Message-ID: <02C79F174E3A4140855A68D816275279@AGB>
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <4F1828F5.18343.1167B04@mike.dennison.ntlworld.com>
In-Reply-To: <4F1828F5.18343.1167B04@mike.dennison.ntlworld.com>
Date: Thu, 19 Jan 2012 16:51:40 -0000
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Subject: Re: LF: Opera speeds
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Mike

OP is  reporting the average  s/n of  the channel  ..

The purpose  of the  various  speed/time  versions  are  purely  the 
minimum  signal  decode  level

The  longer the  time  slot  the  lower the  s/n  capability  , if the  s/n 
is  showing similar , that  is
indication that  the  noise  floor  at  the  RX  has remained  constant 
during the  capture  period, with the
proviso  that  app  66% of the  signal  has been  captured ...as to  the 
distribution  of the  66 . that  has yet
to  be determined

In a test  on 500  I ran   op 4  and  16  at the  same  time , with the 
same  carrier  levels  , OP16 was
predicted to  give  6dB  gain , Eddie , decoded  the  16  reliably  , where 
as the 4  was only  decoded
with  round  6  dB  increase  in Tx out  put ..the  test  also  produced  a 
lot  of local  op15 false  spots  :(

Thanks GL

73 -G.



--------------------------------------------------
From: "Mike Dennison" <mike.dennison@ntlworld.com>
Sent: Thursday, January 19, 2012 2:30 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: LF: Opera speeds

> I have been testing the difference between Op8 (8-second message) and
> Op32 (32 second message). Thanks to the software, receiving stations
> can report on both modes without having to switch.
>
> Reports on my signals from PA0A, PA0AM, G4WGT and F6CNI (between 257
> and 465km) show variable results. The slower speed never produced a
> worse S/N, though sometimes it was exactly the same. Usually the
> result was between 4 and 9dB improvement with the slower speed.
>
> Intuitively, I would assume a 6dB improvement (though I am no digital
> expert), but occasionally better iif QRM is present as I would expect
> this to affect the faster signal more. Is this a reasonable
> assumption?
>
> Not a totally scientific test, but at least it demonstrates that it
> is worth using Op32 when signals are weak.
>
> I have now stopped Windows automatically rebooting my computer in the
> middle of the night so I should be able to monitor all of tonight. A
> nighttime transmit test is scheduled for the weekend.
>
> Mike, G3XDV
> ==========
>