Marine VHF Channels And Frequencies
When you use a marine VHF, the first thing you need to do is to tune in to the channel that you want to use. This is just like tuning your FM radio to the correct station.
The main difference is that marine VHF channels are numbered, so you do not need to remember the frequency of every channel. All frequencies are pre-programmed into a marine VHF radio already.
The main VHF channels and frequencies to be aware of are:
| Channel | Frequency | Use |
| Ch13 | 156.650 MHz | Bridge-to-bridge |
| Ch 15 | 156.750 MHz | Low power only |
| Ch 16 | 156.800 MHz | Distress / Safety / Calling |
| Ch 17 | 156.850 MHz | Low power only |
| Ch 70 | 156.525 MHz | DSC |
| Ch 87B | 161.975 MHz | AIS 1 |
| Ch 88B | 162.025 MHz | AIS 2 |
With VHF channels and frequencies, different countries have different rules about what each channel is used for.
The channels in the table above are the main channels that have almost uniform usage worldwide. This means that these channels are used for the same thing, no matter where you are in the world.
The most important VHF channel is 16. Ch16 is used internationally for distress, safety and calling. It is illegal to use this channel for any other purposes.
Either side of ch 16, you find 15 & 17. The specific use of each of these does change from country to country, but I have included them because they share one specific characteristic. They can only be used on low power (1W).
This is because they are the closest channels to ch 16, and we do not want the use of either of them to interfere with a potential mayday situation.
As they are low power, they are typically used for communication within a vessel, or across a short distance.
Ch 70 is used for Digital Selective Calling (DSC). It is not a voice communication channel.
When you make a DSC call, your radio will use ch 70 to send the alert to the MMSI number that you input.
Finally, CH 87B & 88B are both used for AIS. AIS uses your VHF antenna to automatically transmit your vessel’s information. Both of these channels cannot be used for voice communication.
For more detail about how AIS works, you can read this article: How Does AIS Work?
Aside from these “universal” channels, we have around 60 other VHF channels whose specific usage varies from country to country. In the rest of this article, we will break it down further so that you have a full understanding of the range of VHF channels and frequencies available.
Where are marine VHF frequencies in the radio spectrum?
Marine VHF runs on frequencies between 156 MHz and 161 MHz.
The radio spectrum describes different frequencies and wavelengths of electromagnetic waves.
When it comes to radio communication, we use electromagnetic radiation with relatively low energy, and a long wavelength. Communication frequencies range from 3 kHz to 300 GHz, with wavelengths from 100km to 1mm.
VHF is just one small part of the spectrum that is used for communications.
As you can see from the diagram above, VHF frequencies range from 30 MHz to 300 MHz. Similarly, wavelengths can be anywhere between 10m and 1m.
Pro Tip: Antenna length is directly proportional to wavelength. HF antennas are longer than VHF antennas which are longer than UHF antennas.
Within the entire VHF spectrum, only a small portion is reserved for use in marine VHF specifically. The rest is used for things like aviation, television, radio, DAB etc.
The small part assigned to marine VHF is 156 MHz – 161 MHz.
Breaking down the marine VHF frequencies even further, you get into specific channels.
For example, 156.750 MHz MHz is one channel. 156.800 MHz is another channel.
We label them with channel numbers instead of writing out the frequency every time.
156.750 MHz is channel 15, and 156.800 MHz 16.
The channel numbers are just a consistent way of labelling marine VHF frequencies, standardised across radio manufacturers.
It means navigators only need to remember channel numbers rather than individual frequencies.
Types of VHF channel
We have seen that VHF channels are just labels for specific frequencies within the marine VHF radio spectrum.
The other concept to understand with marine VHF is that you can find two different types of channel.
- Simplex channels
- Duplex channels
Simplex VHF channels
A simplex marine VHF channel is a radio channel where you transmit and receive on the same frequency.
Although we call it “simplex”, it is actually a “half-duplex” channel. A true simplex channel is one where information only flows in one direction.
For example, a true simplex channel would be something like a TV channel. The TV antenna can only transmit, and the aerial on your roof can only receive.
In marine VHF usage, however, we mean that the channel can only carry a single transmission at any one time.
Either the ship station can transmit, or the shore station can transmit. Both cannot transmit at the same time.
These channels are the traditional ones where you make your broadcast, then end it with the word “over” to let the recipient know you are finished.
While the transmission is taking place, it is acting as a simplex channel. One person is transmitting, and the other person is receiving.
Marine VHF equipment contains both a transmitter and a receiver, which is why it is technically a “half-duplex” channel instead. You can immediately switch between transmission mode and reception mode.
