Learn how VHF works, the basics behind the frequencies you see on your radio and what can make handheld batteries very inefficient in our marine radio FAQs

Can I send my marine radio back to any Icom around the world?

Icom UK offer a 3 year warranty on marine products, this is within the UK only. If you are outside UK waters in a UK flagged vessel please contact us and we will advise accordingly.


Why can’t American marine radios be used/fitted in the UK?

All European electronic & electrical equipment must meet stringent technical and legislative standards including Electro Magnetic Compatibility (EMC) Directive tests and must be CE marked to show that they have done so. Products for the US do not have to meet these standards and are neither tested nor carry the CE mark. Equipment that does not meet the requirements of the above regulations can not be licensed for use on European vessels. The terms of the licence will have been broken and the consequences are likely to be a prosecution and criminal record.


My Icom DSC/VHF radio will now not transmit on 25w. In addition the screen goes blank at the start of the transmission for a few seconds. It transmits clearly on 1w with no loss of screen data.

Typically this fault is caused by high resistance on the DC leads to the transceiver. This could be caused by old or poorly insulated power leads. Please call Icom service department for more information.


I recently purchased a boat that included an Icom radio. I have my own MMSI Number can I add it myself?

Unfortunately not, the radio will need to go back to either your local Icom dealer or Icom UK service department.


I have bought an Icom Marine Handheld. I note that it has channel P4. Is this the same as M2? Is channel 37A the same as channel 37?

P4 is the same as M2. M1 or Channel 37A is the simplex version of channel 37. Some marinas will use channel 80 – if this is the case they will let you know as you approach.


I have an IC-M423 and I cannot find in the manual any reference to a back-up battery or micro-chip. If we disconnect the unit, will it lose any programmed channels/tag channels I have inputted?

No, the channels you have programmed will remain in the radio even when disconnected.


How long can buoyant handheld VHF float in the water?

Buoyant handheld VHF radios are not designed to be left submersed underwater and should be retrieved immediately.
Read more


When should I operate on low power?

In general it depends on how far away the radio is that you are trying to communicate with. There are some channels that automatically require the high or low power setting. Keep in mind is that the lower wattage, the less power used, thus the longer the batteries will last.


Will other electronics interfere with my VHF unit?

Yes that is possible. Many electronic devices are capable of generating RF energy which might interfere with radio reception. This can take the form of wideband ‘noise’ which can degrade reception on all channels or interference which will effect just a few channels. This RF energy can be radiated from equipment cabling, so keep leads as short as possible and routed away from the radio’s cabling. Fitting ferrite rings to either end of leads that might be radiating interference can often help. If problems persist, it might be necessary to re-site equipment or antennas.


What do I do if I accidentally press my DSC distress button?

The DSC button on an ICOM radio is covered by a red flip-up cover. This cover must first be lifted before the button can be pressed (so accidental depression is difficult). The distress button needs to be pressed and held for five seconds before it will send a DSC distress message. During this five-second period the radio will emit a loud warning beep every second. If the button is released before the five seconds then the radio will return to normal and no distress message will be sent.

If for some reason you do send a distress message in error, you should call the coastguard immediately and inform them. If you have children, it is very important that you emphasise the likely consequences of playing with a DSC unit.


Can I use my Icom mounted VHF radio, or an SSB radio, on a vessel with a 24V electrical system?

Only if you purchase a separate power converter that will convert 24V DC into 12 Volt DC. All Icom mounted VHF and SSB marine radios are designed to operate with 12V power systems. Connecting them to 24V will result in immediate failure of the radio due to over voltage. It might even damage the radio beyond repair.


My mounted VHF radio, or SSB radio, seems to have a problem. The display lights dim when I transmit (the radio even shuts down by itself sometimes and I’m not getting full TX output power either).

This behaviour is caused by an insufficient power supply, or a bad electrical connection somewhere between the battery (or a power supply) and the transceiver. Check your electrical connections and battery. Pay special attention to the in-line fuse holders and power cord terminals on the battery side.


Are your waterproof marine radios really waterproof?

They are conditionally waterproof. For example, the IC-M21 can withstand being submerged in one metre of water (about 3ft) for 30 minutes with no water intrusion. If the radio ever goes overboard, you should retrieve it as soon as possible. Remember that even submarines will get crushed if they submerge beyond certain depth. We make quality radios, but we cannot change the laws of physics!

If your Icom radio does get submerged then a good practice is to rinse the radio with tap water and dry thoroughly to prevent a salt build up as salt can cause serious corrosion. After repeated exposure to spray all battery contacts should be inspected, cleaned and lightly greased. Knobs should also be removed and control shafts cleaned and re-greased likewise. After any exposure to moisture the radio should be thoroughly dried.


I’m using your optional hailer horn with my Icom marine radio and all I get is feedback!

This is caused by close proximity of the hailer horn to the location of the radio. The hailer horn is very loud, and it should be mounted a safe distance away from the operating location.


I have an Icom VHF marine radio and I’m attempting to contact another VHF operator. But, even though we are very close, we can’t seem to be able to communicate. Stranger still, some channels seem to be working and others do not!

Most marine channels can be used for direct ship-to-ship communication. They are called simplex channels. Some marine channels are duplex, and can only be used for ship-to-shore communications. Duplex means that the receive and transmit frequencies are different for an indicated channel.

Protect Your Marine Electronics against Salt Corrosion

For marine electronics, the saltwater environment is one of the harshest on earth. It’s a fact that over time, whether you are a yachtsman, powerboater or sea angler that your VHF radio and other marine electronic equipment will suffer from salt corrosion.

If corrosion is the bad news, then the good news is there are steps to ensure that your VHF radio continues to be your trusty safety aid. As mentioned in most manuals, it is good practice to clean your radio thoroughly with fresh water after exposure to saltwater. Otherwise, keys, switches and controllers may become inoperable due to salt crystallisation.

This simple, practical procedure will ensure that you can prolong the life of not only your VHF radio, but any other waterproof portable marine electronic equipment that you might be using. But please ensure it is waterproof before giving it a bath!


I’ve tried to enter my MMSI number twice and now my radio won’t accept another attempt. What do I do?

OFCOM requires that all DSC radios are allowed only two attempts at programming the MMSI number (The MMSI number can only be programmed correctly once and you get 2 attempts at inputting a valid number) . Your only solution now is to take the radio to a qualified Icom marine dealer who will be able to program the MMSI number for you.


The display lights dim when I transmit. The radio even shuts down by itself sometimes. I’m not getting full TX output power either

This behavior is caused by an insufficient power supply, or bad electrical connection somewhere between the battery (or a power supply) and the transceiver. Check your electrical connections and the battery. Pay special attention to the in-line fuse holders and power cord terminals on the battery side.