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[Discuss-gnuradio] Basic Tx to demodulated RCA audio?

From: Chris Pezzee
Subject: [Discuss-gnuradio] Basic Tx to demodulated RCA audio?
Date: Thu, 18 Aug 2005 13:37:16 -0700 (PDT)

I have my USRP capturing video/audio from the TVRX daughter card, then
demodulating the audio to baseband and playing to sound card and
dumping to disk.  I can play back the captured audio to the soundcard.

I want to send the captured audio out through the Basic Tx, but after
reading the group archives, I think there may be a problem.
Should I be concerned about impedance mismatching between the Tx
board and an RCA-type audio connection (50ohm out to 75ohm input?)
(I am hesistant to hook up the USRP TX_A output directly to the RCA input
in case there is an overheat/short circuit/bad mojo issue.)
Has anyone done this successfully?
Can I do this directly or will I need an external buffer/amplifier to
drive these signals?

I also read about a 'hole' in the Basic Tx frequency output, but I don't
know if this will be a problem for me.  If I want to output 20-20kHz
signals, will they be filtered at the TX_A output?

If this is not a problem, I should be able to  produce a stereo output by
using TX_A and TX_B for Left and Right, correct?

Eventually, I hope to capture/create NTSC/PAL signals and replay them
through an external modulator for television equipment testing.


BTW, I mounted my USRP in a Velleman G758 case, but the internal mounting
hardware wouldn't quite fit the USRP, so I had a little drill work to do.
It works ok, and now I don't have to worry about kids and cat effects.

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