Chapter 15:
Radio Frequency Interference
Objectives:
Students completing this lesson should be familiar with the causes
of Radio Frequency Interference and how to prevent it.
Apparatus:
- Various types of TVI and RFI filters.
- Samples of Toroid and Snap-Together RFI suppression Cores
Handouts:
- Printable Copy of
Flow Chart of Figure 15.4
- For many years Ralph Cameron, VE3BBM, wrote a column in The
Canadian Amateur (TCA) called Crosswaves. Over the years he described myriad
examples of interference and how the problems were rectified. The task
here will be to go through back issues and select some of the most
common to pass around the class.
- Remind your students that the RAC web site has a section dedicated to resolving
RFI/EMC compatibility problems, hosted by Ralph Cameron, VE3BBM.
(www.rac.ca/emc).
Lesson Plan:
- Go over questions from the Chapter 14 homework.
- Emphasize that is very important unit, especially if one is living
cheek-to-jowl with one's neighbours in a modern subdivision with small
lots, or worse still, living in an apartment house. The problem is
further exacerbated by the proliferation of electronic devices in the
modern home. Your students need to know and understand the various terms
bandied about in the chapter. If possible use an HF receiver to show
them examples of splattering.
- Use an HF transmitter to show TV interference on 80 metres and how a
filter can alleviate this.
- Show how to make a filter that employs a toroid. Also,
demonstrate how a snap-together core makes this task much
easier.
- Show the students various types of commercially available filters:
high-pass, low-pass, bandpass, band-stop, etc.
- The students need to be aware of the frequency ranges of the
Amateur HF bands in order to do some of the Chapter 15 Quiz questions.
This would be good topic for a quick review.
Homework:
- Read Chapter 15.
- Do Chapter 15 Quiz Questions
- Skim Chapter 16
Chapter 15 Quiz:
Printable copy of the Review
Quiz
Answers to Chapter 15 Quiz
1 |
C |
13 |
C |
25 |
C |
37 |
B |
49 |
D |
2 |
C |
14 |
C |
26 |
B |
38 |
C |
50 |
B |
3 |
C |
15 |
D |
27 |
A |
39 |
D |
51 |
D |
4 |
A |
16 |
C |
28 |
B |
40 |
C |
52 |
C |
5 |
B |
17 |
B |
29 |
D |
41 |
C |
53 |
B |
6 |
B |
18 |
A |
30 |
A |
42 |
D |
54 |
C |
7 |
D |
19 |
D |
31 |
D |
43 |
C |
55 |
C |
8 |
B |
20 |
A |
32 |
A |
44 |
A |
56 |
B |
9 |
D |
21 |
C |
33 |
C |
45 |
A |
57 |
B |
10 |
C |
22 |
D |
34 |
B |
46 |
C |
* |
* |
11 |
A |
23 |
B |
35 |
A |
47 |
D |
* |
* |
12 |
C |
24 |
A |
36 |
D |
48 |
C |
* |
* |
Overhead Slide Versions of the Diagrams
- Slide
1
15.1 ¼
Wave Stub
- Slide
2 (Toroids)
15.2 Toroid Core Choke
15.3
Split Toroid Core
- Slide 3
15.5 Key Click Filter