Tag Archives: WSPR

WSPR Testing During the Total Solar Eclipse

Many thanks to Keith (KY4KK) who shares the following message originally sent to his local amateur radio club:

To anyone curious about how the eclipse might impact the ionosphere and amateur radio communications, this may be of interest.

On Saturday, 4/6/24, I set up 2 WSPR transmitters in my back yard. These will hopefully operate uninterrupted through sometime Tuesday afternoon, 4/9/2024. This should provide good baseline information before and after the solar event.

NASA scientists and other professional and amateur space engineers will consolidate data from amateur operators around the world to help understand how this rare event impacts the various layers of the ionosphere.

During the partial eclipse last year, a similar test revealed that several bands showed significant propagation changes for stations along the path of the event.

Tommy Walker (NG4S) graciously provided the WSPR transmitters and one of the antennas I’m using.

The configurations I’m operating:

  • WSPR Lite Classic (20 Meter Band)
  • Frequency: 14.097077 MHz (If you tune your HF rig to as close to this frequency as you can get, you MIGHT be able to hear some of the WSPR traffic going on)
  • Callsign: KY4KK
  • Transmit Power: 20 mW (.02 Watts)
  • Antenna: Chelegance MC-750 vertical – adjusted to resonance (no tuner)
  • Grid Square: FM04be
  • Start time: 00:44 Zulu 4/7/2024

WSPR Lite Classic (40 Meter Band)

  • Frequency: 7.040142 MHz (see above)
  • Callsign: KY4KK
  • Transmit Power: 20 mW (.02 Watts)
  • Antenna: Chelegance MC-750 vertical with 40 meter coil – adjusted to resonance (no tuner)
  • Grid Square: FM04be
  • Start time: 23:10 Zulu 4/6/2024

WSPR is a one-way digital communication protocol using VERY low power (less than .2 Watt or 200 mW). I usually set the transmitters to much lower power than that (.02 Watt or 20 mW) because the weaker signal is more likely to reflect subtle changes in either the antenna or the atmospheric conditions. The sending station transmits a beacon on a specific frequency for each band. The digital package sent by the transmitter contains the callsign of the operator, grid square location and transmitted power in milliwatts. The message is sent slowly and repeated several times. Then, there is a pause and it starts again.

There are amateur receiving stations around the world that are specifically configured to look for WSPR signals. If they can hear me, they record my information and the strength of my signal (how loud it is against the background static – measured in decibels). Their receiver, connected to the internet, then adds information about their station and automatically sends all of it to a central database that is accessible to the public in real time.

Several websites are available to extract the data or view it in map format. All of the ones I use are free and do not require a login. The ones I most frequently use are listed below, but there are others. In general, use my callsign (KY4KK) as the transmitting station, leave the receive station blank and select either 20 or 40 meters.


This site will allow you to pull raw data into a spreadsheet in .csv format if you want to do data analysis.

It also shows the most distant contacts and can display a map
Specifically, I will use this to look at individual stations that recorded me several times during the day. Where was the eclipse during each of the recordings, and did my received signal significantly change?
Also, I will look for differences in how the two bands will be affected.

WSPR Rocks

I like this site for mapping my contacts.

The interface takes some getting used to, but to start, go to the search button, select the number of spots to show, the time frame (10 minutes if you want to see immediate activity only), band (20m or 40m) and TX Call (KY4KK) and click Search. Then you can click map and it will show all of the contacts the station has made in that time frame.

PSK Reporter

This is another mapping program that may have an easier interface.

Display Reception Reports

As I have mentioned to some of you before, I am continuously amazed at how far WSPR transmissions can go with such low power. There has to be magic involved…

Final Disclaimer: When doing a test like this over several days, a lot of things can go wrong. Batteries die in the middle of the night, a dove crashes into my antenna, the dog runs away with one of my antenna radials (all of these have happened). If I see something has interrupted the transmission, I will try to correct it as soon as possible.

