); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY On Saturday 04 August 2007 23:54, Thomas A. Frank wrote:
> Ah, but what if one used the tunnel itself as a waveguide, and > propagated an RF signal down it? For many years I designed Coal Mining Equipment, I can tell you from real world experience that it does not work that way. We found the best "waveguide" experience was in the range of 300 to 420 MHz, but the distance is very limited, hundreds of feet at most. The main problem at different frequencies is the material becomes absorptive at lower frequencies, or reflective at higher frequencies causing to much mutilpath distortion. Look at my site http://www.wearablesmartsensors.com/ under the 'Challenge' section and the blog there for some related information. You can find the results of some of the past real world underground tests here: http://www.msha.gov/techsupp/mcelroyminetestreport.pdf "The Mine Safety and Health Administration formed a committee to evaluate communication and tracking system technology that could be adapted for use in underground mines." NIOSH has a test Mine near Pittsburgh if your inclined to test something. We've just started to look into some old/obscure/esoteric ways of transmitting signals underground. Which we hope will solve this problem, if we can overcome some funding and time issues. -- http://www.wearablesmartsensors.com/ http://www.softwaresafety.net/ http://www.designer-iii.com/ http://www.unusualresearch.com/ _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
