Very Good Podcast I listened through Apple One of the things David mentioned was the fact that those Chinese transmitters start out clean but in a short time they become dirty. Mine done this and I even talked with the electronics engineer for the FCC about this. A lot of the issue is due to under rated parts and cheaply made circuitry. But also note that I also mentioned how the Whole house 3.0 after a longer time will do the same thing.
The characteristics of FM make it extremely easy to have a transmitter that is emitting spurs and harmonics without the operator's knowledge.
Will this hurt those who want to have a C-Quam AM transmitter? Possibly if the FCC goes after non certified transmitters of all types because Procaster, Talking House, Rangemaster seem to refuse making a C-Quam AM transmitter so those who want to continue to use it would be left in the dust of the FCCC starts to push only certified transmitters even AM.
Good to see a admins around here, this place has been going to the Dogs.
Mini FM transmitters seem like such a big market, I wonder why designers haven't improved the circuits enough by this time, it's normal progress. How do other transmitters have this figured out, ham, business band, cellular, police radios and portables in all of those services. You hear about problems, but rarely, considering how many millions of VHF and UHF radios are out there.
Do these small FM transmitters really have spurs and harmonics strong enough to be a problem? There are reasons authorities would bring that up, to play the fears of broadcasters and the public, but is it actually true? Are there sites rating these transmitters?
I like that Bob brought up kits and the practice of gathering parts and building something. That's a great pastime, and why Radio Shack and many other electronic part stores were in business. Electronic products are mostly disposable now, but I'd argue that for building from parts, there's no better time than now, parts are cheap, easy to find all over the world, and just a shipment away.
If you have skills, don't keep them to yourself, teach others or work with those who can't build to get their stations on the air. We can lift the weight of pre-packaged and certified and be free, and learn something while we're at it.
I try to build all of the reasonable kits out there, even just to see how the circuit performs. There's a lot more to a C-QUAM stereo transmitter, it's like you're building two transmitters, because of the stereo exciter section, and several times more complex.
Still, Chris Cuff had a kit out there, and so did Sean Cuthbert, so it can be done. Almost by default those are higher quality circuits, because you need the higher tolerances for AM stereo to work properly.