[evlatests] Holography Phase Dependency on BW

[Rick Perley]

    A quick test was run this afternoon to test whether the 180/90 
degree holography phase effect is really a function of bandwidth (not 
expected), or is actually a function of the SSLO. 
   
    Short Answer:  It's not the BW, but  the SSLO which determines 
whether these big jumps occurs. 

    Method:
   
    Three quick in-beam holography blocks, each consisting of three 
11-step back-and-forth holography scans were set up:

    #1)  1485/1385 (AC/BD) MHz, with 25 MHz bandwidth.  Past experience 
shows we expect no major phase jumps. 

    #2)  1485/1385 MHz, with 12.5 MHz bandwidth.  We expect 180 degree 
phase jumps. 

    #3) 1378.75/1478.75 MHz, with 12.5 MHz bandwidth.  This frequency is 
selected to have the same LO tuning as block #1. 

    Results:
   
    #1:  No major phase jumps.  Two `10-second' jumps are seen, each on 
the first point following the start of a holographic scan. 

    #2:  180-degree phase jumps occured on the first two holographic 
scans.  The third scan was unaffected.  In addition three `10-second' 
variety phase jumps occurred,

    #3:  No major phase jumps.  Two `10-second' jumps are seen, similar 
to #1. 

    Thus, it's not the BW per se, but the actual tuning values, which 
causes the major jumps.