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Trains causing carriers and heterodynes all over the CB band.

Shockwave

Sr. Member
Sep 19, 2009
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If you live within a mile or so of any train tracks and you haven't noticed the band filling up with carriers, it's only because Positive Train Control has not be installed in your area yet. The device in question transmits a 27 MHz. signal from an antenna under every train. This signal is only used to power remote receivers on the track that are recording the trains location and other perimeters. This 27 MHz. signal cannot be interfered with since it carries no information and is only a remote power source. The 27 MHz. RF is rectified into DC on the track.

The entire system is in violation of multiple FCC rules that are not only being ignored, but the equipment being used seems to have been carefully designed to CAUSE interference. First, the CB band allows use of remote control devices only on designated RC frequencies. Since this system is using CB to remotely power another device, it is by definition a remote control device and could only be authorized on RC frequencies.

The fundamental frequency this system operates on is channel 13 but it is loaded with spurs that appear every 40 KHz. up and down from channel 13. The first lower spur lands right on channel 9. Unfortunately I've been unable to find any FCC type acceptance information regarding this system. Not even a file number to look up. If you are within a few blocks of any train tracks the spurs are strong enough to extend right into the CW portion of 10 meters!

I wonder how long before every train in the country has a PTC device installed that could never pass any FCC inspection or rules? What's going on here and who ignored every regulation to press these filthy RF generators into service on the air?
 


That is the only frequency in the 11 meter band designated for use by RF generators (or 5khz. higher) but this system makes no attempt to follow the regulations because it's not capable of producing a clean sine wave. What unmodulated waveform generates strong spurs every 40 KHz.? You gotta see what this interference maker looks like on a spectrum analyser or pan adapter.
 
...EDIT... Positive Train Control has not be installed in your area yet. The device in question transmits a 27 MHz.
..... The 27 MHz. RF is rectified into DC on the track....The fundamental frequency this system operates on is channel 13
... I've been unable to find any FCC type acceptance information regarding this system. Not even a file number to look up....I wonder how long before every train in the country has a PTC device installed ...

sorry you are getting interference, but, PTC is probably not the cause.
It might be something else onboard a train though.

PTC does not use 27 MHz. It uses 217 - 220 MHz.

there is a signal embedded on the tracks that an onboard sensor detects. nothing goes the other direction using the tracks.
some sections of track do have an RF transmitter located adjacent to the track that can transmit a command signal to the train. they are located in a small building with a 220 MHz antenna on about a 10 - 30 foot mast.
PTC-Antenna.jpg


The deadline for implementation is Dec 2018.

you will find all the legal mumbo junbo here.
49 CFR 236.1005 - Requirements for Positive Train Control systems.
 
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OK, I stand corrected. This system is part of new safety requirements and is specifically called Advanced Train Positioning or ATP. Here is a quote from the description:

"In the principle currently in play by eurobalises, the trains remotely power these beacons by magnetic coupling from a high-frequency 27 MHz, high-power signal emitted from an interrogator/beacon reader located under the train. These signals are emitted constantly as soon as the train is moving."

The full PDF can be read at this link: https://cdn.intechopen.com/pdfs/57840.pdf

The same system has been installed in the USA and is in complete violation of FCC rules in terms of frequency allocation and spectral purity. 27.115 MHz. is not an authorized Remote Control channel and neither is every frequency up and down at 40 KHz. intervals. I suspect "high-power" is most likely above 4 watts too.
 
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Might be we need whats making their power,leenyer yeah big train power.
Funny how they can do illegal stuff n its ok.but hey railroads have government support too
 
So that explains the noise on ch13. I wonder how much power I can run before I cause a problem on their system?

You would need to hold the antenna directly over the transponder in the track and then you might trick the system into thinking a train was present. It does not send any data so there is nothing to interfere with. It only supplies remote power to the transponder and that lets the system know where a train is. Since it is "magnetically coupled", the pickup must take place in the near field or right on top of it, otherwise power will not be transferred.

I would strongly suggest no one try and interfere with this system. Think about the harm you could cause if you make an oncoming train stop short on the track, thinking another is in front of it, while more are behind it. While some tricks are fun, it's safety first here.
 
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I read the entire thing... thats not the system on American trains. Nothing on an American train transmits except on the 220 MHz band.

Good Luck
 
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