[evlatests] 10-second tuning failures at X-band

[Barry Clark]

No, L302's failing to lock kills both polarizations.  Sounds to me
like a setup problem - station board putting in wildly wrong delays
or something of that ilk.

On 08/31/2015 08:35 AM, Vivek Dhawan wrote:
>
>
> Sounds lke L302's failing to lock for 10 sec, a fairly common transient
> effect on 1% of the 224 units. But why it is only at X band I cannot explain
> - I assume you changed bands many times after the reference pointing?
>
> On Mon, August 31, 2015 08:26, Rick Perley wrote:
> |      The calibrator survey run, taken last October, has revealed the
> | continued presence of short-lived tuning failures.  The characteristics
> | are quite simple:
> |
> |      1) No fringes at the beginning of a scan, lasting exactly 10
> | seconds.  After this interval, full-valued fringes abruptly occur.
> | Hence, this is not a pointing problem.
> |
> |      2) Roughly 20% of scans are affected, nearly always a single
> | antenna, occasionally two.  This seems consistent with a random
> | process.  There was no clear tendency for any particular antenna to fail
> | more often.
> |
> |      3) The four IFs failed independently, with equally likelihood --
> | failures are always on a single IF.
> |
> |      4) So far as I can determine, this problem only occurs at X-band.
> | (I have checked P, L, S, and C, so far).
> |
> |      5) The on-line flagging system (unsurprisingly) does not flag these
> | failures.
> |
> |      These X-band observations followed X-band referenced pointing,
> | which utilized a different tuning and correlator configuration.
> |
> |      There was also a single incidence (out of 182 scans) where the
> | *last* 10 seconds abruptly lost fringe power.
> |
> |
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