Uhf Cb Defeats `idiot Factor'
The Age
Saturday February 5, 1994
FOR the past several weeks, this column has looked at the various options and suitability of communication radios for caravanners and 4WD owners.
Radios such as RFDS (Royal Flying Doctor Service), amateur and HF CBs have been discussed and this column deals with the ``other band" CB rig. HF (27MHz) CB radios were covered in the previous column, but there is also the UHF (ultra high frequency) CB band and this is very different to the HF type CB.
UHF CB is primarily designed for short-distance communication and is often termed ``line of sight" radio. While this term indicates what range of communication can be expected, it is far from strictly correct.
You do not, of course, need to be able to see another station to contact it. UHF CB, unlike HF CB, does not bounce signals off the ionosphere to achieve contacts over thousands of kilometres. UHF CB signals are ``blocked" by buildings, trees, etc _ hence the term ``line of sight".
Even so, a station on the beachfront at Frankston can speak to a station in Melbourne easily, as the signal travels freely across the bay.
Realistically, however, a UHF contact between vehicles in the CBD of Melbourne would be limited to a matter of several city blocks due to the blocking of signals by high-rise buildings.
The higher the antenna, the greater the distance over which contact is possible, so a base station with an antenna atop the Rialto building will be able to make contacts over a far greater distance than one vehicle to another.
Likewise with vehicles on the Nullarbor Plain and similar areas: as there is little to block signals, contacts are possible over far more kilometres than in and around the suburbs.
However, to enable greater distance contacts, there is the ``repeater". This device does precisely what its name indicates, it takes in a UHF signal and repeats (transmits) it again. As an example, there is a repeater located high on a hill in Frankston that enables a Melbourne-based UHF CB radio to contact, via this repeater, stations on the Mornington Peninsula and surrounding areas, which could not be done normally.
This is called ``duplex" operation; without going into the technicalities, it allows communication over distances not possible without the use of a repeater.
The mode used on UHF CB is FM (frequency modulation) and a UHF CB is not able to speak with a HF CB as they use different frequencies and modes.
There are repeaters established in all Australian states, mainly in and around large cities and towns, and a complete list of these appears occasionally in the bi-monthly magazine `CB Action'.
UHF CBs have 40 channels, with channel five being restricted to emergency use only and channel 40 being popular for general ``traffic" _ communication between vehicles travelling in relatively close company.
It is a favorite service with farmers and outback properties as its range allows good contact with staff working some distance from the homestead, sometimes through a private repeater located on the property.
The advantage of UHF CB in this type of use is that its limited range largely precludes the ``idiot factor" so prevalent on HF CB. For non- CBers, the ``idiot factor" consists of the few operators who make a nuisance of themselves with bad language, interference and general antisocial activity that makes HF CB unpleasant for many.
UHF CBs are generally priced higher than HF units, with prices in the $400 range.
The next and final column on radio communications for travellers will provide a summary of what is best for you.
© 1994 The Age