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




On Thu, Feb 3, 2011 at 3:08 PM, John Rabson <[email protected]> wrote:
> Some years ago, we tried using a small loop to couple a Heyphone (4 W output 
> on 87 kHz) into a running rail in a disused railway tunnel in the English 
> Midlands (we had permission from the owners of the line).  A similar setup 
> was used for receive and we achieved a range of 1.6 km along the line.
>
> 73
> John F5VLF
>
> On 3 Feb 2011, at 20:36CET, Jacek Lipkowski wrote:
>
>> trying to couple to large structures is an interesting experiment, both for 
>> receiving and transmitting (only by induction of course :). think about 
>> power lines, phone lines (but unfortunately nowadays most are very short, 
>> and the rest is done via fiber), natural gas pipelines, railways etc. this 
>> is an example rx experiment: http://www.youtube.com/watch?v=sWsdaSmWg7E , 
>> these structures are usually very well grounded at regular intervals, but 
>> still some vlf will slip through the ground system, so they can be also used 
>> for tx too. a few miliamps at 9kHz into a large structure is detectable from 
>> a few hundred meters.
>>
>> actually the "utilities-assisted earth mode" works not only on transmit. a 
>> loop antenna near a long conductor will pick up a stronger signal (and also 
>> more qrm, so this doesn't always raise S/N).
>>
>> this might not be ham radio (or not radio at all), but is very interesting 
>> nevertheless
>>
>> VY 73
>>
>> Jacek / SQ5BPF
>>