Thursday, January 21, 2010

Induction Train Radio

Washington State University, Pullman Washington, basement of Gannon Hall, October 1962. As I rummage through boxes of slides and negatives and photographs, the garbage can gets filled. What would possess a person to take four thousand mostly blurred shots of squirrels cavorting on our back deck?

Or envelopes full of what I call “black specks?” My wife claimed they were photos of Turkey Vultures. Could have been Bomarc IM-99A Missiles!

But then I find gems, like this one. “The Moon Dawg” show is on the air! Spinning the hits that keep on coming! Behind the dark glasses, yours truly, broadcasting to the residents of Gannon Hall, a men’s residence facility at WSU.

The “Moon Dawg Show” aired on KGH (radio Gannon Hall.) Listener-ship was estimated between zero to as many as a half dozen of my cohorts, downing forbidden tall cool ones on a Friday night up in “suite” 604! Several of us “broadcasting major’s” took turns developing mile high egos, which was not part of the WSU Journalism curriculum!

Clandestine to be sure. KGH was the end product of a handful of “double-e’s” (electrical engineering) majors applying their increasing knowledge of electricity to build an “induction broadcasting” system. Somehow, through a mechanism I had no knowledge of, an Amplitude Modulated broadcast signal was “induced” into the building’s extensive A/C electrical system!

The only way you could listen to the station was to have an A/C plug in radio and tune the dial to 610 AM – more or less. And then apply a mental “filter” to separate the music from the 60-cycle hum and scratchy static. But it was great fun until the Campus Fire Department shut it down.

So what does this have to do with railroading? Well, the mechanism that applied KGH’s AM signal to the A/C wiring throughout Gannon Hall was the same mechanism that allowed the Pennsylvania Railroad to operate its revolutionary “Trainphone” system!

This all came together for me when I recently spotted James Appleman’s recent posting on Railpictures of this magnificent General Motors E-8, with it’s signature “hand rails” on the roof!

The "hand rails" on the roof were the core of Pennsys landmark communication system dubbed "The Trainphone." It was not a radio system as we normally think of one. The signal went over the air in a very controlled manner, using the rails beneath the train, and wires adjacent to the tracks to carry the voice signal.

The Pennsylvania Railroad, working with Union Switch & Signal Company, devised a radio system combining transmitting through the rails, with a carrier induction system. Popular Mechanics magazine, March 1945, did a feature article explaining the induction radio system.

The induction system requires three conductors parallel along the path of the sending unit, be it locomotive or caboose. That explains the two distinctive parallel “hand rails” antennas, running the length of the locomotive. The rails provide the third conductor, and in many cases, wires on telephone pole adjacent to the tracks provided that third conductor.

The signal emitted from the antenna, a radiating “induction field,” a “cocoon of radio energy” around the transmitter in the locomotive, caboose, and other sites. This “induction field” apparently had a range of two or three hundred feet, “inducing” an FM radio signal into the rails and track-side wires.

That “induction field” was similar to the superimposing of Radio KGH amplitude modulated (AM) signal to the residence hall wiring system.

To receive the signal, pickup coils mounted near the rails in some cases, and processed into a voice signal, completing the communication send-receive loop. Shown here is a caboose with a good look at the Trainphone induction hoop. The system was installed on both steam and diesel, allowing communication between the head end and the hack, train to train, train to dispatch and towers.

Using a frequency modulated signal (FM) resulted in a crisp clear voice signal free of static and “hum.” Which is why – before the recent move to digital broadcasting, your old analog TV incorporated an Amplitude Modulated (AM) picture signal coupled to Frequency Modulated (FM) sound signal. (And that’s the easy part to explain; explaining how color is transmitted … !)

So like the A/C lines in the dormitory carried our induced AM signal, the steel rails and lines trackside, became the carrier medium for the Trainphone radio signal. The frequency modulation (FM) spectrum would have resulted in a clear signal, void of “hum” or “scratchiness.” And there you have the basics of the Trainphone operated.

I direct you to the Philadelphia Chapter of the Pennsylvania Railroad Technical & Historical Society, who did a fine job of documenting the restoration of the 5809. There are a number of close up photos of the Trainphone installation and the “hand rails” on top of the E8, well as other aspects of the Trainphone system.

I don't know how channels were assigned, nor how many channels the system could accomodate. Please chime in if you can help expand our knowledge of this interesting communication system.

In 1945 the Pennsylvania Railroad inaugurated two-way train-telephone communication system in main line operation, between Albion, Pa. and North Bessemer Yard in Pittsburgh. Perfected in the 1940's, the Trainphone system was phased out in favor of more traditional radio systems in the early 1960’s. The Pennsylvania Railroad communication systems were considered state of the art and advanced for their era.

Pennsy and Beyond

As early as 1881 – 1887, Thomas Alva Edison invented a system of wireless telegraphy, by induction to and from trains in motion, or between moving trains and railway stations. The system was installed on the Lehigh Valleys R. R. in 1887, and was used there for several years. Edison struggled with induction telegraphy, but never really had any great success.

The principle of radio induction is still alive and well as a method of automatic train operation. In 1972, Japanese National Railways filed United States Patent 3694751. The preamble includes;

An important problem with which railroads are confronted in recent times, is how to deal with the excessive passenger loads and the high travel speeds. A criterion to solve this problem is to transfer train operation from the hands of humans to control by electronic computers.

That is to say, an optimum operation of trains will be realized by installing an electronic computer of an adequate capacity at a central control station, which will exercise an overall control over all trains by means of the computer.

As a matter of fact, you may have already experienced the concept of an “induction” system, similar to radio KGH and the Pennsy Trainphone. Inductive Loop Systems are commonly used in churches, passenger stations, even private homes. They broadcast to hearing aids of the hearing impaired. Or, you may have rented headphones in a museum to listen to presentations in front of displays. One very complex system I've enjoyed was at the Aquarium in Vancouver.

Join the discussion below as we explore this fascinating piece of railroad history. I understand that the Duluth Missabe & Iron Range, and the Kansas City Southern dabbled in the Trainphone induction system, but I’ve been stumped in locating meaningful or credible information about their use.

Photo Credit: "Thanks!" to Jim Appleman for the beautiful Pennsylvania RR photos.

See Also: Induction Train Radio - Two

1 Comments - Click here:

Eric said...

Interesting stuff, Robert, always wondered how about those PRR handrail antennae. KGH is a radio station there, a hospital and my employer here...Kingston General Hospital. High school students at nearby Kingston Collegiate & Vocational Institute have their own local radio station, except in Canada, station names start with C, so call letters are CKVI. Eric

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