In a message dated 1/7/2005 5:49:42 PM Eastern Standard Time, craxd1@ezwv.com
writes:
In my opinion, I dont think any instrument can measure the true unloaded
Q exactly due to too many factors or variables such as stray capacitance
and inductance. They might show something in the ball park but I don't
see how it could be possible to show it exact. Especially networks in a
production enviroment, each will have small differences from one to the
other, so no one will be the same as the other. As you mentioned about
the quality of components, no one will be the very exact same as the
other. Even if measuring a network out of the chassis for an unloaded Q,
it will change as soon as it's mounted inside the enclosure. There's
just too many variables, of course that's just my opinion on the subject.
Will
That's why a Q meter that directly measures the unloaded Q of an inductor or
tank circuit at the operating frequency is so useful. Used wisely the Q meter
will reveal problems in the tank components and can tell you if placement of
the inductor is adversely affecting the unloaded Q - for example if the coil is
placed too close to shielding or other chassis components. It can also reveal
if there are problems in the tuning capacitor or interconnects. No instrument
can measure anything perfectly exactly if you want to nit pick, but a good Q
meter will reveal the unloaded Q to a good percentage of accuracy. 73 Todd
Roberts WD4NGG
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