What are the mobile govenment antennas?

April 10, 2006 10:15 AM

What was the big antenna attached to the federal government pickup truck?

This morning on my way to work (across the Richmond bridge, CA), I was behind a pickup truck with federal govenment plates that had a big antenna array on a mast stuck through the roof of the cab. I believe that it was a Yagi array (I don't know much about antennas, but in my quick search through the net just now that's what they looked like). On each side (left and right of the cab) there were arrays of five parasitic elements attached to the dipole (I don't know if these are the right terms for these parts but I like the big words I find on Wikipedia). On the left side, the elements were perpendicular to the dipole; on the right side, they were set at about a forty-five degree angle. The whole array could be rotated around by hand with a handle attached to the boom inside the cab.

So what is it?

posted by Etaoin Shrdlu to technology (5 comments total)

sounds like a directional antenna for locating the source of radio transmissions (high frequency - fm or tv). perhaps they're looking for a pirate radio station?
posted by andrew cooke at 10:30 AM on April 10, 2006

It's how they relay the thought control beams from the satellites. They were bringing them in for the protest rallies. Stay vigilant.

Seriously, though, was it a 4x4 pickup? Was there any other markings on the truck?

My initial guess it it was for tracking something with a transmitter, like say a weather balloon or a tagged animal.
posted by Pollomacho at 10:31 AM on April 10, 2006

The whole array could be rotated around by hand with a handle attached to the boom inside the cab.


That sounds like a triangulation locator. The FCC used to drive around with loop antennas, taking various readings, until they could find the source of a pirate radio station. It was in my neighbor's attic, by the way.
posted by StickyCarpet at 10:33 AM on April 10, 2006

Some local guys at the university had a setup like this for tracking tagged animals. As others have said, it's probably setup to triangulate a radio signal -- who knows what exactly they're trying to triangulate is.
posted by cameldrv at 11:16 AM on April 10, 2006

it could also be EMI/EMC related FCC enforcement. in other words someone may have complained about excessive TV/Radio interference and the FCC is out trying to find the culprit.
posted by joeblough at 1:13 PM on April 10, 2006