MODERN

AM BROADCAST STATIONS With DDS

DDS EXCITER

OPERATING MANUAL

600w carrier - 2400w p.e.p

What is DDS

IT IS THE INITIALS OF THE WORDS DIRECT DIGITAL SYNTHESIZER, THAT MEANS: DIRECT DIGITAL FREQUENCY SYNTHESIS. MORE SIMPLE: IT IS A CIRCUIT THAT USES A REFERENCE FREQUENCY AND WITH A SUITABLE PROCESSOR PROGRAM THE TRANSMITTING FREQUENCY IS CREATED WITH ENTIRELY DIGITAL TECHNIQUE (WITHOUT USING THE ORDINARY OLD OSCILLATOR TYPE WITH CAPACITORS AND INDUCTANCES) AND WITH THE ACCURACY OF THE REFERENCE OSCILLATOR BY MEANS OF THE MODERN DIGITAL CIRCUITRY.

SPECIFICATIONS ♥ OPERATING FREQUENCY IS RANGE: 520-1800 KHZ. ♥ FREQUENCY STEPS : 1HZ,10HZ,100HZ,1KHZ,5KHz,9KHZ,10KHz. ♥ POWER ADJUSTMENT: 0-600W MAX (0-2400w p.e.p) ♥ MODULATION INPUT LEVEL (FEMALE RCA): 600mv/10k. ♥ ANTENNA OUTPUT: COAXIAL, FEMALE SO239, 50 OHM. ♥ SWR PROTECTION. (NOT ANTENNA SHORT CIRCUIT PROTECTION) ♥ BUILT IN POWER AND SWR METER. ♥ TX LED INDICATOR. ♥ HIGH SWR LED INDICATOR. ♥ BUILT IN MODULATION METER ( V-U METER ) ♥ 24 HOUR OPERATION AT AMBIENT TEMPERATURE < 40°C ♥ THERMAL PROTECTION. ♥ TREE BUILT IN SWITCHING POWER SUPPLIES 110~240V AC ♥ POWERFUL DOUBLE BAND PASS FILTERS. ♥ BALANCED AUDIO (OPTION) ♥ ANTI-SPLATTER FILTER (OPTION) ♥ CARRIER LEVEL POSITIVE CONTROL, (OPTION) ♥ SPECIFICATIONS DEVIATION: ±5~10% MAX (DUE TO COMPONENTS TOLERANCE)

• THERE IS NO ADDITIONAL POWER OUTPUT ADJUSTING TRIMMER INSIDE THE TRANSMITTER!

CONNECTIVITY

AT THE REAR OF THE DEVICE YOU WILL SEE 1) THE GROUNDING BUTTERFLY. IT HAS TO BE CONNECTED THROUGH THICK CABLE TO A PROPER GROUND OR A METALLIC WATER PIPE OR BOTH. 2) ANTENNA CONNECTOR, 50 OHM. 3) RCA AUDIO IN, OR XLR TO BE CONNECTED TO AUDIO MIXER OR LINK. 4) TRANSMIT PTT. WHEN GROUNDED THE UNIT SWITCHES TO TRANSMISSION LIKE WITH THE FRONT PANEL ST.BY-TX SWITCH 5) REMOTE (LINEAR). DURING TRANSMISSION IT GROUNDS THE CONTACT TO BE USED FOR LINEAR AMPLIFIER, RECEIVER/TRANSMITTER SWITCHING, ETC. 6)110~240V AC POWER SUPPLY. THREE LEAD POWER CABLE LIKE THE ONES USED TO POWER COMPUTERS. 7) COOLING FANS. THEY SHOULD NEVER BE COVERED!

THERE ARE SIX FUSE HOLDERS AT THE FRONT PANEL LEFT: 3,5A THE MIDDLES: 12A RIGHT: 12A AT 230V AND SHORT CIRCUIT AT 110V AC. THE FUSE CONNECTED DIRECT FROM ELECTRICAL BOARD 20-25A.

