******BUILD AT YOUR OWN RISK******
2 X BLF188XR HF AMPLIFIER. 1.8-28MHZ.
SETUP: CONNECT A 50 OHM LOAD TO THE OUTPUT. CONNECT THE 50VDC SUPPLY WITH AN AMP METER IN THE CIRCUIT. SET THE BIAS POTS FOR 40 OHMS. TURN ON THE 50VDC SUPPLY.
TURN ON THE BIAS AND ADJUST THE POTS FOR ABOUT 1.930VDC OR 4 AMPS OF CURRENT ON THE AMP METER IN THE 50VDC SUPPLY. THE BIAS SHOULD BE THE SAME ON BOTH DEVICES. ALWAYS USE THERMISTORS IN THE BIAS CIRCUIT.
THIS HEATSINK WAS SALVAGED FROM A 50HP VARIABLE FREQUENCY DRIVE THAT FAILED. GREAT SOURCE FOR HEATSINKS FOR LDMOS AMPLIFIERS!
THE TRANSFORMER HAS 4 TURNS TOTAL WITH THE LAST TURN BEING THE CENTER CONDUCTOR OF THE COAX PASSING THROUGH EACH SIDE. THE COPPER TUBING INSIDE IS THE SINGLE TURN PRIMARY. THE COAX IS USED TO ACCOMPLISH CLOSE COUPLING AND A VERY BROADBAND TRANSFORMER.
THE SHIELDS FROM EACH SIDE ARE CONNECTED TOGETHER AND SOLDERED TO THE TUBING.
THIS IS MY 16:1, 2.5KW OUTPUT TRANSFORMER. THE RATIO IS THE SQUARE ROOT OF THE NUMBER OF TURNS. THIS TRANSFORMER HAS 4 TURNS WITCH EQUALS 16:1.
THE CORES ARE LAIRD 28B1020-100. THE COAX IS TC-12.
HERE IS A DRAWING OF THE OUTPUT TRANSFORMER
UPDATED 12-5-2015