[evlatests] A curious new birdie at X-band

[Keith Morris]

This is the API 1st LO signal, common to both the new and old API systems.



On 7/23/2013 9:50 AM, Rick Perley wrote:
>      As part of the 'receiver rotation' experiment, I've taken wideband
> data covering all of L, S, C, and X bands.
>
>      Looking at the higher half of X-band (10 to 12 GHz), one, and only
> one, piece of RFI is seen.  It's a pure tone, at
>
>      10750 MHz
>
>      This is not a harmonic of 128 MHz (but is close -- the 84th harmonic
> is 10752 MHz).  No other birdies are seen, so this tone is definitely
> special.
>
>      And it's only seen on antennas near the center of the array --
> strongly arguing for a local origin.
>
>      The autocorrelations are useful for diagnosis -- unfortunately, only
> half the antennas provide this (what do we have to do to get them all?)
>
>      Antennas with strong 10750 MHz tone are:
>
>      ea13 at W02
>      ea15 at E02
>      ea22 at N02
>
>      Antennas with detectable tone (but weaker than above list) are:
>
>      ea05 at W08
>      ea09 at W10
>      ea11 at W06
>      ea24 at W04
>      ea 26 at W12
>
>      Antennas with no visible tone (in autocorrrelations) are:
>
>      ea01 at N14
>      ea03 at E10
>      ea07 at E12
>      ea17 at E14
>      ea19 at W16
>      ea28 at E16
>
>      All other antennas provided no autocorrelations.
>      The cross-correlation data are consistent with a local origin, near
> the array center.
>
>
>
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-- 
Keith Morris
National Radio Astronomy Observatory
1003 Lopezville Rd.
Socorro, NM 87801
575-835-7060 (phone)
575-835-7027 (fax)