NATIONAL RADIO ASTRONOMY OBSERVATORY
Green Bank, WV
August 24, 1999
TO: R. Fisher, J. Ford, F. Ghigo, R. Lacasse, C. Niday, T. Weadon,
FROM: R. Fisher
SUBJ.: Minutes of Interference Protection Group 08/24/99 Meeting
In attendance: Fisher, Ford, Ghigo, McKinnon, Niday, Weadon
Minutes of Previous Meeting
Call Outs for Interference
None. As far as we know the interferometer does not have
any interference problems that require the attention of the IPG. The
data analysis process may be excising small amounts of RFI, but nothing
has been reported. This will be revisited when we have better
Action Item Review
design course and local anti-RFI design person
There was a
general discussion of engineering and technician time available for RFI
protection work. Most projects on the agenda are progressing very
slowly due to other commitments of everyone involved. McKinnon will
take this under advisement to his next meeting concerning general
requirements for Green Bank operations. Fisher suggested that one
full-time engineer and a full-time technician could be profitably employed
on all IPG projects but realizes that there are many other demands on
the Green Bank technical staff.
2. Site radio system (Chuck)
Temporary authorization to transmit has been received from the FCC.
3. Microwave oven in
shielded test box (John)
All parts except a few connectors that had to be exchanged are now
Arrangements to mount antennas on the water tower will be made shortly.
The repaired box has been received from the manufacturer. Further
welding on the box to close holes and cracks may be required by our shop
after measurements in the anechoic chamber.
4. Shielded room entrances
5. Monitor station
6. Progress on suppressing
RFI from equipment that has been measured in the anechoic chamber
The laser group has stated that RFI suppression is a long term effort
that will proceed in parallel with other development of the metrology
system. Their interim solution is to turn off the lasers when the cause RFI
trouble. Each laser must be turned off manually, which will require
considerable effort for the three lasers on the GBT fed arm. This will
be discussed with the metrology group.
7. Blanking and sig/ref
switching system system for anechoic chamber (Tim)
The laser supply for the quadrant detector is undergoing further
shielding and filtering and will be remeasured in the near future. It
was noted that Dwayne has done a commendable job of suppressing RFI in
the modules that he has designed and built.
The weather station was noted as a source of RFI and requires
Weadon has completed the software changes to implement blanking on
the anechoic chamber continuum analysis system. A new instruction sheet
has been distributed.
11. RFI considerations for
the new Edcation Center (Frank)
The first of several
vendors of tour center displays will be arriving in Green Bank today.
A brief outline of our RFI suppression requirement will be given to the
vendors, and either Niday or Fisher will be available for consultation
and/or tours of the anechoic chamber measurement facility.
McKinnon reported that he has initiated the necessary actions with
the CORF lawyer to define NRAO's position with regard to medical
devices sharing the 610 MHz radio astronomy band.
A case was noted of the use of a non-diesel vehicle on site to
transport a disabled person on the NRAO tour. This is not an immediate
problem, but a solution involving coordination with telescope operations
and possibly provision for disabled person transport needs to be
Next Meeting: September 14, 0800.