L/C FILTER DESIGN -

THE ANSWERS

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Section 1 - Essential Basics of the Tutorial:-

1 (a). L/C - basics:-

1. What is the L/C for the following frequencies;
(a) 455Khz (b) 7224 Khz and (c) 9 Mhz.

Answers:(a) 122,354 (b) 485.38 and (c) 312.72

2. What capacitor will resonate at the above respective frequencies with the following respective inductors ;
(a) 679 uH (b) 22uH and (c) 3.81 uH.

Answers: (a) 180pF (b) 22pF and (c) 82pF

3. What is the resonant frequency for the following L/C (inductor - capacitor) combinations to the nearest Khz;
(a) 2,533,030 (b) 116,716 (c) 312.72 and (d) 2.53303.

Answers: (a) 100 Khz (b) 466 Khz (c) 9 Mhz and (d) 100 Mhz

Back to L/C .

1 (b). reactance - basics:-

1. What is the reactance of a 100pF capacitor at;
(a) 100Khz (b) 1.5 Mhz and (c) 22 Mhz.

Answers:(a) 15K915 ohms (b) 1K061 ohms and (c) 72R34ohms

Where K and R indicate the place of the comma or decimal point. Wait for a later tutorial to see my rabid tirade about the necessity for this method.

2. What is the reactance of a 22uH inductor at;
(a) 100Khz (b) 1.5 Mhz and (c) 22 Mhz.

Answers:(a) 13R823 ohms (b) 207R35 ohms and (c) 3K041 ohms

3. This is a revision of a previous tutorial:- What capacitor will resonate with the above inductor at;
(a) 7234Khz (b) 1224 Khz and (c) 3.5 Mhz.

Answers: (a) 22 pF (b) 769 pF and (c) 94 pF

Back to Reactance

1 (c). Q - basics:-

1. In our previous tutorial we calculated the reactance of a 22uH inductor at;
(a) 100Khz (b) 1.5 Mhz and (c) 22 Mhz.
What are the impedances if the unloaded Q's are respectively (a) 32, (b) 170, and (c) 110

Answers:(a) 442 ohms (b) 35K249 ohms and (c) 334K518 ohms

2. What is the effective r.f. resistance of the inductor above at the respective frequencies/Q.
(a) 100Khz/32, (b) 1.5 Mhz/170, and (c) 22 Mhz/110

Answers:(a) 0.432 or R432 ohms (b) 1R22 ohms and (c) 27R65 ohms

3. What is the correct method of describing the following resistances and capacitances.

(a) 0.68 ohms, (b) 10 ohms, (c) 220 ohms, (d) 1,800 ohms, (e) 82,000 ohms, (f) 470,000 ohms, (g) 5,600,000 ohms, and;

(h) 6.8 Pf, (i) 180 Pf, and (j) 4.7 uF

Answers:(a) R68 ohms (b) 10R ohms (c) 220R ohms (d) 1K8 ohms (e) 82K ohms (f) 470K ohms (g) 5M6 ohms (h) 6P8 (i) 180 Pf (j) 4U7

Back to Qfor factor-of-quality.
 

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This site was entirely written and produced by Ian C. Purdie* Created: 2nd January, 1999 and Revised: 6th February, 1999

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