19 Oct
2022
19 Oct
'22
8:24 p.m.
On Oct 19, 2022, at 3:10 PM, Chuck Guzis via cctalk
<cctalk(a)classiccmp.org> wrote:
Indeed, FM was one of the undesired side effects of AM unless you had a
well-isolated or crystal-controlled frequency source for your transmitter.
I suppose so, but Idzerda's transmitter produces FM with essentially constant
amplitude. It's a bit surprising given that it uses a carbon microphone as an element
in the tuned circuit, but that's what the oscilloscope shows. And it works very
nicely.
As far as detection goes, a simple AM "slope
detector" sufficed in most
cases for getting intelligible audio.
True, and that's how his listeners heard his broadcasts, since the discriminator had
not yet been invented. That also means, of course, that the "capture effect"
benefit of FM was not available to him, since you need limiters for that.
paul