During a discussion in a german rr forum we asked us how are helperlocos controled in the US? Are they everytime manned, also the midtrain helpers, or are they radio controled? How safe is this system against misuse, maybe from the little boy with its walkie talkie?
Thanks,
Hello Michael ,
The UP uses both manned and remote controlled helpers.( AKA, DPU distributed power units) It a train has a mid train DPU they are assembled at the departure yard. Manned helpers are usually staged on the hill.
The DPU units are linked by a high frequency link and the remote unit must be programmed to the lead unit. The radio link is way out of reach of civilian radio freqs. Might even be microwave i’m not sure.
Yes, but what i want to know is the function of the radio control. How dooes it work and how save is this system…
The only failure in the system is in tunnels. If there are curves in the tunnels they must install repeaters. If something happens to the trailing units control box or loses radio contact, the unit drops its load and goes off line.
Do they use special coded frequencys? If they operate in the VHF band for example, somebody could build a small control unit and cause big trouble, or not?
It might be technically possible to ‘hack’ the frequencies for older versions of DPU and cause trouble, but you’d need an EXTREMELY powerful transmitter as the ‘codes’ are sent continuously (to mimic the effect of conventional MU control signals). If this happened more than once or twice (note I avoid saying ‘with frequency’) a couple of FCC agents with loop directional antennas would figure out the source of the interference, and press Federal charges, fairly quickly and effectively. Since to my knowledge all the DPU wireless activity is on licensed bands, revenge would be terrible and swift; mere possession of the equipment and not being ‘caught in the act of operating’ is enough to send you to the pokey with empty pockets and drained bank accounts…
Modern units use wireless protocols to avoid interference. It’s very, very, very unlikely that someone has the computer time, intent, and secrecy to break whatever kind of protocol is used (e.g. four-key WEP as in wireless networking), but all railroads have to do is go to rolling-key encryption and the task becomes hopeless… except perhaps in 5-to-10-second increments, during which time increasing or decreasing throttle settings are not likely to produce much havoc in typical operations.
What hasn’t been mentioned (and probably wouldn’t be unless I brought it up) are what are called ‘denial-of-service’ attacks, in which some idiot transmits garbage over the radio link with the intent of forcing the remote locomotives to ‘go off the line’ or shut down. This turns out to be rather difficult with proper wireless encryption methods that use multiple spread-spectrum carriers, as some form of wideband or ‘panoramic’ jamming is required, across a wide range of modulation waveforms as well as frequencies, to give the necessary interference between on-train transmitters and receivers.
The European ‘balise’ system of lineside PTC and communications has considered these issues in a different context. There are some fairly good
asking alot of “questionable” questions?