Resonance in the alfa receiver.
Alfa was installed on 21apr04. On 22apr04 pixel 0 of
the alfa receiver was connected to the lband wide cables and brought down
using the old if/lo system (the new iflo had not yet been installed). When
the dewar was warm, a resonance was seen when the omt's were connect
back to back inside the alfa band (below 1520 Mhz). Ganesh want to see
if it had moved after cooling the receiver.
The interim correlator was setup to take 4 25Mhz
bands centered at 1500 Mhz using 1024 channels each. 10 seconds of data
was acquired (while the sky drifted by). The data is plotted as it is read
back from the correlator. The vertical scale is linear in power. The bandpass
of the system (including the iflo filters) has not been removed.
plots show the resonance:
The top plot shows 100 Mhz centered at 1500 Mhz. Black is polA with
red being polB. You can see the resonance (along with lots of rfi) in the
The bottom plot is the 4th 25Mhz band. The resonance is at 1537.7 Mhz.
The resonance has moved outside of the 1220 to 1520 Mhz band when the receiver