High-frequency Cb Radios
The Age
Saturday January 29, 1994
THIS column continues a series on CB radios and looks at HF (high frequency) CB radios and their suitability for caravanners and 4WDs.
As explained last week, a ``full house" 40 channel HF CB has three modes _ AM (amplitude modulation), LSB (lower sideband) and USB (upper sideband).
Without getting into technicalities, the AM mode comprises the LSB and USB modes combined and it is possible to buy a 40-channel AM-only CB considerably cheaper than one with the sideband modes.
An AM-only radio is the most basic type of HF CB and has, generally speaking, a limited range, although sufficient to speak with other vehicles in the near vicinity, such as when requesting traffic information up ahead from a truck travelling in the opposite direction.
An AM/LSB/USB or sideband CB has considerably more range when using either of the sideband modes and can, given the right conditions, contact CBers across Australia and often in other countries.
``Given the right conditions" means that long range contact can not be always guaranteed, as CB radio _ in fact all communication radios _ rely on various levels of the atmosphere to bounce the radio signal over these long distances. Even when travelling hundreds of kilometres away from the nearest town, you may well receive an immediate response, but if conditions are not good, it might require a degree of perseverance before someone hears your call.
CB stations operating from home, and using large antennas, regularly speak with CBers in other countries and this is invariably done using either the LSB or USB mode.
If you are looking for a radio that will provide some security in the event of an accident or vehicle problem, a sideband CB is probably your best bet. It will allow contact with other vehicles but also has the ability _ again, given the right conditions _ to contact a CB station maybe hundreds of kilometres away if required in an emergency.
As a generalisation, the AM mode is used for short-distance communication, such as between vehicles, while LSB and USB are used for long-distance communication.
Channel nine on both an AM only and sideband CB is legally restricted to emergency calls and this channel is usually monitored by a CBer or CB organisation which can arrange for assistance.
Even when you are in an area not being monitored, the chances are good that a CBer will hear your call and respond. There are many instances of a CBer hearing a call for assistance from the other side of Australia and then alerting the local authorities to the problem.
Many touring caravans have a message on the rear of the van that reads something along the lines of ``monitoring channel seven _ call VHWA1234 (the callsign of the caravanner) if you wish to pass".
This message means that the caravanner is listening on channel seven and, if you wish to pass, you can call him and he will move over, or whatever, to make passing easier.
While there is no formal channel allocation, channel eight is considered to be the truckies' channel and channel 40 the traffic channel, used for general chat between vehicles travelling together.
So in brief, an AM-only HF CB is adequate for short-distance communication while an AM/sideband (AM/LSB/USB) offers the likelihood of long-distance contacts.
As a loose guide to prices, an AM-only CB should cost you about $100 to $150, whereas a sideband rig is in the range of $270 to $400. Of course secondhand radios are cheaper.
In the next column we will look at the other form of CB _ UHF.
© 1994 The Age