USCG Advisory re: TV antennas affecting GPS

Doryman

Read all about it HERE.

Warren

localboy · Posted: Mon Nov 09, 2009 6:05 pm Post subject:

Wow. At first I was like "No biggie..I don't have a TV antennae, etc"...but then I read:

DaveS · Posted: Mon Nov 09, 2009 7:36 pm Post subject:

localboy · Posted: Mon Nov 09, 2009 8:32 pm Post subject:

Now that's thinking, Dave. I like it. Twisted Evil

Robbi · Posted: Mon Nov 09, 2009 8:39 pm Post subject:

In the last year or so I have had two instances where my boats position on my GPS "moved erratically across large expanses of land." The first time that it happened, I thought that my GPS was going into a series of last gasp spasms before dying. It was very strange. I wish that I could recall if any other boats were in the area or not. It lasted for less than a minute, but I was zig zagging across large expanses of beach and forest. Shocked

Robbi

thataway · Posted: Mon Nov 09, 2009 9:22 pm Post subject:

The key word here is "active" TV antenna. This problem has been reconginzed for quite some time--and there are other specific areas of interference. The question I have is since this warning was posted in 2002, are these specific antennas even manufactuered currently--and has the problem been fixed?

The times we have lost GPS usually was near an active Military ship--talk about "Active Antennas!....

tpbrady · Posted: Mon Nov 09, 2009 11:24 pm Post subject:

Bob,

If I understand the FCC rules, a device such as these active antennas that causes interference to a service such as GPS that operates in an exclusive protected frequency space, would have to be removed from the market. There are permissible limits for interference, but the distances are meaured in inches or at most a foot or two. The best example of this is police radar detectors. Some of the early models generated frequencies in the 950-1450 MHz area that interfered with some cellular services as well as L-band satellite modems. The FCC forced the manufacturers to withdraw them from the market. It doesn't mean they all go away, it just means that they can no longer be sold.

My Lowrance GPS has always been sensitive to marine radar. They have since improved the shielding in the antenna electronics assembly, but on my current model, if I get too close to one of the Alaska ferries with its radar operating, the GPS goes off line.

thataway · Posted: Tue Nov 10, 2009 5:43 pm Post subject:

Correct Tom,

Often these are Spurious emissions, often a harmonic of the primary frequency. However 2000 feet is quite a distance to cause interference.