Transceiver Range

[Mikebits]

Okay RF guys, I would like your input. What kind of range in meters can one expect from a handheld device transmitting at 868 or 915 MHz with a power output +10 dBm (10mW), and then for +27 dBm (.5W). Data rates up to 600 kbps.
The handheld environment would be places like sewage tunnels, some having bends and turns. (see image). Other environments could be large tanks such as in the next image.
**broken link removed**

 

[Nigel Goodwin]

Basically 'line of sight' - if you can see each other it will work, if you can't it probably won't.

However, there will be some degree of 'bouncing', particularly in a metal tunnel.

The only way to know is to try it in the exact circumstances you want it to work - wanting 600kbps is greatly restrictive as well.

 

[JimB]

Radio wave propagation in tunnels tends to be a bit if a problem.
Many of the problems are caused by waveguide effects.

Have a look here:
https://www.antenna-theory.com/tutorial/waveguides/waveguide.php
And here:
https://www.intechopen.com/books/el...magnetic-wave-propagation-in-circular-tunnels

I have no direct experience of using radio in a tunnel environment, and I would suggest that before you invest a lot of time into this, that you do some simple tests using the basic radio equipment and see how the signal strength varies with distance along the tunnel.
The pessimist in me says that you should be prepared for a disappointment.

What a cheerful helpful guy I am this morning!

JimB

 

[Mikebits]

I have a feeling you guys will be right, multi-path fading will be a true problem. Testing this will prove to be quite difficult because most of these spaces are considered permit required confined spaces and require paperwork and a safety team. I suppose I could look into a construction supply yard and look for a long steel pipe large enough to enter. I really only need about 7 meter range.

 

[Nigel Goodwin]

As long as it's 7m in a straight line you should be fine

 

[MikeMl]

7m won't be a problem in a 2m diameter tunnel. Getting a signal out through an opening that is smaller than 1/2λ x 1/2λ will be...

 

[Mikebits]

I think I am okay for the short haul, which is the main requirement, but I had one of those what if moments, where I thought it would be nice for the guy in the tunnel where his instrument would send data to a data display unit just outside the tunnel for the attendant to view. 10 dBm is like the max level of a sig gen so I don't imagine that working out well, but I do have a way to go up to +27 dBm. To conserve battery power on the remote unit I would want some sort of power control where we start at a high power then drop the power as low as possible to maintain a link. Kinda like they do in cellphones.