[bars] odd/rare/unresponsive callsigns on FTP

[Tim K1DC]

In the last few weeks while operating FT8 I've seen calls from Nigeria 
(ATNO for me), North Korea (ATNO for most everyone) and Antarctica that 
were suspiciously loud and completely unresponsive to my calls.  A quick 
check of QRZ.com indicated that there was no info on these calls.  I was 
experiencing an FT8 'hash collision'.

The short version of the story is that the FT8 protocol uses a shortcut 
(a hash code) to send some callsigns.  In some rare-ish cases it is 
possible for multiple call signs to have the same hash code value.  For 
example (this is a made up example), 'PY2PEACE' could share the same 
hash code as 'P5AXXX'.  So while PY2PEACE is active on FT8 it may appear 
in your decode list as P5AXXX.  You start frantically calling P5AXXX 
with no response.  There is a much longer, and detailed description of 
the issue here: https://bit.ly/49AnNOC

So if you happen to run across a P5 on 10m FT8 and it is not under the 
Mother-of-all-pileups you can simply restart your FT8 software and it 
will rebuild the hash code table.  This will work a lot of the time, but 
not always.  So do a little research on that too-good-to-be-true call 
before you tape down your 'Enable TX' button.

73,
Tim - K1DC
-- 

Courageously sent from a non-Apple device that /includes/ a headphone jack.

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      Tim Carter - K1DC (was KC1RET)

			

	+1.978.710.0133 <tel:1.978.710.0133>

	k1dc.radio at gmail.com

	https://k1dc.com

"Computers are incredibly fast, accurate and stupid; humans are 
incredibly slow, inaccurate and brilliant; together they are powerful 
beyond imagination." -- /Albert Einstein/

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