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Re: LF: 27.925 is correct dial

To: <[email protected]>
Subject: Re: LF: 27.925 is correct dial
From: "Graham" <[email protected]>
Date: Tue, 11 Mar 2014 20:39:01 -0000
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Marcus
 
 Jose  has reduced  the  decoder pass  band  to  50 Hz , this  reduces  the  over heads on the  'decision' process  , it seems  to  be  a  harsh  environment  , compared  with  say  136  . there  where  some  AFC improvements  in  recent  issues  ,  if you  check the  psk-map  for  2  meters  , there  are  a  group  of  EA  stations  running  diffraction/scatter  , over  some  considerable  ranges , system is tacking  the  Doppler shifts 
 
The  decoder  assembles the  recovered blocks  , after the  final  symbol , so there  is  short  time  lag , depending  on the  pc speed  as  to  when the  decode  is  stamped , but as  there is no  link to  'real time'  its  not too  important , web-data also  passes  via the  server  , where  added  information  , range etc  is  added 
 
From the  recent  results , decode  levels  seem  to  be satisfactory   , just need a night  at the  Opera , this  side  to see  if  Bob  can get the  TA decode ! ,
 
73-G,
 
 

Sent: Saturday, March 08, 2014 6:36 PM
Subject: Re: LF: 27.925 is correct dial

Hi Graham,
 
well opds "dBOp" has been calibrated to display SNR on the same "average power" scale as Opera, ie carrier power in 2.5 kHz minus 4 dB. However I concede that opds SNR measurements are not always accurate. Especially with either strong signals, or unstable / incoherent transmissions, the estimate of the carrier power or noise can go wrong by several dB.
 
You mentioned improvements to the decoding algorithm in the latest Opera version - can you give details?
 
73, Markus

From: Graham
Sent: Saturday, March 08, 2014 7:19 PM
Subject: Re: LF: 27.925 is correct dial

...
OP32   min  as used on   136 KHz   , gives  ~  -41 dB  min  , so   OP2H
should run  - 47  , I note  Dex  reached  -48 , which is  -54/55  on
Marcus's  scale

Tnx , G,


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