Recently we carried out our first tests in a marl cave in the south of Limburg (with official permission). Very exciting because so far we had no feeling at all for how the radios would behave in the vicinity of the damp limestone walls. And it was damp, because a sheet of paper with notes would turne into a limp piece of paper within a few minutes, even though it was on a dry plastic surface.
The first tests were very encouraging. As soon as you walk into a side corridor, the signal from the radio relay in the main corridor immediately and completely disappears, even if there is only a few centimeters of damp rock in between. Adding an extra relay transmitter at the corner of the intersecting corridors restores signal transmission. So that already works as planned.
