Railfan Technology > Would PTC Make Railroad Communications Go Digital

Well luckily for the subdivision isn't supposed to have PTC installed until 2016 as I have heard from one of the signal maintainers after popping the subject up, but it has got me wondering, since PTC is a new technology which I'm sure is digital, it's got me wondering if the railroad communications from the Positive Train Control will become digital as well or not? Thanks for your help for whomever provides it

I don't know what they will be using, I'm only guessing at this time. The PTC activities appear to be mostly in the 220-222 MHz range. There may be some in the 160 MHz and 900 MHz bands also. I don't know what each frequency will be used for. At this time in the evolution of technology I would suspect that the communications would be digital FM. It's a natural, taking a digital payload and interfacing it with a digital capable radio. Anything else would require additional equipment (modems, etc...) and would be a less reliable link. The current digital technology would allow a faster throughput with less errors than an analog system.

As far as I know, this has nothing to do with the narrow banding and migration to NXDN although it may incorporate some of the same technology such as the C4FM modulation format.

Here's a bit of good news in case you desire to monitor the PTC frequencies. The Amateur 1.25 meter band from 219 MHz to 225 MHz. On the frequencies allocated for PTC, Amateur Radio is a secondary user. Hams can use the frequencies provided they do not cause interference to the primary user (PTC.) There are radios on the market today that cover the PTC frequencies.

Thanks for asking the question. It's going to cause me to do some research on the project

John

PTC communications will certainly be digital, but PTC communications will be additional and not replace any current communications. So even if PTC is cut in on your local subdivision you should expect to continue to hear voice communications between the dispatcher and train crews just as you did before. Hot box detectors and things like that will continue to be on the voice channels. If you are receiving RF codeline communications using ATCSmon or something like that, they will continue to operate as they did before PTC.
Down the road the railroads will likely work to consolidate and make better use of communications channels, but with the rush to get PTC installed ASAP very little if anything is being done except what is required.

Stephen

wa4umr Wrote:
-------------------------------------------------------
> I don't know what they will be using, I'm only
> guessing at this time. The PTC activities appear
> to be mostly in the 220-222 MHz range. There may
> be some in the 160 MHz and 900 MHz bands also. I
> don't know what each frequency will be used for.
> At this time in the evolution of technology I
> would suspect that the communications would be
> digital FM. It's a natural, taking a digital
> payload and interfacing it with a digital capable
> radio. Anything else would require additional
> equipment (modems, etc...) and would be a less
> reliable link. The current digital technology
> would allow a faster throughput with less errors
> than an analog system.
>
> As far as I know, this has nothing to do with the
> narrow banding and migration to NXDN although it
> may incorporate some of the same technology such
> as the C4FM modulation format.
>
> Here's a bit of good news in case you desire to
> monitor the PTC frequencies. The Amateur 1.25
> meter band from 219 MHz to 225 MHz. On the
> frequencies allocated for PTC, Amateur Radio is a
> secondary user. Hams can use the frequencies
> provided they do not cause interference to the
> primary user (PTC.) There are radios on the
> market today that cover the PTC frequencies.
>
> Thanks for asking the question. It's going to
> cause me to do some research on the project
>
> John

No John, the 219-222 portion of the 1.25 meter band is strictly for users like the PTC project as well as others. Us hams are not to use that portion of the band. Granted there are some anticipated use on the 1.25 meter band coming up with for profit companies, there is objection currently coming from the ARRL directed towards the FCC about granting commercial users more spectrum within the entire 1.25 meter band and to not limit the companies solely to the tiny portion of the band like it is currently. Despite us hams being the secondary users of the 70 cm band, the FCC has been granting businesses parts of the 70 cm band we use causing more concern over whether this band will stay as it started out being used by the government and them us hams. There even discussion ongoing on whether to allocate other UHF bands whose frequencies look appealing to commercial businesses putting using those bands off limits to us hams in the immediate near future.