8-46F: Equipment Faults 3

Question 1

8-46F2

In a RADAR unit, if the crystal mixer becomes defective, replace the:

A. Crystal only.
B. The crystal and the ATR tube.
C. The crystal and the TR tube.
D. The crystal and the klystron.

Answer 1

ANSWER C
The point contact crystals in the mixer can be damaged by any current exceeding 1 mA. The TR switch (tube) helps to protect the crystal from damage. If the crystal goes out, it may have gone bad because of a defictive TR tube. Check out the tube before replacing the crystal.

Question 2

8-46F6

Low or no mixer current could be caused by:

A. Local oscillator frequency misadjustment.
B. TR cell failure.
C. Mixer diode degradation.
D. All of the above.

Answer 2

ANSWER D
Low mixer current could be caused by the inputs of the local oscillator/TR cell failing, or by the mixer diode itself. Local oscillator frequency misadjustment can also cause low or no mixer current.