[evlatests] 9AC locking fixed!

[Rick Perley]

    FYI

-------- Original Message --------
Subject: 	Re: [evlatests] Hysteresis in Tuning failures
Date: 	Fri, 18 Jun 2010 10:02:08 -0600
From: 	Rob Long <rlong at aoc.nrao.edu>
Organization: 	NRAO
To: 	Rick Perley <rperley at nrao.edu>
References: 	<4C1AA239.3050807 at aoc.nrao.edu>



Hi Rick,

We replaced this synthesizer on Monday due to locking issues. We haven't 
seen problems since.

Rob

Rick Perley wrote:
>     An extraordinary phenomenon has been noted. 
> 
>     In the Cygnus A observations taken last Friday, I noted that antenna 
> 9, in IFs A and C, consistently failed to tune to 2500.0 MHz (in OSRO 
> mode 1 with 128 MHz subband width) -- but *only* for the scans on Cygnus 
> A.  Observations of the nearby calibrator J2007+4029 always fringed.  
> How can the LOs 'know' the antenna is on Cygnus A, rather than the 
> calibrator?
> 
>     It seems the answer depends on what was observed on the previous 
> scan.  In all cases, the observation of J2007+4029 at S-band was 
> preceded by an observation (on that same source) at X-band (at 8100.0 
> MHz).  But for all observations of Cygnus A at S-band, the preceding 
> observation was at C-band (at 4500.0 MHz). 
> 
>     It would be very good to understand and eliminate this phenomenon. 
> 
> 
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