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From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
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Date: Sat, 8 Mar 2014 18:19:41 -0000
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Subject: Re: LF: 27.925 is correct  dial
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Ok Paul

Well , Opera  and  Mark's   systems  are  not the  same  , Opera  is 
recovering  data  , with  afc/fec  ,  and the  DS , devised by
Marcus   , is  correlating  the  Opera  encoded  data  pattern and requires 
high  stability etc

But there  are  swings and  roundabouts , Opera  will  decode  with  up to 
50% of the  data  missing , block or  randomly distributed ..

>From observation's  there  could be  6 or more db difference  in the 
reported   s/n levels  , Op is the  average  over the  tx cycle , wspr 
gives  a  peak  level  , Opera  is  complimentary to the ROS  data  mode 
and  indicates  the  path  suitability for  data  tx /rx

Minimum  Op, levels depend  on various  factors  , one being  , keeping  the 
'pulse'  as  close to  original  as  possible , I gained  -3 dB  using a 
'cheap sdr'  on 477K  over the  racal Rx  ..

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,


--------------------------------------------------
From: "Paul Nicholson" <vlf0403@abelian.org>
Sent: Saturday, March 08, 2014 5:58 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: Re: LF: 27.925 is correct  dial

>
> Thanks for that Graham.
>
> I'm just trying to see how far short we are of an opera decode.
>
> I just got another 0.84 dB S/N improvement by shifting the loop
> a little further from the prevailing noise, and by compensating
> for the slight elliptical polarisation of the signal.
>
> Markus reported:
>
> > 2014-03-07 06:51:53 ... -48.9dBOp 100% 19.4dB
>
> so I guess that would now be -48.1dBOp.
>
> But still 2 or 3dB short I think?
>
> --
> Paul Nicholson
> --
>
>