Forum: GNU Radio Re: sending single tone Am modulated using usrp1+wbx

Marcus thanks for your help.

I was trying with 2 antennas (WA5VJB) varying the usrp tx gain but the
results are the same (In this moment I dont have an attenuator). I was
reading a past mail from this list (March 25 2012) and there is a 
similar
problem that I have: the q component is not zero, I send a mail to the 
list
asking for it.

thanks

> Marcus thanks foryourhelp.
>
> I was trying with 2 antennas(WA5VJB)varyingtheusrp tx gain but the
> results are the same(In this momentIdon'thave anattenuator).I was
> reading a past mailfrom this list(March 252012) and there is a similar
> problemthatI have: the q component is not zero, I send a mail to the
> list asking for it....
>
> thanks
>

Consider the attached AM transmitter simulation that uses a complex
signal source for both the modulation source (1kHz tone), and the
carrier (0Hz).

Note that the signal spectrum is exactly as you would expect, and I and
Q are *both* non-zero in the "scope" sink.

Keep in mind that the representation of signals we talk about here is
given by:

x(t) = x1 (t) cos(?0 t) - x2 (t) sin(?0 t)


And that direct-conversion SDR hardware (such as the USRP) uses the I/Q
representation of the signals, in which both the in-phase and quadrature
   components are significant.