[evlatests] P-band status

[Rick Perley]

    Frazer took a nice 1-hour run of some prominent sources at P-band 
last night.  He reports:
-----------------------------------------------
Based on last night's one hour run: 
(TSUB0001.sb23972725.eb24393875.56517.44620590278):

No receiver: 9,19,21 (log says 9 and 19 were powered off or not 
installed; not clear why 9 is missing)

Swapped: 3,8,14,26

bandpass issues: 25YY bandpass looks strange (big "humps separated by ~ 
35MHz across band).  7YY has high frequency ripple across entire band.

Mostly OK: 1,2,4,5,6,7,10,11,12,13,15,16,17,18,20,22,23,24,25,27,28

------------------------------------------------------------------------

    I've looked at the same data, and can add some additional 
characteristics:

    1) ea01 is really weak -- down by a factor of 5 to 10 in power (LCP 
is worst).  After calibration, all the other antennas have about the 
same sensitivity. 

    2) Cross-Polarization:  Six antennas:  ea05, ea06, ea11, ea12, ea14, 
and ea24, have cross-polarization at or higher than 20%.  ea14 is the 
worst -- nearly 40%.  Eight antennas (ea03, ea08, ea10, ea13, ea17, 
ea18, ea25, and ea26) all have cross-polarization less than 5%. 

    3) Switched power is working on most of the fringing antennas:  The 
non-working ones are:  ea01, ea02 (LCP only -- is that 'Y'?), ea10, 
ea11, ea13, ea25.  I'm sorry to report that there is clear evidence of 
'PDif compression' on most of the antennas.  The degree of compression 
is about the same that we see at L band. 

    4) Nine of the antennas sporting switched power have 'reasonable' 
values of system temperature.  The others are all low by a factor ~10 -- 
but cause is obvious, the Tcal values have not been changed from their 
default values.   The antennas *with* non-unity Tcal values are:  ea02, 
ea03, ea06, ea08, ea17, ea18, ea20, ea26 and ea27. 

    And while on the subject of Tcals for P-band:  The current (CD) 
table shows only an entry for spectral window #1 (AIPS definition).  The 
second window's value  is set to 1.0.  If we continue to observe with 
128 MHz sub-band windows, then use something like MORIF to split them 
into useable components, we'll need to have a way to obtain the correct 
Tcal values. 
(I realize that switched power is a low priority for P-band, but IMHO 
it's useful to keep these ideas in mind). 

    5) The data (amplitudes and phases) look very stable.  But when 
calibrated Cygnus A using 3C147, the resulting zero-spacing flux density 
values ranged from 4 to 6 KJy.  Not encouraging.  But this was a very 
'quick and dirty' attempt.  I'll look more closely tomorrow. 



Frazer Owen wrote:
>
> Based on last night's one hour run: 
> (TSUB0001.sb23972725.eb24393875.56517.44620590278):
>
> No receiver: 9,19,21 (log says 9 and 19 were powered off or not 
> installed; not clear why 9 is missing)
>
> Swapped: 3,8,14,26
>
> bandpass issues: 25YY bandpass looks strange (big "humps separated by 
> ~ 35MHz across band).  7YY has high frequency ripple across entire band.
>
> Mostly OK: 1,2,4,5,6,7,10,11,12,13,15,16,17,18,20,22,23,24,25,27,28
>
>
>
> ---Frazer