Basic controls

There are many different makes and models of radio on the market, both handheld and fix sets.

They are all slightly different but there are some controls that are common to all sets, although the manner of control might be different ie. buttons verses knobs.

The instructions below are for an Icom IC-M421 as these are the radios you will be using on our course.


Turning the set on

This model of radio is turned on by turning the higher of the two knobs clockwise. This knob also controls the volume and the ’12 O’Clock’ position is normally about right.

At this point we should always adjust the ‘squelch’ or sensitivity control. This is the lower of the two knobs. First rotate this control fully anti-clockwise. There should be a loud noise coming from the radio. Slowly rotate the control clockwise and stop the moment the noise stops. The squelch is now correctly set up.


Other stations will only hear your transition when they are on the same ‘channel’ as you. Each channel is assigned a number which is displayed as the largest number on the screen.

You can cycle through the channels by pressing the up and down arrows either on the main body of the radio or on the handset.

The is more detail on channels on the channel page of this site [channels…]

If this does not make it clear, see the video below:


So you have turned the radio on and set it to the correct channel. You are now ready to speak on the radio.

Hold the handset in either hand a few inches in front of your mouth. Position the handset at a right-angle to your face so that you are speaking across the microphone and not straight into it.

When you are ready to transmit, press in the button on the side of the handset, keep it pressed while you talk and let it go when you have finished talking.


Think about what you going to say before transmitting and wait 15 seconds before transmitting to check that no one else is using your chosen channel.

You should aim to make all transmissions as brief as is possible while allowing the message to get through. This both saves air time and makes information easy to understand.

When talking on the radio you should speak in a slow and clear voice.


Your transmission range can depend on atmospheric conditions. For example, you will be heard for further for example at times of high pressure.

Your range is also limited by the curvature of the earth ie. the higher your aerial the greater your potential range.

Your range can to extended by selecting high power on your radio. Note, you should always use the lowest power setting that allows you to communicate effectively.

Below however, is a rough guide to probable maximum ranges when the radios and aerials in good condition, in average atmospheric conditions and with no obstructions:

– Between two handheld radios 1.5m above sea level – 5Nm

– Between to fixed radios with aerials at the top of 15m masts – 15Nm

– Between a low 4m aerial and the coastguard – 15Nm

– Between a fixed radio with an aerial at the top of a 15m mast and the coastguard – 30Nm

For more information about VHF “Black Holes” read this RYA article [VHF Black Holes…]


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