Idea for different carrier current coulpling method

That is one of many different coupling techniques. CC works by induction, no direct connection of the transmitter to the power grid lines. Though there are a couple of "dirty" methods that do go the direct connection method, they are not safe nor do they provide constant impedance load to the TX or present a low Q to the power grid's ever changing inductance.

Give your idea a try and let's see how it performs!

RFB

if it works maybe i will start building and selling them

About 5 or 6 years ago (and I know some of
you have heard this) - I had the output of
a 100 mW Panaxis transmitter going into a
big LC. The LC was a homemade BC receiving
loop with a tuning cap. I just cut into the
loop on the outside and fed the transmitter
hot and ground into it.

I tuned that for max strength on a radio. Then
I got a long extension cord, plugged the Panaxis
into it, and wound it over the loop. The
extension cord was only about 20 feet long.

I had to retune the loop because the extension
cord changed it's characteristics somewhat.
I peaked it up for max on the operating frequency
(750 kHz) and the signal was real strong all over
the house. I didn't think to go outside to try it
there.

Go for it.

Best Wishes,
Bruce, DOGRADIO STUDIO 2

be nice to come up with an inductively coupled CC atu that automatically samples the 50 ohm side of line and automatically adjusts the tuning through the course of varying loads to consistently keep the best match possible.

the same theory could be used for outdoor mounted part 15 transmitters using a 3 meter whip.

"the same theory could be used for outdoor mounted part 15 transmitters using a 3 meter whip."

The TH 5 has that. Just connect it to a whip instead of the wire.

The "line" side wont be 50 ohms, more like 2 and less on the hots to neutral and above 50 from isolated earth ground to neutral.

The very wide swing of inductance that occurs on the power grid would require a sampler also capable of "seeing" this wide variance. Not that big of a deal really....but...these variances happen in time intervals and durations from microseconds to hours. Most of the changes take place when the grids are well loaded (evenings/mornings).

Now the trick would be to have the auto-sampler-coupler be capable of tracking these changes closely to maintain maximum RF transfer efficiency, but at the same time constantly provide the transmitter a proper match..ie 50 ohms while the auto-sampler-coupler compensates for the "line/neutral" side of the system.

Another consideration is that the coupler needs to perform as a low Q, high pass filter, and do that while auto-adjusting and maintaining the match to the TX. This is to isolate the TX from the grid and prevent 60 cycle AC energy from feeding back into the output of the transmitter, which would otherwise modulate the final and produce hum.

Hope that gives some guidelines for your great idea for an automatic CC coupler. Go for it!!! 🙂

RFB

it can monitor the RF current and be set to tune for max current during sampling periods. say in 5 min intervals.

kind of a more advanced version of the neon bulb trick where you tune for maximum glow.

Maybe a photocell next to the neon bulb for the feedback loop...

i think a current sensing loop on the low impedance side of tuner. i don't know how much i like the tuner in the talking house.

was thinking more along the lines of a large motorized air variable coil or relay switched taps on an air wound coil with a large motor driven variable capacitor.

"was thinking more along the lines of a large motorized air variable coil or relay switched taps on an air wound coil with a large motor driven variable capacitor."

Reminds me of the earlier tuned circuit couplers. Those were a royal pain in the peak. They constantly had to be tuned to the changes on the line side and never provided adequate attenuation of 60 cycle energy feedback.

They were not very good at isolation between the grid and the TX output. A slight change in line impedance and tweaking of the line side tuning would throw off the match between the input of the coupler and output of the TX...requiring tuning from start to finish all over again...all the while you could be re-tuning right in the middle of a large change on the line side or coming out of a change. It was like riding a swing back and forth.

I recommend working around ferrite core toroid inductors in place of the air wound coils and variable caps. Use a bank of caps switched in or out with relays and the same with the in's and out's of the ferrite core toroid inductors.

Their low Q will give you all the isolation needed as well as the wide window needed to look through the line side changes and adjust for them while at the same time maintaining the isolation factor between line and TX output.

But if going for the old school approach, try to make the couplers individual sections isolated as much as possible to avoid interaction between them and the surroundings. Enclose the whole and set up compartments within the whole to separate and isolate each section from inductive reactions to each other.

RFB

For anyone interested in exploring carrier current this topic of couplers is of great interest. The discussion so far has made me wish for a well documented paper that covers the subject, past and present, with plenty of illustration and clarified detail so it can be easily studied by us "half-wits" who know just enough to realize what we don't know.

Since there is an "old way" of making couplers which constantly required tuning, then that says there is a "new way" of making better couplers.

Where are the schematic diagrams of both kinds?

So let's state what we know....

1.) The transmitter has a constant output of 50-ohms which needs to be matched constantly;

2.) The AC power line only has a "constant impedance" at a given moment in time when there is no "on-line" activity," but every appliance or device that is switched on or off causes the line characteristics to change over a wide range;

3.) AC power lines contain a strong 60-Hz signal-level which must be blocked and kept from back-flowing into the transmitter's RF output circuit, but the "neutralizing" of the 60-Hz signal must not prevent the RF from the transmitter from passing into the AC line. Changes taking place in (2) will cause the properties of (3) to change and will put (1) out of match.

That's all. Make me a detailed paper and report back on Tuesday.