TAG Low Frequency 1 Watt Power Amplifier
This is a Class D transmitter "borrowed" from designs by Lyle Kohler
and Bill Ashlock.
The difference from Lyle's and Bill's designs is in the input circuitry. Since my
exciter produces a linear 10 mW signal into 50 ohms, a hard-limiting driver was
necessary at the transmitter. The input is truly 50 ohms, and has surge protection
through the back-to-back Zener diodes. With six inverter sections available in the
74AC14, I decided to drive the output transistors separately.
I used Lyle's feature of providing a dropping resistor in the DC supply to the output
transistors. Combined with a variable 0-24 VDC supply, this affords operation at a wide
range of antenna impedances. My tuning network provides a nominal 50 ohm load, but there
can be significant variations with wind and weather.
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