PSAT PSK31 Transponder received by Peter Goodhall 2E0SQL May 26, 2015

After building a 28 MHz 1/4 Wave Ground Plane antenna to replace his dipole Peter Goodhall 2E0SQL was able to receive his 10 watt signal through the PSAT CubeSat PSK31 transponder for the first time on Tuesday, May 26.

Peter Martinez G3PLX posted a report to the RSGB Tech Yahoo Group reproduced here with permission:

Finally got my own signal back via PSAT just now and proved  that the uplink frequency control works. The PSAT uplink receiver is about 300 Hz low of 28120 kHz which means that when the satellite is heading straight towards me at +600 Hz Doppler, my transmitter needs to be 900 Hz low.

If I chose to place my own signal on a downlink frequency of 1000 Hz, the transmit audio tone would have to be down at 100 Hz which is too low for my SSB transmitter. So I have chosen 1500 Hz in the downlink.

I will try again on the next few passes. I am just sending “Test de G3PLX via PSAT” continuously at the moment and not listening for replies.  Still not getting a strong downlink SNR so the power control loop isn’t kicking in.

Bob Bruninga WB4APR has made a request to developers of PSK31 software to open their PSK31 frequency tracking to accommodate more than 1 Hz per second Doppler shift. Current implementations can do 1 Hz/s but completely fail at 3 Hz/s.

PSK31 Transponder Frequencies:
PSAT: 145.825 MHz FM 1200 baud AX.25 telemetry – digipeater currently off
PSAT PSK31: 435.350 MHz FM downlink, 28.120 MHz SSB PSK31 uplink. W3ADO-5 PSK TLM beacon on 315 Hz

BRICsat: 437.975 MHz 9600 baud telemetry every 20s
BRICsat PSK31 435.350 MHz FM downlink, 28.120 MHz SSB PSK31 uplink. W3ADO-6 PSK TLM beacon on 375 Hz

Guide to using the PSK31 transponder https://amsat-uk.org/beginners/how-to-work-psk31-satellites/

ParkinsonSAT (PSAT) http://www.aprs.org/psat.html

Fldigi PSK31 software http://www.w1hkj.com/Fldigi.html

Keplerian Two Line Elements (TLEs) ‘Keps’ for satellites launched in last 30 days
http://celestrak.com/NORAD/elements/tle-new.txt

Adding new satellites to SatPC32 and Gpredict
https://amsat-uk.org/2013/11/23/adding-new-satellites-to-satpc32/

Listen to satellite signals in the 145 and 435-438 MHz bands from anywhere in the world using the online SUWS WebSDR located near London. Further details at https://amsat-uk.org/2014/08/15/suws-websdr-moves-to-new-site/

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