Total posts : 45366
“woah. i was under the impression that carrier current is only really effective inside the building you are using to transmit. boy was i wrong!”
The two main ways to run a CC system is coupling to the “HOT” lines or the “NEUTRAL” line.
When coupling to the “HOT” lines, the RF path is completed when the “NEUTRAL” line is connected to the neutral return in the coupler. In this way, the signal is riding on the electrical distribution wiring inside the building.
When coupling to the “NEUTRAL” in the breaker box, the RF path is completed by installing an isolated Earth ground with grounding rods and connected to the neutral return in the coupler. The signal is riding on the power utility neutral line, and can in some cases cover an entire small town.
“why dont standard field strength limits apply when doing carrier current? why is it legal to be covering an “entire town” using carrier current?”
There are standard field strength measurements that apply. It is 47,000/F = 15uV @ 30m. F is the frequency of operation. (15.221) Outside band emissions must be 20db down of the fundamental. (15.209)
It is legal because the signal is limited to the electrical line. It can emit from that line at the specified signal strength and distance per operating frequency.
For example, 580 Khz would spot your measuring point at 261 feet from the emission source…the neutral line. at 261 feet, your signal cannot exceed 15uV.
Now if the power grid distribution is configured in a certain way, such as it is in newly installed CC system by the Op of this thread, that neutral line is obviously a common neutral line spanning across the entire community. It is a small community, and this kind of power grid configuration where the neutral line covers a larger area than it would in a large city, is the reason why this CC system can cover the whole area.
Anywhere along the length of that neutral line that signal cannot exceed 15uV at 261 feet. It does not matter that this line is branching off in different directions covering the whole town, as long as that signal never emits off any of it exceeding 15uV at 261 feet.
Since the neutral line is the power grid current return, as well as the residents and businesses electric service return, the signal gets right where we want it, into the homes and businesses, and 261 feet off that neutral line wherever it happens to be at.
Super cheap? LOL!!! They are not super expensive, but certainly not super cheap either. A new CC system would run about 1,300 or so for both a transmitter and coupler. Extra costs would be ground rods and grounding wire to create the isolated ground system.
Radio Systems makes the currently available units. But you can find the famous LPB series on auction sites or at ham fests or the very rare old drive in theaters that used a CC system for the audio.
The LPB series used for CC vary in model by power range. There are LPB solid state models and tube models. There are also LPB couplers, the best one they ever made was the TCU-30. The LPB series was and still is the very best CC systems ever made. Unfortunately the company no longer exists so auction sites and lucky finds are your only hope there.