Alfa filter bank amps cause aerostat radar to compress system.


 What was added to alfa and when:

       A filter bank before the first mixers was added to the alfa receiver for OH measurements. It has the standard full bandwidth option and a set of filters for OH observing. A 10 db (actually a mix of 10 and 14 db ) amplifiers were added before the filter bank to improve the system temperature. These amplifiers were in the general rf path and affected regular and OH observing.  The relevant dates are:     The 10db amplifiers improved the system performance of the OH observations but caused the regular wide band observations to compress when the radar signals were strong.

Looking at wapp data feb05 thru apr05 to look for compression:

    The wapp pulsar data was recently placed in an idl data archive. This allowed the search of the data taken by P2030 (100Mhz bandwidth, cfr 1420Mhz, 64usec samples) between 01feb05 and 01may05 for signals of the aerostat radar.  The aerostat frequencies (1241 thru 1261 more info) are outside the 1370-1470 Mhz band of the experiment but the radar can compress the entire RF/IF chain. This can then be seen in the p2030 data.
    The processing steps were: The  following plots show the strength of the compression plotted versus various parameters. When plotted versus date, this is the julian date. The tick marks are centered on 12 noon utc for that day (8am AST).


Previous reports of this problem:

This  compression was previously reported in:
processing: usr/p2030/rfirdr/aero/