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

[Mike Revnell]

16ns corresponds closely to the 64 MHz clock the FIFO the 8-bit data is 
on in the formatter prior to the mux that selects the data. I don't 
recall if this FIFO is reset when the 3-bit is turned off or not.

They already have tuned delays after the 3-bit digitizers were installed.

Mike.

Jim Jackson wrote:
> 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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>
>