[RTTY] RTTY Cut Numbers

[Jeff Stai]

Once upon a time I designed error correcting codes for solid state disks.
It was a lot of fun and I would love to jump into it again... But putting
ECC onto a RTTY contest exchange seems a little to me like adding a
gasoline engine to a horse drawn wagon. It might make it more efficient and
reliable, but if you have a horse drawn wagon it's probably because you
just enjoy being pulled around by a horse.

73 jeff wk6i


On Sun, Jan 10, 2016 at 11:51 AM, Kok Chen <rtty at w7ay.net> wrote:

>
> On Jan 10, 2016, at 11:28 AM, G3YYD wrote:
>
> > If the checksum character is in error?
>
> Send "AGN?" of course :-).
>
> You can even automate the "AGN?", but with poor propagation, the back and
> forth could end up sounding like Packet Radio :-).
>
> Sending the serial number twice is a form error detection, that is why we
> use it today, but it is rather inefficient.   And the response to an error
> is similarly, either "I don't need that mult," or sending "AGN?"
>
> Sending the exchange 3 times allow a single error to be corrected, but,
> like repeating something twice, is also inefficient.  Even the rudimentary
> Hamming code is better for correcting single errors.
>
> The "3 copies" methodology has even been used in hardware in spacecrafts.
> Avizienis at JPL called it "Triple Modular Redundancy."  Nowadays, in the
> same vein as error correction codes like the Hamming code (the grand pappy
> of them all), Arithmetic Codes are much more efficient hardware
> implementation than triple modular redundancy.
>
> Happy New Year 2016, David!
>
> Chen, W7AY
>
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-- 
Jeff Stai ~ wk6i.jeff at gmail.com
Twisted Oak Winery ~ http://www.twistedoak.com/
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