8-14B: Pulse Forming Networks Modulation

Question 1

8-14B3

The purpose of the pulse-forming network is to:

A. Determine the width of the modulating pulses.
B. Determine the pulse repetition rate.
C. Act as a high pass filter.
D. Act as a log pass filter.

Answer 1

ANSWER A
The PFN alternately stores and releases energy in approximately rectangular waves, which determines the width of the modulating pulses.

Question 2

8-14B4

The shape and duration of the high-voltage pulse delivered to the magnetron is established by:

A. An RC network in the keyer stage.
B. The duration of the modulator input trigger.
C. An artificial delay line.
D. The time required to saturate the pulse transformer.

Answer 2

ANSWER C
It is the delay line that shapes and determines the duration of the high-voltage pulse delivered to the magnetron.

Question 3

8-14B6

An artificial transmission line is used for:
A. The transmission of RADAR pulses.
B. Testing the RADAR unit, when actual targets are not available.
C. Determining the shape and duration of pulses.
D. Testing the delay time for artifical targets.

Answer 3

ANSWER C
The artificial transmission line in the RADAR modulator is actually a storage element. The moduiator switch controls the pulse-repetion rate, and when the modulator switch is open, the transmission line charges. When the switch is closed the transmlssion line discharges through the series circuit. The transmission Iine simulates the actual lines and allows determination of the shapes and duration of the pulses.