16
CW Operation
The exciter output should be restricted to a level that limits the amplifier to 500 watts
output on a steady carrier or 50 watts reflected power, whichever is greater.
The ALC should not be used to control the power level more than a few percent on CW.
The "ALC" LED should just barely light or flash on CW.
RTTY, FM and Other High Duty Cycle
The transmitting duty cycle, ambient temperature, supply voltage, fan speed and the load
SWR all play important roles in determining the transmit time limit on high duty cycle
modes.
To minimize noise, Ameritron uses only enough fan speed to cool this amplifier for
typical amateur usage. If heavy duty cycle operation is planned the following guidelines
should be followed.
The output power can be reduced to assist with cooling. This is not the most effective
method of improving performance since the power must be reduced 5 times to cut the
heat dissipation in half. The exciter output should be restricted to a power level where
less than 200 watts output or 25 watts reflected power is obtained on long duty cycle
modes.
The fan speed should be increased by replacing or supplementing the airflow from the
standard fan. A fan that delivers at least 80 CFM airflow at .l" of static pressure, such as
the EBM W2S107-AA15-39, will double the cooling and allow 500 watt RTTY
transmissions with 2 minute on, one minute off duty cycles.
The high voltage power supply can be reduced to increase the efficiency at lower output
levels. At 30 volts the ALS-600 will deliver 275 watts of output power. This will allow
a 100% duty cycle with any fan delivering more than 40 CFM at .08" of static pressure,
such the EBM W2S107-AD21-39, or a 5 minute on, two minute off duty cycle with the
standard fan.
Either the exciter drive level or the amplifier "ALC SET" control can be adjusted to limit
the power output in the RTTY and FM modes.
AM Operation
The carrier power of any linear amplifier is restricted on AM to one fourth of the peak
envelope output power. With this amplifier the maximum carrier power on AM will be
around 150 watts.
