# Measurements

### Explanation of question 32

An AM transmitter has a frequency tolerance of ± 1kHz and is transmitting a signal of bandwidth 5kHz in the 20m band. The transmitted signal is checked by a frequency meter of tolerance 10 parts per 100,000. The highest frequency that can be used to ensure no out-of-band working is

1. 14.334MHz
2. 14.335MHz
3. 14.344MHz
4. 14.345MHz

The answer is :- 4

10 parts per 100000 is 100 parts per million, i.e. 100 Hz per

1 MHz = 1435 Hz per 14.35 MHz
= 1.435 kHz per 14.35 MHz

| kHz
Transmitter tolerance | 1
Frequency meter tolerance | 1.435
Half bandwidth | 2.5
| 4.935

Therefore, highest usable frequency = 14.35 MHz - 4.935 kHz = 14.345065 MHz

Nearest practical value = 14.345 MHz.

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