WD7S PRODUCTIONS

HOMEBREW GALLERY-5

8877 AUTO-TUNE HF AMPLIFIER

 

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UPDATED 02-14-2004 THE 8 POSITION AUTOMATIC ANTENNA SWITCH DECODER/DRIVER IS FINISHED AND TESTED.  THE BCD DATA FROM THE AMPLIFIER IS THE SAME AS THE YAESU RADIOS BAND DATA OUTPUT.  THIS ALLOWS THE USE OF THIS SAME PC BOARD FOR A STAND ALONE  YAESU BAND DECODER/SOURCE DRIVER OR AUTOMATED ANTENNA SELECTION WITH THE AMPLIFIER.  IT CAN SOURCE VOLTAGE (@ 500ma) FOR A REMOTE ANTENNA SWITCH OR BAND-PASS FILTERS.   THE DECODER OUTPUT CAN BE CONFIGURED FOR RELAY BANK SWITCHING, (6-WIRE CONTROL CABLE) OR ALL 8 CONTROL LINES SEPARATED, (9-WIRE CONTROL CABLE).  THE OPERATING VOLTAGE FOR THE REMOTE SWITCH CAN BE ANY CONVENIENT VALUE (40VDC MAX) SINCE AN ON-BOARD REGULATOR SUPPLIES VOLTAGE FOR THE IC.  THE DECODER ALSO HAS  MANUAL SELECTION CAPABILITY WHILE  THE AMPLIFIER IS SWITCHED OFF.  ON-BOARD JUMPERS CAN BE SET FOR MULTIPLE BANDS USING ONE ANTENNA (TRI-BAND BEAM etc.).  THIS IS NOT REQUIRED FOR USE WITH THE AMPLIFIER.  THE CONTROL LINE CONNECTS TO THE DECODER VIA A DIN CONNECTOR FOR FAST DISCONNECT DURING ELECTRICAL STORMS.

THE POOR SSB FREQUENCY DETECTION WAS SOLVED BY ADDING A SINGLE STAGE RF PREAMP BEFORE THE SCHMITT TRIGGER.  I BIASED THE TRIGGER AT 2.5VDC AND COUPLED THE PREAMP TO IT WITH A .1MF DISK.  COUPLING TO THE INPUT LINE  IS 20PF.  THE AMP NOW TRACKS FREQUENCY WITH LESS THAN 1 WATT OF DRIVE.  THE FIRMWARE COUNTS THREE 25MS GATE TIMES AND COMPARES ALL THREE BY EQUATION TO CONFIRM SSB FREQUENCY.  BAND HOPPING IS NOW A BREEZE!!  

THE AMPLIFIER FEATURES 1.8-29 MHZ COVERAGE WITH 78 BAND SEGMENTS AND 8 REMOTELY SWITCHED ANTENNA CHOICES AVAILABLE FOR EACH SEGMENT, THAT'S 624 POSSIBLE COMBINATIONS.  THE AMPLIFIER IS MEMORY TUNED AFTER INITIAL SET UP FOR EACH SEGMENT.

BAND SEGMENTS ARE DIVIDED AS FOLLOWS;

1.8MHZ, 25KHZ
3.8MHZ, 25KHZ
7.2MHZ, 25MHZ
10MHZ, 100KHZ
14MHZ, 50KHZ
18MHZ, 100KHZ
21MHZ, 50KHZ
24.9MHZ, 100KHZ
28/29MHZ, 100KHZ

THE AMP USES THE EIMAC 8877 (YU-158) WITH THE  WD7S TRIODE CONTROL BOARD, DS-1 DISPLAY,TU-6B, DS-PS AND HV-2.  THE AMPLIFIER USES STEPPER MOTORS FOR TUNE, LOAD AND BANDSWITCH POSITIONING.  THE STEPPER BOARD IS A THREE AXIS CONTROLLER USING THE ALLEGRO UCN5804B DRIVER IN DUAL PHASE MODE.  EACH DRIVER USES A LM556 TIMER TO DISABLE ITSELF DURING PERIODS OF NO USE.   THE HV POWER SUPPLY IS IN THE AMP CABINET WHILE THE PETER DAHL PLATE TRANSFORMER IS CONTAINED IN A SEPARATE CABINET, EASIER TO TRANSPORT FOR THIS OLD BACK!!