ANTENNAS & TUNERS

MATCHING CIRCUITS TO DRIVE TUBE AMPLIFIERS

GRID DRIVEN

CATHODE DRIVEN

FILAMENT DRIVEN THE TUBES ARE NOT NECESSARY TO OPERATE AT THE MANUFACTURER RECOMMENDED VOLTAGES AS THIS IS POSSIBLE TO EFFECT MODULATION QUALITY. (AS LONG AS YOU MODULATE THROUGH THE DDS EXCITER)

ATTENTION

LONG ANTENNAS, AND ESPECIALLY VERTICALS, HAVE THE BAD HABIT TO BE LOADED WITH STATIC VOLTAGE OF THE ORDER OF MANY THOUSAND VOLTS, FROM CLOUDS ELECTRICALLY CHARGED PRIOR TO STORMS. THIS MAY RESULT TO DAMAGE OF THE OUTPUT CIRCUIT. DURING SUCH WEATHER PHENOMENA WE SHOULD DISCONNECT THE ANTENNA IN TIME TO PREVENT POSSIBLE DISTRACTION OF THE DDS EXCITER OUTPUT. IF THE DDS EXCITER IS CONNECTED WITH RF LINEAR AMPLIFIERS THAT OSCILLATE OR PRESENT ARCING THE OUTPUT TRANSISTORS MAY BE DESTROYED. WE NEVER CONNECT AUDIO POWER AMPLIFIERS TO THE AUDIO INPUT OF THE EXCITE. WE ONLY CONNECT AUDIO MIXERS EQUALIZERS, COMPRESSOR-LIMITERS ETC. SINCE THE WHOLE SYSTEM IS AIR COOLED THE AMBIENT TEMPERATURE OF THE INSTALLATION AREA SHOULD BE LESS THAN 40°C, SO THE HEAT DISSIPATION THROUGH THE HEAT-SINK IS EFFICIENT. IF THE SHELTER WHERE THE DDS EXCITER IS INSTALLED SUFFERS EXCESSIVE HEAT LEVELS WE SHOULD CIRCULATE THE AIR OF THE SHELTER AND PROBABLY INSTALL A FUN BLOWING TOWARDS THE HEAT SINK OF THE EXCITER. THE EXCITER SHOULD NEVER BE INSTALLED FOR OPERATION IN A CLOSET BECAUSE THERE CANNOT BE PROPER AIR CIRCULATION AND MAY BE DAMAGED. TO BE CAREFUL WITH HIGH SWR, OVER-DRIVE MODULATION, LIGHTNINGS, THUNDERS & RFI. DO NOT FORGET TO REMEMBER TO YOUR TECHNICIAN TO PUT LIGHTING & THUNDER PROTECTOR INTO YOUR ANTENNA SYSTEM AND TX. THE GROUND SYSTEMS IT SHOULD THEY ARE IN THE GROUND WITH COPPER AND AFTERWARDS ENTER RADIAL WIRES ROUND THE AERIAL. IF DOES NOT EXIST WAY TO BE PLACED THESE SYSTEMS, THEN YOU CAN USE THAT METAL OBJECT YOU HAVE : (METALLIC GARAGE, METALLIC PIPES OF WATER, METAL FENCING FOR HOUSE, METALLIC ROOFS) ETC. TRANSMITTERS CAN BE DAMAGED FROM THUNDERS & LIGHTINGS. IF YOU WANT TO MAKE CERTAIN QUESTIONS IN THE TECHNICAL DEPARTMENT, FEEL FREE TO DO.

