The result is a very simple, portable WSPR beacon that can be heard all over the world. However, it appears that no band filters are built into this, so you will need to add a bandpass filter for the WSPR band that you are using.

WSPR (Weak Signal Propagation Reporter) (pronounced "whisper") is an amateur radio digital HF mode designed to be decodable even if the signal is received with very low power. Because of this design, even low-power transmitters can be received from all over the world. It can also be used to help determine HF radio propagation conditions as WSPR reception reports are typically automatically uploaded to wsprnet.

If you are interested, Ihar has written about his project in more detail over on Reddit. 

So much for playing radio this weekend. In the last half hour my 200mW Zachtek WSPR transmitter, cycling from 80M to 10M every 15 minutes or so, managed to be heard in 2 places… Both in Boston and presumably by ground wave.

By comparison, here is a half hour block from a good propagation day:

Simply amazing! Enjoy the Aurora!

KM1NDY

Doing a little hammy ham ham research during the solar eclipse at the Ole Farm-O-La…Welcome to the first Technical Bulletin of the KM1NDY – Secret Amateur Radio Journal.

As we are now at the peak of the solar cycle, some radio amateurs are using WSPR on the 28 MHz band for their Pico-Balloons as they travel around the world.

Back in April of 2024, I had a post about reception of the KD9NGV pico-balloon as it made its way off the west coast of Ireland to the North Sea. See post HERE

I often see these pico-balloon on my receive list for 28 MHz WSPR but they're nearly all somewhere far away and the propagation mode is via the ionosphere. What I find interesting about the rare really close passes is that there is no propagation mode as such, the balloon is essentially line of sight to my location.

KJ7VBX-11... On the 8th of May 2024, I noticed that I was hearing the KJ7VBX-11 pico-balloon early in the morning just as it had woken up with the sun shining on it's solar panels. I was able to hear it pretty much all day from 07:40 UTC until 18:20 UTC.

During this time, it travelled from a spot off the west coast of Ireland, over the northern counties of Donegal, Derry and Antrim in Ireland, over the south-west of Scotland and then over Cumbria in England before falling silent for the night.

On the 9th of May, it woke up over the English Channel and then headed over the Netherlands.

The balloon is at an altitude of about 13,500 metres or 44,000 feet. The WSPR transmitter is supposed to be 20-milliwatts. As far as I know, it was launched on the 2nd of May 2024 but there seems to be very little information about it.

Format... Early on the morning of the 8th, I was the only person reporting it and it was the only signal I was hearing so I was able to do some tests without any confusion from other signals.

The WSPR transmitter on the balloon seems to have two formats. The first one is shown above. The transmitter turns on as a plain carrier for 30-seconds and then sends one WSPR transmission. I presume this carrier is to warm up the transmitter which is at or below 0 deg C and the 30 second carrier stops any drifting of the following WSPR signal.

The second format is shown below...

This time, there is a second WSPR transmission after the first one.

This is a sample of the decodes that I got in the space of about an hour...

The short format results in just a KJ7VBX decode.

The longer format results in an additional decode which are shown above in red.

At first sight, they look wrong. The callsign, locator and power levels seem to be nonsense. However note that the callsign field starts with a zero. This is a special data WSPR signal and contains the information about the location, altitude, temperature and battery voltage. It's just the WSJT-X receive software shows it in a format that doesn't seem to make any sense.

In conclusion... The balloon is currently heading over Europe so it's going to be line of sight to a lot of stations. Just listen on WSPR on 28 MHz and see if you can hear it.

On the 28th of November 2023, Perri Moore KD9NGV launched a Pico-Balloon from Illinois in the United States with a solar powered payload that transmits a WSPR beacon on 28.1246 MHz.

Most of the Pico-Balloons launched from the USA tend to take a path closer to about 30 degrees north of the equator and cross areas like the north of Africa and south Asia. In contrast,  the KD9NGV balloon seems to have covered a much wider area and has been reported at more northerly latitudes as shown on the map above.

