VHF question

[gravygraham]

We moved Chatham last week and they use ch80 here. When we were at Ramsgate (ch14) we enjoyed listening to the radio chatter. We're ok communicating with the marina office here but when they're talking with other boats we can only hear the marina office side on the conversation. Anyone know why this is?

Took this pic from the flybridge at the fuel pontoon yesterday.

 

[Caliban]

I was told, when I took my VHF course, that marinas transmit and receive on different frequencies.

Dunno why

 

[l'escargot]

We moved Chatham last week and they use ch80 here. When we were at Ramsgate (ch14) we enjoyed listening to the radio chatter. We're ok communicating with the marina office here but when they're talking with other boats we can only hear the marina office side on the conversation. Anyone know why this is?

Took this pic from the flybridge at the fuel pontoon yesterday...

Surely you remember covering simplex and duplex on your VHF course?

 

[gravygraham]

Surely you remember covering simplex and duplex on your VHF course?

Hmm, March 2005 was a long time ago to a dimwit like me. Do explain for me/us?

 

[l'escargot]

Hmm, March 2005 was a long time ago to a dimwit like me. Do explain for me/us?

I'm not an instructor but a duplex station is one that transmits and receives on different frequencies (as opposed to a simplex channel that transmits and receives on the same frequency) this is quite a good explanation of it from someone else on the forum:

"Ch80 is duplex which means the shore-based station is configured in the opposite direction to your vessel's radio for this channel. So you can speak to the marina and he can speak to other yachts - but the frequency 'swap' means that you can't use this channel for communicating to another vessel. Hence it will often sound as though the marina is having a conversation with no-one - many people assume that the boat he is talking to is simply out of range - not so, you just cannot hear him on this channel"

 

[prv]

Hmm, March 2005 was a long time ago to a dimwit like me. Do explain for me/us?

On simplex channels, everyone is on the same frequency. On duplex channels there are two frequencies, and each radio is set up to transmit on one and receive on the other - which way round is programmed into the radio by the manufacturer and you can't change it (a dealer may be able to). The usual arrangement is that shore stations are one way round, and ship stations are the other. So a shore station can hear all the ships, but the ships can only hear the shore station, not each other. This was for the old telephone link call system.

For some reason, god knows why, when Ofcom or their predecessor decided to nominate a general marina channel, they chose to use a duplex channel. Perhaps they thought "it's a 'shore station controlling many ship stations' scenario", without any practical experience, whereas things would often work a lot smoother on a busy afternoon if everyone could hear what was going on.

A "scanner" radio as used by plane spotters will let you hear the other side if you really want to.

Pete

 

[gravygraham]

Thanks peeps. I remember the terms simplex and duplex but wouldn't have been able to describe them to anyone - until now.

Next question - is there a list anywhere saying which channels are which? Knowing me I'd contact someone on ch16 and refer them to a duplex channel for comms.

 

[DAKA]

if you want to listen to the marina other half of the conversation then put your hand held on USA 80.

 

[l'escargot]

..Next question - is there a list anywhere saying which channels are which? Knowing me I'd contact someone on ch16 and refer them to a duplex channel for comms.

Ofcom list the general ones - the ones to avoid specifically: http://www.ofcom.org.uk/static/archive/ra/publication/ra_info/ra264/ra264.htm although you will find local variations with different organisations such as ferries, water taxis, clubs etc. "adopting" certain channels. The accepted boat to boat channels are primarily 6, 8, 72 or 77.

 

[maby]

...

For some reason, god knows why, when Ofcom or their predecessor decided to nominate a general marina channel, they chose to use a duplex channel. Perhaps they thought "it's a 'shore station controlling many ship stations' scenario", without any practical experience, whereas things would often work a lot smoother on a busy afternoon if everyone could hear what was going on.

...
Pete

I think you'll find it's a hangover from the old days. Prior to the wide availability of mobile phones, there was a network of "Public Correspondence" stations around the coast that would accept calls from ships at sea and patch them through to the telephone network (at a price). In order to work with the telephone network which has no concept of "press to talk", these public correspondence stations operated in duplex mode with the transmitter and receiver working on different frequencies - this allows the transmit and receive to work simultaneously (on a suitable radio) so that you can have a normal telephone conversation without having to punctuate every sentence with "OVER".

