[evlatests] U-Band Failures to Tune

[Rick Perley]

    The 30-hour 'flux densities' observation provides an excellent 
measure of these occasional (and annoying) 'failures to tune'.  In this 
run, there were 105 observations at Ku band, each of which followed a 
K-band observation.  The Ku-band tunings were at 14.517 and 12.700 GHz 
in AC and BD, respectively (in each case, this is the frequency of 
channel #1 in subband #1).  The center frequencies are 512 MHz higher.   
The preceding K-band observations were centered at 22.805 and 18.550 GHz 
in AC and BD, respectively. 

    There were 7 fringing antennas:  7, 10, 12, 14, 20, 22, 24 and 26. 
    The run began on December 26 at 16:42 IAT. 

    The following 'failures to tune' (defined as no fringes detected, 
when there should have been) were noted.  In all cases, the entire scan 
is affected. 

    ea10, AC+BD at 22:27
    ea24, AC+BD at 1/01:11  (i.e., on the 27th at 01:11 IAT)
    ea26, AC only, at 1:03:01
    ea07, AC only, at 1/03:22
    ea10, AC+BD at 1/06:55
    ea22, AC only, at 0/08:27
    ea12, AC only, at 1/08:47
    ea07, AC+BD at 1/11:25
    ea10, AC+BD at 1/13:26
    ea12, AC+BD at 1/16:26
    ea12, AC+BD at 1/16:36 (this is the next Ku-band scan following the 
previously listed failure).
    ea10, AC+BD at 1/18:59
    ea20, AC only, at 1/19:14
    ea07, AC+BD, at 1/19:31
    ea22, AC+BD, at 1/21:19

    Thus, the 'failure rate' can be computed as 15/(105*7)=2.0%.  This 
is of course much too high.