By the 16th of December 2023, it had gone around the world once! By the 19th of February, it had gone around the world three times. By mid April 2024, it has gone around the globe multiple times and the red dots on the map show where it was when I received some of the WSPR signals over the last few weeks.

It then went silent as darkness fell. Once daylight broke again on the 8th of April, it was over the North Sea and GM4WJA started to report it.

At the time of the screen grab, LA3FY/2 in Norway was hearing it and it continued then over Scandinavia. It has since crossed over Russia and at the time of writing is up over the far north of Canada.

KD9NGV Payload... The actual payload pre-launch is shown below.

The 28 MHz WSPR signal is generated by a Si5351 clock generator and the power output is just 9 milliwatts... 0.009 watts!

The antenna is a vertical half-wave dipole made of #36 enamelled wire.  The top half is from the balloon to the U4B tracker (QRP Labs) and the lower half hangs below the tracker.  Three Powerfilm MPT 3.6-75  in a vertical triangle provide the power.  The complete payload weighs 12 grams.

The balloon is described as a "silver SAG Balloon with Helium.".

In conclusion... I have noticed these WSPR pico-balloons many times on the 28 MHz band before but they are nearly always flying over some exotic location. It was just unusual to have one pass so close and be line of sight.

I don’t need to explain the attraction of low power operation; if you’re reading this, the chances are that you are already a convert. I’ve been operating with low power ever since first being licensed in the UK in the late 70’s as G8RYQ, and then G4IFA. One of my first rigs was a homebrew VFO-controlled FM rig for 2M. I don’t remember how much power it put out, but it was at most only a few watts. Then there was an 80M DSB rig, built from a kit, that put out a watt or two. I had a series of 2M FM rigs, including an Icom IC-22A and a Trio TR2200 (1 watt out). I had a hand-rotated 5 element 2 meter beam. To change the beam heading, I leaned out of my bedroom window and twisted the aluminum pole that was supporting it. One of the PA transistors in my Icom IC-22A was blown, so the rig only put out 4 or 5W. I remember using that rig and the beam to talk regularly on simplex with a fellow young ham who was in Wales, 90-100 miles away. I think I used the TR2200 to talk with him as well, which was even more impressive, as the Trio only put out 1 watt of RF power.

My checkered amateur radio life did include one 100W rig. It was a TS520 that I owned for a couple of years in the early 1990’s. Other than that though, every rig I have ever built or owned has been 5 watts or less. After a while doing QRP, 5 watts becomes the norm. 5W is known as “the full QRP gallon”, and it does feel like it! I still run 5W as my default most of the time, on both CW and SSB. Recently though, I’ve been turning the power down, to see how lower power levels get out. A fun moment recently, was when I clearly heard the backwave from my little two-transistor transmitter on the KPH SDR, which is 41 miles away as the crow flies. That backwave was about 1mW, and being able to hear it on a remote receiver was something of a revelation. It was that moment that kickstarted my interest in even lower power levels than the mighty force of the full QRP 5 watts.

Once a day, I check into The Noontime Net on 7284KHz. It is virtually the only time I use SSB. They welcome check-ins from QRP stations. Once a year, they have a QRP day, when operators are encouraged (though not required) to check-in using QRP power levels. There is an honorable mention on their website for the station who checks in using the least power and this year, I took the prize for checking in with 10mW of SSB. The check-in was with Don KY7X in Wellington, NV. The distance between us is 168.5 miles as the crow flies. At an equivalent distance of 16,850 miles per watt, I think that would easily qualify for the QRPARCI 1,000 miles per watt award. Given that most members who apply for that award have achieved it with CW, I think that a QSO of 168.5 miles with 10mW of SSB is even more inspiring.

