[evlatests] Internal Birdie at 1408.25 MHz

[Dan Mertely]

Hi Ken.  One way to test it would be to:

1) Re-run the test as is, and verify the continued existence
of the 1408 MHz signal, then
2) If it is still there, *slightly* move the frequency of the
L301 & see if the signal is now @ 14336 - (the new L301 frequency).

If so, it makes the API more suspect, & we could arrange for a
API on/off test.  As Bryan observed, however, it seems odd that
east arm antennas didn't show stronger RFI than other antennas
if it was API sourced.

-Mert




Ken Sowinski wrote:
> On Mon, 13 Jul 2009, Rick Perley wrote:
> 
>>    We are seeing in recent tests the presence of a strong birdie,
>> centered at 1408.25 MHz.    The characteristics of this RFI strongly
>> indicate is is *NOT* of external origin:
> 
> Here is some numerology.
> 
> The first LO was set to 12928 MHz for this observation.
> The API generates a comb with 298.611 MHz spacing.
> Its 48th harmonic is 14336 MHz, and 14336-12928
> is 1408 MHz.
> 
> Should we try this again with the API turned off?
> If this were the source, I might expect to see other
> teeth of the comb as well.
> 
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