Oxford University Cave Club

Techno-report: the radios

Radio communications between the camps:-

"Top Camp calling. Top Camp calling Los Lagos" The eerie sound of static breaks the silence. Is anyone listening?

Maintaining radio contact between the surface camps has become more valuable with the shift from Ario to the remote Top Camp. The Ario path is deeply eroded and covers varied terrain, but finding Top Camp is much harder through barren and treacherous high karst. Fog, darkness and electric storms cut off Top Camp for all but the most adept navigators. Missing and injured walkers may not be missed for days. Regular radio contact improves safety, as well as helping to co-ordinate supplies, camp guards, drivers and cavers. Fast communication saves much wasted time, effort and frustration. If an injured caver needs evacuation by helicopter then the radio would save hours of risk and uncertainty.

Like most caving equipment, the radios have to survive constant dampness, extremes of temperature, mud, water, rough handling, inadequate funding and ignorance.

An ideal system would receive continuously to allow communication at any time, but this presents too many difficulties; power supply, radio shadows and weather all conspire to make such a system impracticable. Collapsing aerial masts and 20 kilogram lead acid batteries on mountain tops have left their mark on the expedition's attitudes towards ANYTHING with wires.

The success of the 1994 radios helped persuade hardened sceptics to purchase two new hand-held CB transceivers to replace the two old vehicle CB sets that we used last year to good effect.

Two ES220 hand-held CB transceivers were sold to us by MPS at a small discount. They were operated with the full size aerials that worked so well last year. Two travel alarm clocks reminded people when to make the radio calls. Without these, the task tended to be forgotten or happened an hour too late because people's watches still showed UK time. A stock of fifty AA alkaline cells were kept at Top Camp to keep the radio working 24 hours a day if necessary. At base camp, a vehicle power lead conserved batteries. The radio, batteries and a small rubber aerial were kept inside a small padded ammunition cans that served as (uncomfortable) seats when not in use.

Field tests showed that reception was good under most conditions when the large aerials were used at the full 4 Watts power output. With one set using the miniature rubber aerial it became marginal. Operating at 1 Watt output had the same effect. Both commercial and other CB users caused interference on some days, but this was overcome by changing channels.

It seemed that people were naturally wary of holding large metal rods on the ridge above the Top Camp depression during a lightning storm. However, it was not quite as intuitive when it came to tidying the aerial cable. Chaining it like SRT rope is NOT good for it.

Not surprisingly, the radio's were initially treated like suspicious packages. Memories of earlier fiascos had not been forgotten. At first the 9.00 am and 9.00 p.m. radio calls were treated with some complacency, but the usefulness gradually sunk in. After the rescue, the real value was appreciated by everyone and the radio calls became part of expedition culture.

Costing

ES220 CB transceivers (two) £160

Magnetic mount aerials (two) £ 36

AA alkaline batteries (eighty) £ 30

Small ammunition cans (two) £ 7

LCD travel alarm clocks (two) £ 12

Total £ 245

The batteries were largely consumed in eight weeks of normal use with one 24 hour period of use during a rescue.

Chris Vernon