Remember Me?

#1
February 26th 07, 01:42 AM posted to rec.radio.amateur.moderated
 external usenet poster First recorded activity by RadioBanter: Jul 2006 Posts: 17
Formula for Q of resonant circuit?

M J Dowden wrote:
I am trying to find the formula used to calculate the Q of a
parallel R-L-C resonant circuit. There are a number of questions in
the Amateur Extra test pool[1] that ask this and the formula that I
have does not produce the correct answers.
I have been using Q = (2 * Pi * f * L) / R, but the questions in
section E5G of the test pool don't seem to work with that. The
answers that are produced by that formula are among the
"distracters," suggesting that I am making an obvious error that they
expect some people to make.

It's obvious that this formula for Q is not valid for a parallel
RLC-Circuit. If you let R go towards infinity, by this formula,
the Q goes to zero, although it should obviously be infinite,
since the circuit has no losses.

The correct formula is Q = R / (2*pi*f*L) = R * 2*pi*f*C

73,
--
Fabian Kurz, DJ1YFK * Dresden, Germany * http://fkurz.net/
Online Log: http://dl0tud.tu-dresden.de/~dj1yfk/log.html

 Thread Tools Search this Thread Search this Thread: Advanced Search Display Modes Linear Mode

 Posting Rules Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On

 Similar Threads Thread Thread Starter Forum Replies Last Post Mike Homebrew 0 March 2nd 07 07:33 PM Lloyd General 0 February 26th 07 10:02 AM Lloyd Moderated 0 February 26th 07 01:42 AM Cliff Homebrew 5 July 22nd 05 04:43 AM Reg Edwards Antenna 1 January 8th 05 10:27 PM

All times are GMT +1. The time now is 07:44 AM.