[evlatests] R-L delays -- HUGE!

[Michael Rupen]

As Rick, Vivek, and I just discussed, it's probably worth having a look
at the description of VLBACPOL in the AIPS cookbook (also the EXPLAIN
file) to see how AIPS wants you to do this.  As I recall most of that
is to do with deriving the cross-hand pol'n, so if you've already
measured that CLCOR might be all you need.  VLBACPOL should
walk you through how to set that up as well.

Cheers,

          Michael

> Rick-
>
> To correct the R-L delay, you apply the same delay offset to L (only)
> for *all* antennas, in the manner in which you have always done
> so with CLCOR.  This on top of the per antenna L offsets (the big
> component compensating for the offset with R comes out in the L
> differences, of course).
>
> -George
>
>
> On Fri, Jul 31, 2009 at 11:29 AM, Rick Perley<rperley at nrao.edu> wrote:
>>    I'm going through the full polarization data of 3C286, taken at
>> L-band on 3C286 (a strongly polarized source).
>>
>>    There are some remarkable delay issues:
>>
>>    1) Delays within the RR side are generally where we have seen them
>> -- typically 20 nsec.  Two antennas are especially large -- 2 (-77 nsec)
>> and 9 (-88 nsec), w.r.t antenna 1.
>>    2) Delays within the LL side are much larger, with seven antennas
>> having delays more than 50 nsec, and one being more than 200 nsec!!
>>    These are easy to calibrate out, and I did so.
>>
>>    But the biggest surprise comes from the delays in the R-L
>> correlators -- the time delay between the two polarizations.  After
>> removing the 'parallel-hand' delays, I find the RL and LR correlators to
>> have a 305 nsec delay error -- of opposite sign in RL to LR (as it
>> should be), and the same for all baselines (as it should be).
>>
>>    Question to AIPS-experts:  I don't know how to get AIPS to correct
>> for the delay between R and L.  The phase correction ('POLR' in the
>> program CLCOR) is not the correct operation.  Can AIPS do this?
>>
>>    Other than this -- the X-hand amplitudes look good, and are at about
>> the right level.
>>
>>
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>
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