[evlatests] Antenna 4 Ka-band results
Ken Sowinski
ksowinsk at nrao.edu
Mon Jun 16 15:42:12 EDT 2008
My mail reader made a mess of Rick's table. I made it
a little neater and maybe even got all the numbers in
the right columns.
Bob, Brigette, and I spent most of Friday on antenna 4. Weather was
clear, dry (DP ~ 15 F) hot (Temp ~ 85F), and calm.
Detailed results will be given later. I did a relatively quick
calibration of all the data. The results are summarized below.
Freq. Tsys Tr Tat Tspill Tcal T(3C273) Effic.
-------------------------------------------------------------
26232 71.7 42 6.2 23.5 6.10 2.32 52%
28024 49.4 20.5 5.4 23.5 7.55 2.33 52
33144 55.1 22.1 5.17
33160 56.8 22.7 5.15 1.89 42
37000 62.9 29.8 7.8 25.3 3.42 1.70 38
38064 68.0 34.3 8.7 25.0 3.40
39600 74.5 39 9.2 26.3 2.40 ??? ???
-----------------------------------------------------------
Explanations:
Blanks mean that quantity was not determined in these observations.
The Tat, Tspill, and effics. have been determined from earlier
measurements, with results that fit the trends shown in the table.
The Efficiency is based on a flux of 3C273 = 25 Jy. Craig tells me
the VLBA measurements give 28.5 Jy at 22 GHz, and 24.5 Jy at 43 GHz.
The values above will be close to real ...
The ??? in the table are a results of a very unstable measurement of
3C273 power at 39.6 GHz. A best value is 2.0 K, which leads to an
improbable 45% efficiency.
The spillover contribution is too high (compared to K and Q bands)
by at least 10K at all frequencies. The slow rise in Tspill is
certainly real, but is likely due to an increase in the 'real' spillover.
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