cave radio

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cave radio

Postby bobby49 » Jan 9, 2019 10:56 pm

I realize the problems that cave radios have had over the last thirty or so years, especially propagation by induction.

I wonder if something completely different would work. Consider the concept of a daisy-chain mesh Wi-Fi network at 900 MHz. If the first node was placed at the entrance, and then more nodes placed as the cavers go deeper, maybe they could get enough range from node to node to get short messages in or out. If the air passageways were good, and if high performance dipole antennas were used, would this work?

I'm guessing that only the slowest data rates could be supported, too slow for voice. Short coded messages of a few characters might work.

I'm looking at a per-node cost of about $50.
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Re: cave radio

Postby NZcaver » Jan 12, 2019 8:03 am

This concept, and similar versions, have been experimented with in the past.

A voice-over-wifi version that springs to mind is called "Serval Project."



The Australia-based project has been ticking along for years and still seems to be active. See servalproject.org

There's also been some experimenting in caves in the US with UHF ham radio packet data (APRS). See Cave Radio Test Extends Range to One Mile
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Re: cave radio

Postby bobby49 » Dec 28, 2019 5:31 pm

I was reading the account of a cave rescue that happened about fifty years ago. The rescue leader ordered up some 5-watt Citizens Band radios, and they were intended to reach from the rescue command over short distances to two cave entrances, and then (hopefully) for some distance underground. It was never explained how effective that was.
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Re: cave radio

Postby NZcaver » Dec 29, 2019 4:58 am

bobby49 wrote:I was reading the account of a cave rescue that happened about fifty years ago. The rescue leader ordered up some 5-watt Citizens Band radios, and they were intended to reach from the rescue command over short distances to two cave entrances, and then (hopefully) for some distance underground. It was never explained how effective that was.

Check out this issue of Speleonics, scroll to page 8.
https://caves.org/section/commelect/dru ... lncs27.pdf

Caveat - radio propagation in lava tubes/rock can be significantly different to that in karst features, especially damp karst.
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Re: cave radio

Postby bobby49 » Dec 29, 2019 10:36 pm

Some of those radio experiments were dealing with lava caves. I was more interested in the general case of limestone karst caves.
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Re: cave radio

Postby NZcaver » Feb 12, 2020 4:46 am

bobby49 wrote:Some of those radio experiments were dealing with lava caves. I was more interested in the general case of limestone karst caves.

Understood. But even with limestone karst, effectiveness will vary a lot with ground conductivity and other factors. Best to do your own testing in local caves, like I did.
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