[evlatests] 84th harmonic question

[Rick Perley]

    Keith:

    I think that's it -- I was off by 2 MHz in my calculation.  So it's 
not a harmonic of the VLA system, but the first LO of the API ...

    Rick

Keith Morris wrote:
> Rick:
>
> The first LO for the API (both old and new) is 10750MHz.  Do you notice
> the birdie stronger towards the center of the array, or on the east arm?
>
> Shielded chamber tests of the new API LNBs didn't show any emissions at
> the LO frequency, though there was radiation at certain subharmonics,
> which we have found a way to suppress.
>
>
>
>
>   
>>     I've found a birdie at 10752 MHz in the flux data.  In reviewing the
>> 'spectral sweep' tests, I see the same birdie.  It turns out to be the
>> 84th harmonic of 128 MHz.  No other harmonics of 128 MHz are obviously
>> present in X-band.  Can anybody explain why this harmonic turns out to
>> be relatively strong?
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>>     
>
>