01oct13
Hello Folks,

The attached Excel file contains raw data, derivative data from the raw, and
words of explanation.

Phil take note: there are no graphics in this file, so I believe you should be
able to open it with 'Open Office' or similar.

The results seem a bit ambiguous, in large part because we encountered
an unexpected difficulty with apparent leakage around the intended signal
path.  These initial measurement results are presented in "round 1" of the
spreadsheet.

Denis made the suggestion that led to an apparent great reduction in the
problem's severity, but the quantitative meaning of the results hinges first
order on the 2380MHz gain of the ALFA amplifiers, which remains in doubt

I did make an effort to estimate this based on yesterday's data and compute
results based on this estimate, which seems to say that the sliding shutter
is good enough with a fair amount of margin.  This is covered in "round 2A"
in the spreadsheet.

However, I should make direct lab measurements on that gain value on a
few spare LNAs in order to gain more confidence.  It appears likely that
it will be OK, but there is still room for reasonable doubt.  These values will,
once obtained, enable completing "round 2B".

Therefore I do not yet recommend relying on the sliding shutter for S-band
radar protection, especially considering the difficulty in making repairs on
ALFA should the gain estimates used in round 2A prove to be seriously in
error.

Cheers,

Dana