[evlatests] P-band update

[Mark McKinnon]

Additional tests and inspections indicate problems with cabling
on the suspect P-band receivers, so it's likely we won't need
to scavenge P-band receivers from the EVLA antennas afterall.

MM



---------- Forwarded message ----------
Date: Fri, 10 Feb 2006 12:41:50 -0700 (MST)
From: Mark McKinnon <mmckinno at aoc.nrao.edu>
To: evlatests at aoc.nrao.edu
Cc: Mark McKinnon <mmckinno at aoc.nrao.edu>, Charles Kutz <ckutz at aoc.nrao.edu>,
     Frazer Owen <fowen at aoc.nrao.edu>
Subject: P-band


Rick's tests of the P-band system this morning showed that
4 receivers were dead, or nearly dead, and 6 others are in
need of various levels of optimization. The P-band receivers
are difficult to repair in the field because of their location
(in the barrel behind the subreflector).

To repair the receivers in time for regularly scheduled VLA
observations next week, the FE group is taking the following
steps.

   1. Two spares in the lab will be used to replace some of the
      dead receivers.

   2. P-band receivers will be removed from the EVLA antennas
      (13, 14, and 16) as needed to replace additional dead
      receivers on VLA antennas. Jim J. removed the T301 (4P
      converter) from one of the EVLA antennas (14?) yesterday
      because of the 1024 MHz spectral feature found in the
      module by Ken and Walter earlier this week. So, P-band
      is useless on that antenna anyway. It is possible that
      not all the EVLA P-band receivers will be needed for the
      repairs. But the bottom line here is don't expect to make
      tests of P-band on EVLA antennas anytime soon.

   3. Priorities have been established for optimizing the
      remaining receivers. The FE group will do its best
      to make these repairs in time for the observations
      next week, but it is possible that some of the lower
      priority repairs may not be made in time.

   4. FE personnel are making the repairs now and will be
      working overtime tomorrow (Sat, Feb 11) to make
      additional repairs.

   5. P-band receivers will be returned to the EVLA antennas
      after they are repaired in the FE lab.

We'll keep everyone informed on status and progress.

Mark