How much radio power enters a tunnel ?
How much radio power enters a tunnel ?
(OP)
Assuming a 900MHz transmit antenna with 39dBm ERIP is placed 100m away from a train tunnel entrance measuring 20sqm (cross sectional. Also assume a free space propagation from the antenna right to the tunnel opening.
What is the received signal strength inside the tunnel, at x meter away from the tunnel entrance ? assuming 0dBi receive antenna.
What is the received signal strength inside the tunnel, at x meter away from the tunnel entrance ? assuming 0dBi receive antenna.





RE: How much radio power enters a tunnel ?
If the tunnel was lined with absorptive material, then there would be no reflections and the signal strength at X meters would simply be the free space loss pretty much ignoring the tunnel (assumming that the tunnel is straight).
The above two simple cases can put bounds on the answer. It seems that the dominant factor is free space path loss. Any reflections will probably hurt more often than they will help.
J. Harvey
Ottawa
RE: How much radio power enters a tunnel ?