1 ms sqrLaw detection of 1350,1290 radars
The 1290 and 1350 Mhz radars were square law detected
with a 1 ms time constant (500 usec sampling) with the lbw receiver (polA)
. 5 Mhz IF filters were placed about each radar. At the same time 5 Mhz
centered at 1415 Mhz was sampled. The telescope was stationary at az=300,
za=18 deg. The goal was to see any saturation of the 1415 Mhz band
if we integrated the radar pulses over 1 millisecond (the pulse duration's
are 5 usecs).
The radars rotate with a 12 second period. The plots
radars as their beams sweep through the observatory direction. There
are a total of 10 rotations (120 seconds).
The compression of the system with a 1 millisec time constant is small.
It is interesting that both of the radars are drifting relative to a 12
second rotation period. Either i screwed up on the sampling or they are
being driven off of the power grid and the frequency is not exactly 60
Fig 1 top plots the two radars. 1290 is the leftmost beam and 1350 is the
one on the right. The two radars were separated by about .1 seconds in
time. They were both drifting relative to a 12 second period. They
moved by about .2 seconds in 120 seconds (.17% drift).
Fig 1 bottom shows the 1415 Mhz band corresponding to this time. The units
are fraction of Tsys. There is no strong compression evident.
Fig 2 top (1290) and bottom (1350) blowup a single trace (the 7th from
the bottom). The black curves are the 1415 measurements with the
red curve being a scaled version of the radar beam. You can start to see
points (4.62 seconds for 1290 radar) where the 1415 signal has compressed.