Re: MAP65/Linrad

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hi Guy,

> I too am running 2 screens on a single computer,
> one for Linrad and the other for WSJT but intended for MAP65.
> I can't yet run MAP65 in anger, because the 66.666MHz sampling rate
> for my SDR-IQ can not be decimated down to the 96kHz now required by
> MAP65.
Have you tried to decimate by 693=7*9*11 to get 96.199 kHz ?
It will be a 0.2% error in sampling rate "only".

Joe writes:"I have learned that some sound cards exhibit 
errors as large as 0.6% in their sampling rates. The JT65 
decoders presently in WSJT do not attempt to correct for 
such errors, and sensitivity suffers unnecessarily."

So at 0.6% there might be some detection and I would guess
sensitivity loss is quadratic in nature for this kind
of error. Could be worth trying:-)

Another possibillity would be to set the Linrad output 
to 96 kHz. I guess MAP65 does not accept soundcard input
so you would have to run a second issue of linrad to
sample the 96 kHz signal and send it to the network.
(Ridiculously inefficient, but it could work. On my
laptop cpu load is 40%, but it is a Centrino duo)

73

Leif



> Everything seems ok, and I can run tests on MAP65 without Linrad
> falling over.
> 
> The important thing is to have enough RAM.
> Linrad will fall over if enough memory is not available.
> Joe K1JT once said that you need about 1250MB of RAM to run Linrad and
> MAP65.
> I have 1.5GB, just enough I hope, else I will jack it up to 2GB.
> 
> System here is 2.8GHz Celeron running XP.
> Good luck,
> 
> Guy  VK2KU
> > 

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