ADJUSTMENT AND TUNING 1) SET MODULATION BUTTON TO MINIMUM (AUDIO) 2) ADJUST POWER BUTTON (POWER) AT TIME 11 3) LEFT SWITCH AT STAND BY POSITION (ST.BY) 4) PUSH ON BUTTON (ON-RIGHT SWITCH) AND THE DISPLAY SWITCHES ON 5) TURN ROTARY SWITCH AT THE MIDDLE POSITION (SET) 6) SELECT THE DESIRED TRANSMIT FREQUENCY. PRESS THE UNLOCK BUTTON IN AND ROTATE THE BUTTON LOCATED UNDER THE DISPLAY. PRESS STEEP BUTTON IN TO CHANGE THE TUNING STEP. DEFAULT STEP IS 1KHZ 7) SET SWITCH TO TX POSITION (ΤΧ) 8) ROTATE CAL BUTTON (CAL.), SO THE METER NEEDLE GOES TO THE LAST LINE AT THE RIGHT. 9) TURN ROTARY SWITCH TO SWR POSITION (SWR) TO CHECK STANDING WAVE RATIO. 10) TUNE THE ANTENNA TUNER CAPACITORS AND COILS TO GET LOW SWR (IDEAL 1:1) IF NOT POSSIBLE CHANGE FREQUENCY AND RESTART THE TUNING PROCESS. 11) ROTATE THE ROTARY SWITCH TO WATT POSITION AND READ THE OUTPUT POWER ON THE METER. 12) INCREASE OR DECREASE THE OUTPUT POWER WITH THE POWER BUTTON. 13) INPUT AUDIO AND ADJUST THE AUDIO BUTTON SO THE V-U METER SHOWS 100% AT THE PEAKS. ΤHE RF POWER (WATT) ON THE WATT-METER WILL DEFLECT POSITIVE. THE V-U METER HAS ADJUSTMENT FOR THE HIGHER POWER. WHEN MINIMIZE THE POWER MUST MINIMIZE AND THE AUDIO INPUT. ATTENTION : DURING TUNING THE AUDIO SHOULD BE OFF.

DUMMY LOAD ONE OF THE MOST IMPORTANT TOOLS NECESSARY FOR A RADIO STATION IS THE DUMMY LOAD. IT IS A WIDEBAND DUMMY ANTENNA THAT ALLOWS FOR THE TUNING OF THE STATION EQUIPMENT WITHOUT RADIATING TO THE ENVIRONMENT AND PRESENTS NO SWR AT ANY FREQUENCY. IT IS NOTHING BUT 2WATT NON-INDUCTIVE CARBON RESISTORS CONNECTED IN PARALLEL THAT ALL TOGETHER EQUAL TO 50ΩHΜ. ATTENTION ! WIRE RESISTORS ARE NOT SUITABLE CONSTRUCTION FOR A 2400 WATT TRANSMITTER WE NEED 2000 RESISTORS 100ΚΩ 2W CONNECTED IN PARALLEL!!! GOOD CONSTRUCTION!!

CALCULATE ANTENNA LENGTH AS WE ALL KNOW IN ORDER TO HAVE AN EXCELLENT ANTENNA IT IS NOT ENOUGH JUST TO HAVE LOW SWR BUT THE ANTENNA SHOULD HAVE THE REQUIRED LENGTH DEPENDING ON TRANSMIT FREQUENCY. USING THE FOLLOWING CALCULATIONS WE FULLY UTILIZED OUR STATION’S POWER. SUPPOSE THE DESIRED TRANSMIT FREQUENCY IS 1.665MHZ: ((300/1,665)/2) Χ 0,97=87,38 (RESULT IS IN METERS) IF WE FEED THIS ANTENNA IN THE MIDDLE WITH 50OHM COAXIAL CABLE WE HAVE A 50OHM ANTENNA WITH 1:1 SWR.

(THE WELL KNOWN DIPOLE) END FEEDING THE ANTENNA (THE WELL KNOWN LONG WIRE) WE NEED ANTENNA TUNER TO MATCH FOR SWR, AS WELL AS GROUND COUNTERPOISE. THE COIL CAN BE MADE OF AROUND 80 TURNS OF 2-3MM WIRE WITH 5CM WINDING DIAMETER

WE SHOULD NEVER FORGET THE NEED OF GOOD GROUNDING USING COPPER SHEETS AND RODS CONNECTED TOGETHER WITH THICK WIRES AND BURIED IN THE GROUND, ETC.

HOW TO MODULATE THE DDS EXCITER CONNECT THE MIXER OUTPUT TO THE AUDIO INPUT OF THE EXCITER. WE SUGGEST THE USE OF EQUALIZER AND COMPRESSOR-LIMITER FOR MAXIMUM PERFORMANCE.

