Being able to detect the Sun is a key requirement for EME. If you can’t detect the Sun, then you have pretty well no chance of detecting amateur signals reflected off the Moon!

I moved a computer running Linux with the WSJT-X program close enough to use for tests with the antenna on the alt-az mount. The setup was not ideal; the antenna is connected to the radio with 15m of Aircell 5 coax, which is low loss but still loses about 3dB over 10m at 432MHz. That’s a lot for EME! I have a preamplifier in my 70cm PA, but it’s at the wrong end of the cable. Still, it will have to do for the first test.

The output from the preamp goes straight in to the Yaesu FT-817 which I use as a general driver for all my microwave stuff. It’s a bit deaf at 70cm which is why I added the preamp in the PA box.

The FT-817 is connected to the computer through an old interface I originally bought (faster than making it, and it’s not very complicated) a long time ago to play with digital modes. It connects to audio line in and line out on a computer, and has a serial connection for PTT; I have a USB adapter for that now. On the radio side, it connects to the “data” jack on the FT-817 which has lines intended for digital communication.

Here’s the screen with WSJT-X running.

For looking at Sun noise, the “Echo mode” has a neat feature in the waterfall display. Instead of the signal spectrum you can display a “scope” view, where a trace crawls across the screen, allowing you to see a real time measure of total signal power in dB. Probably not super accurate, but I was very pleased indeed to see that I could tell the difference between cold sky and the bit of sky with the Sun in it. This is done by moving the antenna to point well away from the Sun (and hopefully other local sources of noise), then back to the Sun. Repeat! Along with the occasional burst of noise, this can be clearly seen in the waterfall window. I have chopped this out and annotated it:

The red lines split the output into “Sun” and “quiet sky” periods. The difference is obvious. The yellow curves show the bursts of noise.

The WSJT “Echo” mode is intended to test the echos of your signal off the Moon, and it gives a measure of the signal in dB. It look as though I have seen a 1-2dB signal from the Sun; it could be more like 5dB if I put a preamp before that cable!

The orange lines indicate the sections of “Sun” and “sky” noise.

So I’m now keen to listen for some real EME signals, but it would definitely help if I can get a 70cm preamp thrown together before I do.