Communication Concepts EB63 Engineering Bulletin - Manual

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1 RF Application Reports
140 W (PEP) AMATEUR RADIO LINEAR AMPLIFIER
2 – 30 MHz
The popularity of 2 – 30 MHz, SSB, Solid State, linear
amplifiers is increasing in the amateur market. This EB
describes an inexpensive, easy to construct amplifier and
some pertinent performance information. The amplifier uses
two MRF454 devices. These transistors are specified at 80
Watts power output with 5 Watts of input drive, 30 MHz, and
12.5 Vdc. The MRF454 is used because it is a readily
available device and has the high saturation power and
ruggedness desired for this application. This device is not
characterized for SSB. However, IMD specs for the amplifier
are shown in Figures 2 and 3.
THE AMPLIFIER
The performance of the amplifier can be seen in Figures
1, 2, 3, 5, 6, 7 and 8. The quiescent current is 500 mA on
each device. This amount of bias was needed to prevent
“cross over” at the higher output powers during SSB
operation. The amplifier operates across the 2 – 30 MHz
band with relatively flat gain response and reaches gain
saturation at approximately 210 Watts of output power.
Figure 5 depicts the amplitude modulated waveform with
respect to a 100-Watt carrier. Figure 6 depicts the increased
amplitude modulation at 50-Watt carrier. In both cases the
peak output power is equal to approximately 210 Watts due
to the saturation of the MRF454. The 50 Watt carrier is thus
recommended in any amplitude modulated applications.
MOTOROLA
SEMICONDUCTOR
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by EB63/D
ENGINEERING BULLETIN
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Motorola, Inc. 1993
EB63