Is carrier current possible under part 15?

To the best of my knowledge Carrier Current, transmitting radio by way of electric power lines, is 100% a Part 15 technology and that no other form of carrier current exists.

The main rule we usually look at is 15.221 - Operation in the band 525-1705 kHz, which gets into carrier current, leaky cable, and a special radiation allowance for intentional radiator systems on college campuses.

But other bands also have Part 15 carrier current regulations, such as the "baby monitor" long wave channels and shortwave application of carrier current.

The trail of applicable rules can be overwhelming if every cross-reference is tracked.

The FCC enforces carrier current for radiation field strengths surrounding the power lines, but we have noticed no published violations pertaining to carrier current, but that may be because it is not very popular right now, or that people who invest so much for equipment are more likely to use caution.

Excellent news.  I'll look up 221.  Seems ideal for indoor-casting, which happens to be my application.

I'm broadcast trained from a few decades back.  I've been toying with doing a station themed with recreating a historically accurate 1947 AM music news weather channel.  Local-cast using modern hardware but setup for the classic 'valve' feel.  

Cool info, thanks!

Like others, I've tinkered with carrier current.  Connecting the conventional way to the hot and neutral was OK in house and maybe down the street a little but never went beyond the secondaries feeding the houses.

Switching to neutral injection where the neutral is fed the RF and a separate isolated ground is used for the other side, I was hearing my signal all over town.  And it seemed to be following the power lines as when I was inbetween or in an area with rear lot lines I lost my signal.

By the way, Ken is our newest member at The ALPB Forum page.  Welcome aboard!

Since neutral is tied to ground how does that radiate?

Apparently since this is RF, there is enough RF impedance between neutral and an isolated ground to allow the signal to develop on the neutral.

I had the same problem accepting the concept since the neutral is bonded to the earth ground in the circuit breaker box but accepting the idea of RF impedance between the neutral and isolated ground makes sense.

At first I figured I was receiving "free radiate" signal as though the neutral was simply acting as a poor antenna but the signal does seem to follow the power lines on the street.  If I'm in an area where the power lines are "rear lot" lines (not on the street) I have trouble picking up the signal.  This makes it appear the signal is follwing the power lines.

When first configuring my CC system I tied into the 3-wire 220VAC circuit, which is the most conventional way to connect. But it would not properly tune and the SWR (standing-wave-return) was dangerously high.

Next I tried the neutral injection technique, after having a construction worker who happened to be tuck-pointing, drive an 8-foot copper into the earth, and it matched right away and I was in business.

The power-pole transformer feeding the house also serves about ten other homes, and my radio signal followed those lines along the street, per the auto radio.

But beyond my own transformer's lines the signal dropped to nothing right away, at least on the car.

Based on all the reported experience from many CC users over the years, results vary so widely that even the spec sheets from the manufacturers warn about the "wild wilderness" of the power lines when it comes to CC radio.

My transmitters are out-of-service and need nursing, but it will be back.

carrier current coupler

It's good to see others talking about this.

Hi all , No i'm not gone , just working hard.

Never the less if any of you have built a carrier current coupler or have any schematics on this I sure would be thankful for this.

I am looking at AM Stereo with A Chris Cuff transmitter and a linear to get the signal to the carrier current coupler . I would run about 4-8 watts at 1610 AM.

It seems to be one of the best ways to get our signal out farther.

But I won't know until I give it a test.

Anyway I want to build my carrier current coupler unit as the costs of buying one is way to hi for my money these days..

Take care all.

Lefty..

It was just last Saturday when we wondered how you were over at the ALPB Meeting. After all, we are meeting because YOU INVENTED THE ALPB!

By talking about DIY CC Couplers, that is a project that has never been finalized by anybody as far as I know.

RFB had ideas of building a coupler and I know that Bruce MICRO1700 has experimented with self-made couplers, but we have never seen any finished result so-far.

You can get a sort of basic clue about coupling by looking at the schematic for the baby monitors that used LW (long wave), which used carrier current as their mode of operation.

I was going to buy one from Radio Shack but I think now all the baby monitors use wi-fi, so eBay might be the last hope for finding the older gear.

If a coupler were poorly designed the entire house might become a July fireworks display.

I'm figuring I'll homebrew a coupler and drive it with my amt3000.  I'm not expecting much.  My guess is a balun, a good copper rod ground, and a few fuses for safety should be adequate to inject signal into neutral relative to earth ground.

