15. d--para 12d(5), fig.

25, 29

Since the transmitter is pulse-frequency modulated at the same MI of 5,

the increase in bandwidth is approximately 400 percent (fig.

29).

Hence, the

increase in effective bandwidth equals the peak-to-peak deviation times 400 percent

(7.5 kHz x 2 x 400% = 60 kHz).

The effective, or total, bandwidth becomes (7.5 kHz x 2) + 60 kHz = 75 kHz.

16. a--para 13d

Time constant = R x C

C = Time constant/R

C = 75 x 10-6/50,000 = 0.0015 x 10-6

C = 0.0015 microfarad

17. c--para 13c (4), fig.

31

From figure 31 it is seen that a rise from 3 kHz to 15 kHz gives an

increase in response of 12 decibels (db)(17 db - 5 db - 12 db). A 12-db increase

is equivalent to doubling the voltage twice, or increasing voltage amplitude by 4

to 16 volts.

18. c--para 13c

19. a--para 15c

20. c--para 15c

There will be no appreciable interference if the desired signal is twice as

large as the interfering signal.

LESSON 2..................................Methods of Producing FM

All references are to TM 11-668, unless otherwise indicated.

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