Track Error Detection Interference?

[lthanlon]

I just returned from a round trip on the Southwest Chief and recorded digital audio for my podcast throughout the trip. Occasionally, the recorder would pick up a several-second burst of high-pitched electronic blips not unlike Morse Code. I'm thinking this wasn't cellphone switching, since often the interference was way out in the middle of nowhere, where nobody had cell service. Could these digital blips be from track error-detection devices?

My recorder, a Sony PCM-D50, only picked up these blips when the train was in motion -- and during entire stretches of older track, didn't seem to pick the signals up as often. Of course, we were traveling a lot slower on those stretches, too.

 

[caravanman]

Hi,

Audio equipment, recorders, etc, can often pick up radio frequency signals. Hard to say what it is in this case.. it can be caused by sparks from equipment aboard train, such as A/C cycling on and off, door contacts operating, etc. In that case it would probably sound more like clicks or static crashes than beeps. Beeps sound like bursts of information, so it could well be communication from trackside devices.

Ed

 

[Joel N. Weber II]

I'm not sure what the rules are on the railroad frequencies, but on some non-railroad bands, the FCC requires transmitting stations to identify themselves, and Morse code has traditionally been an accepted way to do that identification. It may be that defect detectors that are old enough to predate affordable speech synthesis tend to identify themselves using Morse code.

 

[lthanlon]

Thanks for the ideas about what this interference could be. I'll be posting the podcast in a day or so, and you'll be able to hear it.

 

[Guest]

You might have been picking up Advanced Train Control System (ATCS) data packets. This is the modern radio system that controls the signals and switches along track controlled by CTC and is the successor to the lineside telegraph poles that used to be found along the tracks throughout the country. ATCS operates generally in the 800-900 MHz range, except in the case of a lot of former Burlington Northern trackage which uses a slightly different system that operates on VHF frequencies. Any track controlled by absolute signals or hardwired CTC signals do not transmit these radio signals, meaning that much of the track between Newton and Lamy on the route of the SWC will be silent.

Go to http://www.atcsmon.com/ to read more about ATCS as well as hear a sample of what some of the transmissions sound like. Just note that the map indicating where this system is in place is largely out of date; most of the high-density CTC-controlled track in the United States has been converted to ATCS or a similar type of system.

 

[AKA]

We listen to books on CDs using a small cd player and hear the beeps very often. IIRC always on western trains. I always thought it had something to do with detectors.

 

[jis]

I just returned from a round trip on the Southwest Chief and recorded digital audio for my podcast throughout the trip. Occasionally, the recorder would pick up a several-second burst of high-pitched electronic blips not unlike Morse Code. I'm thinking this wasn't cellphone switching, since often the interference was way out in the middle of nowhere, where nobody had cell service. Could these digital blips be from track error-detection devices?

My recorder, a Sony PCM-D50, only picked up these blips when the train was in motion -- and during entire stretches of older track, didn't seem to pick the signals up as often. Of course, we were traveling a lot slower on those stretches, too.

That sounds very much like interference from some GSM equipment. That could be someone's GSM cell phone or GSM-R equipment if such is used by the railroad. That is why we ask people to keep their GSM phones away from Spekerphones and such. It happens only when a GSM equipment is very close to an audio equipment, like within a foot or two.

 

[lthanlon]

Any track controlled by absolute signals or hardwired CTC signals do not transmit these radio signals, meaning that much of the track between Newton and Lamy on the route of the SWC will be silent.

You are correct -- I did not notice any signals on this stretch. Sometimes, I could minimize the interference by changing the position of the recorder. Closer to the window generally caused the most problems.

 

[ourlouisiana]

Another possibility is the FRED -the telemetry device at the end of train. When we are using our scanner up in Texas to monitor KCS traffic, we get the screetching of the FRED's on a regular basis. Not sure if Amtrak uses the same system.

Telemetry devices make screetching noises.

 

[JayPea]

I've noticed this too. I spend many hours videotaping my journeys (so that whenever I want to go on a train trip, I just have to pop in a video or DVD!) and the audio from my video camera picks up those blips as well. I always wondered what that is.

 

[AlanB]

Not sure if Amtrak uses the same system.

Back when Amtrak was moving freight, FRED could be found on the rear of many Amtrak trains. But with Amtrak back out of the freight business, FRED is gone. Not sure if Amtrak sold them or still owns a bunch, but they definately aren't seeing use on Amtrak with any regularity.

Just as an FYI for those who many not know FRED is Flashing Rear End Detector. It's a device that both provides the red light required at the end of all trains in the US, as well as a device that monitors the air pressure in the brake line. And in an emergency situation where the engineer hits the kill button, FRED dumps the air from the rear meaning that the brakes are being applied from both ends of the train now. That allows for faster stopping then if the drop in air pressure only came from the engine side of the train.