On Jun 23, 11:42 am, Jerry Avins wrote:
Paul Keinanen wrote:

...

Even with a proper S&H (ten nanosecond sampling and several
microsecond hold times) for decimation, the 280 Ksamples/s sounds a
bit low for FM broadcast detection. The higher order (Bessel function)
sidebands are still quite strong with the modulation indexes used, so
truncating the bandwidth to the 100-140 kHz range might not be a good
idea.

...

The IF passband of an FM receiver needs to be at least 200 KHz for good
quality and -- counterintuitive to me -- I'm told that the capture ratio
improves as the bandwidth increases. Back in the 50s, one premium
receiver -- the first I knew of to use semiconductor diodes in the
detector -- had a half-MHz IF.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

Assuming cochannel signals with small power difference, as the BW
increases the weaker
one will hit threshold (knee in the SNRout vs SNRin curve) first. Does
that explain it?

John