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Lesson 6: Practical Circuits

Lesson 6 of 10, syllabus topic T7. The exam asks 4 questions from this topic, one from each of its 4 groups.

Practical circuits combine components into the radios, meters and test equipment in a station.

What you will learn

  • T7A Station equipment: receivers, transceivers, transmitter amplifiers, RF preamplifiers, transverters; Basic radio circuit concepts and terminology: sensitivity, selectivity, mixers, oscillators, Push-To-Talk (PTT), VFO, modulation
  • T7B Symptoms, causes, and cures of common transmitter and receiver problems: overload and overdrive, distortion, interference and consumer electronics, RF feedback
  • T7C Antenna and transmission line measurements and troubleshooting: measuring SWR, effects of high SWR, causes of feed line failures; Basic coaxial cable characteristics; Use of dummy loads when testing
  • T7D Using basic test instruments: voltmeter, ammeter, and ohmmeter; Soldering

1. Read

  1. Antennas and feed lines: SWR: what it does and does not tell youHelps with T7C
  2. Antennas and feed lines: Coax and other feed linesHelps with T7C
  3. Choosing your first radio: Feed line basicsHelps with T7C
  4. Building your own gear: SolderingHelps with T7D
  5. Building your own gear: Test equipmentHelps with T7D
  6. All 44 T7 questions with their answers and explanationsEvery group, with the rule or source behind each answer

2. Explore

  • SWR and feed line loss

    Enter 100 watts forward and 4 watts reflected. The SWR is 1.5 to 1 and 96 percent of the power reaches the load, ignoring feed line loss. A perfect match reads 1 to 1.

    This is exam question T7C04.

3. Practice

Practice one group at a time. A group is ready when you have answered every one of its questions and learned at least 80 percent of them; a question counts as learned when your last three answers to it were correct. To review quickly, go through this lesson’s questions as flashcards.

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