15
OPERATION
This amplifier is equipped with a switch on the front of the Amplifier's Power Supply
labeled Normal/RTTY. This switch is used in the normal position for SSB and CW
operation. The RTTY position is used for continuous carrier modes. This position will
limit the voltage to about 42Vdc no load. This will limit the output power to 350 watts.
In the RTTY position, the amplifier can be operated with 10 minute key down with 50%
duty cycle.
The Amplifier's back panel has an ALC limit control. This control is to limit the amount
of ALC voltage sent to the transceiver. This is necessary due to there is not a standardize
ALC voltage on transceivers. To set the ALC limit control, adjust the ALC set knob on
front of the amplifier to 10 (fully clockwise). Apply enough drive into the amplifier until
the amplifier's power meter reads about 400 to 500 watts.
Note: The amplifier's power
meter should never exceed 700 watts at anytime.
Plug the ALC into the back of the
amplifier (if not already done). Turn the ALC set knob (on front of amplifier) to 0
(counter-clockwise). Key amplifier with RF applied. Adjust the ALC limit control (on
back of amplifier) until the ALC light on front of amplifier just comes on. No other
adjustment needs to be done to the ALC limit control, unless a different transceiver is
used. The only adjustments for ALC will be done on front of the amplifier. Follow the
operator's manual for ALC adjustment.
The following sections describe how to adjust the exciter and ALC control for proper
operation. If the ALC is not used the exciter output controls must be used to limit the
power to the levels described in the text that follows.
SSB Operation
SSB voice operation normally does not have transmit time limits. Reflected power levels
should be kept below 50 watts peak on SSB.
The most accurate way to maintain linear operation on SSB is with an oscilloscope. The
output waveform should be closely observed for clipping or reduction of peaks and
should closely resemble the waveform that the exciter produces barefoot.
If any peak clipping is evident the output power should be reduced until peak clipping is
at a minimum.
The proper operating level can also be determined by operating the exciter at full power
output (not to exceed 100 watts peak) and normal voice modulation with the amplifier
"ALC SET" control fully clockwise. The "ALC SET" control should be adjusted until
the amplifier's RF output meter just begins to drop.
The exciter output level should then be reduced with the audio gain control or output
control until the desired amount of ALC compression is obtained. See the ALC
(Automatic Level Control) section for more details.
