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Re: [linrad] Linrad Questions
Hi Terry and all,
As nobody put response and I have some experience of KK7B R2
with Linrad I think below are worth to read.
Before we go further here is a copy you can download from ARRL.
KK7B's R2 article;
There are three examples of 'R2 with DSP' as far as I know;
N6TX SETI receiver;
Bandwidth of diplexers after mixers were modified for more wider
20KHz, you do need more wider up to 40KHz at least to get advantage
of Linrad and your sound card.
They use Genesys software for their design of the filter.
Rob Frohne receiver;
He uses Motorola DSP56002EVM.
Sharc-R2 Digital I/Q RF receiver;
He removed all the low frequency components
after the dual low noise amplifier.
The Analog Device SHARC EZ-KIT Lite audio input is directly
connected to the output for the two I/Q amplifiers.
I followed this method and two I/Q amplifier outputs connected
to audio inputs of sound card and run with Linrad of course!
No filters (diplexers) were modified (yet in my case) for wider width.
Note these filters are for 300 Hz - 3 kHz bandpass.
It works but maybe due to a noisy LO (HP8640B) and/or lack of
RF filters before audio amplifiers sounds rather noisy.
I didn't go in serious but just wanted a feeling of very simple setup.
Since then one of my good friend gave me a note there is another
approach called Time Machine from Expanded Spectrum Systems.
They use two TUF-1s for I/Q mixers including the same for TX
The price is assembled & tested at $170, $135 for kit.
However I thought this is not good enough for very serious use
of Linrad like me:-)
Maybe Leif and Roger have comment?
I still stick with RX2500.
By the way, who bought and received this box?
I'm still waiting their response to my inquiry of invoice.
Or, even another approach;
Tayloe Detector described in Jul/Aug and Sept/Oct QEX
It's is very interesting for me!!!
I will wait for coming article for more practical design.
Sorry for the long writing...
Kohjin - JR1EDE
At 17:08 02/10/07 -0600, you wrote:
> A few questions. I currently have Linrad running under RedHat 7.3
>using a very old SB16 sound card and taking the receive audio from a
> Could some one give me some good starting values to use in setting up
>Linrad? I really don't know which ones to play with.
> I am thinking of building aKK7B direct conversion binaural I-Q receiver
>but don't know how much difference it might make. Is it worth the effort
>to go to a direct conversion radio with IQ output? With two kids in
>university and another going next year ham radio funds are very limited
>here. If you do how do you net the your transmit frequency?