Mobile APRS SatGate

Enable your D700 as a Mobile SatGate


Note: Back when I took this screenshot, ISS APRS was 145.800 – it is now 145.825 !!

I have my PM5 set up as what I call my “Mobile SatGate”. Whenever I park my truck, I put the D700 on PM5 instead of turning it off in order to assist other users with APRS satellite operations. In this mode, the D700 receives APRS packets from ISS and digipeats them to 144.39 where they can be picked up by terrestrial SatGates for delivery to the APRS-IS. The terrestrial APRS frequency (144.39 in U.S.A.) is set on Band A (left side). I have enabled CTCSS with a PL of 67Hz, so it will mute the speaker without having to worry about touching the volume control. I have set this band to “M”edium power in order not to run my truck’s battery down! I set the beacon rate to 30 minutes for the same reason. I also set the Dimmer to the lowest level. Side B (right side) is set to the ISS downlink 145.825. You can set this with either a memory channel or with the VFO. Set menu 3-I to A:TX B:RX. UIDIGI is enabled (menu 3-K) which turns the D700 into a digipeater. (UIDIGI configuration details below). When the ISS makes a pass overhead, packets are received on Band B and digipeated over to Band A. Another thing you want to do is set your Message Groups to “*” (menu3-P) so that you receive all messages. When you come back to your vehicle, you will know that a satellite pass has occured because you will see all of the messages queued from the pass. You can also check the station list. If the majority of D700 users did this, it would dramatically increase the IGate coverage for APRS satellite users. By setting this as a separate PM, it takes two button pushes to put the D700 in this mode without affecting your normal everyday operating PM. When you want to go back to normal operations it is just two keypresses – PM OFF. Quick and easy. So put those idle D700’s to work!

UIDIGI configuration details for Mobile SatGate operations:
To enable the D700 as a mobile SatGate, enable UIDIGI (menu 3-K). UIDIGI digipeating path (menu 3-L) is set to “SGATE, WIDE, RELAY”. As long as an APRS satellite user includes SGATE as part of their path after the satellite digi, then they will take advantage of this type of setup. By checking stations on FindU, I have found that about 50% of users do this. I have noticed that some use WIDE and RELAY after the satellite part of the path, so that is why I also include them. The ideal path for an ISS digi user would be “ARISS,SGATE,WIDE2-2”. This packet would be digi’d by the ISS, then picked up by a D700 SatGate, and digi’d onto 144.39 with the remaining path of WIDE2-2 which just about guarantees delivery to an IGate.

3 thoughts on “Mobile APRS SatGate

  1. Edward Johnson

    You may have heard this before but the frequency shown on your radio is incorrect for APRS from ISS. 145.800 is used for voice and 145.825 is used for packet. Thanks for writing this as it helped me figure out why I was not getting on the APRS map when using ISS. I was only showing up on the ISS map.


    1. A.J. Farmer Post author

      Hi Edward, thanks for the heads up. Back when I wrote this up, 145.800 was the Digi frequency for ISS and 145.825 was for PC SAT. PC SAT is no longer active now and the ISS Digi is now on 145.825. At the time, I had my D700 scanning between 145.800 and 145.825 to catch both ISS and PC SAT.


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