500W and 600W PEP 1.0-1.8MHz HF RF Power Linear Amplifier AM Radio Transmitter Hard Test!

Hard Test of this PA, check it out!

HPA500SC.x is a unique high gain Push-Pull HF Power Amplifier designed for maximum reliability and durability, Equipped with a sophisticated multi-protection circuit that makes it almost impossible to burn (damaged) by any load mishmash even output is totally open or short circuit. (as long as installation instructions are followed.)
It comes in 2 versions with small differences between them.
HPA500SC.1 is capable to deliver 500W PEP on your 50 Ohm load, antenna or any next RF stage and has approx 3db more gain compared to the HPA500SC.2 that delivers 600W PEP.
Specifically designed for AM modulation transmitters
HPA500SC.1 version normally operates at 125W Un-modulated CW carrier for 100% modulation capability (500W PEP)
and the HPA500SC.2 version at 150W Un-modulated CW (600W PEP)


Specifications:

High Gain Push Pull Class B RF Power Amplifier can only be used for AM, FM, CW and digital modes
(Not capable of SSB modulation)

Output Power:
HPA500SC.1
AM: 500W PEP (125W carrier)
FM, CW, Digital modes: 250W
SSB: NOT Capable

HPA500SC.2
AM: 600W PEP (150W carrier)
FM, CW, Digital modes: 300W
SSB: NOT Capable

Power Supply:
Main: 50V/17A max peak current for the RF Stage (+VP pad on pcb)
Auxiliary: 12V/100mA for the protection circuits, biasing etc. (VC pad on pcb)

Operating Frequency: 1-1.8 Mhz

RF IN:
HPA500SC.1
2W PEP input Drive Power
HPA500SC.2
5W PEP input Drive Power

High-SWR, High-Temperature and Over-Power, complete protection circuit on board.
Almost plug and play design,
no need for any adjustments,
Just install as per instructions and it's ready to operate.

Directional Coupler output for easy Forward - Reflected measurements with just an external Voltage or uA meter.
(F and R pads on pcb)

Basic Low Pass Filtering also included on board.

Installation instructions:
Some minimum RF power technician experience is required as with any project like this.
Always use a heatsink capable to handle an amplifier of this power level and always use forced air to cool down the heatsink. No need for copper heat spreader if your heatsink has at least 10mm of "body plate".
Ensure a minimum air flow also on the component side of the amplifier board.
The amplifier uses 4pcs of high power MOSFETs that needs to be isolated from the heatsink, to do so only use high quality mica glass isolators with a small amount of thermal paste on both sides of the mica, spread the paste in a very thin layer across the entire mica surface.
Never use silicone or plastic or other types of insulators as they are transferring temperature slower and MOSFETs will be damaged.
Apply a small amount of thermal paste to attach the onboard thermal sensor (marked as TPS on pcb)
to the heatsink.
Always use 50 Ohm coaxial cables to connect input and output of the amplifier to previous and next stages.
Never exceed RF input drive power more than 5 times of the nominal.
BSC pad on pcb, short this pad to GND to cut off the bias voltage, (eliminates output Power)