The lowest power I can turn my Elecraft K2 down to on SSB is 1 watt. I achieved the power of 10mW out by connecting an inline attenuator with a fixed attenuation level of 20dB in the antenna lead. It is one of those “barrel” attenuators, with a BNC connector on each end. With the success of a check-in with 10mW under my belt, I resolved to try for even lower power in next year’s QRP Day. This led me to a nifty little kit offered by QRP Guys. It is an inline attenuator, with switchable levels of attenuation of 10, 20, and 30dB. Also included is a bypass switch that allows the operator to easily switch the attenuator out of circuit when on receive. For $25 + shipping, it was the obvious solution to my QRPp needs. I was very close to pulling the trigger, when my “QRPp extreme sports” gene kicked in, and I thought it could be useful to be able to attenuate a signal by an extra 10dB, for a total of 40dB attenuation. This would reduce the 1 watt of SSB from my K2 down to the truly flea power level of 100µW, and the 100mW CW output to the mind-bogglingly low level of just 10µW! Granted, this extra 10dB of attenuation may never be needed, but if and when I succeed in making a QSO with 30dB of attenuation in the antenna line, I may always wonder if it could also have been made with an extra 10dB. It’s the desire to constantly push our achievements just that little bit further.

With that in mind, I decided to build my own attenuator box. There is no circuit design involved really, as it is simply a series of 50 ohm pi-attenuator pads and a few DPDT switches. I took the circuit from the QRP Guys’ attenuator and added an extra pi-section and switch –

All resistors are metal film 3W types. The 100 ohms ones are 1%, while the other values were 5%. If you can get 1% tolerance for all values, then all the better. If you want to calculate resistor values for any other degree of attenuation, you can use this online calculator.

There’s not much to the build. The diecast enclosure, switches, and BNC connectors all came from Tayda. I am not thrilled with the quality of the connectors and switches from Tayda. The terminals were hard to solder to, presumably due to the use of a cheaper alloy than the quality brands such as Kobiconn and Switchcraft use. Nevetheless, I persevered, and managed to obtain a reasonably satisfactory result.

The bypass/attenuate switch is useful when going from transmit back to receive, for ensuring that your reception is not also attenuated.

Daytime band conditions weren’t too good on first finishing this attenuator, though I did manage to just be heard by Don KY7X, 168.5 miles away, with an output power of 10mW SSB, using 20dB of attenuation from an original 1W signal. I’m not sure if it would have been enough for a positive ID of my signal if he didn’t already know who I was. Nevertheless, band conditions were poor that day, so this was a good sign. I decided to hook it up to my VK3HN WSPR beacon (thanks Paul), which puts out 200mW. I applied 30dB of attenuation, for a 200µW WSPR signal – that’s just 0.2mW! Incidentally, to figure out the various attenuation levels, and what output power they give you, there are several online calculators. I found this one to be useful.

Unfortunately, the lowest power level that can be encoded into a WSPR signal is 0dBM, equivalent to 1mW. I’m not keen on misrepresenting the power level, but as I was so eager to see what a mighty 200µW of WSPR could snag me, and as I considered a power level of 20mW (10dB of attenuation of the 200mW signal) to be too high, I decided to WSPR for the night on 40M, and encode the signal at 0dBm. Check out the following results from a night of WSPR’ing. There were 486 spots in total. This is not a lot by normal standards but a good result, I think, for such a low power signal. In this screen grab, they are sorted in order of distance, so these are the most remote spots. AI6VN/KH6 in Maui tops the list, for a distance of 3778km = 2347 miles. That’s 11.735 million miles per watt! In a normal night of WSPRing on 40M with the relatively high power of 200mW, I would expect multiple spots from Hawaii, VK and ZL land, as well as a spot or two from DP0GVN in Antarctica. However, 0.2 mW is a whole new ballgame, and I was very happy to get just one spot from HI –

Here’s the attenuator sitting on my desk, on top of the VK3HN WSPR beacon. It would be nice to have a tidy desk and a nice, clean operating position but every time I tidy it, it slowly gets like this again (the 3rd law of thermodynamics in action!) At the bottom of the stack is the Sproutie SPT Part 15 Beacon, which is currently not QRV. DK, if you’re reading this, you may notice something familiar at the very bottom of this picture –

