I think your best bet is a system used by Motorcycle riders. They have a good range and are waterproof.

I use the Cardo Rider system and while not cheap they tick all the boxes. They will clamp on a helmet, have buttons you can manipulate in gloves and have a vox system (transmit on voice). Of course if you grunt a lot while SRTing that's a thrill for the recipient(s). I have used them in torrential rain for hours and they haven't failed.

Again, depending on the model you can link up to 8 of them and even listen to the radio (perhaps not underground) or your sounds of your ipod.

I have used them underground and they seem to have a good range on a clean pitch.

You do have to velcro the speakers inside you helmet although you could use in-ear ones if you wanted to.

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I have a couple of Baofeng BF 888 16 channel handheld walkie talkies that I use underground. They work well in stopes and also in long passages and shafts.
A USB programming lead is available for them with which you can reprogram each channel (to official frequencies) and also have other features to add such as voice scrambling.
At around £12.00 each they are good value, and if you know a little about this sort of thing, you can use features such as CTCSS and other exotic functions to personalise them.
BTW audio quality on these is excellent.
Waterproof? I think splashproof at best, but then RF and water aren't the best of bedfellows anyway.
Price includes a mains charger too.

I have a pair of these & I'd agree with Roy here.
Comes with a (rather flimsy) headset & does VOX.
Cheap enough to be almost disposable, if you fancy having a go.
BTW Roy, have you played with using 40m for surface/underground comms? I see the new CREG newsletter is carrying a couple of articles on it - any thoughts?
(mind you I don't fancy carting my HF kit round underground!!)

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Never considered 40M although I have thought many times about using Heyphones, (85KHz Inductive) to transmit through the rock, and tnen linking the surface set to a hard wired VOX interface into a 2M rig, or indeed any rig.
I've tried 2M, 70Cm and 446MHz underground using the Baofeng UV5R (another brilliant little ham set) handhelds with surprising results.
It's hard finding volunteers familiar with radio, to conduct trials of this sort.
I seem to be the only ham in the underground village. :lol:
De G7WJJ

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Here's a read:

https://www.mpoweruk.com/papers/Radio_Underground.pdf 

Interestingly, Trevor Wadley is mentioned in this paper, most folks in the radio scene will have heard of him as being involved with the frequency drift cancelling technique aka The Wadley Loop, which is a bit of a miss description, so far as I recall no loop is involved.

Lozz.

Never considered 40M although I have thought many times about using Heyphones, (85KHz Inductive) to transmit through the rock, and tnen linking the surface set to a hard wired VOX interface into a 2M rig, or indeed any rig.
I've tried 2M, 70Cm and 446MHz underground using the Baofeng UV5R (another brilliant little ham set) handhelds with surprising results.
It's hard finding volunteers familiar with radio, to conduct trials of this sort.
I seem to be the only ham in the underground village. :lol:
De G7WJJ

Got a UV5R too - cracking for the money!
Re the 40M stuff, it seems they are using a dipole on the surface, and a whip underground. From what I can glean without buying the current CREG, it's giving better range & depth than a pair of Heyphones!
Perhaps I should stop being so mean & get a copy :-)
Interesting stuff!
73 de
G8NYZ

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Here's a read:

https://www.mpoweruk.com/papers/Radio_Underground.pdf 

Interestingly, Trevor Wadley is mentioned in this paper, most folks in the radio scene will have heard of him as being involved with the frequency drift cancelling technique aka The Wadley Loop, which is a bit of a miss description, so far as I recall no loop is involved.

Lozz.

Ta for that, looks interesting. Must admit I'd assumed the Wadley loop was some sort of reference osc., freq. comp/control loop system for correcting LO drift - looks like it's rather different! Mind you I didn't have the funds for the likes of the RA17, so I didn't look that closely ;D
I'll have a read.

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Here's a read:

https://www.mpoweruk.com/papers/Radio_Underground.pdf 

Interestingly, Trevor Wadley is mentioned in this paper, most folks in the radio scene will have heard of him as being involved with the frequency drift cancelling technique aka The Wadley Loop, which is a bit of a miss description, so far as I recall no loop is involved.

Lozz.

Ta for that, looks interesting. Must admit I'd assumed the Wadley loop was some sort of reference osc., freq. comp/control loop system for correcting LO drift - looks like it's rather different! Mind you I didn't have the funds for the likes of the RA17, so I didn't look that closely ;D
I'll have a read.