Best Regards,

Keith Wyrick – Amateur HAM Scientist

From idea to kit: Adam introduces the Arduino Digital Modes HF QRP Transceiver (ADX-S) kit

Many thanks to Adam (BD6CR) who shares the following guest post about his latest project:

From Open Source Project ADX to Kit ADX-S

by Adam (BD6CR)


Original Design: WB2CBA

Modification and Kitting: BD6CR

I knew Barb, WB2CBA from his uSDX design a few years ago and I introduced both DL2MAN and his designs in my blog. So, when I came across the ADX – Arduino Digital Xcvr a few months ago, I immediately ordered both the ADX (through hole) and the ADX UNO (surface mount) PCB samples.

I started building the ADX UNO and put it in a dental floss case and made a few contacts on park bench. However, the soldering is too much for my eyesight. So, I turned back to the ADX because I don’t need to solder any SMD parts, since both the M328P and SI5351 are module based. I could build the project in 3 hours and it worked the first time.

However, I felt unsatisfied with the strong BCI since the CD2003 radio receiver chip was connected as a direct conversion receiver. JE1RAV mentioned in his QP-7C modification project that he tried JA9TTT’s idea to build a superhet SSB receiver with the TA2003 or CD2003, so I tried and it worked very well. I have decided to name the new circuit as ADX-S, where S stands for Superhet.

I shared the great news with Barb and he encouraged me to carry the flag to make it a kit, since my design D4D was his first digital radio and he loved it.

You can refer to Barb’s page on ADX here.

My hardware modification can be outlined in this schematic. I have added an FL1, PFB455JR ceramic filter by Murata and a C25 coupling capacitor from CLK2 of SI5351 module. The RX audio comes from pin 11 instead of pin 4.

I modified it by cutting two traces on the ADX PCB and it looked ugly, so I redrew the PCB. Continue reading From idea to kit: Adam introduces the Arduino Digital Modes HF QRP Transceiver (ADX-S) kit

Guest Post: Extreme QRP–Testing the AX1 with WSPR and 20mW

Many thanks to Keith (KY4KK) who shares the following report:

Extreme QRP – Testing the AX1 with WSPR and 20mW

by Keith (KY4KK)

Thomas, thanks for all of your activation videos related to the Elecraft AX1 antenna.  I ordered one the day you announced the package deal, and it arrived in less than a week.  I’ve activated a few parks with it already (20m SSB).  Like you and many others, I’m impressed.

I was very interested in Thomas Barris’ (DM1TBE) March 12 QRPer post using WSPR to test his POTA antennas in Germany.  Then I saw Bob’s (K7ZB) post about his ZachTek Flea with 300 milliwatts in CW mode.  To me, extreme QRP represents some of the magic of HAM radio.  I’d like to share one of my most recent WSPR experiments related to the AX1.

About a year ago, a friend (NG4S) loaned me his pair of WSPR transmitters and suggested that I explore building and comparing antennas. I’ve been hooked on antennas of all kinds and WSPR since then.

I began doing WSPR tests on the AX1 the day after it arrived.  With two transmitters set to the same frequency and power output, you can do direct comparisons between two antennas under identical propagation conditions.

I’ve already done a couple of comparisons between the AX1 and other commercial antennas.  But I think the test I just completed might be of particular interest because it pits the AX1 against an antenna I’ve seen you use many times – a 28.5’ end fed with a 28.5’ counterpoise.  I used 24 AWG silicone insulated wire. The end of the radiator was placed on a 19’5” telescoping fishing pole.  This is my preferred POTA mast when I can’t use a tall tree.

I spent some time trying to control other variables so that the only significant difference during the test would be the antennas themselves.

For example, the SOTA Beam WSPRLite Classic transmitters don’t have an ATU.  So, I had to make the antennas resonant on the 20-meter WSPR frequency of 14.097 MHz.  For the AX1, Thomas’ videos helped a lot.  I used a clip-on capacitance hat and adjusted the counterpoise to 15’ 2”.  This gave me an SWR of 1.17:1.  For the end fed, I tried the two UNUN’s I had available and settled on the 49:1, which got me the closest (2.2:1).  I then used a manual tuner to achieve an SWR of 1.29:1.

