Carl Blare

Hello Fellow 15ers

Hello Fellow 15ers

By my blogs I’ve made it evident that I know a little but not a lot about the business of AM RF. Perhaps I’ve seemed flippant at times, but in the main I am very endeared to the low power hobby, and have utmost respect for all the sharing that takes place here.

I’ve explained that I see a corollary between acoustic science and that of electromagnetics, and have not been dissuaded from pursuing this point-of-view.

In acoustics some very long long wave-lengths have been packed into very small packages, and with our 3-meter antenna limit for legal Part 15 AM I believe every antenna experimenter is trying to do the same thing.

Somehow a blog on the web is not the place for a full technical paper on a subject but requires brevity, so I’ll limit what I say.

Think about the PZM microphone (PZM), which faces a capsule downward perhaps a 32nd of an inch toward a 5″X5″ groundplane, and manages to pickup the entire audio spectrum while canceling the normal standing-wave reflections that would occur with a normal microphone located many feet from the room boundaries. That’s why the PZM is also named a “boundary microphone.”

What would be the 3-meter AM radio version of the PZM microphone?