VHF marine

From HFUnderground

Revision as of 16:48, 10 June 2021

VHF Marine Band, marine radio, VHF radio, VHF radiotelephone or even "VHF marine CB" to some people. Worldwide allocation 156-162 MHz. Several country-specific variations. In some parts of the USA, parts of the marine band is allocated to other services (either on a primary or secondary basis). Mixture of simplex and half-duplex (split-channel) allocations. Some channels used as repeaters in certain countries (Australia, New Zealand), as links to landline telephone system (defunct now) or crossband to other marine allocations such as 27 MHz or HF marine.

Like many other VHF / UHF Radio services, the VHF marine band is heavily pirated (or bootlegged) for non-marine land mobile purposes. It is especially popular with hunters, truckers, logging companies and delivery services. While similar services such as plain old CB, MURS, FRS and GMRS exist to fill these needs, the VHF marine band continues to suffer from misuse, especially away from water where enforcement is difficult. So common is VHF marine usage by hunters that it has earned the nickname "The Bambi Band". Although, in the late 2010s, the number of hunting clubs switching from VHF marine to licensed FCC business radio frequencies is steadily increasing, probably more because of interference issues and less because of FCC enforcement.

Internationally, the VHF marine band is set up for either single frequency (simplex) or split-frequency (duplex). On duplex channels, the higher side is the "B" channel, the lower/simplex channel is the "A" channel. VHF marine radios set to "USA mode" operate in simplex mode only, making all channels "A". One will often hear a channel referred to in this manner "channel 22A" for example, simply means channel 22, simplex.

The 156.000 MHz to 156.250 MHz region is shared with Part 90 land mobile in certain parts of the United States. This comprises public safety allocations from 155.9925 MHz to 156.240 MHz (7.5 kHz steps). In some areas, land mobile allocations are prohibited above 156 MHz to prevent interference with VHF marine communications (for example, in the New Orleans area, in certain Canadian border regions, etc.)

VHF Marine Channels - USA Channels - US Channels New and Old Channel Numbering

4-digit channel numbers for simplex frequencies...some channels are still two-digit. USCG recommends use of the 10xx channel designators for the old A designators for simplex channels (for example, 22A becomes 1022). Under the 4 digit channel numbering system, the B channels are re-designated under 20xx series. In other words, channel 27B becomes channel 2027. Since the vast majority of US marine traffic is simplex, it's simply a question of renaming the "A" simplex-only channels. Channels that have always been simplex - such as channel 16, etc. retain their two digit designators.

VHF Marine Channels USA Channels - Simplex and Duplex

Note that channels 02A, 04A, 60A, 61A, 62A and 64A are not available for legal use in the USA. However, some or all of these channels are available in USA mode in many VHF marine radios as simplex channels. Use is usually commercial or non-commercial ship to ship / intership.

Channel 01A (1001) and 05A (1005) are only available for use in very specific areas. These channels are used nationwide for commercial and non-commercial (recreational boats) intership communications outside the VTS zones.

Channels 84, 85 and 86 are still allocated for duplex use only, but many radios sold in the United States include 84A, 85A and 86A as simplex channels in addition to 87A and 88 (or 88A) as simplex channels. Like 02A, 04A, 60A, 61A, 62A and 64A are not allocated for marine use in the USA but many VHF marine radios include some of all of them as simplex channels. They are often used for non-commercial internship communications but commercial fishing communications and other users are found on these channels.

The WX channels may be in order from lowest frequency to highest frequency, the original 3 NOAA Weather Radio frequencies (162.55 MHz, 162.4 MHz and 162.475 MHz) were supplanted by the 4 additional frequencies later on. Weather channels 8, 9 and 10 are only used in Canada.

Channels 24-28 and 84-87 were allocated for "coast station" (radiotelephone) services but these are no longer used. In some countries VHF marine continues to operate as a duplex system, with certain areas implementing repeaters (Australia for example). In other countries such as the United States, the 161 MHz high side ("B" channel) of the duplex pairs for these channels (161.800 - 162.000 MHz) have been re-allocated to other services, including land mobile radio, public safety systems and reserve/emergency interoperability frequencies.

In some countries (including the UK for some channels) semi-duplex is used for ship-to-shore communications, even though no operational benefit is gained using duplex vs. regular simplex.

Land mobile users of the 157.2 MHz to 157.4 MHz and 161.8 to 162.0 MHz frequencies are still licensed as Radio Service Code PC - Public Coast Stations, Auctioned. A licensed user will acquire a block of frequencies as well as a market area. For example, instead of being licensed for 157.2 MHz and 161.8 MHz, a user will be licensed for 157.18125 MHz to 151.20625 MHz and 161.78125 MHz to 161.80625 MHz.

This practice is common in areas where the VHF high band is used for wide-area trunking systems, often for public safety or law enforcement purposes. The 160.2 MHz to 161.64 MHz portion is allocated for use by railroad systems in the United States and Canada (NFM voice and NXDN digital voice/data).

In other countries, a mix of simplex and duplex channel plans are used. The duplex (or B channel) is + 4.6 MHz offset from the A channel. Not all channels are used in duplex mode in all other places, and simplex use is extremely common (as is the US standard of simplex only).

The FCC permits use of the shared marine frequencies discussed in areas away from the coasts and major waterways to avoid interference. Channels 24-28 and 84-87 are officially still allocated to duplex radiotelephone and VHF Digital Small Message Service data services but are heavily used for analog voice communications, usually non-commercial in nature.

Channel 70 (156.525 MHz) is used for Digital Selective Calling (DSC) and voice communications are not permitted.

156.800 MHz - VHF marine channel 16, is the international VHF distress, safety, and calling channel.

VHF marine radio frequency bands (international allocation)

156.000-157.425 MHz Simplex/Duplex on certain channels/in certain areas 160.600-162.025 MHz Duplex 161.975 Automatic Identification System (AIS) 162.025 Automatic Identification System (AIS)

Additional VHF Marine Channels (Simplex) - Not Authorized in USA - European Private Use

On-board or Dockside UHF Marine (portables and on-ship or dockside repeater use)

10 MHz offset (international plan) 10.225 MHz offset (US and Canada channel plan). Input frequencies may be used for simplex purposes as well. International channel plan frequencies interfere with US-allocated GMRS and FRS frequencies. Frequencies are shared with UHF business band in the United States. Elsewhere, other UHF on-board radio systems may be used, including PMR446 or other dedicated systems generally in the 400-512 MHz or 380-520 MHz UHF range.

VHF marine band equipment

Modern ICOM IC-M605 VHF marine band radio with built-in GPS and DSC capability. 156 MHz - 163 MHz simplex and duplex. This radio is tuned to the international distress and calling channel 16 frequency of 156.800 MHz

Older-generation Uniden MC635 VHF marine band radio without DSC capability 156-163 MHz simplex and duplex VHF-FM transceiver. This radio is tuned to the international distress and calling channel 16 frequency of 156.8 MHz.