Duplex VHF channels
A duplex marine VHF channel is a radio channel where you can transmit and receive at the same time. With a duplex channel, you can have a conversation with another party, potentially both speaking at the same time, just like you can on a telephone.
As radio frequencies can only carry a single message at once, a duplex channel actually consists of two different frequencies. Each station transmits on one frequency and receives on the other.
| Station | Transmission Frequency | Reception Frequency |
| Ship | Frequency A | Frequency B |
| Shore | Frequency B | Frequency A |
As they are working on different frequencies, both can transmit at the same time while simultaneously listening to the broadcast from the other station.
A duplex channel just tells your radio to tune in to the different frequencies for transmission and reception.
For example, VHF 84 is a duplex channel where a ship station transmits on 157.225 MHz, and the shore station transmits on 161.825 MHz.
A ship’s VHF would tune its transmitter into 157.225 MHz and its receiver to 161.825 MHz.
How are VHF channels numbered?
VHF channels are labelled with channel numbers. Broadly speaking, they are numbered from 1-28 and 60-88.
The International Telecommunication Union (ITU) assigns a channel number to each frequency for simplex channels, or pair of frequencies in the case of duplex channels.
This standardised set of frequencies and channel numbers is used by marine VHF manufacturers to program their VHFs.
Some countries, like the USA, produce their own standards instead. We’ll cover that in more detail below, but for now it is important to understand that they still use the same general system of numbering channels.
Original VHF channels
Original VHF channels were numbered from 1 to 28.
The idea was that they were spaced at 0.05 MHz intervals across the part of the electromagnetic spectrum reserved for marine VHF use.
For example, VHF Ch 9 and VHF Ch 10 are at 156.450 MHz and 156.500 MHz respectively.
The interval was chosen because that was the limit of what could be reliably used on the available technology at the time.
When frequencies are too close together, radio equipment cannot easily differentiate between the signals, resulting in interference.
You need the interval between channels to be large enough to minimise interference, yet small enough so that you can get sufficient channels within the available space.
As technology improves, however, it becomes possible to tune in to more precise frequencies.
Newer VHF channels
Newer VHF channels are those numbered between 60 to 88.
With newer radio technology, it became possible to assign more channels within the same band of frequencies by reducing the interval between them.
Originally the interval was 0.05 MHz, but the newer technology could half that to 0.025MHz intervals instead.
The result was that you could squeeze newer channels between original ones.
| Channel | Frequency |
| Ch 9 (old) | 156.450 MHz |
| Ch 69 (new) | 156.475 MHz |
| Ch 10 (old) | 156.500 MHz |
Rather than re-name all the original channels, the new ones were given channel numbers between 60 and 88 instead.
As the channel numbers are just labels for frequencies that are programmed into VHF units, it doesn’t matter that they don’t run sequentially. Users only use the labels, they don’t need to remember each of the frequencies.
Pro Tip: Check old vs new channels if you have interference. For example, on Ch 9 it is more likely interference is coming from Ch 69 rather than from Ch 10.
What does “A” or “B” mean in a VHF channel?
VHF channels are labelled with an “A” or “B” when they are a new simplex channel that has been derived from an original duplex channel.
For example, when AIS was developed there was not sufficient space within the VHF spectrum to assign it a new frequency. The only option was to repurpose another channel that was already in use.
You can repurpose a duplex channel and create two simplex channels instead.
In the case of AIS, they started with the two duplex channels, 87 and 88.
| Channel | Type | Ship Frequency (A) | Shore Frequency (B) |
| 87 | Duplex | 157.375 MHz | 161.975 MHz |
| 88 | Duplex | 157.425 MHz | 162.025 MHz |
If you re-designate them as simplex channels, you free up the shore frequencies that are no longer needed. The result is four new channels.
| Channel | Type | Frequency |
| 87A | Simplex | 157.375 MHz |
| 88A | Simplex | 157.425 MHz |
| 87B | Simplex | 161.975 MHz |
| 88B | Simplex | 162.025 MHz |
87B and 88B were given to AIS and renamed as AIS1 and AIS2.
The simplex ship frequencies were retained for voice communication and the “A” suffix was dropped to make it simpler for numbering on a VHF set.
It was only possible to drop the suffix because it no longer acts as a duplex channel anywhere in the world. If it was still used as a duplex channel somewhere, the suffix would need to remain to differentiate between the two.
When you see an “A” or “B” on a VHF channel number, it just means that it was originally one half of a duplex channel.
What is the difference between USA and International VHF channels and frequencies?
VHF radios in the US use different channels to the rest of the world.
The reason for this is that some parts of the radio spectrum that are used for maritime communication internationally have been auctioned off in the USA for use in other industries, like the railways.
This means that if you make a broadcast on some international VHF frequencies within the US, you might be illegally transmitting on an unauthorised channel.
To get around this, most VHF radios give you the option of switching between “USA” or “Int”.
“Int” or “International” gives you access to all the frequencies that are used throughout most of the world.
“USA” gives you access to frequencies that are used specifically in the USA, while also removing access to channels that cannot be used for maritime transmissions in the USA.
A lot of channels are common between both the “USA” and “Int” versions, but the potential for incorrect use of the others means it is essential to make sure your VHF is set on the correct setting.
Lots of USA channels have the “A” suffix
You’ll notice that many channels used in the US are labelled with the letter “A”.
For example, in the US Ch 1A is a simplex channel operating on 156.050 MHz. Internationally, Ch 1 is a duplex channel operating across frequencies 156.050 MHz and 160.050 MHz.
In the US, the second part of the duplex channel, the 160.050 MHz frequency, is used by railways instead.
As a result, only the “A” part of the duplex channel is available for maritime communication. US radios, therefore, give you Ch 1A to use as a simplex channel.
The same principle applies with other international duplex channels that have been repurposed in the USA after part of the spectrum was sold off.
You will also see these channels labelled with a “10” prefix, rather than an “A” suffix. Going forward, it will become more common to have a “10” prefix instead.
For example, the US channel 1A is also known as channel 1001.
Why are channels 75 and 76 missing?
Channels 75 and 76 are both not available to use because they are “guarding” channel 16.
When the lower increments were introduced in between original VHF channels it increased the chance of interference on channels that are close together.
Given its importance, channel 16 was given special protection from interference by removing the new channels that were introduced on either side of it.
Channel 75 is 0.025 MHz below the channel 16 frequency, and channel 76 is 0.025 MHz above it.
List of VHF frequencies in the USA
A complete list of channels and frequencies and their use is available from the USCG: US VHF Channel Information.
| Channel | Type | Frequency | Notes |
| 1A | Simplex | 156.050 MHz | |
| 5A | Simplex | 156.250 MHz | |
| 6 | Simplex | 156.300 MHz | |
| 7A | Simplex | 156.350 MHz | |
| 8 | Simplex | 156.400 MHz | |
| 9 | Simplex | 156.450 MHz | |
| 10 | Simplex | 156.500 MHz | |
| 11 | Simplex | 156.550 MHz | |
| 12 | Simplex | 156.600 MHz | |
| 13 | Simplex | 156.650 MHz | Bridge-to-bridge |
| 14 | Simplex | 156.700 MHz | |
| 15 | Simplex | 156.750 MHz | Low power |
| 16 | Simplex | 156.800 MHz | Distress / Safety / Calling |
| 17 | Simplex | 156.850 MHz | Low power |
| 18A | Simplex | 156.900 MHz | |
| 19A | Simplex | 156.950 MHz | |
| 20 | Duplex | 157.000 MHz 161.600 MHz | |
| 20A | Simplex | 157.000 MHz | |
| 21A | Simplex | 157.050 MHz | |
| 22A | Simplex | 157.100 MHz | |
| 23A | Simplex | 157.150 MHz | |
| 24 | Duplex | 157.200 MHz 161.800 MHz | |
| 25 | Duplex | 157.250 MHz 161.850 MHz | |
| 26 | Duplex | 157.300 MHz 161.900 MHz | |
| 27 | Duplex | 157.350 MHz 161.950 MHz | |
| 28 | Duplex | 157.400 MHz 161.000 MHz | |
| 63A | Simplex | 156.175 MHz | |
| 65A | Simplex | 156.275 MHz | |
| 66A | Simplex | 156.325 MHz | |
| 67 | Simplex | 156.375 MHz | |
| 68 | Simplex | 156.425 MHz | |
| 69 | Simplex | 156.475 MHz | |
| 70 | Simplex | 156.525 MHz | DSC |
| 71 | Simplex | 156.575 MHz | |
| 72 | Simplex | 156.625 MHz | |
| 73 | Simplex | 156.675 MHz | |
| 74 | Simplex | 156.725 MHz | |
| 77 | Simplex | 156.875 MHz | |
| 78A | Simplex | 156.925 MHz | |
| 79A | Simplex | 156.975 MHz | |
| 80A | Simplex | 157.025 MHz | |
| 81A | Simplex | 157.075 MHz | |
| 82A | Simplex | 157.125 MHz | |
| 83A | Simplex | 157.175 MHz | |
| 84 | Duplex | 157.225 MHz 161.825 MHz | |
| 85 | Duplex | 157.275 MHz 161.875 MHz | |
| 86 | Duplex | 157.325 MHz 161.925 MHz | |
| 87 | Simplex | 157.375 MHz | |
| 88 | Simplex | 157.425 MHz | |
| 87B | Simplex | 161.975 MHz | AIS 1 |
| 88B | Simplex | 162.025 MHz | AIS 2 |
List of international VHF channels and frequencies
| Channel | Type | Frequency | Notes |
| 0 | Duplex | 156.000 MHz 160.600 MHz | Private Channel |
| 1 | Duplex | 156.050 MHz 160.650 MHz | |
| 2 | Duplex | 156.100 MHz 160.700 MHz | |
| 3 | Duplex | 156.150 MHz 160.750 MHz | |
| 4 | Duplex | 156.200 MHz 160.800 MHz | |
| 5 | Duplex | 156.250 MHz 160.850 MHz | |
| 6 | Simplex | 156.300 MHz | |
| 7 | Duplex | 156.350 MHz 160.950 MHz | |
| 8 | Simplex | 156.400 MHz | |
| 9 | Simplex | 156.450 MHz | |
| 10 | Simplex | 156.500 MHz | |
| 11 | Simplex | 156.550 MHz | |
| 12 | Simplex | 156.600 MHz | |
| 13 | Simplex | 156.650 MHz | Bridge-to-bridge |
| 14 | Simplex | 156.700 MHz | |
| 15 | Simplex | 156.750 MHz | Low power |
| 16 | Simplex | 156.800 MHz | Distress / Safety / Calling |
| 17 | Simplex | 156.850 MHz | Low power |
| 18 | Duplex | 156.900 MHz 161.500 MHz | |
| 19 | Duplex | 156.950 MHz 161.550 MHz | |
| 20 | Duplex | 157.000 MHz 161.600 MHz | |
| 21 | Duplex | 157.050 MHz 161.650 MHz | |
| 22 | Duplex | 157.100 MHz 161.700 MHz | |
| 23 | Duplex | 157.150 MHz 161.750 MHz | |
| 24 | Duplex | 157.200 MHz 161.800 MHz | |
| 25 | Duplex | 157.250 MHz 161.850 MHz | |
| 26 | Duplex | 157.300 MHz 161.900 MHz | |
| 27 | Duplex | 157.350 MHz 161.950 MHz | |
| 28 | Duplex | 157.400 MHz 161.000 MHz | |
| 31 | Duplex | 157.550 MHz 162.150 MHz | |
| M1 | Simplex | 157.850 MHz | |
| 60 | Duplex | 156.025 MHz 160.625 MHz | |
| 61 | Duplex | 156.075 MHz 160.675 MHz | |
| 62 | Duplex | 156.125 MHz 160.725 MHz | |
| 63 | Duplex | 156.175 MHz 160.775 MHz | |
| 64 | Duplex | 156.225 MHz 160.825 MHz | |
| 65 | Duplex | 156.275 MHz 160.875 MHz | |
| 66 | Duplex | 156.325 MHz 160.925 MHz | |
| 67 | Simplex | 156.375 MHz | |
| 68 | Simplex | 156.425 MHz | |
| 69 | Simplex | 156.475 MHz | |
| 70 | Simplex | 156.525 MHz | DSC |
| 71 | Simplex | 156.575 MHz | |
| 72 | Simplex | 156.625 MHz | |
| 73 | Simplex | 156.675 MHz | |
| 74 | Simplex | 156.725 MHz | |
| 75 | Simplex | 156.775 MHz | Restricted (Ch 16 guard) |
| 76 | Simplex | 156.825 MHz | Restricted (Ch 16 guard) |
| 77 | Simplex | 156.875 MHz | |
| 78 | Duplex | 156.925 MHz 161.525 MHz | |
| 79 | Duplex | 156.975 MHz 161.575 MHz | |
| 80 | Duplex | 157.025 MHz 161.625 MHz | |
| 81 | Duplex | 157.075 MHz 161.675 MHz | |
| 82 | Duplex | 157.125 MHz 161.725 MHz | |
| 83 | Duplex | 157.175 MHz 161.775 MHz | |
| 84 | Duplex | 157.225 MHz 161.825 MHz | |
| 85 | Duplex | 157.275 MHz 161.875 MHz | |
| 86 | Duplex | 157.325 MHz 161.925 MHz | |
| 87 | Simplex | 157.375 MHz | |
| 88 | Simplex | 157.425 MHz | |
| M2 | Simplex | 161.425 MHz | |
| 87B | Simplex | 161.975 MHz | AIS 1 |
| 88B | Simplex | 162.025 MHz | AIS 2 |