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Using the NO-84 (PSAT) PSK Transponder

Posted: 29 Oct 2018 10:49 AM PDT
https://www.2m0sql.com/2018/10/29/us...k-transponder/














NO-84 (PSAT) was launched in 2015 and although its been in orbit for some
time, you will find a lot of people have only used the APRS Digipeater
which is also a payload on the satellite, however, the main payload is a
PSK Transponder.

Uplink is on the 10m PSK frequency of 28.120 USB and it downlinks on
435.350 FM (PSK31), the satellite builders recommend using up to 75w into
an omnidirectional antenna on 10m.





Antennas

In my own experience of using NO-84, I was using a 10m dipole which worked
reasonably well, but I found the best antenna for myself was a 10m GP this
was easy to build with a small fibreglass fishing rod, wire and a dipole
centre I made one for less than £10 (Bargain!)

I found with this setup I was able to activate the transponder with as
little as 10w, however, of course, increasing the power made sure that
NO-84 could hear my signal a lot more.





















Software
Transmitting
Of course, with this satellite doppler is a consideration and although you
can use a standard PSK31 application for transmitting and receive you’ll
see your signal has the Doppler curve on it, however, K0SM has produced a
simple application called DopplerPSK
Setting this up is simple, you download the application which is Java and
launch it and then set some parameters. In Station - Edit Station
InformationÂ*you specify your location like you would with any other
tracking application. You then select the satellite you want to use by
going to Satellite - Choose SatelliteÂ*and select NO-84.
Its worth noting you’ll need to manually update the TLEs, these are stored
in the /tle/ subdirectory.Â*I’d recommend using the
https://www.amsat.org/tle/current/nasabare.txt once you have updated the
TLEs relaunch the application.
Select the output soundcard by clicking on Audio Device in the menu and
selecting the correct one, remember this is the audio going to your radio.
On the main screen of DopplerPSK you’ll notice you have some tracking
information and boxes update the MyCallÂ*with your own callsign and press
update.Â*Notice below that there are prepopulated text inputs and radio
buttons to represent the one that has been selected for now use CQ.
Its generally recommended you transmit the whole time NO-84 is passing
over. The other station will be on a different frequency to yourself,
update their callsign in DXCall and the exchange and hit the UpdateÂ*button,
again then select the message you want to send till the contacts complete.
Then go back to CQ or reply to someone else if their calling CQ, this
method seems to work well.


















The above screenshot is DopperPSKs main screen.


















The above image shows FL-Digi decoding multiple signals, in this case,
2E0SQL and the satellites beacon.









Receiving
To decode the signals, I personally recommend using a PSK application that
supports multi decoding, for instance, FL-Digi, you can watch all the
stations on the passband and your own and carry out your contact with ease.
Remember that if NO-84 doesn’t hear a PSK31 signal on 28.120 the
transponder will not turn on unless it is sending its beacon signal.













Final Thoughts

Hopefully, this gives you some idea how to setup DopplerPSK to complete a
NO-84 PSK QSO. Its worth keeping in mind that activity can be low, so do
not be scared to ask for prearranged contact.









Useful Links

DopplerPSK Â*http://www.frontiernet.net/~aflowers...opplerpsk.html
1/4 Wave Ground Plane Antenna
Calculator Â*https://m0ukd.com/calculators/quarte...na-calculator/










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