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[Linrad] Re: LINRAD+WSE
- Subject: [Linrad] Re: LINRAD+WSE
- From: Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>
- Date: Tue, 27 Oct 2009 18:03:36 +0100
> > As a first test you might try two computers and use a cable
> > between them. You could set Linrad to generate a wide
> > bandwidth with a high sampling rate on the output soundcard.
> I don't understand that,as don't know how to set Linrad to generate
> wide banwidth.
The reason Linrad is so complicated, to newcomers is that you
have a lot of fredom to select what processing you want.
First, get an understanding of the block diagram.
The "first mixer bandwidth reduction" sets the sampling speed
of timf3 to a power of two less than the sampling speed at
your input. The bandwidth is 50% of the timf3 sampling rate.
Then you would have to select CW or SSB, and the widest possible
passband. That would prevent any further reduction of the sampling
speed. The BFO has to be placed outside the passband and the
output sampling speed has to be set well above two times the
bandwidth you have selected.
Select a small size for fft3 and do the filtering in the time
domain (there will be no decimation in this case.)
Just start with Linrad as a conventional SSB receiver that provides
another computer with audio from the soundcard. That should work
directly and involves no complications. Then you can start changing
parameters in small steps and watch the CW skimmer screen to
see what happens.
> In this case it possible to use the output second
> soundcard in first computer with Linrad.
If you want about 40 kHz bandwidth you would have to set the soundcard
to 96 kHz and it might be better to use the Delta 44.
Note that the solution is not ideal. Linrad does not have an
audio I/Q output because there has not been any need for that before
that I have been aware of.
When the portaudio interface is completed it will be possible
to cascade Linrad with Linrad through Jack and then I might find
it easy to add an I/Q output that would fit to any software
that can read data from a soundcard.
Leif / SM5BSZ
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