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Re: [Discuss-gnuradio] Simultaneous RX/TX using RFX2400 Boards.

From: David Scaperoth
Subject: Re: [Discuss-gnuradio] Simultaneous RX/TX using RFX2400 Boards.
Date: Sat, 10 Mar 2007 01:42:01 -0500

On Mar 9, 2007, at 1:44 AM, Tarun Tiwari wrote:

Hi David,
Thank you for you reply.

On 3/7/07, David Scaperoth <address@hidden> wrote:

From your description above, you are transmitting whatever you
receive (is this true?).

Yes, its true and I am interested in  transmitting  the amplified  signal which I receive on the RX2 port.

I'm guessing that the sinusoid is coming from a waveform generator,
or something.  Are you selecting the RX2 antenna?
(subdev.select_rx_antenna("RX2"))  are you using a multiplication
block on the transmitter?  What are you setting the Rx PGA gain to?

Yes,the sinusoid is coming from a waveform generator and that is using usrp_siggen.py on another computer/USRP.

When you send the tone, can you see it on the receiving computer (with an FFT, or an oscope), and what is the signal level? if its pretty low (like 10dB or less), you may have to put a multiplication block in the transmitter.  

Yes, I am selecting RX2, and transmitting on TX/RX without any multiplication block on the transmitter end. The RX PGA gain is 75.

Is there any relation with the decimation and interpolation for RX and TX?

Are you receiving and transmitting at different sampling rates?   I don't see why a sinusoid would be distorted because of one sampling rate over another.  What is the frequency of the tone you are sending?  And the sampling rate? If the frequency of the tone is half (or more of the sampling rate, you may be in trouble).

BTW, What is the distortion you are seeing?  are there lots of images (if there are, you may be transmitting at too high of a signal level)? is the signal taking up too much bandwidth?  FWIW, I have had experiences where it was less about my USRP, and more about my settings on my oscope =)



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