carrier current coupler design?

Much of the available info, some which can be found in the forum library will have a design or two for couplers...very BASIC couplers.

These couplers will work, but they lack a few important things like proper transmitter matching and isolation to the load, lack of effective 60 cycle hum return, and quite honestly bad to one's health by simple shock and/or fire hazard.

Although hard to find and rare, your better off finding a real coupler that is designed with all those safety and features I mentioned. Usually auction sites are where to find them, or you can throw down the mula and get a new one from Radio Systems.

Building one like the LPB or Radio Systems coupler is not too difficult, you just need all the parts necessary and skill in winding toroid transformers, with multi-winding turns of several wires wound together.

The actual power, or raw power one can place onto the line is 50 watts, but your not going to need that much trust me.

With either an LPB or Radio Systems coupler, each are actual couplers, at most your ERP out of the line is 1 watt..if that. Field strength is determined by frequency of operation. The lower the frequency, the longer the distance is for the maximum field strength, or basically when your signal must dump into the noise floor.

Carrier Current is a controlled method of broadcasting..wired wireless. The intent is to keep the signal following an already established pathway..the electrical wiring in a building or neighborhood. It is not the intent to turn the power grid into one gigantic mass radiating antenna like a conventional antenna. Our goal is to get our signal to travel along the length of those power lines so that it delivers a nice clean signal right up to the listener's power socket and wiring..like having all your listeners sitting within 200 feet of your transmitter feeding a short single antenna wire. But here your listener may be 5 miles away because their radio is near the power wires and your signal is riding on those wires. Their radio is not relying on a long distance through the air picking up the signal from a radiating vertical tower.

Study Part 15.221 and the technical specifications in 15.209 for in band and out of band harmonics. Begin your hunt for the gear at auction sites or craigslist. Might even check around at estate sales. It may be awhile but well worth the wait in finding a true to the bone coupler that will make your CC endeavor less painless. I wont kid you, CC is an art form that is in a state of flux and requires unique solutions to overcome problems at every different location. There is no one method fixes all in CC. And sometimes it may take you several days to several weeks finding the right combination of coupling point, grounding method and frequency of operation depending upon load conditions of the grid during a 24 hour period, which btw constantly changes and the coupler must compensate for that while maintaining transmitter load matching and isolation.

The "fake" couplers..as I call them...using a high voltage capacitor, inductor and fuse...is a hazard waiting to happen IMO, and they do not compensate for line side changes nor do they provide the 60 cycle hum isolation and rejection, nor do they provide proper constant transmitter matching when the line side inductance swings back and forth. It would be like watching your VSWR meter swing wildly from minimum to maximum, spiking and surging the transmitter output and POOF...there she blows.

In those resources within the library are some good CC transmitter designs and well worth the consideration..but the couplers...I would not consider those except to perform tests and experiments, but for full time broadcasting no.

RFB

RFB, you one time mentioned that you might design an efficient coupler and I wonder if you are continuing on your self-designed coupler project?

As you pointed out, a good coupler is hard to find.

The coupler I had in mind would be to interface with the TH series transmitters with the external antenna F connector with an impedance of 75 ohms, but should work fine for any other TX unit with either a 50 or 75 ohm output impedance.

I have not looked at working one up for the high output impedance transmitters such as the AMT3K or 5K, though from what I understand those have the ability to run at the lower impedance by way of jumpers and inductors internal to these devices.

I have a working prototype on the bench and at a pause point to consider adding a 10 step wafer switch to select various line side impedance matching and a 5 step wafer switch for capacitive cancellation.

But as I pointed out, this particular prototype is wound on the input side for 75 ohms. Though not far from 50 ohms, for maximum transfer and coupling efficiency, I may have to rewire the input side of the toroid and put a selector there to choose from 75 ohms or 50 ohms.

Of course all the add this and add that adds to the overall cost of the thing..not to mention complexity in the design itself. There is more paperwork here filled with calculations than space being taken up by the coupler itself! I took a break because of a headache. 😉

RFB

RFB, i am interested in your proposed coupler design. i have a little experience with rf design and have built some of my own qrp gear for the ham bands.

can you recommend any literature on carrier current design?

The only real good publication..which is decades out of print is an old 1940's ARRL handbook which has a ton of great info about CC systems. Thing is tho, that publication dealt with the components available at that time. Ferrite core toroid transformers did not come around until the late 50's early 60's. These ferrite core toroid parts were the breakthrough for CC systems.

Before these "space aged" parts came into being, most of the coupling techniques used lumped tuned circuits which were prone to drifting and constant tuning to match up to the lines and maintain transmitter loading. They were not effective in preventing 60 cycle hum, and they did not compensate very well to the varying power grid inductance changes from one hour to the next. They were literally a nightmare to deal with.

My coupler is based somewhat on the LPB's TCU-30 unit, with the exception of the meter, decade bank and selectors. This coupler of mine is intended for the TH V5 units as an alternative to the wire or lack of having the range extender ATU. It is currently set for 75 ohm input but that can be changed..which I am looking into adding a 50 ohm winding along with the 75 ohm winding with the capability to select between these two.

The output is currently wound to see a line impedance of 10 ohms and less. It seems to be functioning well at this point but not everyone's power grid is going to be like mine and so this thing will need to have some selectivity for the line coupling side.

It's not quite ready. 🙂

RFB

Dear RFB

We are lining up to order your eventual CC coupler. I dream about it and place my hopes on it.

If I never do another thing in life, I want to broadcast carrier current.