[amsat-bb] Still trying to decode NO-84 (Doppler)

Robert Bruninga bruninga at usna.edu
Thu Mar 2 15:38:50 UTC 2017

One thing to remember is that you cannot use normal Doppler correcting
software that tunes the radio.  The instantaneous radio steps cause Phase
discontinuities and that completely destroys PSK31.

The only ways to work well is to only try to decode when the bird is coming
right at you or right aways from you and the Doppler is not rapidly

*** OR *** use the special PSK31 Doppler uplink correcting program written
by Andy Flowers found on the PSAT web page… http://aprs.org/psat.html

Here is his page:


This software also allows you to run full duplex so that you can uplink
continuously throughtout the pass and independently receive all downlinks
at the same time.  The radio does not tune, but your uplink audio
compensates for the uplink Doppler so that your trace in the downlink
appears constant to everyone.

Yes, you can run UHF Radio stepped Doppler correction that steps down in
the usual 5 KHz steps 4 times during the pass.  You may still loose an
instant of phase corrupted characters, but only 4 times, not every few
seconds as the SSB radio would try to do if the computer program was trying
to compensate the SSB uplink radio.

That help?


*From:* Fer [mailto:mhz4464 at yahoo.com]
*Sent:* Thursday, March 02, 2017 10:25 AM
*To:* Mark Lunday; AMSAT BB; Paul Stoetzer; Robert Bruninga
*Subject:* Re: [amsat-bb] Still trying to decode NO-84

I am trying too to activate NO-84, 50w on 28.120 MHz with vertical antenna
or dipole with FLDIGI (saw no difference, still weak), good downlink signal
on UHF with SDR-14+SpectraVue as panadapter at 10.7 MHz, beacon decoded in
FLDIGI,   my weak signal  sometime decoded, strong doppler on my signal
despite I correct both with orbitron/wispdde using only fresh keps and GPS
computer sync clock.

Any idea?

73 Fer IW1DTU

here some screenshoot link to dropbox



On Thursday, March 2, 2017 2:51 AM, Mark Lunday <wd4elg at outlook.com> wrote:

0230 UTC pass, saw the bear claw PSK 31 waveform again.  Anyone else able
to see the PSK dowllink?  I am seeing 7 parallel traces, almost like the
transmission is overloading the receiver.

Attempting to attach the file to this email with a capture of what my SDR
receiver is seeing...

On a positive note, APRS is working perfectly on NO84 even at low passes.

Mark Lunday, WD4ELG
Greensboro, NC  FM06be
wd4elg at arrl.net
SKCC #16439  FISTS #17972
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