Channel 80

Piers

Piers

Well-Known Member
Joined
2 Jun 2001
Messages
3,599
Location
Guernsey, Channel Islands
www.playdeau.com
I always thought this was a duplex channel. But in Beaucette Marina where I can hear Beaucette transmitting clearly, I cannot hear boaters calling them at all. This is the same on both my foxed VHFs and handheld.

Am I missing something obvious? Has senility finally got the better of me?
 
Piers said:
I always thought this was a duplex channel. But in Beaucette Marina where I can hear Beaucette transmitting clearly, I cannot hear boaters calling them at all. This is the same on both my foxed VHFs and handheld.

Am I missing something obvious? Has senility finally got the better of me?
Click to expand...

Channel 80 is duplex, but you only hear one side and transmit on the other. The marina will hear you and transmit back out on the channel part you are listening on. They might be able to hear both sides.

If you want to hear the other half channels and indeed Channel 0 a hand held scanner from Maplins will allow this. I have a frequency list somewhere for all the International Marine channels. Also useful for listening to air craft. When I first got mine you could hear the local police - quite entertaining on a Saturday night, but now they have switched to a new digital system their old channels are now quiet.
 
superheat6k said:
Channel 80 is duplex, but you only hear one side and transmit on the other. The marina will hear you and transmit back out on the channel part you are listening on. They might be able to hear both sides.

If you want to hear the other half channels and indeed Channel 0 a hand held scanner from Maplins will allow this. I have a frequency list somewhere for all the International Marine channels. Also useful for listening to air craft. When I first got mine you could hear the local police - quite entertaining on a Saturday night, but now they have switched to a new digital system their old channels are now quiet.
Click to expand...

To listen to both sides of 80, have one radio on 80, and another on US channel group 80A.
 
I used to have an Icom 401 which I set to us channels by the touch of one button, great for jumping the transmission que in busy areas like cowes .
 
It is Monday, and I have learnt something new :-)
I was pondering this last weekend, and thought something was wrong with my VHF, but no...

(from a YBW archive)
######

Duplex operation, as correctly stated in the posts above, is where the offshore station transmits on one frequency and the shore station transmits on a different frequency. So shore stations can only hear offshore stations and offshore stations can only hear shore stations on that channel, (unless you use some of the US channel allocations in Europe where as also correctly stated these channels are allocated as simplex). On large ship installations the vhf uses two quite widely spaced aerials so that one can keep the microphone button pressed all the time during a "link" telephone call to a shore subscriber and the remote receiver aerial is far enough away not to be affected by the local transmission and so a normal telephone conversation can be held with both parties able to talk at the same time.

Whilst the vhf transceivers that we use on small craft have only one aerial we still have to use semi duplex mode, where we press the microphone switch to transmit on the ship frequency and when we release the PTT switch the receiver receives the shore frequency. If you had a second vhf with the receive aerial at the opposite end of a largish (50ft or so) craft, you would be able to have full duplex conversations by transmitting on one vhf and listening on the other simultaneously. On smaller craft the close proximity of transmit and receive aerials would cause feedback, cross coupling and howl problems, hence why we have to use semi duplex.

######
 
FlowerPower said:
It is Monday, and I have learnt something new :-)
I was pondering this last weekend, and thought something was wrong with my VHF, but no...

(from a YBW archive)
######

Duplex operation, as correctly stated in the posts above, is where the offshore station transmits on one frequency and the shore station transmits on a different frequency. So shore stations can only hear offshore stations and offshore stations can only hear shore stations on that channel, (unless you use some of the US channel allocations in Europe where as also correctly stated these channels are allocated as simplex). On large ship installations the vhf uses two quite widely spaced aerials so that one can keep the microphone button pressed all the time during a "link" telephone call to a shore subscriber and the remote receiver aerial is far enough away not to be affected by the local transmission and so a normal telephone conversation can be held with both parties able to talk at the same time.

Whilst the vhf transceivers that we use on small craft have only one aerial we still have to use semi duplex mode, where we press the microphone switch to transmit on the ship frequency and when we release the PTT switch the receiver receives the shore frequency. If you had a second vhf with the receive aerial at the opposite end of a largish (50ft or so) craft, you would be able to have full duplex conversations by transmitting on one vhf and listening on the other simultaneously. On smaller craft the close proximity of transmit and receive aerials would cause feedback, cross coupling and howl problems, hence why we have to use semi duplex.

######
Click to expand...


We always used to call it "Two Frequency Simplex"
Simplex is one side of the call at a time (VHF channel 16 etc)
Duplex is where you can both talk at the same time (standard Telephone etc)
 
You must log in or register to reply here.

Other threads that may be of interest

dgadee
Bending stainless
Replies
9
Views
327
RunAgroundHard
RunAgroundHard
cyberkryten
We finally bought a boat - Merry Fisher 895s2
2 3
Replies
41
Views
2K
Cathy*
C

Share this page

Top