Motorola GM360 Specifications download pdf (Page 15)

Chapter 2

VHF Theory

VHF (Very High Frequency) is primarily used for local communication. The UN

generally uses VHF Motorola radios for handsets, base stations and in vehicles. VHF

range is limited to line of sight. In some areas, repeaters are installed, which extends

the range up to distances of 50 to 100 kilometers. Although all VHF handsets are

programmed with various VHF frequencies they are mainly referred to as channels

when communicating on VHF.

VHF is user friendly, and agencies have a vast number of VHF handset users in any

given region. Being such a user friendly communications device, it can also result in a

lot of misuse. Unnecessary "chatting" on radio networks has occurred and it is the

radio operators’ responsibility to control network discipline, and ensure traffic is only

limited to operational use.

Types of Stations

There are basically two types of stations to be considered. These are:

1. Base Stations: Operate from a fixed or permanent location.

2. Mobile Stations: A vehicle fitted with VHF/HF radio.

A handheld user is not referred to as a “station.”

Spectrum

The VHF radio spectrum is the band extending from 30 MHz to 300 MHz. (The full

radio frequency spectrum can be found at Annex G).

VHF Coverage Guide (Approximate Distances)

Handheld

5W, 20cm Ant

Handheld

5W, Car Ant

Mobile

25W, Car Ant

Base

25W, Base Ant

Repeater

45W, Base Ant

Handheld

5W, 20cm Ant

3km 5km 10km 20km >20km

Handheld

5W, Car Ant

15km 15km 30km >30km

Mobile

25W, Car Ant

40km 60km >60km

Base

25W, Base Ant

100km >100km

Repeater

25W, Base Ant

>100km

Radio Operators Training Manual Version 27/11/2007 13

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Motorola GM360 Specifications Page 15

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