Somewhere between UHF and HF.

we still use vhf for comm's in the fire truck for on fire ground comms.

Pesty

Used them on the ferries in Darwin in the seventies and had one in each boat a base station and one in the car,we could go down the track as far as humty do and could still hear the boats,all was clear and no interference, call sign was Vh5xy.

Cheers for now...William H...Bunbury...WA.

Like any radio network, you can only talk to those on your frequency / system. That is why companies, fire services, police etc have allocated frequencies that are separate from other users. So, yes it is probably pointless having VHF.

UHF CB operates under a licencing system where most channels can be used anywhere. With low power, interference between users is minimal. Channels are re-used in quite close proximity.
Organisations that need the VHF type range have a frequency licenced for a particular location or area. That frequency is not re-used for a significant distance around it. The higher power transmissions can then be used without interfering with other users.

In the 70's the VHF channels were widely spaced at 30kHz and had strong signals. In the 90's DOTAC made more channels available but cut all channes to 12.5 kHz spacing so the signals are not so robust now.

cheers

Well put bleep o

the lower frequencies tended to bend with the curvature f the earth or skip between the earth an the ionosphere and interfere with other networks around the world. The higher the frequency the straighter the path the radio waves take. This keeps us from being swamped by traffic.

In these circumstances more power will not improve anything at ground level because the horizon is not far away. UFH and VHF penetrate well too where there is rain or trees, as far as I remember.

Sometimes, however, we get atmospherics or what they call ducting. This is a layer of air at different temperature than the outside layers and it will take a uhf/vhf signal hundreds of kilometres.

those who used to own (or still do) the 27meg cb's will have experienced talking to America or the other side of Australia when the ionosphere was active with the sunspot cycle. 27meg was supposed to behave like a vhf and not pick up stuff at long distances but it sits in a spot on the radio band where vhf and hf are close together and it behaves as either from time to time.

30meg is where the definition changes from hf to vhf.

So fr as I remember from when I did amatuer radio license.

Owen

HAHAHAHA.......Scratched my head for half an hour before the penny dropped.



Cheers......Lionel.