Re: Amateur Radio G3RUH AX.25 2FSK

[Derek Kozel]

    By far the most common APRS RF mode is 1200 baud AFSK, but 9600 baud
    FSK also exists as a faster and slightly more modern option. There's
    a decent, but not great, number of repeaters and internet gateways
    in place for the 9600 some radios support both.

On 12/08/2020 13:36, Adrian Musceac wrote:

Hi Derek,

Isn't APRS 1200 baud though? 9600 baud packet is quite uncommon nowadays here, historically it was used for BBS access.
I'm also interested in this APRS transceiver.

Best,
Adrian

On August 12, 2020 12:12:09 PM UTC, Derek Kozel <derek@bitstovolts.com> wrote:

Hi Yugal,

gr-ax25 was just updated this month to start supporting the development version of GR 3.9 and if you look one commit back it is is compatible with 3.7, so it does look like it's skipping 3.8. Still, it's a valuable reference for you as you look to create your own implementation.

I'd suggest starting by making a transmitter first and testing it by receiving using existing software. Page 21 onwards here seems to have a good description of the modulator and demodulator.
https://matheo.uliege.be/bitstream/2268.2/6751/1/OUFTI2-COMM-Piron-2019.pdf

I'm excited to see you implement this. It'd be great to see more support for the 9600 baud AX25 mode that is used for APRS. It may not be as good of performance as more modern modes, but there's a bunch of hardware that supports it.

If you're interested in APRS specifically, by far the best reference I know of is W6KWF Kenneth Finnegan's masters thesis on the protocol.
https://digitalcommons.calpoly.edu/theses/1341/

Cheers,
Derek
MW0LNA

On 12/08/2020 05:29, Yugal Joshi wrote:

Hello Jeff

Thanks for replying 

From what I learned in last two days in GNU Radio, it looks like gr-25 is an OOT module.

gr-25 works with GR 3.9 and pybinds and I am using GR 3.8.1.0.

Also I want to implement G3RUH  2FSK AX25 using the core modules of GRC or programming  new OOTs so that I can improve my learning curve. 

Any help would be appreciated from the community.

Thanks and Regards

Yugal Joshi 

On Wed, 12 Aug 2020, 4:45 am Jeff Long, <willcode4@gmail.com> wrote:

Have you already take a look at this?

https://github.com/dl1ksv/gr-ax25

On Tue, Aug 11, 2020 at 4:13 PM Yugal Joshi <yugaljoshi2002@gmail.com> wrote:

Hello all 
I am new to the GNU Radio community.

I am starting an effort to implement a receiver using GNU Radio for the amateur radio whose transmitter operates in G3RUH mode with 2-FSK modulation and AX25 data format.

I designed the project to learn GNU Radio as well as to contribute something to the SmallSat Community of my institution Indian Institute of Space Science and Technology (IIST).

Is anyone else working on the same configurations ?

Anyone who can guide me through the procedural steps I should take to design this receiver(G3RUH mode with 2-FSK and AX25 data format)?

As a background information : 
The AX.25 protocol is a standard for encoding the data that includes a message header,station callsign, destination callsign, message and a simple CRC-16.
The system is widely used for position reporting of the amateur stations

Looking for a directive path to move ahead and a positive response.

Thanks and Regards

--

Yugal Joshi 

B. Tech. Electronics and Communication Engineering

Indian Institute of Space Science and Technology (IIST)

Thiruvananthapuram

Kerala

India  - 695547