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Re: [Discuss-gnuradio] usrp tx documentation/confusion

From: Matt Ettus
Subject: Re: [Discuss-gnuradio] usrp tx documentation/confusion
Date: Fri, 05 May 2006 16:09:33 -0700

On Fri, 2006-05-05 at 15:45 -0700, Erik Tollerud wrote:
> I've been trying to work out how to do some things on the transmit
> side of gnuradio, and I've noticed there's something of a dearth of
> documentation.  Most of it amounts to "its just like receive, only
> backwards."  That's probably fine for people with signal processing
> background (which may be the majority of this community...), but I
> find myself getting confused... by looking at some of the examples, I
> get a sense of how to initialize all the components in python, but if
> I do anything beyond them, I get unexpected results.  For example, I
> took siggen_min2.py and modified it so that instead of outputting a
> pure sine wave, it output sin(wt)+cos(2wt).  This did not put anything
> resembling sin(wt)+cos(2wt) on the output of the tx board. 
> Furthermore, chaging w does not some to alter the waveform at all -
> only calling u.set_tx_freq changed the output freqency.

I agree that there is definitely a dearth of documentation, especially
for TX.

The [unstated] purpose of siggen_min2 is to transmit different signals
to TX daughterboard A and TX daughterboard B.  

In general, without really changing the firmware, any signal sent to
DB-A will output the I signal on one output and the Q on the other.  The
same goes for DB-B.

For what you are trying, I would suggest working with usrp_siggen.py
unless you want to use multiple TX daughterboards.


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