On Sun, Aug 6, 2017 at 1:57 PM, John Ackermann N8UR <address@hidden
<mailto:address@hidden>> wrote:
I also have a QT Frequency Sink as eye candy, and notice that its
display is about 6dB different than the Log Power FFT output. I can
think of a number of reasons why that could be, but my simple
question is... is there an appropriate way to adjust one or the
other to align their readings? (Later I'll send the log power
results into a calibration routine to convert to dBm based on
measured results.)
Also while I'm at it, there's a "Reference Scale" parameter in the
Log Power FFT, set by default to "2". Is there a way to use this
parameter to align the two readings? I tried changing it to "1" but
that threw an error at runtime.
I took a look at logpwrfft's code and the first thing that is done to
that number is ref_scale/2, so you need to pass in a float (1.0) rather
than an integer to not get it truncated to zero. Sounds like something
to fix.
Also, there doesn't appear to be any window applied (or at least
apparent) in the Log Power FFT block. Is there a way to window the
output?
The GRC definition for the block doesn't let you set it but there
actually is a parameter win which defaults to Blackman-Harris.