US vs international VHF standards

[Bjarke Christensen]

Inside my VHF (and older one) there is a jumper (solded) where I can switch
between "US" and "INT".

What is the difference (apart from the channels being used slightly
different) in channel technology/frequences/other ??

 

[Larry]

"Bjarke Christensen" <[email protected](nej, det skal selvfølgelig
være med K da jeg er dansker)> wrote in @dreader1.cybercity.dk:

What is the difference (apart from the channels being used slightly
different) in channel technology/frequences/other ??

Back when VHF-FM marine frequencies were started, the big monster Bell
Telephone/American Telephone & Telegraph monopoly called in a few
political chips and got large blocks of channels reserved for themselves
to operate these channels as "pay phones" for the rich boaters at
exhorbitant prices, of course. These channels were all "duplex"
channels, meaning you transmitted on a whole different frequency than you
received on...making sure noone else could use them outside the telephone
company's for-profit marine operators, whos radios operated the frequency
pair backwards from the boat radios. No phone company, no communications
on those channels.

The international community was unfazed by this ripoff and many of the US
channels that were split duplex were simplex channels in the INT
international bands so marine interests, not phone companies, could use
them. So, the radios had to be configured to operate channels split in
the USA and simplex in the rest of the planet.

Ch Ship XMT Shore XMT Frequencies (Mhz)

24 157.200 161.800 Public Correspondence (Marine Operator)
25 157.250 161.850 Public Correspondence (Marine Operator)
26 157.300 161.900 Public Correspondence (Marine Operator)
27 157.350 161.950 Public Correspondence (Marine Operator)
28 157.400 162.000 Public Correspondence (Marine Operator)
84 157.225 161.825 Public Correspondence (Marine Operator)
85 157.275 161.875 Public Correspondence (Marine Operator)
86 157.325 161.925 Public Correspondence (Marine Operator)

These are the channels in this cozy arrangement still left over after AIS
got 2 of them.

A good combination chart showing the differences with the US in blue is
on:
http://www.navcen.uscg.gov/marcomms/apps18.htm

Of course, ATT's stations, like WOM and WCC are now gone, victims of
satellite and cellular phones. INMARSAT at them alive in the commercial
market.

 

[Bjarke Christensen]

Yes, I know the *usage* differs, but what frequences are different ?

Bjarke

 

[Bjarke Christensen]

Great answer. That explains a lot, among other why I can receive on channel
3.

/Bjarke

 

[Peter Bennett]

"Bjarke Christensen" <[email protected](nej, det skal selvfølgelig
være med K da jeg er dansker)> wrote in @dreader1.cybercity.dk:



Back when VHF-FM marine frequencies were started, the big monster Bell
Telephone/American Telephone & Telegraph monopoly called in a few
political chips and got large blocks of channels reserved for themselves
to operate these channels as "pay phones" for the rich boaters at
exhorbitant prices, of course. These channels were all "duplex"
channels, meaning you transmitted on a whole different frequency than you
received on...making sure noone else could use them outside the telephone
company's for-profit marine operators, whos radios operated the frequency
pair backwards from the boat radios. No phone company, no communications
on those channels.

The international community was unfazed by this ripoff and many of the US
channels that were split duplex were simplex channels in the INT
international bands so marine interests, not phone companies, could use
them. So, the radios had to be configured to operate channels split in
the USA and simplex in the rest of the planet.

No - you've got it backwards.

Under the International band plan, 30 (or so) channels are duplex (two
frequency, suitable to use for ship-shore telephone calls), but the US
chooses to use some of the International duplex channels as simplex,
and shows this use by adding an "A" suffix to the channel number. The
US has _fewer_ duplex channels than the International plan.

Canada is similar to the US, but we change fewer duplex channels to
simplex than the US.

A good combination chart showing the differences with the US in blue is
on:
http://www.navcen.uscg.gov/marcomms/apps18.htm

The table at that link is titled "International VHF Marine Radio
Channels and Frequencies. The US table is at
http://www.navcen.uscg.gov/marcomms/vhf.htm, and I have a list at
http://vancouver-webpages.com/peter/marine.txt which lists both US and
International frequencies.


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
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