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mattsnow / gr-ogn

An Open Glider Network Transport Protocol (OGNTP) receiver and decoder for GNU Radio
MIT License
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only OGN tracker no FLARM? #1

Open dc2mw opened 7 years ago

dc2mw commented 7 years ago

Hello Matthew,

I was able to decode the provided example file with my RPi3, so gr-ogn seemed to work well. Unluckily I was not able to decode some live signals. After some negative experiments - with about 50 gliders in range of my OGN station "WEMDING3" - I began to read your thesis provided in the docs folder.

So GR-OGN seems to be a receiver for the proprietary OGN-Tracker format only. It will not decode genuine FLARM transmission, am I right? I was not aware of the fact that FLARM and OGN-Tracker are using incompatible RF transmissions.

snip commented 7 years ago

Hi,

Just for information, OGN-Tracker protocol is open. See http://wiki.glidernet.org/ogn-tracking-protocol & https://github.com/glidernet/diy-tracker

Flarm one is not.

pjalocha commented 7 years ago

OGN-Tracker format was created as an open format exactly because the Flarm format is closed. Clearly the transmissions are not compatible at the level of the data content. The modulations are compatible, so that same demodulator can be used for both.

mattsnow commented 7 years ago

Hi dc2mw,

Sorry for the delayed reply. I'm glad to hear you were able to get the example working. I'm not surprised that you couldn't receive transmissions from real gliders, as when I tested my setup the successful reception range was found to be less than 100m.

Why this is the case, I'm not sure. It could probably be improved by using an optimised antenna and RTL-SDR Source Block settings, implementing error correction (OGNTP utilises LDPC) and maybe some optimisations in my code.

Unfortunately since this project had to fit within university timescales, I didn't get a chance to try any of the options mentioned. This project only decodes OGN transmissions, which as the other posters have pointed out is open source. Decoding the closed source FLARM protocol almost certainly breaks some laws and therefore wouldn't have got past a university ethics board, which is why my project didn't include this.

Cheers, Matt