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Old 01-14-2010, 7:16 PM
SkipSanders SkipSanders is offline
Silent Key
Join Date: Dec 2002
Posts: 1,125

Originally Posted by Ablice View Post
So, help me out here real quick.

Why the public service freqs (urban) tend to congegrate around the 460MHz band?

And what about the 800MHz?

Lastly, why the highway patrols use low ~40MHz freqs?
All depends on where you are, and what the terrain is like in the area. Also on what's already installed, and how much of your money the local government feels like spending on replacing entire radio systems.

Public Safety use pretty much all bands. VHF High, UHF, and 800 MHz all get used. Now we'll begin to see 700 MHz used, as well.

VHF Low Band tends to get used by agencies that need long range systems, in uneven terrain, without spotting hundreds of radio towers every few miles. This is why Highway Patrols, that tend to have large coverage areas, often stick with Low Band. Sheriff's Offices have this tendency, too.

UHF 450-512 tends to be used in cities, mostly conventional systems. UHF (and 800 MHz) tend to penetrate buildings better than VHF, and much better than Low Band.

800 MHz, and now 700 MHz, tend to be the newest, trunked systems.

San Diego, for instance, was VHF High Band for a long time. So was the San Diego Sheriff's Office. SDSO then moved to a UHF 460 MHz system (because there weren't enough VHF frequencies available for the expansion they wanted to do). Eventually, both the city and the county installed seperate 800 MHz trunking systems.

There are rumbles now that eventually, they might combine their systems, perhaps as a brand new 700 MHz system.
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