Carrier Current and me

There are transmitter designs in the Library section here on the site.

But I have yet to find plans for building a coupler to be able to match the transmitter with the power line.

Radio Systems is the only source of new CC equipment, at about $3k

RFB is the resident expert on CC

All part 15 stations should plan to add CC to their collection of radio stations.

I have been working with homemade
couplers on and off. I did quite
a few experiments back in the spring.

A friend had a coupler he was going to
lend me to use with an LPB RC-6A. I don't
have time for that now, but
will in the future, no matter where we
end up living.

Lefty, you might want to check the
very very long carrier current thread.

And Lefty, how experienced are you in
building electronics? Building a
CC transmitter would be a big big
project.

There is tons and tons of stuff on
the CC thread.

Best Wishes,
Bruce, "GNAT 90.9"

There are a few ways to approach it. One would be as you already hinted to, building a system, which obviously is a big undertaking.

Another way is to use an existing low power transmitter as an exciter and feed a linear amplifier and then a coupler.

Bruce's coupler experiments are a good example for a home built coupler.

Or just keep tabs on auctions and estate sales. Every so often equipment will show up at those places.

RFB

Yup, the carrier current experiments
here will resume when we figure out
where we are going to live.

They sure were fun!

Bruce, Gnat-90.9

What would happen if we ran Carrier Current and another transmitter with an intentional radiating antenna BOTH ON THE SAME FREQUENCY?

The interference we might cause would be our own.

What would it be like?

Carl,

Somewhere on this forum RFB posted about that scenario.

I'm interested in running both carrier current and intentional radiator, as you suggest.

A few years ago, my radio colleague, Erwin, took me to the little sleepy coastal town of Carrabelle, Fla. He told me an engineer there was running a 5 watt carrier current system on 1610. It was 0n the air, and sounded great. Carrabelle is very small, and is mostly laid out like a rectangular grid. The C-C station covered Carrabelle, and a little beyond, but faded quickly once you were out of the town.

Erwin lives in another small coastal town and runs a Rangemaster on 1610. The Carrabelle C-C station appears to be off the air and defunct now.

Nevertheless, that C-C station sounded great and appeared to be totally legal. There are NO AM stations in Wakulla or Franklin counties. So it appeared to be providing a useful service..mostly bluegrass music, and coastal weather and tide information.

I've been intrigued with carrier current ever since.

Carl, we'd be back to your discussion of Part 15 devices interferring with Part 15 devices.

If not perfectly synchronised there would be heterodyne interference and you'd be interferring with a Part 15 device.

(a) blames (b) who says its (c) but (c) said (a) and (b) plotted a conspiracy to take out (c) when it was (c) that started the whole thing!

PARADOX!!!

It's fun to imagine what it would be like to exist in multiple places, multiple dimensions at the same time yet a different time and yet in a different realm, all occupying the same existence.

I think then I would be a "Q". 🙂

RFB

"Carl, Somewhere on this forum RFB posted about that scenario. I'm interested in running both carrier current and intentional radiator, as you suggest."

There is a way to have both..from one transmitter.

And it goes like this:

Transmitter feeds a power divider. One port has about 10 percent of total power to the divider and the other 90 percent. The port with the low ratio would run to a 3 meter antenna, or the leak coax. The port with the high ratio feeds your coupler.

If further attenuation is needed on the low port side, simply attach inline attenuators to tame that down, which will not affect your coupler side.

Obviously you want the CC side to be tuned up and your power level set for the required good coverage but not excess power that's simply inductively putting your programs on the neighbor's telephone.

So if you got your CC side at 1 watt, that low side will have .1 on the low side. One transmitter, one signal, no hetro petro dial a dancin wobbly going on.

Some trouble CC installations used this approach to solve coverage issues in some buildings where that coverage was not uniform. Some would use a leaky coax, others would have a short wire or rod attached to the end of a coax which was fed by the low side of the power divider.

