Re: [IRCA] The "mystery" of 1710khz

[Barry McLarnon <bdm@xxxxxxxxxx>]

On Tuesday 24 January 2006 22:01, Charles A & Leonor L Taylor wrote:
> Barry,
>
> What sort of accuracy (in percentage) can you get with FFT?
>
> I would have used zero-beating a stabilized, measured VFO. Getting the
> VFO within maybe 0.25 Hz of the unknown. The VFO has to be very stable.

The FFT technique is much less fussy than trying to zero-beat to a 
reference oscillator, and it has the advantage that you can see (and 
measure) all of the carriers on a given channel simultaneously.  The 
absolute accuracy depends on the quality of your calibration, and the FFT 
parameters (sample rate and transform size).  I usually set the sample 
rate to 11.025 kHz and the transform size to 64K.  With those settings, I 
can resolve carrier frequencies with an accuracy of about 0.1 Hz.

Barry

-- 
Barry McLarnon VE3JF  Ottawa, ON

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