Radio Communication

Traveling in a convoy with radio communication between the vehicles is not only practical, it is fun as well.

Equipment

Before investing in radio equipment ask yourself the
following questions:
• How far do I need to communicate?
• Will I be on foot or in a vehicle most of the time?
• Are the radios going to be for emergencies, fun communications, business control or for the safety of clients.

Radio equipment is available in the following modes:
• FM (frequency modulation) – crystal clear communications.
• AM (amplitude modulation) – noisy communications, clear for
short range.
• SSB (single side band) – gives the best range and even if no signal is present on the built-in meter the voice quality can be excellent.

Radio equipment will give you the following ranges:
• FM Equipment – up to one kilometer.
• HF Equipment (also called SSB or long distance radio) –
up to 5000km
• VHF Equipment (Mid band range) Mobile radio up to 70 km,
hand-held up to 3 km.
• VHF Equipment (High band range) Mobile radio up to 25 km,
hand-held 0 to 3 km
• AM Equipment (similar to above but better penetration through concrete) 29 MHz (Ski boat type) mobile radio up to 15km,
27 MHz CB radio up to 30km

The information above is approximate and ranges are dependent on output power of equipment, antenna type, terrain, altitude, and in the case of HF, time of day and solar activity and frequency. Hand-held radios are ideal for very short range communications (line of sight).

The advantages/disadvantages of hand-held radios are:
• Size • Reduced range
• Portability • Limited by battery life

With a full charge and intermittent conversation the battery on a typical hand-held, the Motorola P110 gives about 7 hours of use. Extra batteries can be purchased and they are small enough not to get in the way in your pocket or backpack. Batteries can be charged from 220v AC supply or from a cigarette lighter socket, with an optional adapter. Accessories are available to make the use of the hand-helds easier, such as speaker, microphones, headsets with boom microphones, carry cases, etc. Advice on purchasing hand-helds is to look for well-known brands that will be well supported with a spares network in most countries. Motorola products have proved themselves and are probably the most used hand-held radios in the world.

Mobile radio’s VHF midband and highband
Mobile radios will give you a range of up to 70 km depending on the frequency and antenna installation. Mobiles are 5 times more powerful than hand-helds. These are ideal for vehicle convoy applications as well as for hunting, game counting, rescue, hot air balloon recovery, boating and fishing.

The advantages are:
• High power
• Range of up to 70km
• Cannot be dropped or lost.
• Vehicle antenna is efficient
• These radios are very versatile in that they can be programmed for repeater use, the prime source of communications in urban areas.

29 MHZ and CB radio’s
These systems are the cheapest available and are ideal when traveling in convoy with communications up to 15 km. The system is AM and is therefore associated with the usual snap, crackle and pop of this mode. These radios only put out 4 watts of power and have limitations in terms of versatility. When a single side band CB is used, power output increases to 12 watts and you will be able to communicate up to 30 km, albeit with worsening voice clarity.

Advantages:
• Range • Sound quality
• Price • Low power consumption

With all radio communications the single most important factor is well-engineered and accurately tuned antennae. There is no point in spending thousands of rands on a top quality transceiver if you cannot hear anyone because the antenna has not been properly installed.
Magnetic antennas have the advantage of being easy to remove and install but have a number of distinct disadvantages. With vehicles having aluminum bodies the antennas do not stick, even a small amount of dust will cause damage to the vehicle paintwork and overhead bushes can knock it off. Also the antenna cable will have to be fed into the vehicle through the door or window and will result in dust entering the vehicle and the chance of damaging the antenna cable is increased. The only real application would be in a hire vehicle in which you cannot drill holes.
Glass mount antennae are neat and easy to mount and also do not require holes. These antennae are the least effective of all and the only application that they have is on radio repeater systems and then only if you are close to the repeater.
Body mount antennae are therefore the best way to go. If installed properly the vehicle will not rust around the antenna and the antenna’s earthing system will be sound. The antenna cable is mounted permanently and is therefore less susceptible to damage by friction or passengers. In general the higher the gain an antenna has, the better the range over flat ground will be. However, this will be a slight disadvantage in hilly terrain.

Installation
The radio, no matter which type, should always be connected directly to the battery via a fuse, and not to any convenient wire under the dashboard. By doing this, you will isolate any interference from the vehicle’s electrical system which could be misinterpreted as poor reception. A filter can be wired between the power supply and the transceiver to reduce interference. The fuse is purely a protective measure against short-circuit and fire.

Positioning of the radio
The actual transceiver should be positioned so that you can see it without taking your eyes off the road but out of direct sunlight which will damage it. Consideration should be given to keeping the unit out of reach of rising water should you venture into deep water. The perception that radio communication systems can be installed by anyone is generally incorrect all antennae have to be adjusted to resonate at the correct frequency and if this is done incorrectly a transceiver can malfunction and can require repair. Sometimes, only when a home installation is compared with a professional’s can the difference be appreciated. The reasons for this are simple; If an error is made in the wiring of the system a fire can occur with disastrous results. Don’t select an antenna for its looks – go for one that works.

License and regulations
Operators licenses are required for both 27Mhz, 29MHz and VHF radios and are issued by ICASA, the national regulatory body. All equipment must be type approved and licensed before it can be used. Special precautions should be made when travelling in the Third World because often special permissions and licenses are often required. When traveling in the Third World, do without radios if possible – it could save a lot of unwanted aggravation with police and officials.

Maintenance
Prevent water from entering your antenna cables by sealing them with silicone prior. Once water has got into the cable, corrosion will occur and the cables must be replaced. Check the power and antenna cables are not getting pinched under plastic linings and in doors. Check your antenna to make sure that it is still secure on the vehicle as you will be amazed what vibration can do to locking nuts. Check to see that the whip has not been bent or broken, and if it has, replace it immediately and get your local dealer to set up the new antenna before you use it. Using an antenna without tuning it can result in overloading and burning out your radio.