VHF Antennas on Locomotives

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BigJimbo

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I dont want to double post on the Antenna Forum, so I will start my question here:

I remember seeing the 12 to 15 inch 1/4 wave VHF antennas on top of locomotives sometime ago, but noticed over the last few years they are gone.

I do see what appear to be "bar" antennas that are mounted near the front top and sides of the locomotives. Is that what they use as antennas now? Or are their antennas somewhere else that I'm not seeing?

If these bar antennas are in fact what is in use, what advantages do they have/dont have over the old 1/4 whips that I used to see? Does anyone know what kind of wattage the on-board train radios put out?

Thanks to all who respond!
 

SCPD

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I'm pretty sure those antennas are actually uni-directional. (one direction)
And mounted so they radiate forward.
 

JESSERABBIT

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BigJimbo said:
I dont want to double post on the Antenna Forum, so I will start my question here:

I remember seeing the 12 to 15 inch 1/4 wave VHF antennas on top of locomotives sometime ago, but noticed over the last few years they are gone.

I do see what appear to be "bar" antennas that are mounted near the front top and sides of the locomotives. Is that what they use as antennas now? Or are their antennas somewhere else that I'm not seeing?

If these bar antennas are in fact what is in use, what advantages do they have/dont have over the old 1/4 whips that I used to see? Does anyone know what kind of wattage the on-board train radios put out?

Thanks to all who respond!

If you do a search on this Forum for Transmitter Power", you will see that one of the responses was "40 to 50 watts". I hope this helps.
 

DaveH

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This is a "blade" antenna, very rugged, vertically-polarized, roughly
omnidirectional, and the've been around for some time. They're used
with or without a covering (radome) and the UHF version is popular
on transit vehicles (busses etc.) There is (or was) a low-band version
also. Gain is roughly equal to 1/4 wave vertical.

Dave
 

SAR923

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There was also a time that any antenna mounted on a locomotive or caboose had to be capable of being uses as a grab iron in an emergency. I think that rule has since been rescinded but the Sinclair still harks back to that time. The Sinclair and similar antennas are omnidirectional. Radio sites are not always located directly ahead of the locomotive.

Locomotive radios are now mostly special railroad versions of the Motorola Spectra. They can be set for 30, 45 or 60 watts. For some reason, Canada limits output to 30 watts.
 

JESSERABBIT

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SAR2401 said:
There was also a time that any antenna mounted on a locomotive or caboose had to be capable of being uses as a grab iron in an emergency. I think that rule has since been rescinded but the Sinclair still harks back to that time. The Sinclair and similar antennas are omnidirectional. Radio sites are not always located directly ahead of the locomotive.

Locomotive radios are now mostly special railroad versions of the Motorola Spectra. They can be set for 30, 45 or 60 watts. For some reason, Canada limits output to 30 watts.

Thank you for that information.
 

trainman111

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CSX still uses the 14-15" 1/4 wave antenna's on their older locomotives. I haven't really paid much attention the newer locos. I think they probably use the ones from Sinclair.
 

kc0kp

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Sinclair Antennae

Sinclair has made a business out of antennas that almost defy description. For the railroads then made the "anvil" antenna described before and a vertical antenna that was made of tubular steel the was half the height of a 1/4 wave vertical, usually painted black. They also made in the 60s and 70s antennas that were built into rear view mirrors that mounted on a car exterior where the stock mirror would mount. Inside were all sort of coils and tuned coax stubs to match it to the radio and radiate a reasonable amount of energy. They were used by the FBI and the old BNDD for undercover operations.
I installed an anvil on a city road grader because he was assigned to work alleys and kept decapitating the 1/4 wave vertical, usually in less than a week. The antenna was still on the grader when surplused five years later.
I still have a Sinclair on my 73 'Cuda that looks identical to a stock Chrysler antenna but is actually a 5/8 wavelength antenna tuned to 146.500 Mhz. It uses an Antenna Specialist splitter that divides the AM signal to the regular radio and has a PL259 that goes to my handheld 2 meter rig. It was installed in 1977 and still going strongth.
 

kc0kp

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More Sinclair antenna

I forgot to mention, the anvil antenna is a tuned "slot" design, not a J pole. In a slot design, the polarity is the opposite of the longest part of the slot. It is therefore vertically polarized and omni directional. It is also less than unity gain compared to a 1/4 wavelength but because they are so rugged, they will last the life of the locomotive, bus or whatever they are mounted on so they save money over inexpesive wire antennae.
 

icom1020

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Big Jimbo, the 1/4 wave spikes are still prevalent on the newer UP locos out here in the west. Hard to spot but probably a lot cheaper too.
 

BigJimbo

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Well, Don now that you posted that page 11 and I saw the ASP-16, I've seen those on the Norfolk-Southern Locomotives here.

From a distance, I thought those were anything but antennas! It looks like they have both the ASP and Sinclair's on the NS power around Ohio. I did see a CSX train today near Middletown, Ohio that had the 1/4 spike on the top. I bet I hadnt seen one in years.

Thanks to everyone who posted.
 

DPD1

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BNSF has been using a long version of the Sinclair inverted F antennas for it's new low band data system. I forget what area it works in... 50 MHz maybe? Anyway, it looks the same, but just longer. Almost as long as the roof. I found a shot of one once, but I forget where.

Dave
www.DPDProductions.com
Makers of the "TrainTenna" Monitoring Antenna
 

icom1020

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DPD1 said:
BNSF has been using a long version of the Sinclair inverted F antennas for it's new low band data system. I forget what area it works in... 50 MHz maybe? Anyway, it looks the same, but just longer. Almost as long as the roof. I found a shot of one once, but I forget where.

Dave
www.DPDProductions.com
Makers of the "TrainTenna" Monitoring Antenna
Yeah somewhere in the 44mhz, the very long antennas on the DED boxes made by Morad? are for the receivers.
 

Thunderbolt

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DPD1 said:
BNSF has been using a long version of the Sinclair inverted F antennas for it's new low band data system. I forget what area it works in... 50 MHz maybe?
Dave
www.DPDProductions.com
Makers of the "TrainTenna" Monitoring Antenna
As I understand it, their data system is on 72 MHz. They decided to use this band because it allows a less intensive supporting infrastructure than a 900 MHz system would have. Ie, less tower sites.

73s

Ron
 
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