Green Bank, WV


January 22, 2001

TO: R. Fisher, J. Ford, F. Ghigo, R. Lacasse,  C. Niday, T. Weadon
FROM: R. Lacasse
SUBJ.: Minutes of Interference Protection Group 01-16-01 Meeting

In attendance: Fisher,  Ford,  Ghigo, Lacasse, Niday

Minutes of Previous Meeting

Interference Reports
Tests at L-band using the GBT system showed quite a bit of interference across the band.  Some of this may be internally generated.  Some follow-up work is required before more definitive statements can be made.
Review of Action Items:

  1. Site-wide interference suppression policy - position  paper (John, Rick)

John and Rick have not received any feedback from Jewell or McKinnon yet.  This item will be brought to their attention again.  Feedback is required to give guidelines for the version of the policy that will be distributed to the site.
  2. Hand-held HF/VHF radio for power switching RFI detection    (Chuck)
The received has been received!  Chuck is learning how to use the receiver, which offers continuous coverage from 530 KHz to 1.3 GHz.  Modulation is selectable independent of frequency.
  3. Initial Measurements of GBT Receivers   (Rick)
Recently, this has been held up by software problems on the Spectral Processor.  Early tests showed quite a bit of interference, some of it probably self-generated.  All interference seemed to be coming in ahead of the first mixer.  Upcoming tests will require selectively turning off systems to identify offenders.
  4. RFI considerations for new Education Center (John, Frank)
An RFI consultant will be hired at a cost of approximately $20K.  RFI modifications to the building could increase the bottom line by more than $100K.
  5. Progress on suppressing RFI from equipment that has been measured in the anechoic chamber
No progress recently.  However, plan to test on of the new 1 GHz PCs shortly.  Also, additional modifications to the microwave oven enclosure are planned.  These will be tested to see if additional suppression can be achieved.
  6. Monitor station developments (Rick)
A 70 to 1000 MHz antenna has been ordered.
  7. Measurements of PC/Workstation in a shielded box (Chuck)
No progress.
  5. Microwave oven  in a shielded box (John)
See item 5 above.
Additional Discussion

  Wireless Internet

There was some discussion with regards to the new wireless internet systems.  These purportedly include transmitters at Ku band and could be a source of interference.  Rick will look into this a bit more.  There was also some concern expressed about the possibility of the Green Bank School using such a system.  John is on the school's technology committee and stated that meetings are not held on a regular basis.  It seems as if a yearly meeting of the technology committee would be instrumental in assuring that technology requirements of the school are met without causing undue interference to the site.
  Equipment Approvals
As part of an overall plan to assure that site RFI is held to a minimum, the group agreed that it would be good to involve the IPG in the purchasing loop when the equipment being purchased is a potential emitter.
 Next Meeting:  TBD