Nostalgia & History > Locomotive/Caboose Radios

Hello all,

I've begun working with some older electronics (1950's) and have been wondering, what kinda of radios were used on motive power and (cabooses) rolling stock during that era?  Were they thermionic valve (vacuum tube) or transistor based?  What frequency range did they use?, HF, UHF, or VHF?  Any info or pictures (installed equipment) would help.

Thanks,
Jon

I don't know about the insides of a radio but the first ones were tuned for 150 to 160 range SP was 152.55 I think. That was the only channel for many years. The radios were Motorola and as time went on they were interchangeable.  Some had a little selector switch on the bottom of the pak that allowed you to select 74 volts for the engines and 12 volts for the caboose.

I know they used tubes on the old master & slave units and that was why they were so unreliable. They couldn't take the shaking and vibrations. 


Nudge

spnudge Wrote:
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> I don't know about the insides of a radio but the
> first ones were tuned for 150 to 160 range SP was
> 152.55 I think. That was the only channel for many
> years. The radios were Motorola and as time went
> on they were interchangeable.  Some had a little
> selector switch on the bottom of the pak that
> allowed you to select 74 volts for the engines and
> 12 volts for the caboose.
>
> I know they used tubes on the old master & slave
> units and that was why they were so unreliable.
> They couldn't take the shaking and vibrations. 
>
>
> Nudge
161.550

Thank you both.  That helps quite a bit.  I would think if the radios were so sensitive, they'd be set up with some sort of shock mount system.  I'd love to see pics if anyone has any, Google hasn't turned up much.

I believe most of the older radios were Motorola 'Motrac' radios set up for 12 volts or 72 volts. I saw many of the same radios used as base station radios with an adapter to take the 120 volt power supply. The railroad band is 160.215 MHz to 161.565 MHz. Most of the older radios were one or two channel but I remember seeing DRGW Motracs that were 8 channel radios that had a control head with a four position switch and another switch that selected channel banks "A" or "B".

James Nelson
Thornton, CO
www.flickr.com/mojaveflyer

The first radio in my SP company car was a Motorola (VHF -  FM). The actual radio was a tube -  transistor combination but would function almost as soon as it was powered up (not a measurable time delay for the tubes to warm). It was locked and bolted to the floor of the trunk. Thus it suffered plenty of jolts and bounces but never failed. Had to have an FCC check annually as I recall. It had originally been in another car and I think it was new around 1969. I suspect these were the same as the caboose radios and I was told they had 45 watt transmitters. The 3 channel control console used rotary switches and was mounted to and below the dash. Bright green light for receive and red light for transmit. Toggle switch selected scanning on or off.

Next radio was a 4 channel with a push button scanner console. The radio "box" in the trunk still had some tubes according to our radio shop. 

Last radio at my retirement was a 16 channel, fully contained under dash mount. The manual (first and only one I ever saw since these were not given out by the Communications Dept.) had a stern warning. Do not press transmit button if anyone is in contact with the antenna. Could trigger a fatal heart attack.

The very first locomotive radios were a 3-piece monster with seperate transmit, receive and power supply sections. I believe they operated off a dynamotor that produced 115 volts ac. The next versions were the AAR rack mount ones beginning with an all-tube version utilizing a vibrator power supply. Soon technology produced the partially solid state MOTRAC (MOtorola Transistorized Advanced Communications) in the early 60's which were available in a 64/12 volt version for locomotives and cabooses and the transistorized design led to lower current drain thus cooler operation and longer life.These had the round AAR connector on the front which mated with a cable on the mounting rack. Inside the mounting rack were two terminal strips from which wires ran through a conduit to the control head. A mobile version was available for supervisory vehicles and m of w vehicles which were straight 12 volt dc. Early ones were maximum 4 channel and I remember two  special locked metal boxes on EsPee mof w machines containing the transceiver (usually on the roof) and the control box near the operators position connected by a flexible conduit. The Motracs were 25 watts and the Motran were 40 watts in both the locomotive and mobile versions.

Next came the MOTRAN series which replaced the MOTRAC with the only difference being they had no tubes in the transmitter. Some of the radio shops were able to adapt the MOTRAC/MOTRAN to scan but was only somewhat successful and resulted in listening to taxi cabs and paging services more often than the dispatcher!

