[evlatests] K-Band Efficiencies

[Bryan Butler]

the proper flux densities are:
    18440 - 55.4 Jy
    23560 - 83.8 Jy
    26140 - 99.8 Jy
about a 2.5% relative increase.  so the corrected efficiencies are:
    58% at 18440 MHz
    52% at 23560 MHz
    49% at 26120 MHz

	-bryan


On 10/27/05 13:09, Rick Perley wrote:
>    We have measured the K-band efficiency on antenna 14 through
> observations of Venus, at three frequencies, 18440, 23560, and 26120 MHz.
>    The details will be in an EVLA Memo, to be released by next week.   
>    Summary:
> 
>    We used a 5 x 5 raster at 4 points/beam, with off-source baseline
> calibration to remove the system power offset.  A focus adjustment was
> made based on tracking Venus -- the error was about 5 mm for each
> of the three frequences (hence, there is little movement of the optimum
> focus as a function of frequency).  [Note:  Ken Sowinski has measured
> the focus error interferometrically, but does not see so large an 
> error.  His
> observations were made at 60 degrees elevation, while ours were at
> 27 degrees -- perhaps the difference is the known change of focus with
> elevation].
>    Using 54.0, 81.9, and 97.4 Jy as the (unattenuated) flux density of
> Venus, and adjusting by the known opacity corrections at each
> frequency, we find:
> 
>    59% at 18440 MHz
>    53% at 23560 MHz
>    50% at 26120 MHz
> 
>    Minor corrections from pointing and subreflector positioning could
> make small (~1%?) increases in these values.
>    The flux densities used are last week's values, increased by last
> week's secular increase (2.1%/day), as provided by Bryan.  He will
> provide more accurate values later today.  If there is any significant
> change, I'll send around amended values.
> 
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