So far as I remember no PLL, it used a comb filter for band set (crystal osc generates fundamental then harmonics picked off with a comb filter) plus a couple of other tricks, I think the first mixer upconverted to 40 mhz or some similar high frequency, up until recently I had a nice example of the RA17's posher brother, the RA117 complete with an independent sideband adaptor but it had to go to raise funds, still got a copy of the manual somewhere but the house is in bits so no idea where it is at the moment.

Can't say I've tried comms underground, interesting subject though, leaky feeder system seemed to be a common set up in the working mines, I've no idea what the latest tech that's used is.

Lozz.

It's hard finding volunteers familiar with radio, to conduct trials of this sort.
I seem to be the only ham in the underground village. :lol:
De G7WJJ

I'm now thinking of wandering into Box with an FT-817 and various lengths of wire.

73 De G0JPS.

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Talking of Box Tunnel, some official tests were done a while back, involving both professional quality (local Fire Brigade etc) and cheap PMR446 equipment. I can't find the results right now, possibly they were in a long-discarded magazine, but I did find this:

http://www.icomuk.co.uk/News_Article/3794/15721/ 

So if you are wanting to communicate down a fairly straight tunnel, the higher frequencies are best. If two cellphones could talk to each other without the base station, that would be ideal. But they can't, not without serious modifications, and licensing difficulties, because it would affect the network if the signal did not remain underground.

But in most cases that I can conceive of in old mine workings, you need to communicate through rock, not propagate down the tunnel like a mediocre waveguide, so it is LF, with loop antennae, that will work.

Some archived CREG stuff here:

https://books.google.co.uk/books?id=znDFBgAAQBAJ&pg=PA3&lpg=PA3&dq=vlf+communications+underground&source=bl&ots=fh4GQB1bDE&sig=yh0LzA3YMajyk-dO7jzA39nWYoc&hl=en&sa=X&ved=0ahUKEwjjo87EgcjJAhVHORoKHdCTALA4HhDoAQgrMAQ#v=onepage&q=vlf%20communications%20underground&f=false 

Lozz.

Found a reference to the Box tests, so they were not my imagination.

http://www.raynet-uk.net/technical/tunnels.htm 

Unfortunately the link (bottom of page) is broken, but contacting Raynet may be worthwhile as they will have a copy somewhere.

Talking of U/G comms, I've just dug out these pics of the Heyphone being trialled in Cornwall. We (Cornwall MRO) invited them down to test the sets in different mineralised ground, and a variety of geological settings. All tests proved positive with propagation through the rock seemingly unaffected by large metallic and sub metallic deposits (pyrite)
The photos below were taken in Cligga Head Mine

John Hey with his Heyphone
🔗103393[linkphoto]103393[/linkphoto][/link]

John with members of CREG (Creggies) and Cornwall MRO members.
🔗103394[linkphoto]103394[/linkphoto][/link]

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I had another think about this, and the answer is obvious, if it is for climbing a shaft of any reasonable depth. Already been suggested, but needs a bit more detail. Just get a length of leaky feeder cable, connect one end to your UHF transceiver, 50 ohm terminator plus a small weight on the other, and lower it down the shaft. You will then have superb communication with your other portable(s) all the way down. Only problem is cost.

A very cheap. nasty coaxial cable may be sufficiently leaky by itself to do the job, a good quality one will not. You could try Ethernet cable, which is cheap, but is about 100 ohms, so parallel up two pairs. CAT3 will radiate more than CAT5.

Old fashioned 300 ohm twin wire feeder, if you can still find it, will radiate marvellously, perhaps too much, at UHF, and may lose too much of the signal in a short distance. Twin flex, bell wire, etc are all worth experimenting with, as they will all propagate a signal for some distance, while losing some of it to the surroundings, which is what is wanted. You may want a balun to match twin wire to the coaxial antenna socket of a transceiver.

http://www.msdist.co.uk/Using%20Leaky%20Feeder.pdf 

You could also try a cellphone repeater, with the boosted antenna replaced by the leaky feeder, and the network antenna placed where it will see the network. Use your package of free minutes, because you need to call through the network to make these work. The big advantage is that you can select a frequency band by choice of operator and equipment, possibly 1.9GHz or 2.1GHz may be best. Also you can use a small cellphone with headset when climbing, and communication is full duplex without VOX or PTT. At the top end you use any cellphone, or land line if one was available (unlikely at a mine shaft).

http://www.mobileboosteruk.co.uk/?gclid=CNL6mcayzMkCFUWK2wodbhEH6w 

I have not been able to find a source of real cellular base stations that would do the job without connecting via a network. That would not be legal anyway. However a femtocell is readily available. These are a very small base station, typically installed in the home, so that your mobile connects via the internet. Presumably the network side of it could be faked by a small PC and sound card at the top end, so you could use your cellphone underground without needing a phone network to be involved. But the transmit power will be low, which may or may not matter, if you can make it use a leaky feeder.