Why not experiment with a L tuner (random wire) capable of tuning to the 160 meter band. Use proper isolation and it should work?

Will look at that, thanks.  Probably a lot smarter to impedance match rather than try to get the power lines to resonate.  🙂

Hello there!  I'm Bruce,  one of the

people who messed around with home

made CC couplers. 

I made coupling coils and used different

coupling caps, etc., etc., and so it went. 

I WAS afraid of "burning down" my house,

and everybody who messes with this stuff

should be - and also electrocution - you know -

these "pleasant" things that are in your mind.

That is what makes you careful. 

Anyhow - to make the transmitter happy - I

built a 10 dB pad that went between the

transmitter and the coupler. 

My transmitter is a classic old LPB RC-6A

vacuum tube unit - which is 5 or 6 watts out. 

So most of the energy goes into the attenuator,

and the SWR on the transmitter side is always

low.

I made a coupler that was working - at least

partly - meaning that energy was going

into the AC line and staying in the line.  It may

have been very inefficient - but

from that standpoint the experiment was a

success.  It made me happy.  The testing at

neighbor's houses is a long story, but the last

house reached with my CC RF

was about 1000 feet away from my residence.  

And because of the 10 dB pad after the 6 watt

transmitter - as we know - the power going into

the coupler was about 600 mW.

We were faced with the problem of moving from 

one house to another.   A lot of RF gear was moved

and I lost the coupler!  But that's OK.  The experiment 

will continue. 

I don't have a Part 15 station on now.  But there will 

be another one.  

So anyhow - I said a lot of thinigs in this note. 

But the real message is that the RF attenuator

was a huge help.  Anybody who makes one

should be careful and make sure the circuit

and it's components can absorb the RF power

from the transmitter side.  You don't want

the attenuator to burn up!

Bruce, Monitoring Station, Connecticut

(Alao many Part 15 stations in the past  -  and

other weird radio experments - and 

the 1700 kHz over the air operation, which is greatly

missed.)

Carrier Current transmitters are interesting because there is not automatically a "best" RF power to feed into the AC Power Lines. If the coupler achieves a good match into a system you will need less CC output power to meet the FCC field strength limits.

The maximum power allowed in the rules into the power lines is 50-Watts, but that is very often way more than is legally needed to meet the field strength limits.

Confused? Yes, no wonder. The maximum transmitter power allowed for CC is 50-Watts, but the field strength limit must be met regardless of how much Wattage it takes to meet it.

For me 2-Watts seemed to do wonders, but in tests I went up a volt at a time... 3-Watts, 4-Watts, up to 7-Watts... my transmitter is capable of a max of 20-Watts, but nearby radios started to overload at about 4-Watts, so I backed off.

The later model LPB solid-state transmitters have variable RF power controls, but Bruce's tube transmitter needs his external attenuator circuit to reduce the output power.

When working with AC power be sure to jot down a Last Will just in case.

that isolation cap between the homemade coupler and the

AC line.  In the commerically available couplers,

it's already in there, but if you build a coupler

yourself, you HAVE TO put one in or you will

shoot your radio station and yourself to the moon!!!

I can't say any values because no two situations

will ever be the same. 

I could never imagine using a power like 30 or

50 watts.  My 600 mW overloaded the bedroom

clock radio.  The signal was all over the AM dial. 

Every radio in the house was pretty much blown

away. 

As for using a transmitter like the SS Tran AMT-3000 -

yes I would very much like to do that, too.  I treasure

my LPB 6 watt tube rig, but it is 40 plus years old

and is starting to get undependable.  I don't think I

would leave it alone and unattended for too long. 

My AMT-3000, however, will run forever.  It will also go on

620 kHz, where I want to be.  The LPB is on the

best channel I could get a fundamental crystal for,

and it's OK, but is not really where I want to be. 

I think some people have said that the lower on

the AM band you go, the better.  Well, the LPB is

on 1020 kHz, and getting it to run there was difficult. 

(But 1020 kHz was the best crystal I could find for

a useable AM channel during the day - and forget

about nighttime.)

So the SS Tran would be great - even at a low power

level.   Yes, we do have to think about impedance. 

The commercial CC transmitters all want to see

50 ohms, I think.  So the input to the couplers

is always 50 ohms.(?)  The SS Tran's impedance is

nowhere near there, so I am lost.  I don't know what

to do about that.  

Bruce, Monitoring station, CT