[evlatests] 3.2 MHz ripple at P-band

[Paul Harden]

On 10/27/2015 12:52 PM, Rick Perley wrote:
> I'm reducing some data taken last Spring in the 'BnA' configuration.
>
>     Good news -- all antennas worked well, except ea18, which had 
> highly variable gain.  All polarizations appear correct.
CAL switching reported failed on EA18 by Huib on 3/24/2015 during an 
observing run.  Receiver was swapped on 3/30/2015.  Problem ended up 
being a bad connector on the CAL cable, also fixed on 3/30/2015. This is 
to report a receiver change on 3/30/2015 in case before or after the 
observing run you are using.

> The two antennas with the strongest ripples are:
>     ea03 :   +/- 20% in power (i.e. 40% pk-pk).
>     ea28:    +/- 10% in power.

Receivers in the good and bad antennas have been stable for some time 
(no configuration changes):
EA03 receiver installed 7/10/2013
EA28 receiver installed 9/5/2012

> Antenna with essentially no ripple are:  ea02 and ea21.
EA02 receiver installed 3/28/2014
EA21 receiver installed 10/31/2013

I do not currently see any commonality between the good and bad ripple 
antennas.  Some high ripple antennas have the ESD protection board, some 
are VLITE, etc. but so do some of the good antennas.

Some ripple (reflected power) on the long RF cable runs (about 140 ft) 
between the Vertex Room and the receiver in the Apex is normally small, 
but not unavoidable.

We will check a couple of the bad ripple antennas to see if we can see 
anything on a single antenna basis.

I will check Dan Mertely's weekly bandpass plots shortly for anything 
noticeable.

Paul