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Is there any way to turn off the error correction?

I'm enjoying VarAC - the functionality is very good and it works well with reasonably strong signals. But the underlying VARA protocol seems to get in the way as the signals drop. I'm an old-time PSK31 and RTTY user - zero error detection and correction. I could manage a QSO under some pretty terrible conditions - it's surprising how much corruption to the data stream you can accept and still work out what the guy at the other end means. I'm finding that many of my VarAC QSOs fail because the signal drops down into the noise floor and VARA goes into a sequence of repeated NACs and retransmissions. If I look at the monitor window, I can see that most of the text is getting through but it's failing the data integrity checks. I would settle for some garbled text rather than a dropped connection!

Does the client application - VarAC in this case - have any control over the low level protocol? Are you able to do anything to accept the errors and let the QSO continue?

Martin

6 comments

6 Comments

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HB9CVN

Aug 02

the VARA protocol is ARQ, so if you are not interested in data integrity you'd better use any of the FEC modes. The ARQ takes places in the transport / datalink layers, so it's part of the protocol, you can't just turn it off.... It would be interesting to have the capability to read the packets at these layers in the monitor window, and see what's going on in the communication between the modems. It is somehow possible, as many years ago we were doing just that for work on other ARQ protocols, but I guess it would require more work and maybe only few would be interested.

HB9CVN

Aug 02

Replying to

You are comparing apple to oranges. If you want to transport your morning bread, you won't use a 40 T truck. If you want to transport 40 T of goods you won't use a sport car.... Vara, like Pactor, is an ARQ mode. The very idea of an ARQ mode is to preserve the integrity of the data. That's why such modes are used in networks like winlink. ARQ mode will adapt speed when needed in order to get correct packets. Thus, they are slower than FEC mode, where data integrity is not provided. For pure conversational contacts other modes, like Olivia, are faster.

g8fxc

Aug 02

Replying to

Again, fully accepted! I guess the problem is that VarAC has adopted VARA as the transport layer and is beginning to build up a following which would be good to continue to increase. There is virtually zero activity on Olivia - conversational chat modes do not need the 100% data integrity that is required for email...

HB9CVN

Aug 02

Replying to

Discussing technical matters is easy. You can measure, evaluate them. Add the human factor and logic get flushed down the toilet. For conversational contacts, Olivia is very solid and one of the best options. Yet very few use it. VarAc, is based upon VARA and adds the integrity, paying a toll in speed with very low signals. It allows to send files, where the integrity importance is obvious. Popularity of FT8 exploded in the last few years, with very many operators operating fully automated stations and just checking the log once they get home after work.... I personally couldn't be any less interested in FT8; but many others are, and that's perfect to me. I see more of a problem in terms of VarAc popularity with people constantly remaining on the calling frequency and blocking other traffic.

VE6XMB Rob

Aug 02

Perhaps the mode for you is Olivia. She works with very weak signals and has FEC for perfect print down to a very weak signal.