"pltrgyst" wrote in message
news
On 9 Apr 2007 18:53:01 GMT,
(Michael Black) wrote:
A Q-multiplier is a regenerative stage.
It's prime was in the days of the 455KHz IF, where the
improved selectivity
would actually make a difference. At a higher frequency,
it would still
increase the selectivity of the tuned circuit, but not
enough to narrow
the passband for voice or CW.
So what about audio Q-multipliers? Do they function on the
same principle?
-- Larry
Yes. The idea of a Q-Multiplier is to increase
selectivity. They use regeneration (positive feedback) to
decrease the bandwidth of a tuned circuit. The frequency can
be whatever is desired. Q-Multipliers were popular at a time
when most receivers had inadequate selectivity. They are
relatively cheap and, with some limitations, work pretty
well. As receivers with more sophisticated filters (like
mechanical filters or multi-pole crystal filters) became
available the Q-multiplier fell out of use.
BTW, the old regenerative receiver works on the same
principle. In fact, one can see a Q-Multiplier as a sort of
regenerative receiver working at the IF or audio
frequencies.
--
---
Richard Knoppow
Los Angeles, CA, USA
--
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