I want to be able to WSPR on a more regular basis, and have the encoded power information on my transmissions actually be fairly accurate, so the next step was to build an attenuator with a fixed attenuation level of 23dB, to reduce the output of the WSPR transmitter to 1mW. This way, when a spot from me shows up with a power level of 0 dBm, it actually is 0 dBm. This online pi-attenuator calculator was pressed into service, and yielded the following values. If you don’t have a 12 ohm resistor, then a single 330 ohm part will be close enough –

As this attenuator will only be used to attenuate the 200mW output of the WSPR beacon, I used 1/4 W resistors. The two 56 ohm resistors were left over from a cheap resistor kit that I bought years ago. They had short, thin leads, and were ostensibly 1/4W parts. The left-hand one (the one closest to the transmitter) dissipates the most amount of power, and was getting very warm during 2 minute transmissions from the 200mW transmitter. I do think it was sustainable, but would have preferred it to run cooler. I didn’t have any 1/2W or bigger resistors in appropriate values, so decided to parallel 2 x 1/4W parts. There are plenty of fresh sheets of white paper here, but drawing schematics on envelopes is more fun. A 100 ohm and 150 ohm resistor in parallel makes 60 ohms. Using 352 ohms as the “top” resistor (achieved with a 330 and a 22 ohm resistor in series) makes for an attenuation level of 22.7dB, which is pretty dang close –

The two resistors on the left-hand side run much cooler than the single 56 ohm did. The 56 ohm one was a cheapie resistor, and I suspect it’s stated power dissipation of 1/4W was being a bit optimistic. All the resistors in the final attenuator are 1/4W metal film types. The project box came in a pack of 5 from Amazon, for $7.50. I have used the same ones recently to build QRP baluns and ununs. There are all sorts of fun and novelty projects they would be useful for. The lid snaps on. I can supply the link to anyone who is interested –

The increase in power from 200µW was noticeable after the first night of WSPR’ing on 40M with 1mW. Here is a screen grab of the most distant spots received. In just under 10 hours, I had 1114 spots. It’s a lot fewer spots than what I would receive with 200mW, but that many spots with just 1mW sounds very encouraging. I love this little WSPR beacon (thanks to Paul VK3HN once again). Out of 1114 spots, all of the drift figures were a big honking zero, with the exception of a single 1 and a single -1. Instead of the single spot from AI6VN’s remote listening station in Maui, I now had 7. Sure, propagation on different nights could be some of it, but I’m pretty sure the 7dB power increase from 200µW to a gigantic 1 milliwatt was a significant factor.

This QRPp experiment has been a huge success so far, and I haven’t even begun to work on the goal that I had in mind when beginning this. That was to use the switched step attenuator to see how far I can go with very low power on CW, my mode of choice. WSPR is very instructive and interesting, but an actual QSO, even a brief one, carries the extra appeal of contact with a distant person, with all the unpredictable intangibles that come along with that. I do wish there was a way of encoding lower powers than 0 dBm (1mW) into a WSPR transmission, as I would then be WSPR’ing with successively lower powers. I’ve already received a significant number of spots with 200µW of transmitted power. It would be great to see what could be done with, say, just 10µW (0.01mW), if anything. In the meantime though, there will be a lot of 1mW WSPR’ing emanating from the AA7EE radio ranch, as well as some extreme QRPp CW too, with the help of the switchable step attenuator.

It should not have escaped your attention - at least if you live in North America - there there have been/will be two significant solar eclipses occurring in recent/near times:  One that occurred on October 14, 2023 and another eclipse that will happen during April, 2024.  The path of "totality" of the October eclipse happened to pass through Utah (where I live) so it is no surprise that I went out of my way to see it - just as I did back in 2012:  You can read my blog entry about that here.

Figure 1: The eclipse in progress - a few minutes before "annularity". (Photo by C. L. Turner)

The October eclipse was of the "annular" type meaning that the moon is near-ish apogee meaning that the subtended angle of its disk is insufficient to completely block the sun owing to the moon's greater-than-average distance from Earth:  Unlike a solar eclipse, there is no time during the eclipse where it is safe to look at the sun/moon directly, without eye protection.

