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Hand-held UHF CB radios – usage in caves

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    Peter Freeman
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    This topic is covered in some speleological texts and has been well-experimented with over the years, along with various phone systems and the more usual lower-frequency radio devices (the RDF-type loops, the Nicola Phone System, etc). However, I know that I and many other local cavers have had a personal interest to see whether the cheap and easy-to-use UHF CB’s could be of practical use to us inside caves.

    I remember that on my first visit to Slocombe Cave back in 2004 Peter Robertson and others tried using a pair of transceivers between the pitch-head and inside the cave. I’m unsure of the outcome then, but I think they didn’t work much further than the bottom of the ladder.

    My own first trial was in DD4’s Bowling Alley passage over two years ago. I found that the useful range in there was about 150m – once around a couple of corners the reception deteriorated. That passage is predominantly straight-ish but with kinks, and is 5m tall and 1m wide.

    My next experiments were on pitches at Murrindal, an early example being the big pitch in M14 Baby Berger. Here there were no problems with range, but the usability of the devices was poor in the adverse and busy conditions of climbing or preparing pitches. The main issue was accidentally pressing buttons as you scraped against the cave: the channel would be inadvertently changed, repeater-mode invoked, call-signal repeatedly sent, etc. This can be ameliorated somewhat by using the keyboard-lock function that is available on most hand-helds, but I didn’t get around to trying that for quite some time!

    My latest experiences in Elk River Cave have been good. Communication to a lone diver through a sump by primitive rope-tugging is fairly unsatisfactory, so on our last two dive events there Jim Arundale and I have maintained contact via UHF radio. It has been very successful, providing a large gain in confidence, especially for the nearside worrier! The transmission has been of good quality through fully-submerged sump lengths up to 8m. Water ingress while in use has been a problem, despite the units being transported to site in watertight jars. I will next try actually [b:3jqigk5r][i:3jqigk5r]using [/i:3jqigk5r][/b:3jqigk5r]the hand-helds inside transparent zip-lock bags.

    It has often occurred to me that the medium might also be useful for testing proximity in caves that almost, but do not quite, connect. I think they would work through short sections of boulder-ruckle. Whether the technique would be more effective than the traditional shouting or hammering remains to be seen.

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