[evlatests] Holography Phase Dependency on BW

[Barry G. Clark]

Aha.  So, in holography a scan change glitches the Flukes.  So to
make holography go, make the Fluke frequency a multiple of 10 MHz.

>     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.
>
>
>
>
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