The sun will be mostly blocked, however, meaning that those in the path of "totality" experienced a rather eerie local twilight with shadows casting images of the solar disk:  Around the periphery of the moon it was be possible to make out the outline of lunar mountains - and those unfortunate to stare at the sun during this time will receive a ring-shaped burn to their retina.

From the aspect of a radio amateur, however, the effects of a total and annular solar eclipse are largely identical:  The diminution of the "D" layer and partial recombination of the "F" layers of the ionosphere causing what are essentially nighttime propagation conditions during the daytime - geographically limited to those areas under the lunar shadow.

In an effort to help study these sort of effects - and to (hopefully) better-understand the propagation effects, a number of amateurs went (and are) going out into the field - in or near the path of "totality" - and setting up simultaneous, multi-band transmitters.

Producing usable data

Having "Eclipse QSO Parties" where amateur radio operators make contacts during the eclipse likely goes back nearly a century - the rarity of a solar eclipse making the event even more enigmatic.  In more recent years amateurs have been involved in "citizen science" where they make observations by monitoring signals - or facilitate the making of observations by transmitting them - and this happened during the October eclipse and should also happen during the April event as well.

While doing this sort of thing is just plain "fun", a subset of this group is of the metrological sort (that's "metrology", no "meteorology"!) and endeavor to impart on their transmissions - and observations of received signals - additional constraints that are intended to make this data useful in a scientific sense - specifically:

• Stable transmit frequencies.  During the event, the perturbations of the ionosphere will impart on propagated signals Doppler shift and spread:  Being able to measure this with accuracy and precision (which are NOT the same thing!) adds another layer of extractable information to the observations.
  

• Stable receivers.  As with the transmitters, having a stable receiver is imperative to allow accurate measurement of the Doppler shift and spread.  Additionally, being able to monitor the amplitude of a received signal can provide clues as to the nature of the changing conditions.
  

• Monitoring/transmitting at multiple frequencies.  As the ionospheric conditions change, its effects at different frequencies also changes.  In general, the loss of ionization (caused by darkness) reduces propagation at higher frequencies (e.g. >10 MHz) and with lessened "D" layer absorption lower frequencies (<10 MHz) the propagation at those frequencies is enhanced.  With the different effects at different frequencies, being able to simultaneously monitor multiple signals across the HF spectrum can provide additional insight as to the effects.
  

To this end, the transmission and monitoring of signals by this informal group have established the following:

• GPS-referenced transmitters.  The transmitters will be "locked" to GPS-referenced oscillators or atomic standards to keep the transmitted frequencies both stable, accurate - and known to within milliHertz.
  

• GPS referenced receivers.  As with the transmitters, the receivers will also be GPS-referenced or atomic-referenced to provide milliHertz accuracy and stability.

With this level of accuracy and precision the frequency uncertainties related to the receiver and transmitter can be removed from the Doppler data.  For generation of stable frequencies, a "GPS Disciplined Oscillator" is often used - but very good Rubidium-based references are also available, although unlike a GPS-based reference, the time-of-day cannot be obtained from them.

Why this is important:

Not to demean previous efforts in monitoring propagation - including that which occurs during an eclipse - but unless appropriate measures are taken, their contribution to "real" scientific analysis can be unwittingly diminished.  Here are a few points to consider:

• Receiver frequency stability.  One aspect of propagation on HF is that the signal paths between the receiver and transmitter change as the ionosphere itself changes.  These changes can be on the order of Hertz in some cases, but these changes are often measured in 10s of milliHertz.  Very few receivers have that sort of stability and the drift of such a receiver can make detection of these Doppler shifts impossible.
  

• Signal amplitude measurement.  HF signals change in amplitude constantly - and this can tell us something about the path.  Pretty much all modern receivers have some form of AGC (Automatic Gain Control) whose job it is to make sure that the speaker output is constant.  If you are trying to infer signal strength, however, making a recording with AGC active renders meaningful measurements of signal strength pretty much impossible.  Not often considered is the fact that such changes in propagation also affect the background noise - which is also important to be able to measure - and this, too, is impossible with AGC active.
  

