VHF radio question

scuby

when you hear the coast guard/harbour master etc talking on channel 16/12, should you not be able to hear the person talking back to them as well or does it depend on the VHF radio you have ?

Pigeon Reaper

Some of the ship-shore channels are duplex so you won't hear the other ship calling unless you have a specialised radio but this only applies to specific channels. With channel 12 it's more likely that you can pick up the more powerful shoreside radio with a high antenna at the docks but may not be within range to receive the other station calling. VHF works on line of sight and the transmission power so alot depends on the location and local environment. With 16 you should always hear both sides if they're within range.

NUTLEY BOY

Some channels are simplex and some are duplex.

On a simplex channel both sides of the conversation are on the same frequency. Therfore, you should hear both sides.

On a duplex channel the shore station transmits on one frequency and receives on a different one. The same applies to the ship station. That might need further explanation ! ;

For a given duplex channel the shore station will transmit on frequency A and receive on frequency B. The ship station will receive on frequency A and transmit on frequency B. This means that shore and ship are able to talk to each other on the same channel. Thank goodness for modern electronics where you only twiddle a knob for the channel as distinct from longer range radios where you have to tune transmission and reception working frequencies !

For practical purposes most duplex transmissions are not actually duplex in operation. The theory of duplex is that it is supposed to be like a telephone where two parties can converse at the same time.

If you have a serious interest in this you can hear both sides of a duplex conversation with a scanner by programming the two frequencies adjacently. However, that is probably illegal so I won't suggest it ! Please remember that what you hear is to be regarded as private and not for onward retail even if you intercepted it on a public or open channel.....

Tabnabs

All true, but the previous post is more apt for 16 & 12. Harbour VHF are not generally duplex as it helps to know what shipping movements are occurring for everyone's safety.

But Coast Guard generally is duplex and you post applies then obviously.

If in doubt, here's a list