Hand portable 2 way radios can be vital for emergency response, crisis management and other business continuity related scenarios. This is a short article designed to inform the reader the basics of how to use them effectively. We have also created a Powerpoint file for use in training sessions.

General Features

There are a wide variety of radio types and terminology, this article refers to European Private Mobile Radio 446 (PMR446) system of unlicensed devices but is equally applicable to other countries similar systems such as Family Radio Service (FRS) in the USA and Canada, LPD433 and SRD860 in addition to licensed devices.

PMR446 uses 8 channels separated by 12.5 kHz starting at 446.00625MHz.
FRS uses 14 channels separated by 25 kHz starting at 462.5625MHz

Range is dependant on factors such as terrain, weather conditions and design. Typically maximum range is 2-3km but this can be reduced in heavily built up areas and for planning purposes an average figure of 1.5km should be used.

Of course, limited range means that interference from other users becomes less frequent and reduces the need for complex frequency management licensing common with other types of radio device.

Common Controls

Power Switch

Fairly obviously turns the device on but also usually doubles as the volume switch. It may sound obvious but always check the device is on.

Channel Selector

It is important to understand channels with private mobile radio. PMR446 can use 8 channels, FRS has 14. These frequencies or channels are shared amongst all users so under heavy local use some interference/congestion may be experienced. Simply changing channels will usually solve the problem but in order to provide even more channels most systems now use additional techniques to provide sub channels. These techniques are Continuous Tone Controlled Signalling System (CTCSS) and Digitally Coded Squelch (DCS).

CTCSS transmits a sub-audible tone with the regular voice audio. The receiving radio, set to the same CTCSS tone, will only receive audio if it contains that sub-tone. Interference from other users on the same frequency is therefore rejected (unless they are also on the same sub-tone).

DCS ("Digitally Coded Squelch") is a digital variation on CTCSS and consists of different codes each created by a group of 23 bit encoded "words".

CTCSS provides up to 50 channels and DCS 83 although some handsets may implement more.

Channels and sub channels are selected by a rotary control or up and down buttons depending on the handset

Volume Control

Adjust the volume depending on ambient noise

Squelch Control

Squelch control is used to control the noise coming form the speaker when not transmitting. If no squelch control were available the radio would output a constant radio hiss noise and be very off putting. Squelch suppresses this background noise. Different handsets implement squelch control in different ways, some using manual controls and others using preset or automatic controls.

Manually adjusting squelch consists of turning the squelch dial or control down until you can just no longer hear the background hiss. Too much and you will not be able to hear genuine calls.

Talk Button

Hand portable 2 way radios are NOT mobile phones, they allow simplex or one way conversations. On a normal telephone both parties can talk and hear and the same time. With radio devices only one person can transmit at a time, when transmitting you cannot hear and vide versa.

All devices have a ‘push to talk' button that switches on transmit mode. Until this button is released no one else will be able to transmit.

If everyone talks nobody can understand so a degree of discipline or procedure is required when using 2 ways radios (described later)

Speaker and Microphone

Usually integral to the device but some device accessories can include external speakers and microphones including voice operated microphones. Speak into the microphone in a normal manner

Batteries

Some devices will use integral rechargeable batteries and others removable standard batteries usually AA types.

Antenna

Antennas are usually integral to the device and where possible make sure it is vertical when in use to achieve the best reception.

Voice Procedures and Other Advice

General

Speak only when you need to and keep it short

If a number of users are on the same network or group it may be advisable to arrange a call sign system or use centralised control

In an informal network then using first names and minimal voice procedures will probably be OK but in order to maximise the benefits that 2 way radios can provide a small degree of control is needed, use the appropriate degree of control and procedure depending on the situation.

Using Call Signs

Call signs enable others in the group to identify who is talking and by who we mean function not person. For example; control, North Gate, Facilities, First Aid 1

These call signs should be agreed in advance and well understood by all potential users. Call sign lists are often created and fixed to the radio itself

Calling Someone Else

Think about what you want to say before saying it

Press the talk button and say the following

HELLO - 'the call sign that you want to talk to' or 'all call signs'

THIS IS - 'your call sign'

MESSAGE - 'whatever you want to say'

END - If you want an answer say Over if you don't want an answer say Out

The word Out signifies that no answer is needed and Over means come back to me with an answer

Don't forget to release the call button

Responding to someones call

Wait a short while (this gives others the chance to interrupt if urgent)

PRESS THE CALL BUTTON and wait a second

YOUR CALL SIGN

MESSAGE - your answer to their question

END - Out or over

Don't forget to release the call button

This is the general format for holding a 2 way radio conversation where transmission is good. Other formats may insert an invitation from the called party to start talking, i.e. the message is only transmitted when the called party is ready for it.

other voice procedure

Don't talk in codes or jargon but simple plain language

A number of formal voice procedures can be used that aid clarity, these are sometimes called pro words

To repeat critical information the sender would say

'I say again....'

To ensure that the called party has fully received all the information a readback request can be made. This is usually done at the end of the message for example

'the police liaison officer will be at your location at 1400 hours, readback over'

The called party then says

Call sign, 'I read back the police liaison officer will be at my location at 1400 hours over'

If you make a mistake during transmission simply say 'wrong' and repeat the section of your message. This lets everyone know that the correct message is

Where complex figures and numbers, for example a vehicle licence plate are to be transmitted use the word 'figures' to prefix the numeric element and make use of the phonetic alphabet

For example

ABC 123F would be spoken as

Alpha Bravo Charlie Figures One Two Three Foxtrot

Training

We have also created a Powerpoint presentation that you can use for training or awareness purposes and is provided as is, ready for you to modify or use. All we ask is that you credit us and just let us know how it is received.

The is in the file library in the communications section. You will need to register and log in to download the file.

Summary

These simple voice procedure techniques will vastly increase the efficiency of 2 way radios in any crisis situation but like any system it must be used and tested before it is really needed

Document Author: Harvey Fawcett

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