Warren,

The transmit signal was coupled inductively into the rail using a standard cave 
radio resonant loop. The signal was recovered at the receiving end using a 
similar loop.

If I recall correctly, the signal was starting to drop off noticeably at 1.6 
km.  The tests were done in an area where there is substantial interference 
from LORAN C, so it may have been  signal-to-QRM rather than signal-to-QRN that 
set the maximum range.

Also, the receiving operator complained that walking a good mile on railway 
ballast* was making his feet hurt, and he would have to walk the mile back to 
get out of the cutting.  

*Note that it is not wise to walk on the sleepers (railroad ties?)  as it is 
all too easy to lose your footing if they are wet or greasy.  I have been there!

73 John F5VLF
              G3PAI

On 4 Feb 2011, at 16:22CET, Warren Ziegler wrote:

> John,
>    If this was conduction through the rail, why was it limited to 1.6kM?
> Was this the length of unbroken track?
> 
> -- 
> 73 Warren K2ORS
>                 WD2XGJ
>                 WD2XSH/23
>                 WE2XEB/2
>                 WE2XGR/1