NATIONAL RADIO ASTRONOMY OBSERVATORY
                          Green Bank, WV


MEMORANDUM                                       January 29, 1998

TO:       R. Fisher, R. Lacasse, R. Norrod, M. McKinnon, C. Niday,
          T. Weadon, G. Hunt
FROM:     R. Lacasse
SUBJ:     Minutes of Interference Protection Group 1/27/98 Meeting

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


RFI Call-outs

     There was a complaint from Backer about a particular IF
channel in the spectral processor.  This was isolated to the IF
rack itself.  

     A birdie present in the C-band system will be investigated in
the lab in the very near future.  It is not clear whether this
feature is externally or internally generated.

     McKinnon will try to make a series of procedures to do horizon
scans with the 140'.  This would be useful for finding the
direction of external interference.

     With reference to the interference identified by Lockman
(report appended to the 1/13/98 minutes), follow up observations
are planned to try to identify the non-Glonass interference. 
Fisher will observe in parallel with the spectral processor to try
to better characterize the interference.

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, a reporting system should also
be capable of including a plot of the observed interference.

PC Data Acquisition System

     Progress towards a continuum receiver has been made.  The PC
data acquisition system hardware and software are now working
together.  Some programming needs to be done to tailor the data
acquisition to our needs.  Schiebel is doing the programming. 
Fisher requested that this be given fairly high priority.  

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.  To date, minor software
problems have prevented a demo.  However, a demo should be possible
within the next week.

Monitor Station

     Amplifiers have been received.  Three 380' runs of RG213 or
equivalent coax, plus a control cable are still needed to get the
system running.

Status of New Equipment

     The new spectrum analyzer has been received, and tested by
Niday.  Since there is no doubt that there will be requests to
borrow it, a discussion of the appropriate policy followed.  It was
decided that the unit could be made available to others by request,
but that the IPG would be the highest priority user.  In addition
it was decided to place a fairly large "IPG" sticker on it, and to
purchase a non-metallic cart that would be loaned along with the
spectrum analyzer, to help prevent damage.  The non-metallic cart
would serve double-duty as a test stand in the anechoic chamber.

Equipment Testing

     Gareth Hunt requested that RFI test results somehow be made
more generally available.  A suggestion was made to include a link,
on the IPG home page, to the spread sheet which summarizes the
devices tested and the test results.  Interested parties requiring
additional information could then contact Niday or Lacasse.  The
time required for performing a test, from set up through report
writing, is one to two days.

     Fisher requested that tests of the shielded enclosure for PC's
and workstations be moved up in priority.  

Next Meeting

     February 10, at 0800.