Assembly Guide for the 222 MHz Kilowatt Amplifier Board


First, assemble the input board, installing the 9 to1 transformer last

*** if using a BLF188XR, use a 68 ohm resistor in place of the 150, and a 330 ohm in place or the 250. ***

Install the output board components


Once you install the boards, and you are ready to test, here's the recommended method:

  1. Connect the output to a wattmeter and a kw dummy load

  2. Connect the input to your driver through a wattmeter


    • CAUTION - for the initial test, you should place a 3 to 5 ohm 50w power resistor in series with the VDD, or use a current-limited power supply (limited to 5a). If there is a short from a stray wire strand, or a weak capacitor lets go, it will create an arc powerful enough to vaporize board traces, transistor tabs, etc.


  3. Turn on the 50v main supply voltage, but not the bias; there should be no current drawn

  4. Turn on the bias and note the idling current drawn from the 50v supply. Adjust IDQ for 2 amps. Note: the current drawn by the bias supply (usually12v) is not what you are measuring must measure the idling current (IDQ) the LDMOS draws from the 50v supply.

  5. Shut off the power supply, and remove current limiting.

  6. Drive with 1 watt or less. You should see an increase in drain current and at least 200w with 1w drive.

  7. Increase drive until you have 1kw out. Input power should be less than 5w, and drain current about 30A at 50v