[Test-Equipment] RE: Tuned circuits

Mon, 25 Nov 2002 11:24:23 +0800

Hello Gianfranco,

The following discussion makes the following assumptions:- (1) the tuned circuit in your RS active aerial consists of an inductor and a capacitor in parallel and, (2) your primary interest is to increase the loaded Q for the purpose of narrowing the passband and you are willing to forsake other considerations like circuit loss.

At resonance, the loaded Q is the ratio of the equivalent parallel resistance to either the reactance of the inductor or capacitor (|jXl| = |jXc| at resonance). So, either minimizing the inductance, or maximizing the capacitance will have the effect of increasing the loaded Q.

The RS active aerial is a real gem. Good luck in restoring it.

Chin-leong, 9W2LC.

-----Original Message-----

From: "canale" <[email protected]>
To: <[email protected]>
Date: Sat, 23 Nov 2002 16:19:51 +0100
Subject: [Test-Equipment] Tuned circuits

In a flee market in Germany I purchased a piece of an active antenna =
built by Rhode &Schwarz.
Some parts are missing and I am rebuilting them to restore the former =
functionality.
The key part of the device is a front end tuned circuit that is =
digitally tuned activating relay and consequently
adding or subtracting capacitance or inductance from the tuned circuit.
Obviously it is possible to tune the circuit on a selected frequency =
with many different combinations of capacity /inductance.
To optimize the Q of the resonant circuit for the selected frequency it =
is better to maximize the inductance or the capacitance ?
Somebody told me the inductance but I do not understand why.
Has anybody an explanation ?
Thanks
Ciao
Gianfranco