Re: [Discuss-gnuradio] window sizing issue

[Eric Blossom]

On Fri, Mar 16, 2007 at 05:30:44PM -0400, address@hidden wrote:
> Thanks-
> 
> I'm using the DC-30 MHz basic RX board.  So by recording the input signal, 
> recording the value displayed on my "time series" window, and knowing the 
> gain (0-20db if memory serves) I can calibrate the hardware so that I can 
> back out the original voltage levels at the input?  What impact does the 
> signal processing have on the absolute magnitudes?  If there is some 
> magnitude attenuation caused by the FIR filters, is it frequency 
> independent?
> 
> thanks,
> eric

Not to discourage you, but the USRP was designed as a software radio
peripheral, not a precision calibrated measurement device.

You will have to calibrate _everything_ in the path, and of course
that includes the signal processing in the FPGA as well as anything in
the host-based signal processing path.  And yes, pretty much all of
this varies depending on a large variety of settings.  E.g., you'd
want to calibrate for each possible FPGA decimation rate that you're
interested in.

Also, any calibration you make is going to be temperature dependent.

Eric