NATIONAL RADIO ASTRONOMY OBSERVATORY Green Bank, WV MEMORANDUM April 28, 1998 TO: R. Fisher, R. Lacasse, R. Norrod, M. McKinnon, C. Niday, T. Weadon FROM: R. Lacasse SUBJ.: Minutes of Interference Protection Group 4/28/98 Meeting In attendance: Fisher, Lacasse, McKinnon, Niday, Weadon Minutes Approved as previously distributed. Call Outs None. Site Radios The use of hand-held radios on site has proliferated recently. RSI has used quite a few in their construction effort, and some NRAO personnel are using them for various purposes. All members of the IPG feel that a plan for site radios that minimizes the interference potential is sorely in need. Fisher distributed an updated draft of IPG thoughts on a site plan. Niday reported that the site communications committee is divided into two camps: one is pushing low freq radios (about 30 MHZ) to minimize interference potential, while the other is pushing high frequency (about 450 MHZ) radios to maximize structure penetration. The members of the IPG are fearful that enforcing stricter limits on off-site users than on site users could pose a problem in court someday. Also it was felt that it was better to be pro-active, mitigating interference before it contaminates observations, rather than reacting to complaints as they come up. Finally, the cost of a site communication system was discussed. An inexpensive high frequency system may be available from RSI when they complete construction of the GBT. However it was cautioned that available money should not be the only guiding principle; money can be found if the priority of a system is high enough. Interference Reporting System Fisher and Lacasse reported on their experience with the prototype RFI reporting system. Fisher will collate comments from the rest of the group at the end of the week. ****Action Item: IPG group to evaluate RFI database system. On Using the Spectral Processor from the Anechoic Chamber As presently configured it is inconvenient to use the spectral processor from the anechoic chamber. It was recommended that the IPG PC be moved to the anechoic chamber control room to allow control of the spectral processor from there. Further, it was recommended that a means of cycling power on equipment in the chamber, from the control room, be designed and installed. PC based Continuum Detector The purchased equipment has undesirable limitations. It has been decided to purchase additional hardware which promises to work considerably better. Interference Monitoring Station Fisher is pursuing the mounting of antennas on the 140 foot with Liptak. He is also obtaining drawings of the GBT to look into mounting possibilities near the tip of the feed arm. ****Action item: Niday to look into rotators for the antennas. Next Meeting May 12, at 0800.