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I live in the San Francisco Bay area and there's this little thing going
on called the America's Cup.

It's being broadcast on TV (at least here in the USA), usually after a
two hour delay (ie, after the actual races have concluded so as to not
draw people away from watching in person shoreside).

The audio from the broadcast, which included real-time reporting and
commentary by sailing luminaries such as Gary Jobson, is broadcast live
on Marine VHF frequency 20, so you can actually hear the commentary as
you watch the races from your boat (as I did a couple of weekends ago).

Here in the US about a third of the VHF radio channels we use are
different from what the rest of the world uses.   Generally they are
simplex channels whereas their international brothers are duplex. These
US-unique channels are often designated with an "A" after the channel
number (for example, to talk to the US Coast Guard, one uses Ch 22A)

Because of this difference, most VHF marine radios come with a switch
labeled "USA" and "International" that switches between the two sets of
frequencies.

I got into a confusing argument with several very knowledgeable
colleagues about the America's Cup broadcasts because they were
broadcast on Channel 20, not 20A.   "That requires switching your radio
to 'International' to listen, doesn't it?"   "No, it's just on my
radio"  I finally discovered that both Channel 20 (duplex) and 20A
(simplex) are authorized for use in the USA.

I've got a fixed mount radio on my boat and two hand-held VHFs, all of
which are 10 or more years old.   They give me just one choice of VHF
Channel 20 (which I'm guessing is 20A).    (I also just bought a new DSC
VHF radio, but haven't had a chance to install it and see a 2013 view of
channels)

Adopting both 20 and 20A for use in the USA seems to be recent. But I
can find no information about when this change took place.

Does anyone on this list know (or, even better, point to some history on
the adoption)?

Thanks

Lu

   

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