OpenGD77

I always confused with APRS. I believe people use the term "APRS" interchangeably with "Positioning report". Sometimes they can have APRS over DMR, most of the times they refer to FM, VHF/AFSK/AX.25/APRS. I, personally operate APRS mostly on 144.39Mhz (FM) and 10.1478Mhz (USB).

Now, I'm very confused when trying to put "APRS" on the layers.

So, I'm trying to put "APRS" on the OST layers model to be able to understand it. please help me, I'm not quite sure what I'm doing. Which layer is the APRS, I can't put it. OR it is not a protocol to begin with?

VHF FM APRS (144.390 in the US.)
OSI layers
7 (Application)
6 (Presentation)
5 (session)
4 (Transport)
3 (Network)
2 (DATALINK) ---> AFSK / AX.25 / FM
1 (Physical) ---> VHF RF

HF USB APRS (10.1478)
7 (Application)
6 (Presentation)
5 (session)
4 (Transport)
3 (Network)
2 (DATALINK) ---> AFSK / AX.25 / USB
1 (Physical) ---> HF RF

UHF DMR APRS
7 (Application)
6 (Presentation)
5 (session)
4 (Transport)
3 (Network)
2 (DATALINK) ---> FM / TDMA
1 (Physical) ---> UHF RF

KA1CM wrote: ↑

Tue May 27, 2025 12:57 pm

....
UHF DMR APRS
7 (Application)
6 (Presentation)
5 (session)
4 (Transport)
3 (Network)
2 (DATALINK) ---> FM / TDMA
1 (Physical) ---> UHF RF

3 (Network) ---> select data from DMR stream (e.g. at BM)
2 (DATALINK) ---> FM / TDMA / embedding Data in DMR stream

I'm not a network guy, but that seems to make most sence to me