[evlatests] High frequency sensitivity/tuning

[Ken Sowinski]

On Thu, 28 May 2009, Rick Perley wrote:

>    a)  K-band.
>
>    Antennas 15 and 23 did not tune to 20.515 MHz in IFs A and C.  The
> failure occurred both times in two different observations.
>    Antenna 13 has noticeably poorer sensitivity than the others at all
> frequencies -- a factor of at least two worse.
>    Antenna 24 in IF 'B' only has poor sensitivity at the two highest
> frequencies attempted (23.7 and 26.0 GHz).

This might be an inappropriate attenuator setting.

>    b) Ka-band.
>
>    Antennas 9 and 24 have poor sensitivity -- a factor of two or more
> worse than the others -- at all frequencies.
>    Antenna 1, IF 'B' did not tune at all for three of the four
> frequencies it was commanded to:  32.375, 30.575, and 28.775 GHz.  It

This, too, might be due to inappropriate attenuator settings.

> did tune to 26.975 GHz. Curiously (and uniquely!), IF 'A' tuned
> correctly for all four.  (All other apparent failures to tune involve
> both polarizations of a given IF).
>    Antenna 28 gave no fringes at all -- I believe this is a known
> problem.
>
>    c) Q-Band.
>
>    It's difficult to make  global assessments, due to weather.  It
> seems clear that antenna 24 is notably less sensitive than others.  This
> is significant since before its recent move, it was the best, or nearly
> the best, Q-band antenna.

It was fine a week ago at startup.  I noticed today that it was
not very happy, but poor weather made it difficult to tell why.