[evlatests] ea21 at P-band

[Paul Harden]

Walter Brisken wrote:
> I've reset the attenuators on ant 21, IFs B & D .  Both IFs wanted 12 dB 
> more attenuation.  

There has always been a level of uncertainty as just how to deal with 
the power levels of the narrow-band 74MHz and P-band signals within the 
otherwise wide EVLA IF.

I based the design on providing the T302 LSC Converter with about -30dBm 
power from the 4/P Converter, or, a litle higher than the input power 
from the L, S and C band receivers.  Granted, these total power levels 
are based on two greatly different bandwidths.

There is some latitude in the 4/P Converter in the output IF level.  I 
would appreciate hearing from anyone involved in P-band testing and 
observing if they feel the output power from the 4/P Converters needs to 
be increased or decreased to get some empirical value we can use as a 
standard.

For comparison, the output IF power from the 4/P Converters are as follows:

-34dBm  Ant. 21 (with the increased gain headroom)
-28dBm  Ant. 17 and 23
-24dBm  Ant. 14 (old design with the LO leakage problem)

The Ant. 14 unit power is quite high, in an attempt at the time to get 
better signal to noise with the LO leakage power.  The new converters 
have virtually no LO leakage in the IF.

We are about to begin construction of the 4/P Converters to get caught 
up and have a converter for all past and present EVLA antennas in the 
next month or so.  These will be based on -34dBm output power.  Again, 
if anyone feels this IF power needs to be adjusted, please let me know.

Paul Harden