600 PA project :
|1.||A magnetic loop antenna has a narrow VSWR bandwidth. When the TX is accidentally mistuned to another frequency than a narrow band loop antenna is, you can harm the PA.|
|2.||When using SDR
software, you can easily jump to an unwanted frequency,
by accidentally clicking on a wrong place on a screen.
Use a foot switch to activate the TX.
broadband amplifier can show nearly 600W output on the meter, by driving it with more
power than 1Wrms. But this is not advised.
Why ? A single ended NXP test circuit enables 320W max output and 80% efficiency. These results are only possible due to the use of a resonating output matching circuit. But a balanced broadband amplifier with broadband output coupling (like this A600) is NOT able to deliver 640W without severely overdriving it. Resulting in strong IMD, and a higher chance of damaging the power FETs. Max. undistorted and safe output is 400Wp.
Maximal drive power.
Driving this amplifier with more than 2.6W
damage the gates of the FETs.
Also : replace D6
by a fast +/-5v bipolar surge arrestor diode CDSOD323-TO5SC .