[evlatests] Spectacular Ku-band Sensitivity Results

[Robert Hayward]

We were all quite impressed with the prototype Ku-Band receiver, but I
certainly can't take much of the credit. I may have done the top level
design and carried out the evaluation of its RF performance in the lab but
it was Jim Ruff who did the mechanical layout, Dan Mertely who was
responsible for the RF design and Brent Willoughby who did the final
assembly.

We mustn't forget Srikanth who designed both the feed and the
phase-shifter and Ed Wollack (NASA Goddard) who designed the OMT. The
folks at the Machine Shops at the VLA and at Green Bank precisely cut a
lot of metal for all of its various components while Gerry Petencin
electroformed and gold plated many of the important bits back in
Charlottesville. And, of course, its super low-noise LNAs came from Marian
Pospieszalski and the guys in the Amplifier Group out at CDL.

There are a lot of proud fathers for this baby...

-Bob Hayward


>     Bob Hayward and I have spent the last two days on antenna 24,
> measuring the performance of the prototype Ku-band (12 -- 18 GHz)
> receiver.  A full report will follow in a few days in the form of an
> EVLA memo.  But the results are so good that I thought a quick
> communication via this channel might be useful.
>
>     The usual suite of measurements were made, using the 'gold standard'
> power meter.  Measurements were made in a 200 MHz-wide window centered

Actually, it's a 100 MHz bandwidth filter...

> at 11.6, 12.2, 13.2, 13.8, 14.9, 15.9, 16.9, 18.0 and 18.5 GHz.  Note
> that the first and last are well outside the defined band.
>
>     Essential results for Tsys and Trec are given below.
>
> Freq        Tsys         Trec
> ---------------------------------
> 11656      41.1         23.1
> 12168      32.5         14.7
> 13192      28.0         10.4
> 13832      25.0           5.7
> 14856      25.8           5.3
> 15880      28.8           8.6
> 16944      28.3          10.7
> 17968      32.9          15.2
> 18480      132           114
> ------------------------------------
>
> The values of Trec (and Tcal) match the lab results very well.
>
> Spillover and antenna efficiency data were taken, but are not yet
> reduced.  It is clear however that the efficiency will be close to the
> expected values -- about 0.5.
>
> The Tsys values easily beat the Project Book requirements.  Kudos to Bob
> Hayward and the FE group for putting together such a fine system.
>
> We return to the site today to perform similar tests on the wide-band L
> and S band systems.  Results will be distributed when ready.
>
>
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