DL7APV in JO62jr

What was wrong if it did not work to run first 432 EME QSO?

There are several things that might can go wrong or must be optimized

I cannot hear the big gun

Bad condx due Faraday

Polarization does not fit

Local QRM

QRG correct?

Doppler setting




·       Try again at other time or day

·       If possible, change pol. Maybe the big gun can do but only HB9Q and NC1I can do. Im fixed Hor.pol. So, with me try again! EU to US we often have cross pol. means TX on V pol. and RX is on H-pol. better! But not many can change pol. for this.

·       Can be a killer for an EME qso. Due to its partial broadband noise hard to detect. If possible, check if there are antenna directions with less S-Meter detect? Birdies just look for a free qrg and moved sked to.
Night times without TV from neighbour might help?

·       If no GPSO or good beacon is available it is not easy to check correct qrg. The modern TRX are within a good range, but +/-1KHz could be possible due to aging. Have a look around +/- I CQ mostly longer time.

·       Doppler can be up to 1KHz on 432, so in worst case I have to look +/-2KHz for DX signal. In MAP65 I see the whole EME Band but with reduced sensivity.
With WSJT-X and the automatic Doppler correction it is easy to be transceive. I use CFOM what means constant frequency on moon. CQ 432063 CFOM means if Im on the moon the qrg is 063 and will be constant there. On earth the qrg moves with moon path and is different at every QTH. BUT WSJT-x calculates this that everyone will be on correct qrg.

·       Procedure is set TRX to 063 ( in my case) go to <view> astronomical data, enable doppler correction and set CFOM

·       free view to moon, special if no elevation is possible


The big gun don’t see me

Bad condx

Cross Polarization



What helps

·       Bad condx, faraday and doppler see above

·       In some cases, it is possible that the pol. Rot. Is not reciprocal means that the signal arrives in H-pol. but you have to TX V-pol. that the other station can hear you. So, if possible, try to turn pol. if possible, maybe +45° or -45° will do.

·       20-50W with a >10el. will do in most cases, but cable loss may one reason why the power level is not enough. Moisture in a cable is a problem I had myself and it may not visible by bad SWR

·       If TX is barefoot a low loss short cable is a must (<2dB!!!)

·       Low frequency drift of the transceiver (<10Hz per minute). When only receiving a big gun the drift should be low as the TRX not get warm. But when answering the heat causes the drift of the oscillator(s) of the radio. You can see the drift if you response to the big gun with max. power. When the big gun begins to drift it is a good indication that your radio is drifting. These drift causes big loss of sensivity on the RX side.

Best solution is to lock the radio by an external precise Oscillator, like a GPSO e.g. LeoBodnar for IC9700

·       Reduce power by 1 or 2 dB maybe 3dB

·       Open the frame and add a fan for the test

·       Add a PA which needs not much driving power from TRX







Update feb 2023