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Re: [Discuss-gnuradio] Just wondering why?
From: |
Adrian Hodgson |
Subject: |
Re: [Discuss-gnuradio] Just wondering why? |
Date: |
Thu, 02 Nov 2017 09:28:21 +0000 |
On Thursday, 2 November 2017 04:52:29 GMT Kevin Reid wrote:
>
> This is true about the hardware, but gr-osmosdr, which is being used here
> according to the original post's screenshot, expresses all gain stage
> settings in dB. The RF amplifier is represented as a gain control with a
> numeric value that can be either 0 or 14 but no other values — it cannot be
> entered as a boolean through the gr-osmosdr API, and if you try, 1 dB will
> be rounded to the nearest valid value of 0 dB (amplifier off).
>
> If one is interested in the relevant code, see:
> hackrf_source_c::get_gain_range
> hackrf_source_c::set_gain
> Kevin Reid
I basically turned the RF and IF gains up to full, that was all I was doing
there, just to see how sensitive the unit would be, The stage gains are not
an issue for me.
> Okay, I think I know what you're doing - I didn't look inside the
> resampler block the last time.
>
> If you scale the interpolation in the resampler block, you change the
> output sampling rate of the resampler block - which no longer matches
> the quadrature rate - or the input sampling rate of the nbfm block.
>
> In short, the plumbing is screwed up.
>
> You need to scale the quadrature rate - or the input sampling rate of
> the nbfm block so it matches the output sampling rate of the resampler
> block after you re-scale the interpolation.
>
> -- Cinaed
I am changing both the lowpass filter decimation and the resampler integration,
so that it keeps the same rate/quadrature rate at the input to the QT
frequency plot. and for the input to the audio stage, they do not change.
At least I believe not.
Adrian