[evlatests] Updated T304 Auto Level Control Software

[Ken Sowinski]

On Wed, 14 Nov 2007, Keith Morris wrote:

> A trial version of the updated ALC controller software has been loaded
> onto ea25-t304-a and ea25-t304-c.

I just had a look at this and it needs to be repaired or
abandoned.

1.  In general when switching to a new band two successive
trials produce different results.  The first is wrong by
a dB or two, and the second right on.

2.  At L band the RF attenuator just doesn't know what to do.
It oscillates by many dB for a while and then settles down at
a more or less random and often wrong place.  Looking at the
change in measured power with attenuator steps the response
is very not very linear, even at the -20 dB set point.  I
suspect this is because L band is mixed up to 11-12 GHz
placing the 1 GHz of noise well beyond the frequency spec
of the power detectors.  The other bands all produce more
noise below 11 GHz.

I suggest looking for any obvious errors in the new implemtation.
If that fails, we should revert to the previous software for
in the 25 A and C downconverters and think more carefully about
what to do.