Hi Dave,
Dave Blaschke wrote:
K1JT wrote:
In principle, any hardware that can be made to work with Linrad should
also be usable with the Linrad-MAP65 combination. At present this is
true only if the sampling rate can be set to 96.000 kHz (four
channels, two I-Q pairs) or 192.000 kHz (two channels). If you want
to try MAP65 and don't have xpol, a simple way to get started would be
to put nothing into the Y channel (or perhaps put the X signal into
both X and Y inputs). I have tried this in my station and it works --
although of course no polarization information is produced for the
received signals.
The SDR-IQ can provide effective I-Q sampling rates of 55.555,
111.111, 158.730, and 196.078 kHz for a single polarization.
For some reason my post to Linrad mailinglist
linrad@antennspecialisten.se is bouncing.
I'm using SDR-IQ. Is it a certainty that the SDR-IQ cannot handle
sampling rate values outside those shown above; such as the 96.000 kHz
required by MAP65? I would like to test this. (Or am I misunderstanding
the requirements?)
I don't have an SDR-IQ or any of its documentation, but as I
understand it the A/D sampling rate is fixed at 66.667 MHz.
Resampling and decimation is then done in a specialized
chip (by Analog Devices, I think). I imagine this means
that only certain output sampling rates are possible -- ones
related to 66.667 MHz by the ratio of small integers.
Perhaps someone else with better knowledge of the SDR-IQ can
correct me, or otherwise elaborate.
I can see how to set the sound output sampling rate under Linrad to
96.000 kHz, but how does one manually set the sound input sampling rate
to this value? Or is a pre-programmed value chosen by Linrad whenever
SDR-IQ is selected as the input device during setup?
When you use the SDR-IQ with Linrad you don't need a Delta44
or any other soundcard for input. A/D conversion takes
place in the SDR-IQ, so the input sampling rate is
determined there. As I mentioned above, the SDR-IQ also
does decimation to provide a smaller bandwidth (190 kHz or
less) at its output. The output from SDR-IQ (input to
Linrad) is digital, not analog.
My second question: Has a revised version of Linrad been released that
will detect the SDR-IQ under Linux? I am currrently running the Windows
version.
I expect Leif will correct me when he returns home, if I am
wrong about this. I believe the most recent version of
Linrad (both Windows and Linux) can always be found at the
bottom of this page
http://www.sm5bsz.com/linuxdsp/linroot.htm
along with a brief description of changes from previous
versions. The most recent (stable, released) version can be
found on the Linrad Home Page:
http://www.nitehawk.com/sm5bsz/linuxdsp/linrad.htm
-- 73, Joe, K1JT
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