[evlatests] K-band OSRO1 observing, Saturday/Sunday

[Jim Jackson]

Mike,

In reference to what Rick mentions about Ant 15 IF-A below -  do they 
need to re-run delays on this antenna (and the others with 3-bit 
digitizers) due to the new firmware in the DTS module?

Alternatively, could switching between the 8-bit and 3-bit digitizers 
the way you are currently doing it cause delay changes?

Jim


At 04:07 PM 6/28/2010, Rick Perley wrote:
>     A ten-hour run on Cyg A, in OSRO1 mode, was run Saturday
>night/Sunday morning.  As at the low frequencies, I cycled around three
>frequency pairs, in this case, these are in K, Ka, and Q bands.
>
>     At K-band, three positions were selected, corresponding to the two
>lobes and the center of the source.  The frequencies chosen were 19.0
>and 24.0 GHz (BD and AC, respectively).  Calibration was done on the
>nearby source J2007+4029, and 3C286.
>
>     In general, the K-band data are very good.  In no case was more than
>15 seconds of flagging required at the beginning of each observation --
>it seems there are no significant 'setup' issues.
>
>     FITLD found 3.3% of the data were integer zero -- most of these are
>associated with antenna 6B (see below).
>
>     The notable issues found are:
>
>     1) Antenna 20 has a period oscillation in its gain -- this is known
>to be a pointing effect, and work is believed underway to correct this.
>     2) Antenna 15, IF 'A' had a rather large delay error -- 16 nsec.
>All others were less than 5 nsec.
>     3) The Cross-Hand delays are 2.2 nsec in IFpairs AC, and 8.0 nsec in
>IFpairs BD.
>     4) Antenna 13, IF 'B', and antenna 22, IF 'D', gave no fringes
>throughout.
>     5) Antenna 6, IF 'B' also provided no fringes -- in this case, the
>data were all integer zero.
>     6) Antenna 27 was extremely weak in IF 'B; (amplitudes low by factor
>~100), and very weak in IF 'D'.
>     7) Antenna 5, IF 'B' gave integer zero data for the first 1.7 hours,
>then 'sprang to life', and was fine the rest of the way.
>
>     Initial imaging shows fine results, except that, as at the lower
>frequencies, the noise in the Cyg A images is at least 50 times too
>high!  This is likely to be due to errors in calibration, the specifics
>of which elude me.  Images of the nearby point-source calibrator provide
>50,000:1 DR images which appear perfectly noise dominated (noise is
>about 90 microJy, using 120 MHz bandwidth and 1000 seconds of on-source
>integration).  This is high than theoretical, but probably not too far
>off, given the time of year.
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