• Time-stamping recordings.  Knowing when a recording starts and stops with precision allows correlation with other's efforts.  Fortunately this is likely the easiest aspect to manage as a computer with an accurate clock can automatically do so (provided that one takes care to preserve the time stamps of the file, or has file names that contain such information) - and it is particularly easy if one happens to be recording a time station like WWV, WWVH, WWVB or CHU.

In other words, the act of "holding a microphone up to a speaker" or simply recording the output of a receiver to a .wav file with little/no additional context makes for a curious keepsake, but it makes the challenge of gleaning useful data from it more difficult.

One of our challenges as "citizen scientists" is to make the data as useful as possible to us and others - and this task has been made far easier with inexpensive and very good hardware than it ever has been - provided we take care to do so.  What follows in this article - and subsequent parts - are my reflections on some possible ways to do this:  These are certainly not the only ways - or even the best ways - and even those considerations will change over time as more/different resources and gear become available to the average citizen scientist. 

* * *

How this is done - Receiver:

The frequency stability and accuracy of MOST amateur transceivers is nowhere near good enough to provide usable observations of Doppler shift on such signals - even if the transceiver is equipped with a TCXO or other high-stability oscillator:  Of the few radios that can do this "out of the box" are some of the Flex transceivers equipped with a GPS disciplined oscillator.

To a certain degree, an out-of-the-box KiwiSDR can do this if properly set-up:  With a good, reliable GPS signals and when placed within a temperature-stable environment (e.g. temperature change of 1 degree C or so during the time of the observation) they can be stable enough to provide useful data - but there is no guarantee of such.

To remove such uncertainty a GPS-based frequency reference is often applied to the KiwiSDR - often in the form of the Leo Bodnar GPS reference, producing a frequency of precisely 66.660 MHz.  This combination produces both stable and accurate results.  Unfortunately, if you don't already have a KiwiSDR, you probably aren't going to get one as the original version was discontinued in 2022:  A "KiwiSDR 2" is in the works, but there' no guarantee that it will make it into production, let alone be available in time for the April, 2024 eclipse. 

Figure 2: The RX-888 (Mk2) - a simple and relatively inexpensive box that is capable of "inhaling" all of HF at once. Click on the image for a larger version.

The RX-888 (Mk2)

A suitable work-around has been found to be the RX-888 (Mk2) - a simple direct-sampling SDR - available for about $160 shipped (if you look around).  This device has the capability of accepting an external 27 MHz clock (if you add an external cable/connector to the internal U.FL connector provided for this purpose) in which it can become as stable and accurate as the external reference.

This SDR - unlike the KiwiSDR, the Red Pitaya and others - has no onboard processing capability as it is simply an analog-to-digital coupled with a USB3 interface so it takes a fairly powerful computer and special processing software to be able to handle a full-spectrum acquisition of HF frequencies.

Software that is particularly well-suited to this task is KA9Q-Radio (link).  Using the "overlap and save" technique, it is extraordinarily efficient in processing the 65 Megasamples-per-second of data needed to "inhale" the entire HF spectrum.  This software is efficient enough that a modest quad-core Intel i5 or i7 is more than up to the task - and such PCs can be had for well under $200 on the used market.

KA9Q-Radio can produce hundreds of simultaneous virtual receivers of arbitrary modes and bandwidths which means that one such virtual receiver can be produced for each WSPR frequency band:  Similar virtual receivers could be established for FT-8, FT-4, WWV/H and CHU frequencies.  The outputs of these receivers - which could be a simple, single-channel stream or a pair of audio in I/Q configuration - can be recorded for later analysis and/or sent to another program (such as the WSJT-X suite) for analysis.

Additionally, using the WSPRDaemon software, the multi-frequency capability of KA9Q-Radio can be further-leveraged to produce not only decodes of WSPR and FST4W data, but also make rotating, archival I/Q recordings around the WSPR frequency segments - or any other frequency segments (such as WWV, CHU, Mediumwave or Shortwave broadcast, etc.) that you wish.

