Measurements

Explanation of question 27

The modulation depth of a transmitted AM signal can be measured by

1. a moving coil ammeter in the transmitter output circuit
2. a wattmeter in the transmitter power supply
3. displaying the modulated output waveform on an oscilloscope
4. connecting an S.W.R. meter between the transmitter and the antenna

The answer is :- 3 If the modulated output is displayed on an oscilloscope, a visual indication is given for a 100% modulation depth. The actual depth can be calculated very simply.