Hello Matej.

I am very sorry and disappointed because I carefully click on SAVE every time when burst came on 70cm and on 2m, but nothing was saved on 2m PC. I discovered this on the evening in Saturday. My father has WSJT 5.9.6 on his laptop. Is there a problem with SAVE function in that version? Nothing was saved at all. So I can only comment on what I have noticed listening and looking simultaneously on both PC.

My father used 60W power on 2 m, so QSO with RA3WDK (same direction as RW3WR and 100km further) take more time to complete and I could compare 3 reflections. As expected, I noticed no reflections on 70cm outside time window when 2m reflections appears. Only strong enough reflections on 2m (in my case at least 15dB over noise) produce reflections on 70cm. We received, for example, around 15s burst on 2m and at its peak we receive 300ms burst on 70cm. There were many bursts on 2m that produced nothing on 70cm.

I did not noticed any significant Doppler shift during RW3WR sked (and other QSO's I made) on 70cm. Once on the right frequency, one can leave tuning knob as it is. So low number of reflections on 70cm is not caused because not hearing reflections that are outside receiver passband. We do not hear them because traces are not ionized enough to produce reflection also on 70cm. Wind speed at 100km altitude is up to 200km/h and ionized traces traveling at the same speed so Doppler shift is therefore below 100 Hz on 70cm. High Doppler shift during burst I noticed only at the beginning of the strong burst (on 2m and I also heard the same one time on 70cm), when ionized cloud is forming when dust particle entering earth atmosphere.

The longest burst I ever heard on 70cm was from RW3WR and it was 3s long. It was -500Hz off my frequency. This is practically the same amount I find for him later on your home page. Because of significantly shorter reflections and smaller number of reflections, exact frequency is the most critical factor for completing 70cm MS QSO. Saving the band with Perseus SDR (I had it with me) would help, but I did not use it this time (have only two computers with us).

Now I am working with MENINA 432/21 transverter (prototype) and stability of my frequency is good. Before, with SSB Electronic 432/28 MHz transverter, the situation was bad. Stability of oscillator in SSB transverter is not good and I drifted 400Hz during my first MS QSO with GW4DGU back in 2004 Geminids (with 100W and 8x26el) and I did not decoded few bursts because of that. JT65 was almost impossible.

I do not remember any article about 70cm MS in any radioamateur magazine. I think I read something in ARRL Handbook once, but I am not sure. TNX for your article in last DUBUS.

I did not tried 23cm MS. I suppose, based on degradation of signals on 70 compare to 2m MS, that 23cm is almost impossible. But I would be very happy if someone will prove this wrong...

Sorry that we did not complete EME QSO this Saturday. I had problems with my elevation rotor. I saw you on waterfall, but no decode. Hope we will complete soon also EME.

73 Sine - S53RM

Hello Matej.

Before I have information, that wind at 100km altitude is around 200km/h. Now I find on internet, that maximum wind speed is up to 360km/h. That gives you 150Hz of Doppler shift on 70cm. But we have antennas pointed to each other and reflections take place between us, when working 70cm MS, so Doppler effect is around 0Hz. (Like on 10 GHz rain scater, if rain is directly between two stations - one can hear very little distortion on ignal). If we follow backscattering than Doppler on 70cm could be up to 300Hz.

73 Sine - S53RM