3.17 Power Supplies

Practice

B-003-17-01
If your mobile transceiver works in your car but not in your home, what should you check first?

The power supply

The speaker

The microphone

The SWR meter

B-003-17-02
What device converts household current to 12 VDC?

A low pass filter

A power supply

An RS-232 interface

A catalytic converter

B-003-17-03
Which of these usually needs a heavyduty power supply?

An antenna switch

A receiver

A transceiver

An SWR meter

B-003-17-04
What may cause a buzzing or hum in the signal of an AC-powered transmitter?

A bad filter capacitor in the transmitter's power supply

Using an antenna which is the wrong length

Energy from another transmitter

Bad design of the transmitter's RF power output circuit

B-003-17-05
A power supply is to supply DC at 12 volts at 5 amperes. The power transformer should be rated higher than:

17 watts

2.4 watts

6 watts

60 watts

B-003-17-06
The diode is an important part of a simple power supply. It converts AC to DC, since it:

has a high resistance to AC but not to DC

allows electrons to flow in only one direction from cathode to anode

has a high resistance to DC but not to AC

allows electrons to flow in only one direction from anode to cathode

B-003-17-07
To convert AC to pulsating DC, you could use a:

transformer

capacitor

diode

resistor

B-003-17-08
Power-line voltages have been made standard over the years and the voltages generally supplied to homes are approximately:

120 and 240 volts

110 and 220 volts

100 and 200 volts

130 and 260 volts

B-003-17-09
So-called "transformerless" power supplies are used in some applications (notably tube-type radios and TV receivers). When working on such equipment, one should be very careful because:

DC circuits are negative relative to the chassis

chassis connections are grounded by the centre pin of the power source's plug

the load across the power supply is variable

one side of the line cord is connected to the chassis

B-003-17-10
If household voltages are consistently high or low at your location, this can be corrected by the use of:

a full-wave bridge rectifier

an autotransformer

a variable voltmeter

a proper load resistance

B-003-17-11
You have a very loud low- frequency hum appearing on your transmission. In what part of the transmitter would you first look for the trouble?

the power supply

the variable-frequency oscillator

the driver circuit

the power amplifier circuit