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
on 2013-01-08 01:37
on 2013-01-08 01:58
> 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.