TWO-WAY RADIO CONSIDERATIONS FOR 4X4 DRIVERS:

These high-power radios operate on low RF frequencies, typically between 1.8 ~ 30MHz, at RF levels of about 100W. They offer greatly extended operation, but they do have pitfalls. The operating range varies with a local ground-wave signal providing about 30Km radius, but this is in general not too reliable and nor is the radio designed for ground-wave communications. HF comes into its own with the reflected Sky-wave signal, which signal that is reflected off the Earth’s Ionosphere, which is constantly varying in height from above the Earth’s surface. The RF path can be compared to a tennis ball bouncing up and down as it is thrown hard into the ground.

The distances obtained by HF are virtually anything from 300Km upwards but the operating frequency (and therefore operating range) is very much influenced by the height of the Ionosphere at the time of transmission and therefore these radios are generally allowed to operate on three or four frequencies to allow for the changing conditions. Weather conditions play a major part in obtaining clear reception, as the system is essentially an AM one. Atmospherics and Lightning would cause difficult reception, as would electrical impulses.

Because of the need for various operating frequencies, you will have to consider using an “Automatic Antenna Tuner”. Each operating frequency requires the antenna to be a certain fixed length to provide for maximum signal transfer and also to prevent damage to the radio. This is done either by the use of an Automatic Antenna Tuner, or you could carry four stainless steel whips & HF Coils and change them as you change frequency – not too practical!

HF/SSB licences, although obtainable, are fairly restricted due to the limited number of available frequencies. This is not a bad thing in itself, as it is comforting to know that there might be other users on the same frequency should you be stranded in a remote area and in need of assistance. You are allowed to use HF across borders, provided you have the necessary Radio Communications Licence from both Country’s Regulatory Authorities.

Successful HF radio operation requires a learning curve, but for those traveling long distances where there is no other means of communication, it is a blessing.

Pros: Greatly enhanced RF coverage

Cons: Price, adversely affected by bad weather, long antenna/s

KENWOOD TK90 HF/SSB Radio

VERTEX VX2100 HF/SSB Radio