Too many possibilities...

I've had great success using 446 pmr sets (license free) in a 50 metre shaft. I was 10 metres away from the shaft on the adit station, and the surface station was anything up to 30 metres from the concrete cap. Comms fully quietening both ways.

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I've had great success using 446 pmr sets (license free) in a 50 metre shaft. I was 10 metres away from the shaft on the adit station, and the surface station was anything up to 30 metres from the concrete cap. Comms fully quietening both ways.

That seems ok Roy.

A possible option for going deeper (or further in) might be 50 meters of standard 50 ohm coax with whatever length of 50 ohm leaky feeder coax connected to the descending end of it, I'm not sure myself as to whether or not the PMR antennas are detachable or fixed? If fixed it shouldn't be too difficult to make them detachable eg: fit a 50 ohm socket to the PMR and 50 ohm plug to the antenna for the surface or base station or both.

Flat twin feeder should radiate as has been said in an earlier post as it will no doubt be unbalanced in a mine exploration environment, it might be worth experimenting with that as it's relatively cheap compared to coaxial leaky feeder cable.

Water on standard 300 ohm flat twin will cause extra losses, it should be less so with ladder line.

Another possibility to reduce cost might be alternating the standard coax with separate lengths of leaky feeder along the length of the run.

Lozz.

Just to keep us on topic here - Theses Chinese radios are really good for the money and deserve a little more experimentation in the underground environment. They would be perfect for large areas such as in Cwmorthin for setting up photo shots, rather than shouting yourself hoarse or using whistles and hand signals.
As for connecting stuff to it, the antennas on the UV5R and the BF888 both use a SMA type connector, and by using adapters you get them to fit just about anything. See pictures below

UV5R antenna socket SMA type
🔗103403[linkphoto]103403[/linkphoto][/link]

SMA to BNC adapter

🔗103406[linkphoto]103406[/linkphoto][/link]

BNC to SO239 Adapter

🔗103405[linkphoto]103405[/linkphoto][/link]

All adapters connected to the radio and yes, it’s quite a totem pole, but using combinations of this little lot will connect to almost any antenna

🔗103404[linkphoto]103404[/linkphoto][/link]

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I have a BF888, unfortunately it is illegal for use as a PMR449 set, because it is not type approved for that application, has many more channels, has too much transmit power, and has a detachable antenna (which means that effective radiated power might be increased by a directional antenna).

But I don't have any problems using it on the PMR449 channels. Just not when the authorities are looking. You can also use it in the business channels, but only if you have a licence, which could be held by a club or organisation and cover umpteen sets for one reasonable fee. Gives a choice of frequencies in low and high band VHF, and UHF. You are required to "self-coordinate" with other users, in other words don't set up next door to your local taxi company on the same channel.

https://secure.ofcom.org.uk/busrad/terms 

Or, but only if all users are licensed hams, just use your normal frequency allocations. Non-hams can legally receive but not transmit.

Deep underground, where signal will not propagate to the surface, who cares... Otherwise, please just be careful. I would hate anything I have said to get someone into trouble.

Just a note on the 888. although there are 16 channels in the rig, and only 8 frequencies/channels available in the UK, I program the first 8 as standard channels and the remaining 8 the same but with the voice scrambler activated. And yes power output is above legal limits, but these things are being sold everywhere and without any warnings in the instructions. you can hear them at any time by scanning the bands, and folk are quite open about what sets they are using. With power levels 5Watts and below, it is hard to discern who is using what power output, unless the monitoring station is sat outside the front door. Propagation varies with weather conditions so trying to get an accurate handle on power is difficult at a distance.
I guess we'll need to wrap this thread up soon before we........ARRRRRRGHHHH!.......SIMON!.......NOOOOOOOOOO!........:lol:

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Have I dreamt it OR can you not select two different power levels on the 888s...
I'm sure I remember selecting the higher option when I programmed mine 😉
Also from memory not ALL 888s have the scrambler function even though they look AND are sold as being the same.

Ooooooo Radio chat!

We have used both 2m and 70cm in slates mines in North Wales when working with great success. Granted its not been a huge distance and not much physical rock between. But 3 floors of cwmorthin and 3 chambers apart was ideal when we were rigging things up.

MW6FEF

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