NATIONAL RADIO ASTRONOMY OBSERVATORY Green Bank, WV MEMORANDUM December 22, 1998 TO: R. Fisher, J. Ford, F. Ghigo, R. Lacasse, R. Norrod, M. McKinnon, C. Niday, T. Weadon FROM: R. Lacasse SUBJ.: Minutes of Interference Protection Group 12/22/98 Meeting In attendance: Fisher, Ford, Lacasse, Niday, Norrod, Weadon Minutes Approved. Call Outs Niday received a request from Behrens to help locate interference seen in the GBT prime focus receiver. It turned out to be self-generated, and was entering the receiver through a loose connector. Expenditures About $8K was spent on fiber optic RF modems for the monitoring station. Also a 200 to 1000MHz calibrated antenna was procurred. GBT Feed Arm Servo RFI Testing Analysis is not yet complete. Subreflector Actuator Heaters and Heater Controllers RFI testing of this system to commence this morning. All agreed that the IPG should insist that this system meet the same strict limits that are imposed on other systems in the vicinity of the feeds. Site Communications With a repeater at the intood/outdoor test facility, site-wide coverage was achieved with a 1 watt ERP. Equipment will be procurred shortly. Mobile RFI Cart The cart has a UPS and battery. It needs a few modifications to facilitate its use. Shielded Box for Workstations and PC's Awaiting test. Air Force Use of GPS L3 Signal at 1383.3 MHz Dan Mertly of the VLA is involved in negotiations with the Air Force about the use of this test signal. Apparently the Air Force wants to change the 1 minute/week restriction on the use of this signal. Sizemore is monitoring this for Green Bank. Technical Seminar Fisher reported that this is coming together. Guidelines still need to be developed for radiators within a shielded room. A suggestion was made that a document that would serve as a reference come out of this effort. It was reported that Arecibo is presently fighting significant internal interference problems. Next Meeting: Jan 12, 1999, at 0800