Then came the MICOR series which replaced the MOTRAC/MOTRAN and still mounted on a AAR rack with 4 channels (or 8 with a mod kit) and lasted until the clean cab 97 channel Spectra. The MICOR was a bit more sophisticated in the mobile version having 8 channels and factory installed scan and singletone as well as DTMF to access the PBX system and you could even get it with a speech scrambler module!

The practice of utilizing run through power made even a 8-channel radio unpractical and Motorola came out with the SPECTRA 97 channel 45-watt clean cab radio which is the standard today with a few modifications such as narrow banding and digital capability. A mobile version with both front mount and remote mount versions was the most popular railroad mobile with power output up to 110 watts. A narrow band capable Spectra was the last offering known as the ASTRO series and many are still in operation on short lines and regionals. 

Unfortunately Motorola for some strange reason decided not to go after the railroad market in order to concentrate on the government and public safety market with their proprietary digital systems leaving the railroad industry to come up with "whatever works" out of the industrial radio catalogs.  UP for one has gone to a supplier that they own for locomotive radios and Kenwood for their mobiles and portables. I'm unfamiliar with what the other Class I's are using but the old Motorola's can't be beat for reliability and clarity.

Dick Samuels
Oregon Pacific Railroad  

@ EMDSW-1

So it sounds like the equipment was set up about how I had imagined (and may like to try to replicate).  I was considering trying to build something up resembling an "aircraft black box" with aviation style circular connectors and the like in a ceiling mounted rack.

The aviation plugs we used in the Navy were, Cannon plugs. I think that is a brand name.
They were great when we were at our shore base but could cause all kinds of troubles
when we were on the carriers. Good luck on your prodject........Swede.....Albany,Or.

A Southern Pacific Motorola Caboose Radio as found in a preserved C-40-1 Caboose on the Niles Canyon Railway at Freemont, CA.

Cheers,
Jack

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That's just the control head. The cable below goes to a large heavy box.

Speaking of the SP and radio's. As I understand it GN crews couldn't talk to SP trains between Klamath Falls and Chemult. This was I guess because each railroad was on their own frequency. When a GN train would get stopped the conductor had to go to the phone booth and call the dispatcher to see what was going on as it was CTC by this date. Anyway I suppose this happened all over the place in the early days of radio with two or more railroads sharing track and only 1 or 2 channel radios.

In 1966-67 I drove a road service and tow truck wih mobile radio, business VHF. The owner's son worked for a communications company and set up our mobile radios. The mobile units were Motorola 12 V and in a big box under the seat. The base station was in the living room of his upstairs apartment in the building we were in. The building was on top of a hill providing about a 20 mile range. Of interest the base station was a large open rack bigger than a refrigerator. It was an ex-railroad caboose radio. It was full of vacuum tubes with a very large finned air cooled output amplifier tube. Very sci-fi with a purple glow! The head unit was three stories below in our garage office. It was a single channel shared with many other businesses. Crude but effective.
Gonut

Most railroads weren't using radios in the 1950s.

@ Gonut1

I figured the assemblies would have been of good size.  I can only imagine the size of the battery bank that would have been carried as well.

Santa Fe used Bendix and Motorola radios in the 1960s and 70s.  By then, they had solid-state inverters in the power supplies, although the few remaining Alco High-Hood switchers use 110 VAC radios with vibrator power supplies.  The most common units I worked on were Bendix 1R54Cs, which ran off the70 volt starter battery in locomotives.  Cabooses had 12 volt systems powered by a generator mounted on one of the trucks, those radios were 1R24C types.  We also had some Bendix 12 volt radios for cars and trucks, and I vaguely recall some 6-volt models for the Fairmont motor cars.  The earlier radios with separate transmitter, receiver and power supply modules were the MRT-8s.  They were mostly found in old Alco switchers, some of which had been converted to standare AAR racks, but many of them still had MRT-8s, which were starting to show their age.  The module connectors in the backs of the MRT8 racks and the latches that held the modules in place got old and loose, and some bright sould in one of our shops devised a clamping bar made of angle iron.  The bar was held in place bolts threaded into other pieces of angle iron mounted between the modules.  If an MRT-8 needed service, the prudent tech would have a socket wrench with 7/16 hex socket in his pocket before climbing on one of these units.

Photo: The silver box behind the smokestack is the radio cabinet with the MRT-8 setup inside.  Note the grab irons on the end of the hood.  The tech had to climb up onto the top of the hood, walk past the smokestack (which, if the engine was running, had rich, fragrant Alco smoke issuing forth).  I have more stories to tell, but I'll save them for  Railroaders' Nostalgia.

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