219.6 & 219.605 MHz transmitters

[Squad10]

There have been a number of recent bank robberies throughout the Chicagoland area.

Some bank money packs have embedded GPS/cellular data transceivers that may be polled for position.

219.6 or 219.605 MHz pulsed (2mW) transmitters are also contained in the money pack allowing DFE (Direction Finding Equipment) to be used when within approximately a 100 foot radius from the money pack.

I suspect these frequencies are used on a nationwide basis.

 

[Mick]

With remote building top receivers a police agency can get a signal from a long distance. They work very well this way.

 

[Hooligan]

Those & other freqs in the same spectrum are allocated nationwide for radiolocation services. The system out here in Northern California that's very popular with banks & LEAs is called "ETS" & uses a single freq in that spectrum for the transmitters hidden in 'bait packs,' etc.

LEAs generally DON'T want base stations that can hear the signal from great distances away, because they use a series of fixed-location base receivers in a region as the basis for determining a general location of a bait pack. Then they get mobile units in the area to try to home in on the signal. A few personnel will also have a handheld receiver for close-in work. Out my way, the county manages a series of 'ETS' receive antennas located atop some hilltops, a hospital roof, and the closest receiver to me is actually just on the roof of a 3 story bank. The transmitters are very low power, using an inefficient antenna, so the signals generally don't really travel far, hence the numerous remote receive sites.