[evlatests] X-band power levels

[Ken Sowinski]

On Wed, 15 Sep 2010, Rick Perley wrote:

>    My 'demo science' run, taken on Sept 2, has shown some issues at
> X-band.  Six antennas have power levels well below the norm -- and one
> of them is spectacularly low.
>
>    They are:
>
>    Antenna 6 R and L:   6dB low
>    Antenna 10, R and L:  12 dB low  *******
>    Antenna 13, R and L:  5 dB low
>    Antenna 16, R only:    7 dB low
>    Antenna 20, R and L:  6 dB low
>    Antenna 23, R only:   6 dB low
>
>    Antenna 10 is certainly special:  Not only is its power low, but
> it's cross-polarization is far too high -- 10 to 12 %, when nearly all
> the other (old-style) X-band antennas are 1 -- 2%.  However, this is not
> an issue with R and L being interchanged.
>    Polarization calibration does not correct for for antenna 10's
> apparent high polarization -- we have an apparent failure of closure,
> but the reasons are (to me) quite unknown.  The high polarization alone
> is not likely -- at C-band, where the antennas are normally this highly
> polarized, we get excellent calibration results.
>
>    Curiously, antenna 20 is also highly cross-polarized -- 6 to 10%.

I will add the clarification that when Rick uses the word
'power' above he means correlated power, not the RMS signal
power measured in the downconverters.