Good AM Radio Transmitter Circuit?

[RoGeorge]

Here in EU/Romania, I remember as explicitly forbidden to intentionally transmit inside any broadcasting bands, no matter the power (but I might be wrong).  Though, there are ready made FM transmitters in the broadcasting 88-108MHz band, very low power, and they can be bought legally (mostly used for inside your car, to use the car's FM radio when there is no line input to connect your own player).

Just out of curiosity, those OTR records preserve the commercials, too, or just the shows?

[armandine2]

from Open University T327

[mojoe]

Just out of curiosity, those OTR records preserve the commercials, too, or just the shows?

Many have the commercials.

Interesting tidbit - for many years, the Jack Benny program was sponsored by Jello. During WW2, the sponsor changed to Grape Nuts cereal, due to the civilian sugar shortage.

And the most famous/infamous radio broadcast of all time was "War of the Worlds", dramatized by Orson Wells. I often listen to that program around Halloween. I think that there must have been only one surviving transcription disk of that broadcast. I have listened to several recordings of that broadcast, from different sources. All of them sound the same, including the part near the beginning, where the disk skips.

[MathWizard]

Cheap, simple & may be good enough.

I know there's TX's with 2-3 BJT's. I'm making an all BJT TX, and I'm already up to 7-8 BJT's, before any final output stage, or the audio input section.

I better make 1 of these 2-3BJT versions again, and see what they look like on a scope. If mine can't do as good as 1 of them, I hope an RF textbook will explain why.

[vorosj]

I constructed an AM signal source designed for old nostalgic tube radios.
It's based on the code found at: https://hackaday.com/2022/05/24/the-stm32-makes-for-a-cheap-diy-usb-soundcard/

I made modifications to the code, introducing additional lines to generate the carrier signal using a timer. The device resembles a USB soundcard. The modulation achieves around 90%, resulting in sound quality superior to typical AM broadcasts due to the broader bandwidth. The output involves a large coil for a near-field connection, resulting in negligible radiated energy.
Some pictures: