Re: P3 amplitude calibration

Posted by Alan Bloom on Aug 31, 2010; 6:18am
URL: http://elecraft.85.s1.nabble.com/Re-P3-amplitude-calibration-tp5479952p5481315.html

Actually, you don't need to calibrate the P3 at different levels.  The
ADC is linear within a tiny fraction of a dB over its whole range, so
once you calibrate at one level, all levels should be accurate.

But you bring up a good point about needing a different signal source
for each band.  I guess I should include a "global" calibration that
applies to any bands that haven't been calibrated.

Alan N1AL


On Mon, 2010-08-30 at 13:36 -0700, Mike Scott wrote:

> Given Alan's plans, I detect a need for an XG3 now that he wants to make the
> P3 amplitude calibration per band.
>
>  
>
> The XG3 could be ten band 160 through 6M accurate 50 uV and 1uV source.
> Actually I might want something other than 1 uV as that is an awkward value
> between S3 and S2.
>
>  
>
> So a 10-band source with -73 dBm and -103 dBm outputs might be better
> because -103 dBm would be S-4 for those who like 6dB per S-unit and S-3 for
> those who want  5dB per S-unit.
>
>  
>
> AE6WA
>
> Mike Scott
>
> Tarzana, CA
>
>  
>
> ----------------------------------------------------------------------------
> -------------------
>
> Alan N1AL said:
>
> On my list of features to add is amplitude calibration, similar to the
>
> S-meter calibration in the K3.  I plan to make it per-band to account
>
> for variations in the K3 RF chain and to separately measure the gain of
>
> the K3's preamp and the attenuator.  This level of accuracy isn't really
>
> needed for normal operation of a radio, but as an ex-Agilent/HP engineer
>
> I'm kind of a perfectionist when it comes to measurement accuracy.  :=)
>
>  
>
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