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Oct 2nd, 2007 at 10:30pm
Interference is an art form, which is to say that identifying the many possible sources and correcting them almost becomes a specialty in itself. In the early 90's I was employed at the IDB Communications teleport in Culver City, CA. I spent about 1 week on the roof with a company we hired, Comsearch, where we effectively identified many different interfering sources that were impacting my Intelsat IBS services (sync data in those days). The short list:
- aircraft on approach at LAX, cyclical in nature which makes sense at about 10 minute interval. The altimeter radar just out of band, but of sufficient RF signal strength/level to saturate the LNA. Filter mentioned in above response corrected. We placed filters on about 100 RF RX ports shortly thereafter.
- Street sweeper, once weekly. As he swept Keystone St. just West of my 8 meter C-band antenna located about 20 ft off the ground up on a load frame. The spark of his steel brushes thrown off as they ponded the street caused broadbandimpulse noise/interference.
- Once weekly gardner with his weed-wacker. That was a good one. Ignition noise from the sparkplug wire connection. Again broadband/impulse noise/interference.
- Arc welding, big problem! Again, broadband noise/impulse noise/interference.
Goes without saying, add altimeter filters for approach aircraft, let the grass grow, sweep the street with a broom and by all means keep the welders away!
Obviously this is tongue in cheek, but tracking down interference takes time, and in most cases a spectrum analyzer and portable interference feed horn. The more obvious interference types can be dealt with accordingly without an analyzer.
In the case of ignition noise from the street into a 13 meter antenna we had recieving signals from the 307 satellite were mitigated in part by the placement of thin gage steel sheets grounded to earth on the chain-link fence at the property edge. There are other shielding techniques that can be applied as long as you don't block your line of site to the satellite.
Good hunting!
P.S. If you go to Google Earth and fly in by satellite to 10525 West Washington Blvd, Culver City, CA USA you can see the teleport facility, and get a sense for what it was like.
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