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3.3 FEEDLINES AND ANTENNAS
This unit will work with any antenna as long as SWR at the OUTPUT of the amplifier is less than
2:1.
Warning,
never exceed 20 watts maximum
reflected power.
Try to keep SWR
below 2:1. Make sure all feedline and antenna connections are good.
4.0 SSB AND LINEAR MODES
SSB and AM operation requires linear amplification of signals.
If the amplifier is not linear,
mixing products occur.
These mixing products make the signal bandwidth increase, they are
referred to as "'splatter".
Amplifier gain changes with power level.
One design goal of this
amplifier was minimizing the effects of non-linearity, and reducing needless splatter.
Unlike tube amplifiers, solid-state amplifiers go into gain compression long before
they saturate.
Even
though
this amplifier can produce
160 watts or more
on
carrier,
do
NOT
expect
to run
160
watts
PEP
and
have
acceptable
IMD
performance!
In AM operation, carrier power is normally 25% or more of the peak envelope power as indicated
on a true peak-reading meter.
Unmodulated carrier output power should not exceed 5 watts.
Peak-envelope output power should not exceed 100 watts when measured on an accurate peak
reading meter.
4.1 SPLATTER AND DISTORTION
At low power levels, amplifier gain is affected by bias settings.
If bias is set too low, turning
drive power down can actually make the ratio of distortion-to-signal worse (not better)!
This amplifier has an active-bias system, which forces the bias voltage to a fixed level.
This
system is vastly superior to conventional resistor/shunt-diode bias for maintaining operating-bias
as drive power, temperature, and supply voltage varies.
At high power levels, three main problems limit linearity and cause splatter. All three problems
are reduced or cured by turning the drive power down.
1.) Output-device
current
amplification
(in this case
transistors
are
used)
is a problem.
Transistors, unlike most vacuum tubes, show a gradual decrease in gain as drive level
increases. It is important this amplifier be operated in the area where the gain-slope is linear
or "rounded" in a sine curve to minimize splatter and IMD.
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