caver.adam wrote:Communication is a big problem. Basically, (anything over VHF) is only effective for a few feet beyond line of sight. In a cave with many turns you may require dozens, hundreds, or even thousands of repeater stations for high frequency communications.
It would not take thousands of repeaters. As a bit of possibly entertaining information, CMAP gives the maximum depth and the maximum width of a breadth first search of the survey data. I am not up to date with the data, but as of 2009, it took 247 survey shots to reach the deepest point in Lechuguilla. For Paxton, a 7.3 mile maze cave in Virginia, it takes 127 shots. This would be for communicating to a rescue already in progress.
A search would take more repeaters. For that, see Rich Breisch's book, Lost in a Cave.