Sunday, 09 March 2014 01:23

APRS over Satellites

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APRS Digipeating over satellites:

Using a Kenwood TH-D72A HT to send and receive APRS messages through satellites

I will attempt to document confirmed satellites, along with the correct path, frequencies, and any other relevant information.  Trying to locate accurate information in one place is next to impossible, either the sites are out dated, or only give partial details of what is needed to work these satellites.  I found it difficult without experimenting myself to really see what works and what doesn't.  I will post my results as I continue experimenting.

  • NO-44 (PCsat1)
  • ISS


I suggest making sure you can easily transmit your APRS status and messages onto the local APRS network (144.390 in US) first to make sure your radio settings are correct.  Set your radio TNC band to the correct uplink frequency, downlink friequency on your receive band, and change the PATH (which would typically be WIDE1-1, WIDE2-1 on the standard APRS 144.390 US network) to the PATH of the satellite.  Manually open up the squelch on the radio and listen for the data being sent from the satellite.  Close up the squelch, send your position beacon or message and with any luck you will be heard by the satellite.  Even the satellites that have been confirmed to work, may not be 100% operational, especially the cube sats may go down or change modes of operation.

Also keep in mind in order for your packet to make it the the APRS network, there will have to be a satGate monitoring the downlink frequency, therefore some of these may only work point to point.



There are a variety software apps to choose from to assist in working satellites.  I am using an HT that has a built in TNC so there is no other software required (aside from tracking the satellites) to be able to work the satellites.  If you don't have a similar setup you will need some sort of TNC (software/hardware) to connect your PC to your radio.  I will be experimenting with that at a later date and document it on another page. 

  • Tracking

There is an abundance of software to assist you in tracking satellites for all platforms.  I only use "Satellite Tracker" free for my iphone but search around and you will find what will fit your needs best.



Satellite Tracker Free This is the app I use and has worked out well.  It is very basic, but the price is right.


Web based: This site is pretty cool, you can get 10 day predictions of different satellites based on the location you enter.  The site isn't the easiest to navigate but it can provide you with all of the pass predictions you need.



  • NO-44 (PCsat1) - VHF

ACTIVE - may not work 100% of the time - daylight only

Uplink: 145.827 MHz
Downlink: 145.827 MHz
Path: W3ADO-1
Mode: 1200bps AFSK

20140516 - I was successful in sending my position, status, and an email using my HT and a (dual band) 1/4 wave mag mount antenna mounted on top of my truck, confirmed via that it was received by several satGates and sent to the APRS network.

Raw packets:

2014-05-16 19:04:50 CDT: KC9BUD-7>3Y5P9V,W3ADO-1*,qARKC2NFF-10:`p'Ql!-[/>=
2014-05-16 19:05:03 CDT: KC9BUD-7>APK003,W3ADO-1*,qAR,N9GKE-1::EMAIL-2  :mark Hello from Dayton via the NO-44 sat{49
2014-05-16 19:06:14 CDT: KC9BUD-7>3Y5P9V,W3ADO-1*,qAR,HUMBOL:`p'Ql!2[/>Dayton or bust!=
2014-05-16 19:06:51 CDT: KC9BUD-7>3Y5P9V,W3ADO-1*,qAR,KY4J-10:`p'Ql!2[/>Dayton or bust!=

20140521 - I tried to send a message today and I believe it may not be functioning correctly.  I am only using a 1/4 wave antenna and 5W, but I seemed to have heard something come back after I transmitted but it was very weak and sounded incomplete.  I also noticed the W3ADO-1 beacon hasn't shown up on the findu website so that may also confirm this.  I'll try again shortly.


  • NO-44 (PCsat1) - UHF

Not Confirmed

Uplink: 435.250 MHz
Downlink: 145.827 MHz
Path: PCSAT-1, -11
Mode: 9600bps AFSK


  • ISS (Zarya)- VHF


Uplink: 145.825 MHz
Downlink: 145.825 MHz
Mode: 1200bps AFSK

20140522 - I was successful in sending out a beacon via the ISS, but did not have enough time to send out a message from my HT.  I was using a telescopic whip and the opening I have with that setup to hit the ISS is so short, I couldn't type fast enough :).  Next time I'll have the message waiting to be sent.

Raw packets:

2014-05-22 09:08:22 CDT: KC9BUD-7>4R1U0Q,RS0ISS*,qAR,N0AN-13:`t++l#)[/>=


  • ISS (Zarya)- UHF

Not Confirmed - Down?

Uplink: 437.550 MHz
Downlink: 437.550 MHz
Path: RS0ISS-4, -11
Mode: 1200bps AFSK



For satellites that downlink on odd frequencies (if they even work - I'm learning as I go along here) there is no easy way to confirm that you were able to digipeat your signal correctly unless you or someone else are receiving and decoding the downlink signal as well.  For the satellites that are part of the ASTARS (APRS Satellite Tracking and Reporting System), there are satGates that receive their traffic and send it off to the APRS network so you can easily confirm if you are making it or not.

  • ISS - You can go here and see if your recent attempt has been seen by the ISS.

  • NO-44 (PCSat-1) - You can go here and see if your recent attempt has been seen by the NO-44 (PCSat-1).

  • Callsign Search on APRS network

For additional troubleshooting, you can view and search Raw APRS packets  This has been very helpful especially just starting out to see what is getting out, what is coming to me, etc.  You can use asterisk's (*) after a partial call sign as well to help find what you're looking for.  This however will only search packets from the callsign, and not to the callsign.

To see both to and from you can go here and search the callsign.

Going + adding the callsign to search for, will show your both to and from the callsign.  (ie:  Note asterisk's do not work and you need the full callsign along with SSID if applicable.




Read 19708 times Last modified on Thursday, 24 September 2015 15:10
Algis Salys

Creator and owner of  Linux enthusiast, electronics tinkerer, and likes to spend time in the workshop building and creating new projects.