22
ɀ
Place the amplifier in
OPERATE
position (fig. 2, ref. 7). Be sure the amplifier
BAND SELECT
(fig. 2, ref. 3) matches the band selected on the transceiver.
ɀ
Place the transmitter or transceiver into transmit in FM, AM, RTTY, or CW
modes. The green
TX LED
(fig. 2, ref. 5) should light. The Forward power scale
(fig. 2, ref. 1) should increase to very roughly ten times the initial exciter power
reading. Reflected power should remain very low, and the PA current should
increase on the right meter 0-70 scale (fig 2, ref. 1) when in the Id Multimeter
position. Only the
TX
and
BAND SELECT LED’s
should illuminate.
ɀ
Briefly, increase exciter power until the amplifier reaches 600 watts output, or
increase power until the exciter reaches maximum power without exceeding 600
watts amplifier power. Watch the
Id
MULTIMETER
position on the right meter 0-
70 scale, and never exceed 30 amperes. Target
Id
reading is 25 amperes or
less.
ɀ
After verifying all of this, and understanding control locations and function, the
amplifier is ready to operate.
ɀ
This amplifier produces approximately 600 watts PEP output power with
approximately 70-90 watts PEP drive. This is nominal power, and can vary
slightly from band-to-band.
ALC Adjustment
It is unfortunate, but radio manufacturers do not have standardized interfaces. Because
of this, ALC requires some initial adjustment. If the ALC voltage is too low, the ALC will
not provide good control of power levels. If the ALC loop gain is too high, the ALC can
cause a “power bounce” as power attempts to settle at the desired ALC power
threshold. This overshoot, dip, and recovery is caused by slow radio ALC response
time. Excessive ALC control loop gain aggravates power bounce.
ALC attack bounce shows on a steady carrier (such as RTTY, CW, or FM) as a high
initial peak power reading followed by a deep null. The deep null is followed by a slow
settling to the desired power level. On SSB, it will show as a slow warble or modulation
of power levels, especially at the very start of voice transmissions.
If ALC attack bounce is observed, the ALS-706 will require ALC gain adjustment. The
ALS-706 has a small flat-blade screwdriver adjustment for setting ALC gain. This
adjustment is accessible through a small hole located on the left cabinet side behind the
front panel, near the panel meter.
High Duty Cycle Modes
When operating the amplifier with high duty cycle modes such as FM, RTTY, FT8, or
other digital modes reduce the power input so the output is less than 600W and the PA
current is less than 20A. Also if the thermal cutout trips very often reduce the power to
eliminate temperature cutouts.
Summary of Contents for ALS-706
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