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Re: PSK-31 MFSK Hell via AO-10



Hi Moe,

you wrote:

>
> The limitations of PSK31 with doppler shift is not a fundamental limit with
> DPSK but rather a limitation imposed by the PSK31 application programs.  On
> HF, an aggressive AFC is bad due to all the interference and signal
> congestion.  The typical limit imposed with most programs is about
> 1-2Hz/Sec.  As a little experiment, I changed the AFC filter constants in
> WinPSK and was able to track 20Hz/Sec psk31 signals.  I'm not a satellite
> guy so don't know what the typical doppler shift rates are so don't know if
> this is enough.  Much more than 20Hz/sec and the AFC loop gets more tricky
> and you also have the issue of running outside the audio bandwidth during a
> QSO and having to retune the receiver.

concerning the doppler shift of AO-10:

For 146 MHz  91% of the time < 0.5 Hz/sec
             94% "  "   "    < 1.0 Hz/sec
             98% "  "   "    < 2.0 Hz/sec
             max. shift        4.0 Hz/sec (around perigee)

For 435 MHz  85% "  "   "    < 0.5 Hz/sec
             90% "  "   "    < 1.0 Hz/sec
             92% "  "   "    < 2.0 Hz/sec.
             max. shift       12.0 Hz/sec (around perigee)


But the low duty cycle of Hellschreiber if a serious argument.
The batteries of the old bird AO-10 are not in the best shape...

73, Udo, DL7OL ***




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