Ham radio technology used in Thailand cave rescue

Your prediction came true: Even without damnation:

https://deadline.com/2018/07/thaila...ix-ceo-michael-scott-movie-rights-1202424314/

 

In my paper-log, from 1st May, 1994, at 13·30 to 13·40 BST, is a 7.074Mhz SSB contact with GB4CRO (a euphemism for) the Cave Rescue Organisation. They had a team 1000ft underground at White-Scar Cave, and a surface operator, who is obviously the relay, up on the surface. They were experimenting with means to communicate, maybe it was the system described above. Obviously neither 40m HF, nor UHF would pass through that much rock, if any rock.
One disadvantage of the paper-logbook: - not too much room for lengthy descriptions or blurb.

I believe the experiment was to relay conversation from 1000ft down in the caves to operators around the land.

NB. Whilst they were talking to me, both the log and my memory record very clearly, an emergency was declared near their location and so the 'exercise' went 'live' as we now so prosaically call the phenomenon, when drill becomes real-time.



10-minutes of QSO recorded in the log. Yes, I remember it very clearly. I spent a lot of time rag-chewing on 40 in those days. A lot ...

And I have actually, as a student been either down in those caves, in the old wet suit; either there or Malham Cove ... which I also remember clearly, as I do remember having to share a bed with my caving partner in digs that night. Yoikes!

WHITE SCAR CAVE
Yorkshire Dales National Park
https://whitescarcave.co.uk/

 

Kenneth, Looks like you're correct. Uff da! Only us guys with a last name ending with a "sen" know these things Hi

'73
Doug

 

There is no "87 KHz" in the SI unit system. It's "87 kHz" in the LF (30 to 300 kHz) segment of spectrum.

As the original post indicates, hams also have problems with terminology for the standard frequency segments. Many refer to the new 472 to 479 kHz band as LF when it is well within the MF (300 to 3000 kHz) segment.

I suspect there is now a junk yard full of new tech wonders that were brought to the cave site that were of little or no practical use.

 

Cave Radio voice communication on 7 MHz SSB with low power handheld transceivers... works quite well for distances up to about 1 kilometer (a half mile) through rock... and a mile or more with dipoles deployed laying on the cave passage floor... a few watts SSB.

In my experience as a long-time expedition caver, cave rescuer, and cave surveyor: 7 MHz SSB is vastly superior to LF or MF for voice communications.

Early cave radio experimenters focused their efforts on building LF and MF systems because:

• They also wanted highly directional DF loop antennas and beacons.
• The early research by mining engineers indicated LF got through rock better.

But, for portable voice SSB communications, there are other factors which greatly influence the success of through-the-rock comms.

One of the biggest factors by far is the efficiency of small packable antennas:

• A handheld LF loop has an RF transmit efficiency below 0.1%.
• A coil-loaded HF whip antenna on an HT (or just a length of wire laying on the floor of the cave passage) can have an RF transmit efficiency of more than 3% to 5%.

That HF antenna efficiency advantage provides much greater signal strength than the absolute HF-vs-LF frequency attenuation curve through rock indicates.

I've tested 7 MHz and 187 kHz side-by-side underground.
The HF system wins out every time in distance through the rock.

See the following Speleonics Magazine article:
185kHz Radiolocation and 7 MHz Communication Experiments in Bigfoot Cave 6~8 September 2002 -by Bonnie Crystal, KQ6XA



http://hfpack.com/kq6xa/185kHz_Radi...Bonnie_Crystal_KQ6XA_Speleonics_July_2004.pdf


Mizuho MX7S 7 MHz SSB 2W Handheld Transceiver units utilized in Cave Radio communications.


Mizuho MX7S 7 MHz SSB 2W Handheld Transceiver units utilized in Cave Radio communications.

PS. The 80 metre band also works well if dipoles can be deployed on the surface and underground. However, practically speaking, the longer wire lengths are somewhat unwieldy to deal with.

 

Actually, a very sophisticated type of handheld radios were used throughout the rescue operation. In essence, each handheld acts as a repeater. The signal path is dictated by an algorithm that ensures re-routing in case of failure / no reception, so in the end all radios communicate and information flows. This is pretty recent Israeli technology. More about it here:

http://www.wired.co.uk/article/thai-cave-rescue-boys-news-tech

An excerpt:

"To help, the Israeli company flew one of its engineers out to Thailand last Monday, along with 17 radios equipped with mesh technology. These devices, built in the UK by Entel, have software developed by Maxtech that enables them to broadcast and be used as a relay simultaneously. This means that they can communicate over a range of up to two miles, without direct line of sight, or the need for any physical infrastructure such as radio towers to bounce signals off."


73 de Nando EA4BB

 

Hi Nando EA4BB,

It was nice of them to send the Entel MaxTech radios to the Thai rescue operation.
Good for public relations as well.
But, Entel MaxTech radios are just UHF DMR, nothing more.

Speaking from experience: UHF is pitifully inadequate inside a cave, it can not go through limestone cave rock, such as the Thailand cave is made of.

UHF is line-of-sight.
Cave passages are meandering, crooked, and bent.
The UHF does not bounce through the limestone rock passages, and it doesn't go far through solid rock.
In a linear cave, loss of one link in a UHF DMR mesh would cause a break in the repeater functionality.
This break in the repeater mesh would cut off surface-to-underground comms.

UHF is great for the outdoor pump teams and for staging rescue/dive gear near the entrance... maybe 50 to 100 metres (150 to 300 feet) inside the entrance of the cave.
But, there was probably no need for repeaters or mesh DMR at the cave entrance, because UHF simplex is superior for such close proximity working within a hundred metres of each other.
The Incident Command Center and staging area was right at the entrance to the cave.

UHF is not a viable solution for inside-the-cave rescue operations, even with a handheld/repeater every 50 metres throughout the entire cave.
For an inside-the-cave communications team, a UHF system would be an absurdly stupid thing to maintain or deploy.


[En mi experiencia: UHF DMR es inadecuado al dentro de una cueva. No puede atravesar la roca de la cueva de caliza, como la cueva de Thailand.]

 

My dad Jack G0FQN was involved in GB4CRO and getting it up and running back then i was their on only one day for a few hours before taking my mum back to the caravan.
73,
Mark.