AM Carrier-Current Coupling to one of the railroad track rails? Been done???

[ThaDood]

Speaking a few weeks ago on 10M  Chit-Chat, the dude about 20 miles West of me, mentioned where a friend, in the late 60's, coupled his AM MW transmitter to the railroad tracks by his house then, and close-by houses heard that signal a long ways. WOW!!!! I've thought about that, and here's a story of someone who finally did that! COOL!!!!! In theory, it should be permissible under Part 15 rules, if Field Strengths are not exceeded. However, like the power line companies, rails for the railroad are also used for data & control remotes. One problem that I could see is that the coupling RF impedance will change from wet to dry to wet, and especially when a train comes by, shorting out between the two rails. And, near the railroad crossings, it's my understanding that those are activated via sensing a low value continuity. Like, 1 Ohm, and lower in DC continuity, the lights & bells go off, and the gates will come down. So, don't have a short between the two rails. (I'm sure that someone from like Conrail, or Pacific Rail, CSX, RTD, etc., can confirm this.) Even better, if you have abandoned tracks next to where you live, and those rails go for miles, than that could really make for a nice AM Carrier-Current Coupling. BTW, if you have Gas Pipelines by you, I would not recommend coupling to those, since most of your signal would be just wasted to going underground, and the pipeline's Corrosion technician might see weird readings at the Corrosion Control Rectifiers. Tempting, but I wouldn't try it.   

[tybee]

Same subject came up a month or two ago at part15.org. Evidently there was actually a company that supplied the service of railroad track transmission in the 1940s, as described at : https://en.wikipedia.org/wiki/Trainphone

Trainphone was the Pennsylvania Railroad's system for voice communication between crews on moving trains, dispatchers, and tower operators. ..... It did not use radio, but rather electromagnetic induction. Railroads did not own any radio frequencies at the time, .... The trainphone system was first tested in 1936 and perfected by 1943.

The system used the track itself, or lineside telegraph wires, as the "shore" transmitter. The trainphone signal — low frequency current in the hundreds of kilohertz— was passed through the track or wires and induced a corresponding current in the locomotive or car's receiving antenna. The range was only a hundred feet or so, but this was sufficient. ... [/i]

Equally interesting is the s document from the Defense Technical Information Center (DTIC) which Artisan-radio found:
https://apps.dtic.mil/sti/citations/AD0822478

USE OF RAILROAD TRACKS FOR CARRIER TELEPHONY AND AS LONG-WIRE ANTENNAS FOR TRANSMISSION OF LONG-WAVE RADIO SIGNALS.

ARMY ELECTRONICS COMMAND FORT MONMOUTH NJ
Report Date: 1967 Jun 01
Abstract:
Investigations were made of the performance characteristics of manmade structures i.e., railroad tracks, buried pipes, and sewer lines for VLF signal transmission. .... Signal transmissions over a distance of up to 15 miles were achieved with a consumption of less than 10 watts nominal 48 kHz transmitted power. A single ferrite loop was used as a receiver. Impulses picked up along fences and other metal structures denote signal re-radiation by railroad track. Results of these experiments indicate that railroad tracks act as signal ducts, and possibly, long-wave antennas..."