The challenge is to design and build a Linear Amp for CW use, capable of delivering 40 watts, using only BJT.

( No MOSFET & No Vacuum Tube )

Any kind of BJT can be used, but expecting designs with available transistors in India, so that other Hams can replicate the design and use.

Any kind of circuit combination is allowed. Single end, push-pull, paralleled single, paralleled push-pull or combined output.

Supply voltage to be limited to a maximum of  25.2 V. The idea is to make it usable with Lithium Ion battery . So 6 x 3.7v = 22.2V to 25.2V 

There is no limit for power consumption.

There must be a third order, fixed/tunable low pass filter at the output.

Power will be measured after the low pass filter.

Any CLASS allowed.

Input power 500mW to 1 W across  50ohm PAD

Testing Criteria

• All measurements will be carried out with a 50 ohm dummy load connected

• Measurements

  • DC power in

  • RF power output - with input signal at 7.0 MHz

  • RF power output - with input signal at 7.1 MHz

  • RF power output - with input signal at 7.2 MHz

  • RF power output - without input signal 

• Spurious emissions and self oscillations should not be present.

• Output power should be steady and the amp should withstand continuous key down for 120 sec

Resources:

BJT: https://en.wikipedia.org/wiki/Bipolar_junction_transistor 

Third-order filter:  "A third-order filter requires at least three reactive components: one capacitor and two inductors, two capacitors and one inductor" - quoted from https://eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Operational_Amplifiers_and_Linear_Integrated_Circuits_-_Theory_and_Application_(Fiore)/11%3A_Active_Filters/11.04%3A_Section_4- 

Designing and Building Transistor Linear Power Amplifiers  Part-1 :  https://www.arrl.org/files/file/QST%2520Binaries/QS0209Campbell.pdf 

Designing and Building Transistor Linear Power Amplifiers  Part-2 : https://www.arrl.org/files/file/QST%2520Binaries/QS0309Campbell.pdf