Absolutely... hand me a hammer and I'll knock out morse code until my arm tires.

Dan - Owner
http://www.Hi-TecDesigns.com

Thanks for that  - but I was looking for voice and data coms
to monitor workers in enclosed spaces.Overa range of a few Km

In what condition is the vessel located (i.e., is it at the bottom of the ocean, in the middle of the desert, etc.)?  Do you have line of sight?  What data rate do you require?

You'll need an external antenna... trying to broadcast internally through a steel sheet would require enough power to cook the occupants.

Dan - Owner
http://www.Hi-TecDesigns.com

Thanks for your response.It is actually on a factory floor.Line of sight from inside is doubtful. From your response
what we will probably do is have a portable transmitter
on each worker transmitting to a central station inside the enclosure - that connected to an external antenna transmitting to a remote data station.

I am not that familiar with radio my backround is more electrical engineering but would it be possible to use the

Steel vessel as an antenna or would that be impractical

Gauss' Law.  You can't change the external field from inside a closed system.

TTFN

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There are probably some rules (OSHA or local equivalent) that might require that the access hatch be left open and that the people inside be wearing a safety harnesses (not so much for falling, but so that if they collapse, someone can pull them out without entering the space themselves).

If these assumptions are true, then it wouldn't be difficult to provide them with walkie-talkies (the usual sort with BNC antenna jacks on top) and long antenna extension cables running outside (tied to the harness) to some external magnet mount antennas. All of this gear is readily available and off-the-shelf.

You can have reliable communications by installing a WLAN repeater, sometimes referred to as a range extender by some companies. Istall the repeater on this inside, run an antenna external to the enclosure.

There are passive repeaters, (basically two back to back antennas connected together), but they are not really going to help.

Hi Robert Thanks for your response - great idea according to my research Wlan repeaters are specifically for extending
the wireless capability of wireless internet to laptops pdas and the like.I am going to be using industrial grade data transmitters and recievers dont think wlan repeaters  be able to be integrated in such a system.But if it can be done - I would be happy to hear how.

The other option, although more cost, woule be to place a client/device side radio on the exterior, connected to an AP radio on the interior to build your own repeater.
We do this with the inductrial radios to get over and around large obstructions, and will work in your situation.

Shifting from radiation to conduction may lead to an answer.  Coupling the antennas to the steel shell and by a copper conductor cable from outside steel to monitoring/transcieve location point may work beyond your expectations...       ralph g.   GerwingR  Vancouver Metro BC.Ca

Maybe using some piezoelectric transducer and ultrasound, you could pass messages through the steel.  Metals carry sound very well, but I don't know an off-the-shelf solution of this kind.

Sorry, too thick.  I could do something like 2 mm thick steel.  5 mm attenuates too much.  Would be low data rate too, something like 2 kbps.

Would be a little better if it was stainless steel.

I haven't a mechanical background, though I guess vessels should include some quartz, templated glass windows, or at least small light pipes of some suitable design for optical communications through the walls.

Doors could also be electrically isolated from the vessel wall, forming a 2nd conductor(wall to ground).  Communication devices could take power while passing messages through the door.

Regards,
Gonzalo

I specialise in providing RF solutions in confined spaces such as tunnels and underground stations. Most systems use radiating cables or antennas within the confined space linked to a base station or repeater. A relatively small space could be covered by a single antenna, although more complex areas may require several. Much will depend on the frequency of operation and the power budgets. Can you provide any more information regarding the frequency of operation, transmitter power and the size of the area to be covered? Can you run cables into the steeel vessel?