RadioBanter - View Single Post

July 18th 05, 06:03 AM

wrote:

Q alone won't determine sensitivity.

Very true. In fact the opposite is usually the case when it comes to
function. In a good hi-q xtal set one often has to sacrifice
sensitivity for selectivity...and vice-versa. Tighter coupling=more
sensitivity but less selectivity because of loading effects. If you
want sensitivity, go outdoors and hang wire or add sound-powered
headphones. If you want selectivity, tweak the ckt.

But still, by aiming for highest Q you at least have something to work
with when trading off.

Crystal radios are somewhat like a house of mirrors. Changes at one end
reflect at the other end of the ckt. The old razor-blade radio is an
example of everything being done the worst way but it still works. As
you improve on the scheme each component becomes more and more critical.

-Bill