Until we get authors adding Full duplex and AFC to their PSK31, here is a scheme that will work.
Focus on the OVERHEAD pass. Horizon to Horizon. Because during these passes, the satellite is coming right at you for the first 5 minutes, and directly away from you for the next 5 minutes. This means the Doppler is nearly constant high during the first 5 minutes and then a rapid shift to a constant LOW for the last 5 minutes. And horribly shifting for the middle 1 minute.
Your signal will have very little Doppler on the downlink and most anyone with any kind of PSK31 decoder will decode you fine.
Don't do any frequency transmitteirn shift on the uplink or as KO6TZ says, you will cause people to lose lock..
When the satellite crosses overhead, you can then shift your TX frequency UP by 1.15 KHz and people will see you more or less back where you started... maybe.
Bob, Wb4aPR -----Original Message----- From: AMSAT-BB [mailto:[email protected]] On Behalf Of KO6TZ Bob Sent: Sunday, May 31, 2015 4:39 PM To: [email protected] Subject: Re: [amsat-bb] PSAT 1925 pass
Some of the traces I watched were pretty horribly Doppler shifted and
not sure if MixW is able to decode that >coming up from ten meters and drifting like the ones I sw.
From me experience on DO-64 and FO-29 using PSK31/63, I found adjusting for Doppler on the SSB up-link is a double edged sword.
When the frequency is updated for Doppler, you loose sync for a few characters. If you don't correct the frequency, you will exceed the AFC limit of most programs, except WINPSK.
WINPSK doesn't support multi line copy. Also using DigiPan in "munti" mode, there is no AFC. The s/w just creates another line.
Pick your poison.....
KO6TZ Bob
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The HAM software programs that offer the PSK modes offer a combination of feature.
Here is a matrix of the features that may be of value working the PSAT satellite.
AMATEUR PSK PROGRAMS FEATURES
DX/SX =A= FULL DUPLEX Y,N,NA =B= 2 INSTANCES 1,2,SB =C= REC CHANNELS OR SB/MULTI 50,3K =D= AFC Hz 31, 1K =E= BPSK TOP RATE Y,N =F= Tx MONITOR W/F N,1,2,3,8 =G= MULTI S/B HIGHLIGHT ALERT LIMIT
A=B=C=D=E=F=G
WinPSK DX=NA=1=3K=63=N=N WinPSK(SE) DX=NA=2=3K=31=N=N FlDigi SX=Y=SB=50=1K=Y=1 DigiPAN SX=Y=SB=50=63=N=3 MixW SX=Y=2=50=125=N=? DM780 SX=N=SB=?50=125=N=8
participants (2)
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KO6TZ Bob -
Robert Bruninga