There is QRS Quality of Received signal. Then there is Q, which is used in
Filter design, and also there is Loaded Q, also used in filter, or
selectivity design. Q is related to the losses of a tuned section, the L and
C, R, the more R the less Q, less selectivity, more stages needed. There is
a formula to calculate Q in terms of L,C and R. Remember the old TRF stages
in early AM radio? More the better, and there is a formula for calculating
the series of selectivity stages of equal stages. The more stages of
selectivity, or more narrow the selectivity, more broadband noise rejection,
the more sensitive the radio is, and sounds better.



"Art Unwin KB9MZ" wrote in message
...
A question was asked about what use was 'Q'
To me Q showed its value with the introduction of the National Radio
HRO
a receiver with 2 RF stages and 3 IF stages. This receiver as
excellent receiver because it recognised that the mixture of
frequencies produced not only a desired frequency but also many other
undesired frequencies and while we used to use spark gap tranmissions
that were extremely wide the introduction of higher density spectrum
use produced a zillion frequency mixtures which are of no use.
The HRO by decreasing the spectrum received to exclude errant
frequencies increased the Quality (Q) of signal reception by
expanding the difference in signal level received compared to the
level of errant frequecies received ( noise). This difference can be
analogous to the gain of an antenna
where noise introduced into a receiver must be overcome by the
required signal gain or there is no communication. The HRO did this by
its then unheard of
3 I.F. stages which provided a low noise floor. So Q does have a use
as it is inextricably bound to the Quality of communications and
everything that goes with it, it cannot be ignored.

More to come, let the attack begin.

Art