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[Discuss-gnuradio] Re: transmitter code

From: Eric Blossom
Subject: [Discuss-gnuradio] Re: transmitter code
Date: Wed, 16 Sep 2009 10:06:09 -0700
User-agent: Mutt/1.5.18 (2008-05-17)

On Mon, Sep 14, 2009 at 08:01:17PM -0700, harshal jadhav wrote:
> Hi Eric,
> I have a few questions regarding MIMO + GNU RADIO.
> 1. How can i use MIMO with GRC?
> If i use one USRP sink, it considers one whole USRP board. I cannot use two
> daughter boards of the same USRP board using USRP sink.

Josh is the right person to handle this part, though it's just a
matter of setting up the transmit mux and interleaving the samples.

> 2. In gnuradio-examples/python/usrp/fm_tx_2_daughterboards.py  can i use
> flex 900 boards?


> I have tried implementing the example with the flex 900 board but it shows
> more of noise. I changed the sinusoid signal frequency to 4000 Hz and 10000
> Hz. While running the code it asks for carrier frequency for both the
> signals. I have given the frequency to 900 MHz.

Your baseband frequency needs to be representable without aliasing
given the baseband sample rate.  With interp=400, the baseband rate is
128e6/400 = 320kS/s, so you should be able to represent anything from
about -150kHz to +150kHz.

For your MIMO usage, set both the side-A-tx-freq and side-B-tx-freq to
the same value, say 906e6.

The example multiplies the signals by 10000.  Try using a smaller
value for if_gain, say 4000.


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