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Re: [Discuss-gnuradio] Simultaneous TX/RX Sample Code for RFX (FLEX) 400

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] Simultaneous TX/RX Sample Code for RFX (FLEX) 400
Date: Sat, 20 May 2006 21:11:53 -0700
User-agent: Mutt/1.5.9i

On Sat, May 20, 2006 at 08:59:00PM -0700, rdmiller wrote:
> Eric,
> Thank you very much for the reply.  I noticed that I was actually modifying
> a very old version of usrp_rx_cfile.py (found at
> http://www.koders.com/python/fidB649E66943F7649C67371CB015D6E5ACAE276523.aspx).
> I've taken a look at the latest version from cvs and have a question
> regarding the proper way to add the call to select_rx_antenna( ).   It
> appears that the mux value is set based upon user input or another method,
> and that this may result in improper operation using RX2.  I've tried
> setting the rx_subdev_spec to 'RX2' from the command line argument with
> error.  The message is to use 'A', 'A:0', or 'A:1' when using the A side of
> the usrp.  When trying 'A:1', an error also results.  So, when I run the
> code I am using 'A:0' as the input.  I am therefore fearful of having bad
> mux values even though the modified code (listed below) runs without error
> in terms of creating the data file.  My question is whether or not there is
> a simple alteration to the code below that will result in using RX2 for
> receiving data while transmitting simultaneously from RX/TX?

The subdevice spec has to do with selecting either the daughterboard
on the A or B side.  It has nothing to do with the selection of the
TX/RX vs RX2 antenna port.  The mux is set up depending on the A vs B

Your code looks right.  Sorry, not near a USRP to test it right now.

> Although I am aware that the signal will need to be attenuated severely, I
> am unsure what the RF front end of the RFX-400 is spec'd for.  With a 20 dBm
> signal at the TX, I am planning to use anywhere from 40 to 60 dB of
> attenuation.  I believe this will give me a -20 to -40 dBm signal at RX2. 
> This should be acceptable, right?  Thanks again for your help, it is much
> appreciated.

I'm not sure.  Matt's the guy to answer this (unless it's already on
the daughterboard data sheet).  He's at the Dayton Hamvention now ;)


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