[evlatests] More on S-band birdies ...

[Dan Mertely]

Actually, I now notice that the L301 1st LO uses the 512 comb
out of the L300, not the 128 comb.  It is the L302 that uses
the finer resolution 128 MHz comb.  Still, could the 512 comb
output have 128 MHz "artifacts" that pass through filtering
because they are below filtering and isolation spec cut-off?

-Mert


Dan Mertely wrote:
> It has the sound of being the 128 MHz comb output from the
> L300 reference, being up-converted by the L301 which uses the
> comb as a reference.  ...Maybe different manufacturing
> "techniques" produce slightly different leakages in the L301?
> At 9cm, different wiring placement within the module might
> attenuate some lines, while enhancing others.
> 
> Terry Cotter could render a more insightful opinion.
> 
> -Mert
> 
> 
> Rick Perley wrote:
>>     In looking at the autocorrelation spectra, we find the peculiar RFI 
>> at S-band is more peculiar than previous reported:
>>
>>     The separation between the birdies is 128 MHz, not 256MHz.  They are 
>> all 'centered' at 3200 MHz.  Different antennas show different RFI 
>> lines, but all of them are n*128 MHz away from 3200 MHz. 
>>
>>     In this experiment, subband 6 contains 3200 MHz in channel 577.  
>> (Because the subband separation is 128 MHz, all birdies are in channel 
>> 577 of the relevant subbands). 
>>
>>     Antenna 8 shows them strongly in subbands 4, 6 and 8, and weakly in 
>> subband 7
>>     Antenna 9 has a very strong signal in subband 5, and none in any other!
>>     Antenna 15 shows them weakly in subband 6 and 8.
>>     Antenna 24 has it only in subband 6.
>>     Antenna 27 shows them weakly in subbands 6 and 8.
>>     Antenna 28 shows it strongly in subbands 4 and 8. 
>>
>>     An explanation is wanting ...
>>
>>    
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