AMERITRON AL-572, Инструкция по эксплуатации

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Ameritron AL-572 Instruction Manual
22
T
UNING
WARNING: The transformer must be wired correctly for your line
voltage. This amplifier is normally shipped wired for
standard 120 Vac operation. See the "
T
RANSFORMER
C
ONNECTIONS
" section on page 15 for details.
Important Note: If you have installed the optional electronic grid protection circuit to
prevent control-grid damage, this amplifier will quit operating if the grid
current exceeds a safe pre-set limit. The overload circuit responds much
faster than the grid current meter. The overload circuit will respond to
excessive grid current before the operator can observe the increase on the
grid current meter. The grid overload circuit can be reset by momentarily
placing the "STBY-OPR" switch in the "STBY" position.
Many exciters generate high-level RF pulses when first keyed. These short duration pulses may
greatly exceed the exciter's operating output power setting. Unexplained activation of the grid
overload circuit may indicate the existence of this common exciter problem.
Never under-load the amplifier to reduce the output power. The amplifier "LOAD" control must
be set to a high enough position (clockwise) to prevent excessive voltage and arcing in the tank
circuit or excessive grid current. Repeated tripping of the grid overload circuit or intermittent
arcing probably indicates the "LOAD" control is adjusted too low.
The goal of the following tuning procedure is to adjust the amplifier tuning and loading to
provide maximum output at maximum exciter power. Avoid depending on the exciter's power
control or ALC to maintain reduced power output, and peaking the amplifier at this reduced drive
level. If the exciter suddenly puts out more power, the sudden surge of energy can cause splatter
or cause the amplifier to arc.
Overshoot is especially troublesome with radios capable of operating at more than 100 watts
output power. For example, in several tests of popular 150 watt output radios, several radios
adjusted to provide less than 100 watts output power during carrier conditions "spiked" above
200 watts before their ALC systems took control. The transcient output power pulse is fast, often
lasting only a few milliseconds. The rapid speed of the pulse prevents normal peak reading
meters or non-storage oscilloscopes from clearly indicating the problem.
Overshoot problems are common, and we recommend slightly over-coupling the amplifier to the
load. Overcoupling is accompished by advancing the LOAD control slightly beyond the point of
maximum output power with full exciter drive (not to exceed 110 watts).