[evlatests] Ka band LO harmonic leakage

[Ken Sowinski]

It was suggested today that we avoid tuning the L301-1 to 14720,
which results in LO of 44160 after the tripler.  This imposes
a serious change to tuning advice we have offered observers.

For Ka band the block diagram shows that the LO is filtered to
only allow 44 to 49 GHz.  In accordance we limit the allowable
L301-1 settings to lie between 44160 and 48768 MHz, thus the
new LO restriction limits the range from 44928 to 48768 MHz.
The result of this is that the 32 GHz limit we have advertised
for the AC basebands must now be raised to 32768 MHz.  A nice
power of two but a serious change to what we have allowed in
the past.

We should still do a test to verify that a different tuning
does reduce the birdie; it is not clear whether we should
change the tuning choices that are currently made.