Before the song and dance begins, yes there is the concern about the low side pushing a wire, which is why the leaky coax approach is best.

But who says you can't hang a 10 foot long piece of leaky coax terminated with the proper load at the top and spreading it's love over your typical ground radial system? As long as that signal hits the 157,000/F 15uV measurement point on target, well your following the leaky coax rules in 221.

Though I have never seen a 10 foot chunk of leaky coax hung vertically over a ground system and properly terminated, but may be something there to investigate. 😀

RFB

From my simplistic way of interpreting what RFB has proposed, the free radiate output would fail under Part 15.209.

My thoughts are that the definition of Part 15.219 states the power input to the final RF stage excluding filaments is limited to 100 mW.

In this case, the transmitter final RF input power is far in excess of that. If there were a complaint filed the subsequent inspection would point this out and state the station would be subject to Part 15.209 and would fail the field strength limitation.

There may be a way to accomplish RFB's splitter method of feeding CC and radiated...

The side chain aimed at the radiant system can be designated a cable system, as are used for radio/video cable systems. Not leaky cable, but shielded fully enclosed cable, terminated at its end in 50-ohms.

But a 3-way tap somewhere along the cable can feed an AM repeater amplifier, which is a final stage alone, with 100 mW input power adjustment, and proper LPF on the output to the 3-meter stick.

Such a repeater was once to be found in the library section, but I couldn't find it just now in a quick search.

Such a cable system can be extended all the way from one end of a lot to the other, with 3-meter antennas at any point along the way each driven by its own repeater. Good loading coils can be added as well. Power to the repeaters can be phantom carried on the coaxial cable.

But for all the effort it may be overkill because the radiant signal would be happening in air space already reached by the allowed radiation from the power lines.

I withdraw the whole concept.

"If there were a complaint filed the subsequent inspection would point this out and state the station would be subject to Part 15.209 and would fail the field strength limitation."

That's what the inline attenuators are for, so that the free radiate output meets that 209 field strength limit.

That's not hard to do especially in a confined space where just a tad bit of free radiate helps, which you can get from either a leaky coax or a free radiate piece of wire meeting 209 field strength limits.

If your intention here is to try to pass that free radiate as a 219 well duh! 😉

Besides, you cannot have an LPB TX 2-20 transmitter feeding your 219 setup even if that transmitter is adjusted to only put out half of 100mW. This isn't about 219, its about 221 and 209.

The approach Carl hints to is again similar in how an extended cable fed 239 system would work. At each interval along the main feed cable, a small junction box with an antenna is adjusted for 250uV @3m. Then 100 feet or so another box, and another.

Same can be done with MW, except the better way is to simply run an array of leaky coax. Placed just right, and the lower band frequencies, that could cover a nice sized area with solid clear legal signal.

RFB

RFB, I guess I missed the part where you said this would be a 15.209 installation. So I'm still guessing that a full .1 watts to a 3 meter antenna would exceed that limit.

Most agree that 15.219 field strength far surpasses 15.209.

I like Carl's idea of using it to feed remote repeaters. This is a very old idea published some time ago. Somewhere in the archives here should be a schematic from that publication I posted here. The coax signal can drive multiple repeaters providing both DC power and modulated RF to each repeater on the line.

"So I'm still guessing that a full .1 watts to a 3 meter antenna would exceed that limit."

That figure was just a base example without going through all the blah blah, and to save on typing! :p

"Most agree that 15.219 field strength far surpasses 15.209."

So do I. As I said in both post and response post, it is a limited area "fill in" technique used in CC systems. Not any sort of thing to intend to shoot a signal like a 219 system.

And yes one method of extending the 219 system is feeding an array of 3 meter whips at intervals along a main feed coax.

The same method, a main feed coax, is used in two other ways. The leaky coax method, and a regular coax feeding multiple couplers for CC.

Hope that helps! 🙂

RFB