I just updated the http://aprs.org/psat.html web page to clarify how PSK31 uplink and downlink should be approached. We should have done that a year ago!
Bob, WB4APR
*From:* Robert Bruninga [mailto:bruninga@usna.edu] *Sent:* Thursday, March 02, 2017 10:39 AM *To:* AMSAT BB *Cc:* Robert Bruninga *Subject:* RE: [amsat-bb] Still trying to decode NO-84 (Doppler)
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 changing.
*** 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:
http://www.frontiernet.net/~aflowers/dopplerpsk/dopplerpsk.html
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?
Bob
*From:* Fer [mailto:mhz4464@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
https://www.dropbox.com/s/ec2i14l62u4ij3w/NO-84%202%20mar17%20uno.jpg?dl=0
https://www.dropbox.com/s/l1k3a3h8atyys5l/NO-84%202mar17%20due.jpg?dl=0
On Thursday, March 2, 2017 2:51 AM, Mark Lunday wd4elg@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@arrl.net http://wd4elg.blogspot.com SKCC #16439 FISTS #17972 _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb