Budget marine radio scanners are easy to find as the VHF channels used by ships are included in almost all radio scanners with some of the cheaper models doing a very good job of receiving these transmissions. No special decoding is needed as everything is sent in “the clear” and by monitoring the calling channel you can usually find some activity but this does depend very highly on your location and how high up the receiver is.
The range of VHF marine transmissions at sea is short because most antennas are low down with taller ships fairing better as their antennas are mounted on high masts. The signals soon get blocked by the natural curvature of the earth and as with all line of sight communication increased performance is less a matter of power and more of height with activity on the VHF marine channels dropping off quickly as you move inland unless you have a high vantage point overlooking a busy shipping lane or port.
Marine Scanner Equipment
Because the system has very low technical requirements there is no need to spend a huge amount on a radio just to listen to boats and ships. Many entry level scanners will give you everything needed to do the job with the only extra bit of equipment needed being a good outside antenna if you are setting up a home base scanner station.
Another way to listen is to purchase one of the many cheap two way marine radios on the market but this route does have a few drawbacks.
1. Buying one of these radios means its limited to receiving marine signals only whereas you’ll probably pay the same (or less) for a capable scanner that can be used to listen to so much more.
2. Actually transmitting on marine VHF means that by law you must have a license which is going to add cost to the purchase.
Marine Scanner Frequencies
VHF marine signals are located between 156 and 162.025 MHz and work on a 50KHz channelized system. Nearly everything operates in simplex mode meaning a traditional two way radio system where only one person can speak at a time. Some ship to shore phone calls are handled in duplex mode by giving each transmitter its own channel to allow simultaneous telephone like conversations but these are seldom heard at marine VHF.
Most contacts are started by using the calling and distress channel at 156.800 MHz before moving off to another channel making 156.800 MHz a good place to listen for activity. Many channels are shared between areas and users with some restricted for coast guard use only keeping them clear of private transmissions.
For a comprehensive look at the allocation of VHF marine channels you can visit Wikipedia’s VHF marine page
Listening to Marine Scanners Online
There are a number of audio streaming services where you can listen to marine scanners online but due to not having total control over the scanner it can be limited with access only available via the internet. There are many of these scanner “portals” which give a good glimpse into VHF/UHF radio traffic from around the world. For further information read our post on internet scanner feeds
Buying Used Scanner Radios
Over the years much of the transmissions picked up by radio scanners have changed by either switching to different frequencies or moving over to complicated trunking systems which has made the usefulness of older scanner equipment limited with today’s RF communications.
The VHF system used at sea has embraced a little but of digital technology but is essential the same meaning that much of the older scanning equipment that can be purchased very cheaply through auction sites is ideal if you just want it for marine transmissions (providing it will cover the frequency range from 156 to 163 MHz and be able to receive in FM mode).
Marine Antenna photo courtesy Wikipedia