Having been away from home for a while I was keen to “get back on the radio”. EME conditions were looking good, degradation very low, Moon near Perigee and Moon pass times good, i.e. not in the middle of the night. Unfortunately I’d taken all the EME gear off the dish in preparation for a winter overhaul prior to my trip so all I had installed on the dish was the feed for my QO-100 system.

For those of you unfamiliar with EME operation, there tends to be a number of variables occurring during a receive / transmit period, in particular at the higher microwave frequencies. Two key ones are, not only is the Moon position changing in both AZ / EL, the signal being received is also changing frequency due to Doppler shift. Both of these are going to influence getting a successful decode and the optimum signal strength. My 10GHz EME system is configured to minimise the effect of these, a noise meter enables me to ensure that the dish heading is optimised and the WSJT-X software is able to automatically change the receive / transmit frequencies via CAT control.

I’d copied the DL0SHF beacon in the past using a modified LNB but never tried with the current QO-100 feed setup where the 2.4GHz helical feed sits on the front of the LNB. This arrangement can have a detrimental effect on the LNB receive performance. Something I’ve not quantified or really considered as an issue when used with the QO-100 transponder. Whereas with EME every 0.1dB counts.

To receive the beacon (on 10368.024 MHz) using the LNB I would need to use SDRConsole (or similar) tuned to the output of the LNB around 618.024MHz and pipe the audio output from SDRConsole into WSJT-X using VAC (Virtual Audio Cable)

Whilst my AZ/EL rotator setup is capable of finding the Moon and tracking it, it is not optimised to track in 0.1 degree increments and received signals are typically several dB down compared to when the dish is manually peaked on Moon noise.

I was fairly confident that I would get some form of decode, but without Doppler correction and Moon noise alignment just how well would the beacon be decoded?

I used the Doppler correction display from WSJT-X to determine the frequency I needed to tune SDRConsole to and looked carefully at the waterfall hoping to see some form of trace. A few nudges of the AZ/EL controls and the beacon was showing on the waterfall. The WSJT-X Doppler screen showed that the beacon received frequency was moving LF by about 1Hz a second. I manually adjusted the SDRConsole frequency at this rate and nudged the dish position to maintain the brightest trace on the waterfall. The results were surprising!

I was able decode the beacon at best -7dB, this was within 1dB of my best ever decode using my optimised W2IMU feed and DU3T WG LNA. It was unfortunate that I could not do a real-time side by side comparison of decoded signals to see how the two receive systems compared.

SDRConsole now has the ability to measure Sun / Moon noise when running in Continuum Mode. Whilst this is not the best time of the year to do Sun Noise measurements it will be interesting to see what results I can get and how they compare to those calculated by VK3UM (SK) EMECalc software.

This proved to be an interesting test and once again showed how a simply modified LNB can form a very good receive setup for the 10GHz amateur band. You can find an example / additional information here.