TAG Low Frequency 1 Watt Power Amplifier

Credits: This is a Class D transmitter "borrowed" from designs by Lyle Kohler and Bill Ashlock.

Features: 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.

Back to Home