From: <John.Dickey_at_email.protected>
Date: Tue, 18 Aug 2009 10:26:47 +1000

Hi Folks,

    Well, okay, I'll admit that there is something wrong with the
phases to Ceduna, at least occasionally. We've talked a lot about
what could be causing it, and the most likely culprit is the Agilent
Synthesizer. We plan to remove the Agilent and send it back to Hobart
for diagnosis, but I don't think we should try to do that before the
September VLBI run. Phil E says that the only scheduled experiments
for that run are at 6.7 and 8.2 GHz. So maybe the current status of
the Ceduna system is going to be okay for those experiments. Then
we'll plan to send the synthesizer back to Hobart right after that run.

    Does anybody have any problems with that? We can reconsider if
there are strenuous objections.

cheers,
jd

On 17/08/2009, at 4:07 PM, Richard Dodson wrote:

>Hi
>
>I am sure you guys know the system best .. but - as Hayley is saying
>I think - there is detectable phase coherence (i.e. common to both
>frequencies) for the data at Ceduna, but it is rapidly (timescales on
>the order of ten seconds) varying about 1 radian. Thus I don't think
>it is thermal (as that should just be a random phase spread, not a
>wander (correct?)).
>
>I note that V255 and V257 look pretty good.
>
>Richard
>
>>>Below is a copy of the email I sent to Jim and Simon last
>>>Friday. I think
>>it's quite possible that there are very short phase jumps that
>>could cause
>>the loss of gain at the high frequencies in the Ceduna data. But
>>since the
>>phase is very stable long term at the lower frequencies (S band),
>>then the
>>phase must quickly return to the maser standard (on a time scale
>>short
>>relative to the correlator averaging time).
>
>
>>As I see it the problem is not big phase jumps but low-level, rapid
>>fluctuations.
>>
Received on 2009-08-18 10:27:13