[Lowfer] Strange Stuff on 508.5

[Mike Staines]

>>The error correction adds a lot of overhead to the data being sent, and 
>>the back-and-forth further slows things down.

Welcome to the whacky world of digital radio.

Mike - WM1KE
Former President - NorthEast TCP/IP Assn.
Former Director - North East Digital Assn (NEDA)

----- Original Message ----- 
From: "John Andrews" <w1tag at w1tag.com>
To: "600 meter group" <shmrg at piobaire.mines.uidaho.edu>; "Discussion of the 
Lowfer (US, European, &amp; UK) and MedFer bands" <lowfer at mailman.qth.net>
Sent: Sunday, January 06, 2008 8:11 PM
Subject: [Lowfer] Strange Stuff on 508.5


> For those of you who have been wondering what all the racket has been 
> recently on 508.5 kHz, Jay and I have been playing with a program 
> mentioned on the ARRL site:
> http://www.arrl.org/?artid=7933
>
> No new modulation schemes are involved, and we have mostly been using 
> PSK31 and PSK63, which are built-in. The NBEMS software implements ARQ 
> (automatic repeat request) error correction to send files and emails in 
> error-free form. Checksums are embedded in the text, and the sending 
> computer stops periodically to effectively say "did you get that?". The 
> other station then automatically responds with an OK to go ahead, or a 
> direction to repeat something that was missed.
>
> The banging back and forth is interesting to watch, but the only station 
> who gets that error free file is the receiving station. Anyone else 
> monitoring will see patterns of clear text and codes.
>
> The obvious application for this is emergency communication, and we are 
> just starting to evaluate its use at 600 meters. MFSK16 is one of the 
> modes included, and we will certainly be trying that as well as the PSK 
> modes. The error correction adds a lot of overhead to the data being sent, 
> and the back-and-forth further slows things down.
>
> We'll be on at 0200 UTC tonight (9 PM EST), playing with some email and 
> text files. Feel free to watch, but don't be disappointed if the clarity 
> is a little underwhelming. As a receive-only operator, you'll gain nothing 
> with the NBEMS software, and will see exactly the same stuff on your 
> favorite program.
>
> John Andrews, W1TAG
> _______________________________________________
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