THE CPU BOARD CONTAINS THE BS2P-40 BASIC STAMP,  PRESCALER FOR THE FREQUENCY COUNTER, 1 OF 10 DECODER + SOURCE DRIVER FOR THE TUNED INPUT RELAYS,  4 PORT OPTO ISOLATOR FOR THE  BCD BAND DATA  OUTPUT (USED FOR THE REMOTE ANTENNA SWITCH),  AND AN OPTO ISOLATOR FOR FAULT LINE CONTROL (DURING BAND CHANGING OR ANTENNA SELECTION).  A ZIF SOCKET WAS USED FOR THE BS2P-40 AND IT'S WORTH EVERY PENNY!  BAND CHANGE TAKES <1 SECOND AND IN-BAND SEGMENT CHANGE TAKES <500MS AND IS ALLOWED WHILE TRANSMITTING. 

A 2X24 LCD DISPLAYS TUNE CAP POSITION, LOAD CAP POSITION, BAND, FREQUENCY SEGMENT AND CURRENT ANTENNA SELECTION. 

THE CABINET MEASURES18.5" W X 17" D X 7" H AND IS BUILT FROM .080" ALUMINUM WITH 3/4" ALUMINUM ANGLE AT THE CORNERS.  THE ANGLE IS HAND TAPPED FOR THE PANEL SCREWS.  "RATTLE" CAN PAINT WAS USED ON THE AMP WITH DRY-TRANSFER LETTERING UNDER THE CLEAR LACQUER FINAL COATS

THE TANK CIRCUIT (L-PI-L) USES A 300NH COIL AT THE ANODE TO OBTAIN A REASONABLE RL VALUE FOR MATCHING ON 10/12 METERS.  IAN WHITE'S (G3SEK)  SPREADSHEET HANDLED THIS EXTRA "L" INDUCTOR PERFECTLY.  NO PARASITIC SUPPRESSOR WAS USED (OH NO!!) AND THE AMP IS UNCONDITIONALLY STABLE ON ALL BANDS.  FULL BREAK-IN QSK CAPABLE AS ALWAYS.

I'VE SCANNED THE TANK CIRCUIT SCHEMATIC FOR THOSE THAT ASKED.  THE CODE IS WRITTEN IN PBASIC 2.5 VERSION2, BETA 2.1, PLEASE CONTACT ME IF YOU WOULD LIKE A COPY.  PLEASE BE AWARE IT IS WORK IN PROGRESS!!  IF THERE IS ENOUGH INTEREST I CAN MAKE THE CPU AND STEPPER BOARDS AVAILABLE.

SOME EARLY TEST NUMBERSTHE EXCITER WAS MY FAITHFUL SHOP RADIO, ICOM IC-736.  INPUT SWR ALL BANDS, 1.1:1 OR LESS.   I MEASURED THE DRIVE LEVELS WITH A BIRD 43 USING A 50W SLUG.  THE FM OUTPUT VALUES WITH THE NYE VIKING METER WERE SPOT ON WITH THE BIRD 43 USING A 2500W SLUG  

FREQUENCY DRIVE-PEP OUTPUT-PEP EP  IP  ma IG  ma HARM/SPURS
1.9 28 1500 3650 675 10 -58dbm
3.75 36 1500 3650 675 15 -54dbm
7.150 44 1500 3650 675 10 -50dbm
14.200 53 1500 3650 750 15 -54dbm
18.100 38 1500 3650 750 15 -58dbm
21.200 55 1500 3650 750 15 -60dbm
24.900 55 1500 3650 675 10 -55dbm
28.500 55 1500 3650 750 15 -45dbm

 

 

 

 


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