3.12 Install 1N5819 diode
This diode D33 is the diode with a black body, and a white stripe. It is installed vertically. It
must be orientated correctly, with the white stripe on the diode matching the white stripe on
the PCB.
This diode protects the radio against reverse polarity. So that if you connect the power to
the board the wrong way around, you do not destroy it. A Schottky diode is used because
the forward conducting voltage drop is less than an ordinary diode. However, on transmit,
the voltage drop across this diode can still be up to 400mV. This reduction in voltage does
slightly decrease the output power.
IF you want to squeeze every last milliwatt of output power out of the radio, and IF you trust
yourself NEVER to connect the power supply in reverse by mistake, then if you just install a
jumper wire instead of D33, it would give you a little higher RF power output. It is very
strongly recommended to install D33.
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