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Dear Tom

http://en.wikipedia.org/wiki/Mobile_phone_signal
https://en.wikipedia.org/wiki/Water_well
http://en.wikipedia.org/wiki/Tunnel
http://en.wikipedia.org/wiki/Coal_mining
http://en.wikipedia.org/wiki/Walkie-talkie

1. Are there limitations for Mobile Phone Signal Transmission/ Reception from Underground Areas viz Tunnels, Coal, Oil Mines, Wells etc ?.

i.e. 20 feet, 50 feet, 125 feet, 150 feet below etc

2. Can there be any methods to boost the Mobile Phone Signal reception so that the underground worker/s may be able to communicate with their wireless devices ?.

3. What are the communication channels  modes for underground manpower viz to communicate with office workers on ground level ?.
Using the elevator/lift to travel up and down the ground level
could be the only solution for communication ?.

4. Can Walkie - Talkie (two way radio communication) device work
in Underground areas ?.

Awaiting your reply,

Thanks & Regards,
Prashant S Akerkar

Answer
Prashant,

My responses to your questions are as follows:

1. Are there limitations for Mobile Phone Signal Transmission/ Reception from Underground Areas viz Tunnels, Coal, Oil Mines, Wells etc ?. i.e. 20 feet, 50 feet, 125 feet, 150 feet below etc

RESPONSE: Yes indeed there are limitations. The ground provides a fairly strong shield against radio signals. The strength of the signal which can received at a particular depth will depend on many factors, including the type of soil/rock/moisture layer which exists between your location and the surface, the signal strength transmitted by the surface radio, and the frequency. In additional, even if the transmitter on the surface has adequate strength for you to hear the signal, the surface signal may be a more power signal coming from a tower - a handheld device may be unable to transmit a strong enough signal back to be heard by the surface station. One issue with Mobile Phones in such environments is that higher frequencies are blocked more effective by the ground than low frequencies.

2. Can there be any methods to boost the Mobile Phone Signal reception so that the underground worker/s may be able to communicate with their wireless devices ?.

RESPONSE: Yes, probably the most effective would be a local repeater underground which would receive the signal and re-transmit it on the surface, and vice versa. There are issues that must be addressed even with this approach. the devices used in the underground environment may have safety concerns, for example in a coal mine, explosive gases may be present and as a result devices use in that environment must meet specific safety approvals to ensure that they do not provide a source of ignition for such gases. This would be required for both the handheld and for any other electrical/electronic equipment used in that environment. Qualifying the equipment can be expensive. Equipment used in  other underground environment may also be subject to such requirements though that would be considered on a location by location basis.

3. What are the communication channels  modes for underground manpower viz to communicate with office workers on ground level ?.
Using the elevator/lift to travel up and down the ground level
could be the only solution for communication ?.

RESPONSE: Radio is could be used, or a most cost-effective option for many environments may be a simple wireline form or communication. If radio is to be used, a low frequency radio system would be preferable as low frequencies can often penetrate the ground where high frequencies would not. Low frequency systems for such environments are available.

4. Can Walkie - Talkie (two way radio communication) device work
in Underground areas ?.

Again, how effective it is depends on the frequency. In most cases they would be good only for short distances and a system of repeaters would likely be necessary.

I hope that this helps.

Regards,
Tom
http://tjstechnical.com

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Tom Smith

Expertise

I can answer questions regarding product approvals, including areas such as Product safety, Electromagnetic Compatibility (EMC), Telecommunications, Environmental requirements such as RoHS (Restrictions on Hazardous Substances), WEEE (Waste Electrical and Electronic Equipment), and international approvals requirements.

Experience

I have been involved in product approvals for over 25 years, working both for major manufacturers, design organizations, and two major testing laboratories. I have experience putting products into countries around the world, working with various approvals agencies, and have been involved in various standards development agencies (Product Safety, EMC and Telecom). I was the Senior Approvals Engineer at the first private telephone approvals laboratory in Canada, and have been involved in the development of Industry Standards for telephone and telephone products.

Organizations
- Senior Member of IEEE - Association of Professional Engineers, Geologists, and Geophysicists of Alberta (APEGGA) - Professional Engineers of Ontario (PEO) - Terminal Attachment Program Advisory Committee (TAPAC) which is under the jurisdiction of Industry Canada (Department of the Gov't of Canada) - Canadian Standards Association

Education/Credentials
B.A.SC (Electrical Engineering)

Awards and Honors
- Only Approvals Liasion Engineer (ALE) ever appointed by AUSTEL (AUSTEL is no longer the authority in Australia, and the ALE program was also replaced in 1997) - Former Deputy Approvals Liasion Engineer appointed by the British Approvals Board for Telecommunications (BABT)

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