Comment:  I have written about the RX-888 in previous blog posts:

• Improving the thermal management of the RX-888 (Mk 2) - link 
• Measuring signal dynamics of the RX-888 (Mk 2) - link
  

Full-Spectrum recording

Yet another capability possible with the RX-888 (Mk2) is the ability to make a "full spectrum" recording - that is, write the full sample rate (typically 64.8 Msps) to a storage device.  The result are files of about 7.7 gigabytes per minute of recording that contain everything that was received by the RX-888, with the same frequency accuracy and precision as the GPS reference used to clock the sample rate of the '888.  

What this means is that there is the potential that these recordings can be analyzed later to further divine aspects of the propagation changes that occurred during, before and after the eclipse - especially by observing signals or aspects of the RF environment itself that one may not have initially thought to consider:  This also can allow the monitoring of the overall background noise across the HF spectrum to see what changes during the eclipse, potentially filling in details that might have been missed on the narrowband recordings.

Because such a recording contains the recordings of time stations (WWV, WWVH, CHU and even WWVB) it may be possible to divine changes in propagation delay between those transmit sites and the receive sites.  If a similar GPS-based signal is injected locally, this, too, can form another data point - not only for the purposes of comparison of off-air signals, but also to help synchronize and validate the recording itself.

By observing such a local signal it would be possible to time the recording to within a few 10s of nanoseconds of GPS time - and it would also be practical to determine if the recording itself was "damaged" in some way (e.g. missed samples from the receiver):  Even if a recording is "flawed" in some way, knowing the precise location an duration of the missing data allows this to be taken into account and to a large extent, permit the data "around" it to still be useful.

Actually doing it:

Up to this point there has been a lot of "it's possible to" and "we have the capability of" mentioned - but pretty much everything mentioned so far was used during the October, 2023 eclipse.  To a degree, this eclipse is considered to be a rehearsal for the April 2024 event in that we would be using the same techniques - refined, of course, based on our experiences.

While this blog will mostly refer to my efforts (because I was there!) there were a number of similarly-equipped parties out in the fields and at home/fixed stations transmitting and receiving and it is the cumulative effort - and especially the discussions of what worked and what did not - that will be valuable in preparation for the April event.  Not to be overlooked, this also gives us valuable experience with propagation monitoring overall - an ongoing effort using WSPRDaemon - where we have been looking for/using other hardware/software to augment/improve our capabilities.

In Part 2 I'll talk about the receive hardware and techniques in more detail.

Stolen from ka7oei.blogspot.com

[END]

Bartgeier: mit bis zu 2.9m Flügelspannweite der grösste Vogel, denn man hier in den Alpen beobachten kann.

FT-8 ist heutzutage die dominierende Betriebsart im Amateurfunk. Sie hat SSB und CW zu einem grossen Teil verdrängt. Das geht so weit, dass man glaubt, dass die Ausbreitungsbedingungen miserabel sind, weil auf dem Band nichts zu hören ist. Bis man dann auf den FT-8 Kanal stößt: fröhlich zwitschern die FT-8 Signale um die Wette. Ganz besonders ist mir das bei der diesjährigen Es-Saison aufgefallen. Ohne FT-8 hätte ich oft gar nicht bemerkt, das das 6m Band offen ist. Beim neuen 4m Band war es noch ausgeprägter. Ich kann mir nicht vorstellen, wie ich in SSB oder CW innert der wenigen Stunden, die ich QRV war, 23 Länder hätte erreichen können. Und das nur mit einem auf den Dachbalken genagelten Drahtdipol und 20W. FT-8 ist für den Sporadic-E Funker ein Segen.

Aber auch auf KW hat sich die DX-Landschaft dank Joe Taylor dramatisch verändert. Wenn nicht gerade ein Contest läuft, findet man wieder Platz, um ein längeres Gespräch in SSB zu führen oder zu telegrafieren.  

