RF Deck
80m/160m RF Amplifier
The rf amplifier is capable of 500 watts carrier output, including 80m and 160m operation.
Two coils are used in the output tuned circuit for 80m and 160m operation, where the 160m coil is shorted for 80m. Also, drain bus shunt capacitance is added for 160m operation. Both of these band switching actions are performed by two open frame relays. A front panel switch is used to energize the relays for 160m operation.
The tuning capacitor is a 500pf 3.5kv unit, and the loading capacitor is a surplus 2000pf broadcast unit that has been padded with three 470pf multi layer ceramic (MLC) capacitors.
Two low voltage power supplies are used to power the 12v bandswitching relays and DEIC420 driver ICs. The driver IC power supply regulator circuits are mounted on the heat sink, and are switched by a small 120VAC relay, which is energized by an external keying voltage.
This class E amplifier uses 2 push-pull modules of 5 FQA11N90 MOSFETs each. The MOSFETS in each module are paralleled by large brass gate and drain buses. Double-sided copper clad circuit board is used for the grounded source bus. Each gate bus is driven by a DEIC420 driver IC, and each drain bus has 3X470pf shunt capacitance (plus 1000pf for 160m). The gate and drain buses and modulated DC power inputs are protected from over voltage by transient voltage suppressor (TVS) devices (Transorbs).
The rf amplifier was modified in conjunction with the VFO IXDD414 driver modification. The RG-58 inputs to the DEIC420 drivers are now simply terminated with 3W 50ohm resistors to ground. Also, the 2000pf per module shunt capacitance shown on the schematic was reduced to 1500fp due to the use of multilayer ceramic (MLC) capacitors.
RF Amplifier Construction
Heatsink Construction
RF Amplifier Tuning
See testing and tuning photos and details for more waveform pictures.
The rf amplifier was designed by Steve Cloutier WA1QIX. The design revision used to build this amplifier is detailed in this schematic. The current revision of this schematic may be found at www.classeradio.com