First look at the Faa radar using the pdev spectrometer
On 22jan07 the pdev spectrometer was used to look at
the faa radar. The configuration was:
The lower band contained the radar, the upper band cutoff at 1380 Mhz.
internal 156 Mhz clock in pdev
dump time 10 ms, pshift=0x1777, dshift=4
sky center frequency = 1375 Mhz. Subands centered +/- 75 Mhz from rf freq.
20 seconds of data sitting at az=10,za=18 (max for faa radar).
Alfa beam 0 was used for the observation
show the radar data (.ps) (.pdf):
The dynamic range and channel isolation from the polyphase filter bank
look like they are doing a good job of containing the radar.
Page 1: 20 second average spectra. Red is pola, green is polB. The
amplitude of the radars has been averaged over all time (when the radar
is on and off). There is an image of the radar about the center of the
band (dc). This comes from the imbalance in the i/q mixers being used to
go from 250 Mhz down to base band.
The Top plot is linear in power. The signals go off the page.
The Bottom plot is db's above Tsys. The averaged radar signal is 23 db
above tsys. The instantaneous radar value will be much larger than this
(from the low duty cycle).
Page 2: spectral blowup about radar freq. These plots blowup the
frequencies about the radars (1330 and 1350.04). Red is polA and green
is polb. The vertical scale is Db's above Tsys.
The vertical dashed lines are space 160 kHz (except for the center that
The frequency sidelobes correspond to a square pulse that is 6.25 usecs
long (sinx/x with 160 Khz sidelobes). The first sidelobe is about 13 db
below the peak. The radar pulse is supposedly 5 usecs long (so mayber there
is some filtering).
The ringing continues for at least +/- 1 Mhz from the radar cfr.
The 9 level correlators are not able to measure this structure (do to compression).
Page 3 total power vs time. The total power is computed for each
10 millisecond sample and then plotted versus time. The top plot is the
upper band (no radar). The 2nd plot contains the radar. The two bottom
plots are time blowups around 3 seconds (when the 12 second rotation of
the radar pointed at the observatory).
The radar main beam takes about 100 milliseconds to sweep through the observatory.
The upper (non radar band) shows compression when the radar points at ao.
This is probably coming from the if/lo.
PolA beam0 total power has a shorter and longer response than polB. Is
there something wrong with polA or are we seeing a polarization of the