NATIONAL RADIO ASTRONOMY OBSERVATORY
Green Bank, WV
December 21, 1999
TO: R. Fisher, J. Ford, F. Ghigo, R. Lacasse, C. Niday, T. Weadon
FROM: R. Lacasse
SUBJ.: Minutes of Interference Protection Group 12/21/99 Meeting
In attendance: Fisher, Crews, Lacasse, Norrod, Niday, Ghigo
Minutes of Previous Meeting
Review of Potential RFI Sources on the GBT HVAC System
Fred Crews led the group through a discussion of potentail RFI sources
in the GBT HVAC system. The discusssion is separately documented
in a memo by Fred which will be submitted into the IPG archives.
GBT Laser Ranging System and the 85-3 Telescope
Ford elaborated on his earlier e-mail concerning the use of 85-3.
He is concerned that RFI by the laser system will hamper proposed work
on 85-3. He suggested that the level of RFI be calculated based on
previous measurements. The difficulty with fixing the laser system
at this time is financial, not technical.
RFI Monitoring with the Interferometer and 20-meter
The spectrum analyzer formerly used in the 140 ft. control room is
now in use in the Interferometer/20-M control room. It is presently
connected to the 20-meter, S-band LCP signal. By adding splitters, the
327 and 610 MHz signals from 85-3 could also be monitored. Frank
is considering writing software to save the spectrum analyzer screen to
disk periodically. He notes that there is a persistent signal in
the 20-meter IF at 842 MHz, corresponding to 2342 MHz at the receiver input.
This signal does appear to be modulated. The signal disappears
when the telescope is pointed towards the lab.
Next Meeting: January 18, 0800.