Feedlines And Antennas; Ssb And Linear Modes; Splatter And Distortion - Mirage B 1018 G User Manual

If possible, especially if cooling might be marginal and there is no external air blowing across the
heatsink, mount the amplifier with heatsink fins vertical. This allows natural convection to
circulate air. See section 1.0 for details.
Warning, the safe maximum temperature of the heatsink is 140°F. If the heatsink
feels too hot to hold, it is almost certainly too hot for safe operation.

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 25 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.
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