MEMORANDUM March 23, 1999
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 03/23/99 Meeting
In attendance: Fisher, Ford, Lacasse, Niday
Minutes of Previous Meeting
Call Outs for Interference
Action Item Review
1 - Technical Seminar on RFI Suppression Requirements and Techniques
First part of seminar, covering the "Why" of RFI suppression, will be given by Fisher tomorrow. The next part, covering the "How", will be given by Niday and Schiebel next week.
2 - Use of Spectral Processor with anechoic chamber
The replacement monitor has been installed.
3 - Site Radio System
Essentially all hardware has been received. Licensing still has to be done. Then some testing with transmitters on the water tower will be done.
4 - Monitor station and anechoic chamber development
Construction of continuum detected power system is in progress. All parts are in and shop work is complete. Assembly and test are imminent.
5 - Microwave Oven Enclosure
A commercial enclosure was purchased ($1500) from EMCOR. Modifications to the enclosure will be made to improve the shielding and make it suitable for an oven enclosure. Delivery is expected in April.
Possibly a bigger problem in the same band are 2.4 GHz video links, commercial products used in transmitting video around households to avoid re-wiring. Niday stated that these are generally spread spectrum, and are Part 15 compliant. They are limited to +30 dbm ERP. Bands from 902 to 928 MHz and around 5.8 GHz are used similarly.
This discussion diverged into a philosophical one. Why should NRAO bother to shield and filter commercial equipment, like microwave ovens, much better than its neighbors? In some cases, our efforts make little or no difference in the noise floor at the telescopes. However, they do set a good example and keep us from being our own worst enemy. Also, they make a statement to visitors, especially those whose must qualify equipment for operation in the Quiet Zone.
6 - Shielded Room Entrances
7 - RFI Considerations for new Education Center
8 -Harmful Levels Document
Will be handed out at seminar.
9 - Lab RFI Suppression Efforts
9 - Use of Interference Reporting System
No comments made.
10 - Interference at 1612.17 MHZ
An L-band antenna with a rotor will soon be mounted atop the 140 ft. and used on maintenance days to monitor this band. The shop is presently building mounting hardware.
11 - RFI Monitor for Education Center
12 - Cal and Sig/Ref Switching System for Anechoic Chamber
Next Meeting: TBD