[linrad] Re: Brief correction

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hi Roger,

> I used to derive my frequency data like this:
> 
> /*
> freqpre=fg.passband_center;
> freqpre=freqpre*10E6;
> freq=(mix1_fq_mid[fftx_nx]);
> freq=freq*10;
> freq=freq+freqpre-480000;
> freq=freq*100;
> */
> where fg.passband_center and mix1...are linrad variables.  This now
> gives erroneous results when in WCW mode.
The info in mix1_fq_mid[fftx_nx] is only valid when the AFC has
locked to a signal. In case AFC is deselected or the AFC failed
the data may be incorrect. The number 480000 is ui.sampling_speed/2
and it should be applied only in I/Q mode. 

> I now derive my frequency data like this:
> 
> freqpre= hwfreq*1000000.0 ;
> freq=freqpre;

This should be correct always. Linrad looks at the flags and selects
the frequency actually in use for conversion to the baseband and adds
the bfo offset 'bg.bfo_freq' in ssb mode.

Look at the routine 'frequency_readout' in baseb_graph.c. for
details.

73

Leif / SM5BSZ


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