Two way communication system

[viktor92]

Dear all,

 

I am looking for a two way wireless communication system from location A to location B. Location A is operator booth which needs to communicate with location B.

There are 8 locations B which sometimes are under water, so that means I will need really strong signal. The farthest B point is around 150 meters from point A.

 

Can you please advise any products which can match with my requirements.

 

Many thanks,

Viktor.

[cedd]

Interesting article about the air-water boundary here;

http://news.mit.edu/2018/wireless-communication-through-water-air-0822

In short, making the jump between air and water with RF communication is hard work. If you want to talk under water, we're in to the realms of LF, and you haven't got the space for an LF aerial, trust me!

Wireless systems are available for diving, but they're not radio-based. They're basically a conversion to much higher ultrasonic frequencies and then conversion back at the other end.

Interesting wiki article here on diver communications which might be worth a read;

https://en.wikipedia.org/wiki/Diver_communications

 

I'd suggest if possible that a wired system be used. At least for the underwater locations.

[paulears]

After dropping a waterproof marine radio in the sea last year I had the idea of seeing if they worked, and having another in a waterproof sleeve, I tried. Sea water is a very effective dummy load. I couldn't even get arms length!

[sunray]

After dropping a waterproof marine radio in the sea last year I had the idea of seeing if they worked, and having another in a waterproof sleeve, I tried. Sea water is a very effective dummy load. I couldn't even get arms length!

 

I confirm this is the case, even with fresh water.

 

Radio and water just don't mix unless you have lots of space and are prepared to spend big (and I really do ben very big) bucks.

[adam2]

Agree, unless you have a military sized budget, radio simply does not work underwater.

 

What sort of messages need to be passed ? if simple yes/no type messages would suffice then coloured signal lamps might serve, they can be waterproofed fairly readily. If proper 2 way voice communication is needed then some form of underwater wired intercom, as used for diving will be needed.

 

If a person is underwater for more than a few seconds they will of course need diving gear that uses either air bottles or a compressed air line from the surface, whoever supplies this should be able to supply underwater intercom units.

 

 

 

[mac.calder]

Some more details would be good...

 

You have 9 locations then your 'master' and 8 remote sites- do you ever need the remote sites to communicate between each other (your B sites)? Or will your master be involved in relaying messages between the subs? How many people will be on comms at the remote sites?

 

Some locations are underwater.... so communicating with divers? Will the divers be wearing Full Face Masks? Are they open circuit, closed circuit or on umbilical? In a pool or ocean?

 

Does it need to be wireless "all the way" - or can local antennas be put up near some of the B sites.

 

What I have done in the past for a rather large event that included an aquatic show with safety divers:

 

• Riedel Artist 32 Matrix with 1 client card and 1 4 wire card
  
• Riedel Acrobat Wireless Master
  
• 1 x Riedel antenna at each remote site (up to 5 users per antenna) - required a Cat5 cable run to each.
  
• 1 x Fuji Fit Phone Model-103N surface station - 2 pair audio cable required
  
• 1 x Fuji Fit Phone Model-102N underwater station per diver - divers wearing full face masks
  

 

There are some things to note:

 

1 - we were using trained safety divers who were trained in the use of full face masks and closed circuit rebreathers (to manage bubbles).

 

2 - Comms was treated as being 80% reliable - when we were cuing them we would count them in and or count them out - a traditional standby-go sequence ran the risk of being missed. Additionally we ran a backup 3 colour cue light system to the pool. The safety divers also had a CO2 charged 'safety sausage' in the event of an emergency that they noticed they could quickly deploy that to alert the surface (it used a little CO2 bulb).

 

3 - This would have been an expensive system to own - we were renting

[Jivemaster]

Divers in full head masks are used to having a full two way intercom on wires like their breathing mixture. Otherwise divers use coloured lights to make cues. Using water as the transmission medium usually means using full ultrasonic transmission with transmitters and receivers and often it's only one channel per location.

 

www.youtube.com/watch?v=8g5SWUReApI

 

Cheap and easy by NASA standards!

[Andrew C]

Agree, unless you have a military sized budget, radio simply does not work underwater

Funnily enough, my father was working on this problem in the early 60s. With the aforementioned budget.

[Jivemaster]

Military long distance comms and through water comms tends to be in the VLF band and have an extremely low data rate -probably sub 100 baud. It's purported to use the full length of the national grid as an antenna.

 

For "amateur" or "budget applications it's simple wireless doesn't pass through water. Proper modern hard hat dive suits will come with sealed and waterproof but cabled comms built in.