Ye Poor Man's AM Carrier-Current Coupling Unit! DIY'ers, run with it!

[ThaDood]

https://archive.org/details/ye-poor-mans-am-carrier-current-coupler-10-5-2024-experimental       Experimental Medium Wave Band Carrier-Current Coupling Unit for Broadcasting via FCC Part 15 Rules permissibly. I have had very limited time to work on this project, therefore, I am leaving it to the Open-Source DIY'ers out there to go ahead and run with this. There is no physical, electrical, connection from a transmitter's RF Output to the power lines, but it is all LC, (Inductively & Capacitively.), done to couple Radio Frequency signal to the AC power line. This will help alleviate the hazards and fear of electrical AC shock. That said, care and safety still needs to be observed. Power levels tested were as low as 2 milliwatts. VSWR stayed below 1.5:1 from 530kHz to 1710kHz. However, best coupling effectiveness seemed to be around 1200kHz. One possible problem with this method of coupling is that there is little, to no, Harmonic Suppression. Therefore, it is suggested to use a well filtered transmitter with this method of Experimental Coupling. Components are all listed on the crudely drawn schematic, and should be readily available. Try this and permissibly broadcast around your neighborhood, or just up and down the street. Ranges will very with power lines locations. You may get a few hundred feet, or even a few thousand. Go to it, and good luck!
BTW, while you are there, on Archive, check out the whole page for schematics, interviews, construction projects, manuals, etc., download and use. https://archive.org/details/@thadood   That page is growing, when I have time to add to it.

[Dave Richards]

This made me think of something. With the more conventional Part 15 AM transmitters that use a regular antenna as the radiating element, most of us have learned that re-radiation of the transmitted signal by the AC wiring of the building leads to 60 cycle hum. With carrier current, the sole intent is for the building wiring to radiate the signal. This begs the question - isn't 60 cycle hum a big problem with this type of broadcasting, and how can it be avoided?

I have virtually no knowledge of carrier current broadcasting, so apologies for the rather basic question.

Good point about the lack of harmonic suppression.

[ThaDood]

Hello Dave: What you are asking about is the plague of having Ground-Loop-Hum coming through the transmitter. There are techniques to help curve that, a lot. (1) - Do not use switching, non-transformered, power supplies, but use linear power supplies that use a total isolation step-down transformer. (2) - The other place to use 'Isolation Transformers' is at the audio stages. Mine, is at the STL to Audio-IN of the AM610 Carrier-Current transmitter. I bought the Radio Shack ones, while they were available. They are very effective. (3) - Have your transmitter and Coupler Unit grounded to its own independent Earth Ground, not the house wiring ground, or the indoor plumbing. If, you use the house wiring, and, or plumbing, then that can lead to two problems, Ground-Loop-Hum, where the components are the lesser path to a grounding potential, and also can lead to RF feedback into the transmitter. These techniques will help a lot to tame Ground-Loop-Hum. Now, walking through the house, with a portable in your house, you may notice some hum & distortion in various places inside from your AM Carrier-Current Station. Why??? Multipath of signals coming to your receiver from everywhere. You take your radio outside and your station's signal cleans right up. Less other signal path sources of your signal coming to your radio, and outside you want it that way anyway. Signal going to the power lines and radiating mainly from those. I hope that this INFO helps. Believe me, I didn't just learn this overnight. And, I'm still learning.  Oh yeah!!!! Boomer, of WAG AM690 found on the MBCF.net blogs someone thinking of trying Ye Poor Man's Carrier-Current Coupling Unit. (Scroll down a ways there.) https://mbcf.boards.net/thread/3143/carrier-current-coupler-construction COOL!!!! That's the idea.

[tybee]

Dan Braverman, former president of Radio Systems, Inc had addressed this very subject during an interview with Radio Survivor back in 2018. You can listen to the entire hour episode from the link down below (actually one of my favorites), but here's a  one minute clip featuring the part where he explained the reason it happens - which is quite different than what the Dood had to say; Mystery of Summer Camp Radio - clip (1:12): https://drive.google.com/drive/folders/1zR-yRhaNnhGdCAIYR4z4oM8w5i25GvRA

FULL EPISODE:
Podcast #148 – Solving the Mystery of Summer Camp Radio
"Did you know that upwards of 350 radio stations were established at summer camps across the United States? Dan Braverman, President of Radio Systems, Inc., joins us to share the history of summer camp radio, including his own experience setting up a camp radio station when he was just nine years old. Still involved with his youthful camp, Radio Free Ramah (WCRP) at Camp Ramah in the Poconos, Braverman chats about the power of hyper-local radio and how he built a radio business by initially setting up AM carrier current radio stations at summer camps."
https://www.radiosurvivor.com/2018/06/podcast-148-solving-the-mystery-of-summer-camp-radio/

[Dave Richards]

That's a lot of good info ThaDood. I have one of those Radio Shack audio isolation transformers. Guess I'd better hang onto it. Score!

Rich - I didn't hear any explanation of why it happens in that clip, other than him saying that the RF signal shares the wiring with the 60 cycle AC power, and that the hum can be all-pervasive. That's not really an explanation; just a general comment.

[tybee]

I know Dave, it was supposed to be a joke. Reason cc hums.. I guess it wasn't as cute as I thought.