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Re: [Discuss-gnuradio] Basic Tx works with USRP and usrp_siggen.py

From: Matt Ettus
Subject: Re: [Discuss-gnuradio] Basic Tx works with USRP and usrp_siggen.py
Date: Fri, 15 Apr 2005 11:01:26 -0700
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Quoting Anastasopoulos Achilleas <address@hidden>:

> I hooked up an analog osciloscope on the Basic Tx daughterboard and tested
> the usrp_siggen.py. It seems to work!
> A couple of questions:
> 1) what are the units of amplitude? (the default is 16e3)

The signal into the USRP is a 16-bit signed number.  32767 is full scale.

> 2) why does the amplitude change if I change the frequency?
>    I guess it is related to a constant multiplicative factor in
>    the interploator?

Do you mean change the baseband (software) frequency, the DUC frequency, or the
sample rate?

> 3) What is the expected relationship between  the I and Q channel
>    outputs? I see the same signal with a phase shif, but not sure
>    where the phase shift is comming from.

90 degree phase shift.


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