RadioBanter - View Single Post - phase angle and impedance of resonant circuits

August 30th 05, 11:51 PM

wrote:

All,

I'm an Advanced studying for my Extra, and so far I am getting 66% on
the practice exams without even studying after about 3 years of
homebrewing. I need a few extra points to make it over the top, and
since I am a builder (of sorts) I would like to do it using the
electrical principles part of the exam.

However, the questions pool provides the answers but not how to get
them. I'd rather be able to understand how to arrive at it without a
calculator.

Problem class 1: impedance and phase angle of RLC parallel circuit
where component values and frequency are known.

Problem class 2: impedance and phase angle of RLC series circuit where

component values and frequency are known.

Could I calculate these graphically using tip-to-tail summation of
impedance vectors?

From what I understand, |Z| = 2 pi F L, |Z| = 2 pi / (F C), |Z| = R
But how can I get the phase angle or the conjugate pair so that I can
do the vector addition?

Thanks in advance,

The Eternal Squire

I was going to ask what study materials you're using -- but you're not,
are you?

IIRC this is discussed in the ARRL handbook, which you should have if
you're homebrewing.

You calculate the series circuit impedance by adding the impedances of
the parts, which you can do graphically, or by adding all of the real
parts and all of the imaginary parts. You must calculate the parallel
circuit impedance as 1/(the circuit admittance), the latter being the
sum of the admittances of all the parts.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com