NATIONAL RADIO ASTRONOMY OBSERVATORY
                     Green Bank, WV


MEMORANDUM                            February 18, 1998

TO:       R. Fisher, R. Lacasse, R. Norrod, M. McKinnon, C. Niday, T.
Weadon
FROM:     R. Lacasse
SUBJ.:    Minutes of Interference Protection Group 2/10/98 Meeting

     In attendance:      Fisher, Lacasse, McKinnon,  Niday, Weadon


Approval of Minutes

     Fisher requested that his name be substituted for McKinnon's in the
action item to perform test observations.  No other changes were
requested.  Minutes were approved as amended.

     
RFI Call-outs

     There were no call outs during the past two weeks.

     A birdie seen in the C-band system on the telescope was not seen
during tests of the receiver in the lab.  When the receiver goes back on
the telescope, additional tests will be performed to attempt to isolate
the cause.


PC Data Acquisition System

     Progress toward implementing a PC-BASED continuum receiver
continues.  Schiebel will design hardware which includes digi-switches
for selecting sampling and switching rates.  These will control two
hardware counters.


Switching rates of 0.01 Hz to 1.0 KHz in a 1, 10, 100 sequence will be
available.  Sampling rates of 10 Hz to 20 KHz in a 1, 5 sequence will
also be available.


IPG Interface to Spectral Processor

     The IPG plans to use the spectral processor as a sensitive back
end.  An IF link has been installed from the anechoic chamber to the
140', and a TTL link has been installed from the 140' to the anechoic
chamber, providing the capability of doing switched spectrum
measurements.  Also, Fisher has developed an interface to the spectral
processor for use by the IPG. Fisher successfully gave a demo to Niday
and Lacasse.  The user interface is fairly straightforward and similar
to a spectrum analyzer.  Further enhancements are planned to simplify
the plotting of results.


Equipment Testing

     Gareth Hunt requested that the IPG test the recently received NT
server computer.  This will be done after the machine is tested and
configured by the computer division.  If the shielded enclosure is ready
in the same time frame, this computer can be used to test its
effectiveness.

     Niday took an action item to provide Fisher with a test version of
a spreadsheet that summarizes the equipment tested by the IPG.  The
summary will be posted on the IPG web page.

Interference Reporting System

     McKinnon reported that he had preliminary discussions with Dana
Balser about the best means for the 140' operators to report
interference.  The consensus was that a web-based system would be
preferred because it is an interface with which the operators are
already familiar, and is easily accessible by all.  Perhaps not on the
140', but certainly on the GBT, it should be straightforward to include
a plot of the observed interference in the report.  Some type of search
capability will also be included.

     The VLA maintains a Cal Source catalog in a very similar format to
what is needed for the RFI data base.  Whether the source code for this
system can easily be adapted will be investigated.


Next Meeting

     February 24, at 0800.