Für FT-8 braucht es keinen guten Standort mit Platz für grosse Alugebilde und lange Drähte. Die teure Kilowatt Endstufe kann man sich auch abschminken. FT-8 ist eine QRP-Betriebsart. Sprachkenntnisse braucht es auch keine und man läuft nicht die Gefahr von Bandpolizisten und Besserwissern dumm angemacht zu werden.

Aber es gibt eine Betriebsart, die noch besser ist und weitere zusätzliche Vorteile bietet. Sie heisst WSPR und ist im Digitalpaket von WSJT-X enthalten. WSPR, gesprochen "Whisper" (Flüstern) ist nochmals effizienter als FT-8 - d.h. etwa 10 mal empfindlicher. Man braucht noch weniger Leistung und Antennenpower um ferne Stationen zu erreichen. Zudem sind viele der Stationen, mit denen man eine Verbindung herstellen kann, rund um die Uhr QRV. Auch braucht man während dem "QSO" nicht unbedingt an der Station zu sitzen. Der Computer macht seinen Job auch ohne Funker. Ja, ich weiss: Um eine unbediente Station zu betreiben, braucht es ein Bewilligung. Der Funker muss vor dem Sender sitzen und diesen kontrollieren können. Doch wie bei vielen Dingen im Leben gilt auch hier das Rumpelstilzchen-Prinzip: "Ach wie gut, dass niemand weiss, dass ich Rumpelstilzchen heiss." 

WSPR ist die ideale Betriebsart für den introvertierten Funkamateur. Dieser braucht sich nämlich nicht mit Stationen herum zuschlagen, die ihm auf seine Aussendungen antworten. Die Antworten treffen nämlich alle automatisch ein: über den heimischen Computer. Man kriegt auch nicht unverlangt diese Pappkärtchen, QSL genannt. Und trotzdem kann man sich an den vielen Verbindungen und dem DX freuen und interessante Weltkarten ausdrucken, welche diese Verbindungen dokumentieren.

Aber es macht nicht nur Spaß zu testen, wie weit man mit seiner QRP Station kommt. WSPR ist auch die ideale Betriebsart, um Antennenvergleiche anzustellen. "Ist jetzt die Magnetloop besser oder die T2FD?" Man stört dabei niemand und muss auch keine CQ-Rufe absetzen, auf die jemand antworten könnte. 

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.

With a bit of work, one can successfully feed an array of LF-HF receivers from one broadband antenna.

The post KX4O SDR Receiving Electronics appeared first on Ham Radio . Magnum Experimentum.

The recommended band hopping sequence cycles through 10 bands over a 20 minute period according to this table:

The multi-band U3S is capable of adhering to such a sequence. There are however three considerations that need to be taken into account. 

First, for frequency stability reasons, it has been recommended to start with transmission at high frequencies and move to lower frequencies, i.e. the opposite of the recommended band hopping sequence. See recommendation #5d in QRPLabs Application Note AN001. My experience with a U3S with a 25 MHz TCXO driving the Si5351A is that it makes no difference for stability if the order is reversed according to the table above. The same applies to my other U3S which has the standard crystal with the Si5351A, but enclosed inside the QRPLabs OCXO box. Despite the oven being unpowered, just the thermal shielding seems to be enough to ensure stability no matter which order the frequencies come in.

Second, the U3S needs time for GPS calibration of the frequency from time to time. Typically the calibration interval is 60 seconds. There is no time in the above sequence for that. A calibration interval can however be squeezed in in these ways:

• Skipping bands. By skipping some bands, initially or at the end. I typically transmit on the higher bands, from 17 m and up, in order to detect when there are openings. Then there is time from 00 to 12 for calibration every 20 minute. The 'frame start' in that case is 12. 
• Longer frame. If transmission on all 10 bands is desired, one can transmit every 40 or 60 minutes instead of every 20 minutes, leaving a 20 or 40 minute break. This is done by transmitting with a 'frame length' of 40 or 60 rather than 20 minutes, and with a 'frame start' of either 00, 20, or 40.