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Re: LF: VO1NA - 137.7770 kHz

To: <[email protected]>
Subject: Re: LF: VO1NA - 137.7770 kHz
From: "Markus Vester" <[email protected]>
Date: Fri, 7 Jun 2013 00:47:25 +0200
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Hi Graham,
yes it's true that the opds correlation detector does not attempt to directly decode any of the Opera 28-bit message contents (ie. the callsign). But you do get more than a single yes-or-no information. Opds tells you fairly reliably which entry from the predefined callsign list actually produced the hit. The list currently contains 28 candidates which makes up about 5 bits worth. Also it measures the TX carrier frequency down to a milli-Hz out of a 100 Hz range, which in itself could be used to encode another 17 bits... So I'd say it gives you less than 28 bits but certainly more than one bit.
Best wishes,
Markus (DF6NM)

From: Graham
Sent: Thursday, June 06, 2013 7:13 PM
Subject: Re: LF: VO1NA - 137.7770 kHz

Where  as Op is  designed to  use  standard tx/rx  and  soundcards  with
afc  routines , Marcus  is  running  a  correlation  process  , looking  for
the  pattern  match , this  in effect  is  decoding  a single  data  'bit'
and  stability  will  affect his  decode  system , but  with another 10 dB
s/n it  may extend the  range  considerably !

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