To: rsgb_lf_group@blacksheep.org
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From: N1BUG <paul@n1bug.com>
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Date: Fri, 14 Apr 2017 07:29:31 -0400
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Subject: Re: LF: 136 OP32 LAST 24HR
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Status: O

Thanks for the additional explanations Graham. That helps clarify 
things for me.

I had five full decodes of 2E0ILY last night with no more than 5% 
fade on the worse of them. Looks like Opera is going to keep the 
trans-Atlantic season going for a while.

73 Paul


On 04/13/2017 12:14 PM, Graham wrote:
> Thanks  Paul,
>
> Yes , that's  a  full  decode ,  -40 is round the  switch over point ,
> The  % fade is  the  amount of lost  'bits'  along  the  time  line ,  the
> graphic , simply  shows , 'where'  the  bits  where 'lost'
> A decode or Dynamic  spot  may be achieved with a  loss  up to approx   60%
> of the  data ,  either randomly , or  in block's   along the  time line .
> The  displayed  s/n  is the  average over the  Tx period , as  is  the
> Frequency [ recovered  audio] average  of the  Tx
>
> Using Manchester coding ,  There  are  no  synch requirements ,  each  bit
> contains ''data  and  sync''  , so  its  impossible  for the  system to
> loose  lock,  ie,  any bit that  is  recovered is  usable , so  interim's of
> static  / noise ,  the  duration of the  Tx pulse  compared to the  noise
> bursts is  'very long' , this coupled with tailored dsp  routines , provides
> good  performance on the  lower bands ,  as  dose  the 'dispersed'  decoder
> version , deployed at VHF , which provides  immunity  to Doppler  , Luis
> EA5DOM ,  used the  Op1  [ 60 second ]  to achieve  EME on 23 cm , with
> round 50% data loss ,
>
> 73-Graham
> G0NBD


-- 
Paul
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