A-005-02: RF power amplifiers
A-005-02-01:
The output tuning controls on a transmitter power amplifier:
allow efficient transfer of power to the antenna
allow switching to different antennas
reduce the possibility of cross-modulation in adjunct receivers
are involved with frequency multiplication in the previous stage
A-005-02-02:
The purpose of using a centre-tap return connection on the secondary of transmitting tube's filament transformer is to:
prevent modulation of the emitted wave by the alternating current filament supply
reduce the possibility of harmonic emissions
keep the output voltage constant with a varying load
obtain optimum power output
A-005-02-03:
In a grounded grid amplifier using a triode vacuum tube, the input signal is applied to:
the cathode
the plate
the control grid
the filaments
A-005-02-04:
In a grounded grid amplifier using a triode vacuum tube, the plate is connected to the pi-network through a:
blocking capacitor
by-pass capacitor
tuning capacitor
electrolytic capacitor
A-005-02-05:
In a grounded grid amplifier using a triode vacuum tube, the plate is connected to a radio frequency choke. The other end of the radio frequency choke connects to the:
B+ (high voltage)
filament voltage
ground
B- (bias)
A-005-02-06:
In a grounded grid amplifier using a triode vacuum tube, the cathode is connected to a radio frequency choke. The other end of the radio frequency choke connects to the:
B- (bias)
ground
filament voltage
B+ (high voltage)
A-005-02-07:
In a grounded grid amplifier using a triode vacuum tube, the secondary winding of a transformer is connected directly to the vacuum tube. This transformer provides:
filament voltage
B- (bias)
B+ (high voltage)
Screen voltage
A-005-02-08:
In a grounded grid amplifier using a triode vacuum tube, what would be the approximate B+ voltage required for an output of 400 watts at 400 mA with approximately 50 percent efficiency?
2000 volts
500 volts
3000 volts
1000 volts
A-005-02-09:
In a grounded grid amplifier using a triode vacuum tube, each side of the filament is connected to a capacitor whose other end is connected to ground. These are:
by-pass capacitors
tuning capacitors
electrolytic capacitors
blocking capacitors
A-005-02-10:
After you have opened a VHF power amplifier to make internal tuning adjustments, what should you do before you turn the amplifier on?
Be certain all amplifier shielding is fastened in place
Make sure that the power interlock switch is bypassed so you can test the amplifier
Be certain no antenna is attached so that you will not cause any interference
Remove all amplifier shielding to ensure maximum cooling
A-005-02-11:
Harmonics produced in an early stage of a transmitter may be reduced in a later stage by:
tuned circuit coupling between stages
larger value coupling capacitors
greater input to the final stage
transistors instead of tubes
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