With the introduction of mobile phones, this network has pretty much ceased to exist - none of the British stations are still operating - I think there may still be a few around the Spanish coast. This left us with a large number of unused duplex channels and the various users of marine radio have taken some of them for applications where there is no real need for a three-way conversation. It would probably make more sense to redesignate them all as simplex channels, but that would require every marine radio in Europe to be modified - never going to happen! The radios that most of us use are not really duplex operation - they just operate split frequency simplex on a duplex channel.

 

[Denis O]

We moved Chatham last week and they use ch80 here. When we were at Ramsgate (ch14) we enjoyed listening to the radio chatter. We're ok communicating with the marina office here but when they're talking with other boats we can only hear the marina office side on the conversation. Anyone know why this is?

Took this pic from the flybridge at the fuel pontoon yesterday.

Slightly off topic but I lived in Chatham from birth till about 48 years old and I've never seen it look that good. Looks more like St Katherines dock than a hole like Chatham. It's also the first time I've seen a picture of Chatham without a chav in sight

 

[Croak]

if you want to listen to the marina other half of the conversation then put your hand held on USA 80.

That is my new bit of information for today, thank you.

 

[maby]

Slightly off topic but I lived in Chatham from birth till about 48 years old and I've never seen it look that good. Looks more like St Katherines dock than a hole like Chatham. It's also the first time I've seen a picture of Chatham without a chav in sight

There's a world of difference between St. Mary's (where the marina is) and Chatham town centre. On those few occasions that I need to park my car anywhere near the old High Street, I always expect to come back and find it up on four piles of bricks!

 

[Denis O]

There's a world of difference between St. Mary's (where the marina is) and Chatham town centre. On those few occasions that I need to park my car anywhere near the old High Street, I always expect to come back and find it up on four piles of bricks!

Of course there's a world of difference, albeit less than 2 miles and less as the crow flys. Just amazing how an area can look so good.

And just think, Strood is only a tunnel away and that makes Chatham look like Regents Park.

 

[AllanG]

if you want to listen to the marina other half of the conversation then put your hand held on USA 80.

Do you know if this USA 80 channel is available on all hand helds? Mine's an Icom IC-M71, but it's on the boat so I can't check.

 

[gravygraham]

It's also the first time I've seen a picture of Chatham without a chav in sight

He was behind the camera!

 

[maby]

Do you know if this USA 80 channel is available on all hand helds? Mine's an Icom IC-M71, but it's on the boat so I can't check.

Most handles I've seen can get it, but you probably will have to set it to the American channel set which means that you can't use it to transmit in this country.

 

[prv]

I think you'll find it's a hangover from the old days. Prior to the wide availability of mobile phones, there was a network of "Public Correspondence" stations around the coast that would accept calls from ships at sea and patch them through to the telephone network (at a price).

Errm, yes, I know - that's what I meant when I said "the telephone link call system" in my post. It explains why duplex channels exist, but not why "they" decided to pick one of them for the standard marina channel. They could just as well have nominated one of the simplex "port ops" channels instead.

Pete

 

[maby]

Errm, yes, I know - that's what I meant when I said "the telephone link call system" in my post. It explains why duplex channels exist, but not why "they" decided to pick one of them for the standard marina channel. They could just as well have nominated one of the simplex "port ops" channels instead.

Pete

Ah, well - it is probably just down to the fact that there are not many simplex channels available and they consider marinas to be a secondary user group. Port ops really do need the ability to hold three way conversations - marinas generally do not. All the simplex channels are heavily used round our way.

 

[DAKA]

Do you know if this USA 80 channel is available on all hand helds? Mine's an Icom IC-M71, but it's on the boat so I can't check.

almost certainly has a USA feature, you may need your manual as you may have to press "mode" as you turn it on.

As mayb says you will need to switch it back to int before you can speak to marina on 80 , otherwise everyone in marina will hear you except marina.

my suggestion was to use your main vhf for transmit on 80 and your hand held on usa 80 to listen.


if anyone ever leaves their vhf on usa by accident it really doesnt matter

almost all the channels that you are likely to use are the same , the only one really that is different is ch 80.

you can still mayday on 16, chat with your mates on 6 , 77 etc