By Joan Vlok, September 2001
Ron Zeeman has been quietly running around the Silvermine Nature Reserve, doing some radio communication developments for High Angle Rescue and Access group. Ron is using a ’guide-wire’ technique whereby he runs a cable through the cave. His radios are then held close to the wire, which effectively ’guides’ the radio signal through the cave passage to the receiver, which is also held near the cable.
The first test was carried out on Saturday the 15th September at Ystervark Grot. Ron tried to couple a VHF Radio onto a guide wire so that communication links could be obtained throughout the cave. Unfortunately there was not much range improvement. So it was back to the drawing board.
On Monday the 1st October, we returned to Ystervark Grot for the second test. Once again the guide wire was laid throughout the length of the cave as far as Chamber K. Outside the entrance to the cave an FM Radio receiver was attached to the transmitter, which was in turn attached to the guide wire. The FM radio acted as a continuous source for the prototype cave radio transmitter. The most difficult part of the exercise was getting consensus on which radio station to tune into! KFM won. [This probably indicates the average age of the testers.- Ed.]
This radio operates on a much lower frequency than the VHF sets used in the first test. The radio proved to be extremely promising as far more range was achieved than with the VHF radios. When clipping onto the guide wire, with the receiver between 44m and 50m into the cave we were able to listen to 'sbquo;Caravans and the News.'sbquo;
Ron continued to do further tests that day, and discovered that if the wires outside the cave were 'sbquo;bared'sbquo;, there was an even greater range. Ron will be carrying out further tests to try and increase the range, so that everybody who is involved in the rescue will be able to 'sbquo;clip on'sbquo; and have communications. Once the increase in range has been achieved, Ron will combine the units into a transceiver, that will allow anyone with a set who is near the cable will to be able to listen and talk to anyone else with a set near the cable.