LDMOS MRFE6VP61K25H 1.8-54MHZ 1.25KW SOLID STATE AMPLIFIER
**********ALL INFORMATION CONTAINED HERE IS BELIEVED TO BE ACCURATE. BUILD AT YOUR OWN RISK.**********
THIS AMPLIFIER WAS FEATURED IN JANUARY 2015 QST MAGAZINE. THE AUTHOR IS ANDREW BUCKLER K2OP. ALL THE CONSTRUCTION DETAILS ARE THERE AND ONLINE.
IT WAS VERY EASY TO BUILD AND ASSEMBLE. I USED WHAT I HAD ON HAND. I MADE THE BOARDS WITH A DREMEL TOOL. I HAD THE COPPER BECAUSE I ALWAYS KNEW SOLID STATE AMPS WERE GOING TO GET CHEAP SOME DAY, THE DAY HAS ARRIVED!
THESE TRANSISTORS ARE $185.00 FROM RF PARTS. IT IS AS EASY AS IT LOOKS! GIVE IT A TRY, YOU WON'T BE SORRY. I MUST THANK JIM W6PQL FOR ALL HIS HELP! LOOK AT HIS WEBSITE FOR SOME GREAT INFORMATION ON LDMOS AMPLIFIERS.
THE TRANSISTOR IN MY AMP IS A MRFE6VP61KHSR5, I WAS FLOW SOLDERING IT TO THE COPPER SO I DID NOT CARE IF IT HAD MOUNTING TABS. THE AMPLIFIER IS FINISHED AND WORKING WELL. 30 WATTS INPUT = 1.25KW OUTPUT! THAT IS WITH THE 10DB ATTENUATOR ON THE INPUT. ALWAYS USE THERMISTORS IN THE BIAS CIRCUIT.
DON'T LET THIS BE YOU! KEEP THE 50VDC CURRENT UNDER 30-35 AMPS.
OLD VARIABLE FREQUENCY DRIVES ARE A GREAT SOURCE FOR HEATSINKS FOR LDMOS AMPLIFIERS
THE PROXXON KT-70 COMPOUND TABLE FOR MAKING THE BOARDS.
ALWAYS INSTALL AN AMP METER ON THE 50VDC SUPPLY. DO NOT LOAD OVER 30 AMPS.
****ALWAYS INSTALL THERMISTORS IN THE BIAS CIRCUIT!**** THE 10K AND 22K RESISTORS SHOULD BE THERMISTORS.
STARTED ASSEMBLING MY SECOND AMP. MAKING A FEW IMPROVEMENTS AND WOULD LIKE TO COMBINE THE TWO FOR A NICE LEGAL LIMIT AMP.
I USED LIQUID TIN TO COAT THE BOARD
BOUGHT THIS 12VDC BRUSHLESS FAN AT RADIO SHACK. THE RED BLADES LOOK NICE. VERY QUIET, JUST RIGHT.
I FINISHED MY 3KW OUTPUT TRANSFORMER AND WANTED TO DO SOME TESTING. I BUILT THIS AMP WITH A BLF188XR AND IT WILL DO 1500 WATTS INTO A DUMMY LOAD. THE NEW OUTPUT TRANSFORMER DOES NOT EVEN GET WARM. NOW TO FIGURE OUT HOW TO PUT TWO DEVICE ON ONE BOARD FOR A COOL 1500 WATT AMP.
THIS AMP IS ALL HOMEBREW.
INFORMATION: CHECK OUT W6PQL.COM FOR INSTRUCTION TO BUILD THE INPUT TRANSFORMER. GO TO HIS AMPS CONSTRUCTION PAGE, A LOT OF GOOD INFO. THE CORES FOR THE INPUT TRANSFORMER ARE LAIRD 28B0375-300 I BOUGHT THESE FROM DIGIKEY. THE COAX IS TC-24, BOUGHT FROM COMMUNICATIONS CONCEPTS.
THE OUTPUT TRANSFORMER I ORDERED FROM COMMUNICATIONS CONCEPTS, PART NUMBER:RF2067-9. TRANSFORMER CORE IS 2000. 9:1. TYPE 67 MATERIAL. COAX WOUND. THE RESISTORS IN THE BIAS CIRCUIT ARE .5 WATT. MY HOMEBREW OUTPUT TRANSFORMER IS MADE WITH LAIRD 28B1020-100 CORES, THE COAX IS TC-12 FROM COMMUNICATION CONCEPTS.
I MADE THIS BLF188XR DESOLDERING TOOL WITH 1/8" COPPER PLATE. I USED THE 1/2" SQUARE ALUMINUM TO FORM THE COPPER. UNFORTUNANTLY I NEEDED IT TO REMOVE A SMOKED DEVICE. I PUT A 10-32 SCREW THROUGH THE BACK AND BOLTED IT TO THE TIP OF A 100 WATT SOLDERING GUN. HEATS UP IN 2 MINUTES, WORKED GREAT.
HOPE YOU NEVER NEED ONE!
THE SET-UP PROCEDURE. CONNECT THE OUTPUT TO A 50 OHM LOAD. CONNECT 50VDC WITH AN FLUKE AMP METER IN THE CIRCUIT. CONNECT THE BIAS AND ADJUST THE POT FOR 2 AMPS ON THE 50VDC POWER SUPPLY. THAT'S IT. YOU ARE READY TO OPERATE. TAKE THE AMP METER OUT OF THE CIRCUIT FIRST. HI
MY LATEST AMPLIFIER
I USE A 3PDT RELAY FOR TRANSMIT. THIS ACCOMPLISHES THE BIAS AND RF CONNECTIONS. THE 50PF CAP CANCELS OUT THE INDUCTANCE OF THE RELAY.
