Wednesday, September 28, 2011

ARRL Homebrew 3 Challenge Update: VSWR protection circuit

Had to install a VSWR protection circuit to protect the 100 watt output transistor from greater than 10:1 reflection.

The comparator measures VSWR, trips an S/R flip-flop which then biases an NMOS that shorts out the bias supply varactor diode regulator circuit, thereby turning off the PA.  A buzzer sounds to indicate VSWR fault.

To reset, the power must be cycled on the radio.