Talk:Carrier current

European Systems are not carrier current

Think the article is confusing these systems with true "carrier current" systems. A carrier current system uses public electric lines as an antenna with the intention of the signals radiating from the lines to be picked up on conventional broadcast receivers. The "European systems" are (intended to be) closed networks which use electric or telephone lines to carry programming to subscribers (often using dedicated/proprietary equipment). While signals from the latter systems may sometimes also radiate short distances this is unintentional and is regarded as a flaw rather than the aim of these networks. The nearest analogy to carrier current used in Europe is probably the "induction loop" systems used in some British hospitals and universities to distribute programming to receivers located on campus. Even these are not true carrier current systems as they use dedicated wiring rather than electric mains. I would suggest moving the section to an article called "cable radio" or "wired radio" 94.2.188.218 (talk) 19:57, 2 August 2015 (UTC)

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Highway warning systems

The following, which I added (in 2014), was deleted, with no explanation. Would someone please explain why it is wrong?

It is still used for highway emergency warning systems ("Tune AM 1680 for message when flashing").

These are commonly seen in the U.S. Thank you. deisenbe (talk) 19:02, 1 June 2017 (UTC)

But that's for cars rolling along the highway - not carrier current at all. --Wtshymanski (talk) 19:19, 1 June 2017 (UTC)

Are you sure they're' going through the air? Typically, at least 50 years ago, the signals went through power lines, until they hit a transformer, which stopped them. Cornell's station worked that way, got almost to Elmira. If the highway warnings were broadcast, there would be an FCC permit, and there isn't, though I've only checked AM Florida 1600-1700. Carrier current stations do not require a license (~https://www.fcc.gov/media/radio/low-power-radio-general-information#CARRIER) deisenbe (talk) 19:52, 1 June 2017 (UTC)

Travelers' Information Stations won't be found in the AM broadcast database; they have their own, accessible via https://www.fcc.gov/media/radio/travelers-information-stations-search Hertz1888 (talk) 20:19, 1 June 2017 (UTC)

We're still talking about something you tune in on your car radio, right? There's no wires attached to your car. So, no carrier current. --Wtshymanski (talk) 22:07, 1 June 2017 (UTC)

As noted above, and in the Wikipedia Travelers' information stations page, in the U.S. these are normally small over-the-air transmitters that have to have licences, and for the stations I've heard it is not uncommon for them to include their call letters as part of their standard recorded messages. But now that I think about it, are there "tunnel radio" transmissions that use carrier current? There are no long tunnels nearby where I live to check, but it would make sense to use carrier current to reach drivers that are underground.Thomas H. White (talk) 22:19, 1 June 2017 (UTC)

But unless there's a wire from transmitter to receiver, it's not carrier current. The tunnel systems probably use a leaky feeder (will that be red or blue?) system. Not carrier current.--Wtshymanski (talk) 22:23, 1 June 2017 (UTC)

Carrier current transmissions can be picked up for short distances, on the order of 60 meters, from the electrical wiring that is conducting the signal. (I remember to listening to WUVA, on 640 kHz, as a carrier current station on my portable radio, even when it wasn't plugged in.) The FCC rules allow for even greater distances for colleges, as long as the signal is restricted to the campus.Thomas H. White (talk) 22:32, 1 June 2017 (UTC)

Do we know if the roadside information systems use existing roadside power wiring, or do they have their own feeder lines not used for anything else? --Wtshymanski (talk) 00:01, 2 June 2017 (UTC)

This is getting too indented, so I'm going back to the left margin.

It's not correct that carrier current implies a wire connection. That's not radio at all, it's a PA system or something like it. All alternating current (AC) systems emit "waste" signal. Every TV and radio set and cell phone does, although it can be so tiny as to be undetectable without special equipment. In the U.K., I understand, engineers in vans drive around with sensitive detection equipment trying to find unlicensed TV receivers by picking up this waste radiation given off by the receivers. (TVs in the UK are licensed and there's a fee.) Put a big AC (AM radio is AC) voltage on a wire and it's going to radiate for quite a few feet, in all directions; that's carrier current. (If you want to get into the physics of it, FM and TV are also AC, but it's much more complicated, and in the US, to my knowledge all Traveller's Information stations are AM.)

I was not aware that the FCC had a category for these stations. I've learned something. Thank you. deisenbe (talk) 02:08, 3 June 2017 (UTC)