You only hear the shore station side. Your and the other boaters radio
transmit on a frequency that the radios do not receive.
Bill

"Scott Downey" wrote in message
...
sure, the duplex channels are separated so each person transmitting does
not
step on the other persons transmission, therefore both could talk and be
heard if you had 2 radios or a special radio where you could hear and talk
at the same time.

But if you have 2 boaters both on the same duplex channel talking to one
shore station on its own complemntary channel, each boater should be part
of
the same conversation. There would be no difference between them as they
would both be using the same duplex channel. So therefore another boater
ought to be able to listen in if tuned to the same duplex channel that the
other boater was using talking to the shore station.

Does anyone sell a special radio that allows one to hear and talk at the
same time? I dont see that in the catalogs. Using 2 radios is a work
around,
I suppose.

"Charles T. Low" wrote in message
.. .
No, here's how it goes with duplex:

All of the boaters' radios listen to channel 4017 (hypothetical) on
frequency 200.150 MHz (hypothetical) and transmit on 200.220 (I'm just
making these numbers up).

The land station does the reverse. Follow that information on to its
logical
conclusion and I think you'll see what I mean. A boater and a land
station
can carry on a conversation just fine, but two boaters cannot.

The question is why, and I think it's because more highly-qualified
radio
operators can use duplex to carry on a two-way conversation, like on a
conventional telephone, using a different radio for receiving than
transmitting (although the two radios could both be in the same box -
like
a
telephone!). The way we recreational boaters do it, at least to my
knowledge
and in my experience, is to carry on a one-way conversation, e.g.
transmit,
then another one-way conversation on another frequency, i.e. receive,
although you don't have to change your channel setting to do that - the
radio changed frequencies for you, but without changing the same channel
number, when you switch back and forth between transmitting and
receiving.
But one radio can't receive and transmit simultaneously, whether in
simplex
or duplex mode, so it doesn't make any difference, to the recreational
marine VHF radio operator, whether it's duplex or simplex - except for
other
eavesdropping boaters.

Is that any clearer?

====

Charles T. Low
- remove "UN"
www.boatdocking.com/BDPhoto.html - Photo Contest
www.boatdocking.com
www.ctlow.ca/Trojan26 - my boat

====

"Scott Downey" wrote in message
...
Ok that makes sense that other boaters would only hear the coast guard
shore
station, BUT what about the guy on the boat the CG shore station is
talking
to?
Isn't he in the same position as anyone else listening? If another
boater
is
on the same frequency as the one the CG is talking to wont he hear
both
sides? Is the duplex send frequency at the shore station different for
each
duplex channel?
I have heard this before and still dont understand it.