I also wanted to deal with the difference in power output between the two transmitters.  Although they’re identical, and both set to 20 milliwatts, there is no way to ensure both are actually producing that output level.  Based on tests by NG4S, one of the transmitters runs at 19 milliwatts.  The other actually outputs 27 milliwatts.  So, my plan was to run the test for 48 hours. At the end of 24 hours, I would switch the transmitters (and callsigns) so that both antennas would benefit (relatively equally) from one of the transmitters being stronger.

At the end of Day 1, I reviewed the data from the two transmitters on dxplorer.net/wspr.  The end fed averaged a 5.7 dB gain over the AX1 based on reports from receiving stations that spotted both transmitters in the same 10-minute block (simultaneous spots).

On Day 1, the stronger transmitter was on the end fed.  The maps below are from WSPR.rocks.

AX1 – Day 1

End Fed – Day 1

I was pretty impressed that the AX1 got into Europe and Africa on only .019 Watt!  I always have good luck with end feds, so was not too surprised to see this one perform well. Continue reading Guest Post: Extreme QRP–Testing the AX1 with WSPR and 20mW

How I found the best antenna for my SOTA/POTA activations

How I found the best antenna for my SOTA/POTA activations

by Thomas (DM1TBE)


Until January this year I had a German “Klasse E” / CEPT-novice amateur radio license (equivalent to the US General Class), which limits the use of HF to the 10-,15-, 80- and 160-meter bands. When I started with SOTA I used homemade single band end-fed antennas most of the time. However, that is only feasible for the 10- and 15-meter bands.

Unfortunately, both bands are very moody and sometimes they have not worked at all. Unlike the UK for example, FM is uncommon for SOTA in my home association DM (i.e. Germany Low Mountains). You can be lucky and get your 4 QSOs, but I did not want to rely on pure luck.

Therefore, I bought an end-fed half-wave antenna for 10-, 15-, 20-, 40- and 80-meter bands, after some experiments with 10-80-meter end-fed half-wave antennas, from a small German company called ANjo.

Although I could not use the 20- and 40- meter bands at that time, the EFW80-10P (en: auto-translated) antenna gave me the possibility to use the 80-meter band. The antenna could also be tuned for 15. It has a mechanical length of 23.6 m / 77 ft and a coil for the 80-meter band. It is pretty lightweight with 0.4 kg / 14 oz and allows up to 30 watts PEP – more than enough for me. 80-meters is not the best band for daytime SOTA activations, but in 21 months doing SOTA activations, it worked 37 times and tipped the scales for an activation from time to time.

It was sometimes a bit tricky to raise the long wire into the air, but it always worked … better or worse …somehow … like here in the woods along a trail.

In January this year, I upgraded my license and a new world of HF-bands opened for me. Although I have learned a lot about propagation for the exam, I am in favour of a German saying: “The difference between theory and praxis is larger in the praxis than in the theory”. Continue reading How I found the best antenna for my SOTA/POTA activations

Using WSPR Data to Study Propagation 40 & 20 Meter Bands

Many thanks to Jim (KX4TD) who writes:

Hi Thomas,

I am a subscriber and ham radio operator circa 1974. Like you (and a lotta hams) I started as a SWL using a transistorized Lafayette Radio receiver.

Last evening, I listened to the April 2022 Wireless Flirt podcast from Ireland where you were interviewed about the comeback of SW radio. Well done Thomas! You are one articulate dude!

I currently have a uBitx that I use for base and portable operation. We share an interest in POTA and other QRP field operations.

My latest obsession is WSPR. Attached [linked below], please find some of my WSPR findings on 40 meters.



Click here to download PDF: “Using WSPR Data to Study Propagation on the 40-meter and 20-meter Bands”

Thank you so much for sharing this and for the kind words, Jim! It’s strange, but I’ve yet to dive into the world of WSPR. I actually have a QRPLabs QCX+ transceiver kit I purchased specifically to explore WSPR. I just need to find the time to build it now! 

Thanks again for sharing your amazing report!