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Author Topic:   VHF Marine Band Channels
jimh posted 08-31-2014 09:50 AM ET (US)   Profile for jimh   Send Email to jimh  
In the Americas region, the VHF Marine Band channel plan has allocated Channels 78A, 19A, 79A and 20A as SIMPLEX channels. Formerly these channels were the SHIP TX channel of a DUPLEX channel allocation, typically used with shore stations to provide marine radiotelephone connection to land telephone services. Because cellular telephony has replaced almost all of the marine radiotelephone to land telephone services, these channels have been converted to simplex use for vessels. These changes have been in place for some time. (The exact epoch of the change is not know to me.) The details are as follows:

78A or 156.925-MHz is for Non-commercial use

19A or 156.950-MHz is for Commercial use

79A or 156.975-MHz is for Commercial use, except Non-commercial in the Great Lakes only

20A or 157.00-MHz is for Port Operations

Note that for Great Lakes boaters these allocations provide two additional non-commercial channels for use for boat-to-boat communication, 78A and 79A.

The Non-commercial channels available are thus:

68
69
71
72
78
79--only in Great Lakes
80--only in Great Lakes

Cf.: http://www.navcen.uscg.gov/?pageName=mtvhf

In the future, c.2017, more old duplex channels will be converted to other uses. It is anticipated that 80, 21, 81, 22, 82, 23, 83, 24, 84, 25, 85, 25, and 86 will be allocated for use with digital modes. In addition, channels 27, 87, 28, and 88 may be put to use for new functions in the automated identification system (AIS). Finally, a new channel, called 2006 at 160.9-MHz, will be used for testing of new communication applications.

There is also some indication that the channel designators might change. Instead of calling the old ship TX frequency of a channel the "A" channel, the prefix "10" will be prepended. Thus

78A --> 1078
79A --> 1079

and so on. The shore station frequency of the old duplex channel, formerly designated with a "B" suffix will be give a "20" prefix, thus

78B --> 2078
79B --> 2079

and so on.

Plans are also in place to create two new AIS channels by taking channels 75 and 76, which have long been left unused in order to serve as guard bands to the primary emergency channel 16 (156.800-MHz), and using them for present-day-type AIS service. Channel 75 would be AIS 3 at 156.775-MHz and Channel 76 would be AIS 4 at 156.825. One advantage of AIS on these channels: the AIS transponder's antenna would not have to be re-tuned for the very high end of the VHF Marine Band. Presently AIS 1 and AIS 2 are at 161.975 and 162.075-MHz, respectively, and the typical small boat marine antenna is not sufficiently broad band to have a low VSWR at those frequencies. Present-day AIS transponders generally need a specially-tuned antenna in order to get a good match for the much higher than usual frequency used by AIS.

These changes are global allocations by the World Radio Conference. It does not mean that every nation will immediately change their use of the VHF Marine Band to conform. If all these changes are implemented in the USA by the FCC in 2017, a great number of radios presently in use will not be able to use the new channels.

Hoosier posted 09-01-2014 10:11 AM ET (US)     Profile for Hoosier  Send Email to Hoosier     
Please explain this "a great number of radios presently in use will not be able to use the new channels.", a channel is a channel, if my radio can tune to it now, I should be able to use in the future, right?
Jefecinco posted 09-01-2014 10:40 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     
Dave,

On my VHF a good many channels are not available.

Butch

jimh posted 09-01-2014 10:42 AM ET (US)     Profile for jimh  Send Email to jimh     
Your radio won't have some of the new channels. For example, Channel 2006, 2078, 2079. Your AIS receiver or transponder won't have AIS 3 or AIS 4 reception or transmission. Your radio won't have digital modes for the new digital channels.
jimh posted 09-01-2014 01:48 PM ET (US)     Profile for jimh  Send Email to jimh     
On further research, I found there is more to these new channel allocations for the USA than appears at first glance. There are two fundamental problems:

--part of the VHF Marine Band spectrum in the USA has already been allocated to other services, and

--part of the VHF Marine Band spectrum in the USA has been auctioned off by the FCC to other users.

An article and chart prepared by the Coast Guard gives details. See

http://www.navcen.uscg.gov/?pageName=apps18

The frequencies shown in BLUE are already allocated to other services, and those shown in GREEN have been auctioned off and are no longer available to the maritime users.

jimh posted 09-02-2014 06:45 AM ET (US)     Profile for jimh  Send Email to jimh     
For present day allocations, here is a concise summary of VHF Marine Band channels and their authorized uses from the FCC:

http://wireless.fcc.gov/marine/vhfchanl.pdf

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