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Re: First-time user of linrad

<Reply from Leif who is currently unable to access the site directly>

Hello Chris,

> However, despite my best efforts with the configs and reading Leif's
> website end-to-end I can't get the system into proper I/Q mode - eg
> with 48KHz sampling I see the spectrum mirrored about 24KHz.
OK. This means that the Linrad setup is correct and that two
audio channels are read by Linrad. (Otherwise you would only
see 24 kHz total bandwidth.)

> I've
> tried with two sound devices: internal ALC888 and external USB SB Live
> with the same results so it doesn't look like a driver issue. The
> sound system itself (ALSA) seems to work ok in stereo as evidenced by
> other programs like baudline so I should be able to get both I & Q
> channels into the PC ok.
Connect a sinewave to your antenna input and set the frequency
for your two frequencies to be separated by a couple of hundred Hz
in a normal receive mode.

Then use the "I=SOUNDCARD TEST MODE". Here you should see two
traces on screen for the two audio inputs. There are two
possibillities. One signal might be missing, or you might
have the same signal from both inputs. You can now try to
disconnect the I and Q signals one by one and find out what
happens. You can press '+' '-' to change scale, 'P' and 'R'
to pause and resume so you can see a frozen image and check
whether the phase shift is correct. (Should be 90 degrees.)

> So I guess in my unfamiliarity with linrad I've goofed up the
> configuration somehow.
I do not think so. It seems you have a hardware problem.


Leif / SM5BSZ

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