[esa-t474] calibration tone harmonic

[Yury Kolomensky]

	Hi Bino,

it's more likely the 2nd harmonic of ~83, mirrored into ~33-34 MHz.  
The second harmonic would show up because of amp or mixer  
nonlinearity, or digitizer nonlinearity or errors. It's down from the  
main peak by almost 40 dB, which is actually pretty good for these amps.

Yury

On Feb 29, 2008, at 1:10 PM, Bino Maiheu wrote:

> Hi All,
>
> After a suggestion from Alex and overcoming my own laziness, I've
> studied a bit more in detail the residual from the calibration tone
> fits. It reveals there is a clear harmonic around 33 MHz. Plots are in
>
> https://www.hep.ucl.ac.uk/elog//T-474/100
>
> Since we have our IF mirrored from the 2nd nyquist band at 17 MHz  
> ( from
> 83 ) and 33 MHz is strangely equal to 50 MHz (fNy) - 17 MHz...  
> Possibly
> non-perfect image rejection filter ? Alex, Yury ?
>
> Cheers,
>      bino
>
>
>
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