In attendance: Acree, Beaudet, Cutshall, Fisher, Ford, Lacasse, McCullough, Niday, Sizemore
This was a special meeting with several purposes. First, new members of the group were introduced. Second, resources available to the group were summarized. Finally, projects, both planned and current, were summarized.
Four new members joined the group. Jeff Acree is a new hire. He will chair the group, and direct the operation of all RFI related matters. Carla Beaudet, another new hire, will initially will be fixing RFI problems. Wes Sizemore, an NRAO employee for many years who has been in charge of processing quiet zone applications and has generally concerned himself with off-site interference, was welcomed to the group due to the expansion of the scope of the group. Finally Ryan Cutshall is a student who will be working with Rick Fisher on RFI suppression techniques.
A list of resources available to the group was compiled, mostly from memory. Acree will follow up on this and produce a better list. The following items were listed:
RFI Monitor StationsIPG "deer stand"Data Acquisition SystemCovers 200 - 1000 MHz with a log periodic antenna and 1.15 to 1.8 GHz using a horn antenna.40-foot
Approximately 60 db of amplification follows the antennas.
Signals are routed to the Jansky Lab from the station via fiber modems which cover DC to 2.5 GHz.Covers the band from 0-1300 MHz with both an omni and directional antenna.
The directional antenna is mounted on an AZ/EL rotor and is comupter
controllable including the capability of tracking satellites.
The system has approximately 50 dB gain. The antennas are mounted on a 50' tower and
are connected to an ICOM R-9000 receiver and HP-8563A spectrum analyzer.
The HP-8563A is also computer controllable.Capable of 500 Ms/s. To be used to characterize interference.Spectral Processor
FPGA and A/D on board.FFT-based spectrum analysis system. It can give the RFI Monitor Station the same sensitivity to interference as the GBT since the GBT is looking at the interference only in its sidelobes while the monitor station can peak up on it.Anechoic Chamber
Shared with the GBT.Fully shielded anechoic chamber. Dimensions approximately 35 x 15 x 15 ft.Spectrum Analyzers
Shared with indoor antenna range.Anritsu - good to 8.5 GHz,Signal generators
HP 8563A - good to 26 GHz, portable,
HP8563E - good to 26 GHz, portable, excellent device,
Tek 472Frequency Synthesizer DC to 26 GHz,Scalar Network Analyzer
HP 8672A 2 to 18 GHz Signal Generators (qty2)HP 8757A. Not top-of-the line, but useful for measure amplifier responses, etc.TurntableScientific Atlanta, 100# capacity
Radios for interference monitoringThe following projects, some underway and some planned, were listed:ICOM R10 (portable, 100 KHz to 1.3 GHz),
ICOM R9000 (2GHz),
ICOM R7000 (portable, 1.8 GHz),
AOR handheld (1.3 GHz),
AOR 3000 (desktop scanner, 1.3 GHz)
NRQZ administrationNext Meeting: 1-22-02processing of applicationsRFI surveys
verification of propagation models
verification of compliance
identification of uncoordinated transmitters
monitoring of local environmentGBT IF Monitor (survey of GBT IF bands)RFI complaint logging
Monitor Station survey (archive of monitor station, vs time, vs direction)
One should assume that these surveys will be publically available.So far we have gotten little help from astronomers and operators. We hope to train operators to identify interference and possibly triangulate on it using the monitor stations. When complaints of RFI are made, we plan to capture observers' enviroments using GBT logging facilities to get details of when and where interference was seen.GBT Monitor StationPresently only in planning stage.RFI Research
Should be very close in design to existing station.
Very useful for compliance verification since it will measure fields very near the GBT focus.
Fisher to provide Acree with a block diagram.Fisher to take responsibility for this project.Equipment Testing and Fixing
Goal is to increase immunity to RFI.
Plan to use the Data Acquisition System to characterize RFIThis has been the main focus of the IPG group thusfar.
The goal is generally to bring NRAO equipment into compliance with ITU-R limits .
Items that are being worked on, or soon will be, include the laser ranging system, the GBT HVAC system, the lightning detector, the data acquisition module, the blue GBT warning lights, and the GBT servo system