[evlatests] R-L delays -- HUGE!

[George Moellenbrock]

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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