10-milliwatt WSPR signal on 28 MHz heard in Ireland - 28th May 2021

Friday 28th May 2021: I left the radio monitoring the WSPR frequency on 28 MHz for whole day and I heard signals from all over Europe including DP0POL on the German Icebreaker ship near the north of Norway.

At the end of the day, I got an interesting e-mail from Andreas, DL2KCL about my reception of his very low power WSPR beacon during the day.

Andreas wrote... "You received a transmission from my homemade WSPR-TX on 10m. The TX puts out 10 mW directly from a Si5351A-chip. No PA. It runs from a single rechargeable D-cell with a DC/DC-converter (85 mA).

The antenna is a piece of about 2.5 m thin wire wound on a 18 cm PVC tube in resonance on 28.2 MHz. There is no additional counterpoise."

I checked back through the WSPR logs and amazingly, I had heard the 10-milliwatt signal from DL2KCL a total of 77 times during the day. The weakest signal was -27dB which is buried way in the noise. The strongest signal was -12dB which would have been just about audible to the human ear.

The photo above shows the transmit antenna which is just a quarter wave of wire wound on an 18cm PVC pipe. To hear such a low power system 77 times during the way just goes to show how good conditions must have been.

On my side, I was just using a simple CB type half wave vertical so there was no additional gain to pull in weak signals.

Analysis: The one crucial part of equation is the distance... 1075kms. During the Sporadic-E season, signals in the 1000 to 1500km range are a bit like the sweet spot on 28 MHz. 

There are a lot more openings on 28 MHz compared to the higher bands like 50 MHz and signals around 1100kms are at the very least 6dB stronger than those out around 2200kms just due to the fact they are closer.

The signals at 1100kms are also coming in around 8 degrees above the horizon which allows it to clear local obstructions at either end of the path. 

Antennas on 28 MHz will probably have more gain at 8 degrees above the horizon in comparison to say 1 or 2 degrees and a 2000km skip distance.

It just goes to show how good the 28 MHz band can be when the conditions are right.