https://en.wikipedia.org/wiki/Template:AM_Stereo_radio_stations_in_the_United_States
Only 88 stations
"Stereo talk is effective if the staion is doing live talk with two persons, one on each channel."
Like this:
That is a very nice demo. I can see the draw to do it..
My idea was that since a loopstick could receive on the AM band so much better than a little piece of wire, and it could be tuned with a capacitor for resonance, that it would also be a great transmit antenna.
I had a little transmitter oscillator of some kind feeding the loopstick and the standard transistor-radio poly capacitor across it. It did work, sounded pretty good, but went about 30 feet max. Now I got more range by attaching a short wire to the top of the tank, the way the Radio Shack AM broadcaster kits worked.
The old Radio Shack AM broadcast kits used an air core loop on a plastic frame, not a loopstick! I thought it was to save money, or to teach kids how to wind a coil, but it was probably more efficient that way.
Since I'm learning about electronics, later I found out that the ferrite in a loopstick is used as a signal concentrator, so that the smaller loop can pull in more signals. Loops are low noise antennas that respond to the magnetic portion of the wave, and the ferrite bar helps a lot, but they just don't have the surface area to send out lots of signal on mediumwave.
For reception, high gain amplifiers have to be used, since pickup is low. Noise is also correspondingly low, so the system works.
Another problem that might be happening in transmit is that ferrite is not normally used in high-Q circuits with high power signals, so it might "saturate" and absorb a transmitted signal more. Ferrite is usually used for broadband coupling, like baluns and RF transformers at low impedances, and loss is very low, but a loopstick as we use them is putting a high voltage across the ferrite, and it might lose more.
That's where more study should be done on air coils and loops like on that guy's receiver page.
I've done extensive testing on this transmitter. In its current form, it's a joke. The modulation is low, the audio is dull, and you can't adjust anything. On a TX11a tuner, the stereo is unreliable. Mounted outdoors, I couldn't get it to broadcast in stereo at all. (Even the ASMAX transmitter, which is also very mediocre, had solid stereo when mounted outdoors, although its RF output was paltry.) I'm sticking with my SSTran AMT-5000's. Especially when connected to the external coil/pipe antenna described on the SSTran website, they blow everything away with both range and with audio that's loud, punchy, and clean. Yes, they may not be in stereo, but range and loudness are more important, especially in Part 15 broadcasting. Yeah, I would love to go stereo like everyone else. But until someone designs a Part 15 Cquam transmitter with the range, the clean loudness, and the design intelligence of an AMT-5000 - AND can connect to an external loading coil/pipe antenna combination for maximum performance - I'm not going to waste any more of my time on toys!