[evlatests] 4 meter results

[Paul Harden]

Ken Sowinski wrote:

> To keep from overdriving the VLA T5s lots of attenuation is
> needed in the downconverter.

The LCP/RCP output power from the 4/P to the LSC Converter is set at 
about -35dBm, to be consistent with the approximate input power from the 
L, S and C receivers.  If this is excessive, I can reduce the 4/P output 
power by an amount specified.  Or, I can do so to one or two as an 
experiment.  There are 4 4/P Converters awaiting antenna installation.

How much is "lots of attenuation?"

> The fringes on BD seem to be real and went away when one of the
> antennas was pointed far off source.  The AC data was incoherent
> and did not look any different when an antenna was driven off
> source.  All the synthesizers in both antennas claim to be in
> lock at the right frequencies.  We must be missing something
> fundamental.

Just for some clarity:
The LO to the 4/P Converter is a fixed 1024 MHz, which is applied to 
both polarizations via a power splitter.  This comes from the L300 
Reference Generator.  4-band is upconverted to 1098 MHz and P-band to 
1332-1372 MHz simultaneously.  The output of the 4/P Converter is LCP 
and RCP.  The conversion to AC and BD IFs is done in the LSC Converter 
via the two L301 LOs.

Therefore, problems with the AC IF pair would originate in the LSC 
Converter or L301 LO1, or further downstream.

For such narrowband signals, wouldn't both L301s be set to the same 
frequency?

Paul Harden