Subj : Re: VARA Modem
To   : Vk3jed
From : echicken
Date : Wed Feb 23 2022 03:06 am

  Re: Re: VARA Modem
  By: Vk3jed to echicken on Wed Feb 23 2022 12:49:00

 Vk> DMR and to a lesser extent, Fusion (the FT-70 is reasonably priced too).

Yeah, $240 CAD for the FT-70 is not bad, but more than I'm willing to spend right now to check out yet another DV mode. Tempting though, since a local friend is a fan of it and says there's decent activity here. Perhaps I'll see a used one in a flea market soon.

 Vk> become available. M17 is a 100% open source DV mode. It uses the Codec2

I like the idea of M17, but I haven't kept up with it. Do you have any direct experience with it?

I'll happily get on board with M17 when I can buy a built rig (or one requiring minimal assembly) and have some other people to talk to on it.

 Vk> Direwold is more tolerant of maladjusted radios. It actually uses multiple
 Vk> modems in parallel on receive to process signals with different levels of
 Vk> twist between the two tomes and takes the best decoded output. Direwold

Well, that's pretty cool. Thanks for the overview.

 Vk> also has an extension to the AX.25 protocol that allows lower BER (and
 Vk> more decoded frams) at low SNR. This extension is backwards compatible
 Vk> with standard AX.25, and the extra error correction is ignored by standard
 Vk> TNCs. This is because the extension is a wrapper around the standard frame
 Vk> that contains the extra FEC, and a standard TNC simply sees the standard
 Vk> frame within. 

Sounds like (and presumably is) FX.25. A nice idea, but unfortunately it comes with all the baggage that is AX.25. I understand why, but I just can't get excited about it. Not that I'm well qualified to have an opinion on the subject, but I just find AX.25 and its various bolted on improvements (and documentation) to be a bit of a mess.
  
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