WHY 50 ohm? THERE IS GLOBAL AGREEMENT AMONG THE RF OEMS TO STANDARDIZE THE USE 50 OHM CABLES AND SWR/POWER METERS FOR THEIR CONVENIENCE.

CULTURE AND TECHNICAL ISSUES AS HUMAN IS CREATIVE AND COMPETITIVE SO ARE THE RADIO STATIONS AND THEIR OWNERS ALWAYS TRYING TO HAVE GREATER COVERAGE RANGE AND QUALITY MAKING THE “BEST STATION”. FOR ALL THESE TO HAPPEN THE FOLLOWING SHOULD BE AVAILABLE: GOOD OSCILLATOR WITH DDS FREQUENCY CONTROL WITHOUT NOISES AND SPURIOUS RADIATION. THE SOUND PATH SHOULD INCLUDE THE SMALLEST POSSIBLE NUMBER OF HIGH QUALITY LOW DISTORTION STAGES. THIS MEANS THAT IF WE USE A MIXER WITH A FIRST STAGE PREAMPLIFIER AND A FINAL PREAMPLIFIER WITH 2% DISTORTION EACH, AT THE END WE GET THE SUM OF THE DISTORTION OF ALL THE DEVICES: 2%+2%+2%=6%. IT WOULD BE BETTER THEN TO MODULATE USING ONLY THE MIXER. RADIO STATIONS ARE STRIVING TO INCREASE POWER IGNORING THAT WHAT MATTERS MOST IS A VERY GOOD AND EFFICIENT ANTENNA SYSTEM AND AN ADVANCED TRANSMITTER WITH GOOD SPECTRUM PURITY AND LOW NOISE / DISTORTION. THE GOOD GROUNDING SYSTEM, THE PROPER ANTENNA LENGTH INSTALLED AT A HIGH TOWER IS A REQUIRED COMBINATION FOR SUCCESS.

TERMS OF WARRANTY & PROPER OPERATION

ATTENTION

THE DEVICE IS COVERED BY FULL ONE YEAR WARRANTY OF GOOD OPERATION AND AGAINST DEFECTIVE MATERIALS. IT IS EXTENDED TO THE REPAIR OF REPLACEMENT OF DEFECTIVE MATERIALS IN OUR LABS WITHOUT ANY COST. EXCEPTIONS OF WARRANTY OUTPUT TRANSISTORS, THAT THEY CAN BE DESTROYED DUE TO: 1Α) THUNDERS OR STATICS THROUGH THE ANTENNA OR POWER LINES. 1Β) OSCILLATING OR ARCING OF RF POWER AMPLIFIERS FED BACK TO THE DDS EXCITER. 1Γ) AUDIO CONNECTION TO THE WRONG DEVICES. (NOT AUDIO MIXER, EQUALIZER & COMPRESSOR-LIMITER) 2) WHEN DAMAGES ARE CAUSED DUE TO IMPROPER USE NEGLIGENCE OR CIRCUIT MODIFICATIONS FROM THE USER AND GENERALLY FROM NON AUTHORIZED PERSONS. 3) DAMAGE AT THE POWER SUPPLY DUE TO OVER VOLTAGES OR POWER LINE STATICS OR RF FEEDBACK OR POOR AIR CIRCULATION. 4) DAMAGES CAUSED DUE TO REPLACEMENT OF FUSES WITH ONES OF THE WRONG VALUE OR TYPE. 5) DAMAGES CAUSES DUE TO INTEROPERABILITY PROBLEMS OF OTHER DEVICES FROM OTHER MANUFACTURERS CONNECTED TO THE DDS EXCITER. 6) TRANSPORTATION AND POOR MAINTENANCE DAMAGES.

VISIT US ON THE INTERNET: www.pll.gr E-mail info@pll.gr Tηλ: 210-2824273 mobile 697 38 33000 THANKS FOR YOUR PREFERENCE, ALWAYS AT YOUR SERVICE. ANASTASIOS TOURIS RF ELECTRONIC ENGINEER, SV1EDT