I'm doing a simple flowgraph to determine the peak value (dBFS) within an FFT. The Log Power FFT sends vectors to a Max block which outputs the result -- it seems to be working reasonably well.

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.

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?


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