MODERN AM BROADCAST STATIONS AM STEREO CQUAM WITH DDS DDS EXCITER OPERATING MANUAL 20W CARRIER - 80W PEP
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: 520-1710 KHZ. FREQUENCY STEPS: 1KHZ POWER ADJUSTMENT: 0-20W MAX CARRIER (0-80W PEP) MODULATION INPUT LEVEL: 700mv/600 OHM BALANCE. MODULATION INPUT CONNECTOR: FEMALE XLR 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 BUILT IN SWITCHING POWER SUPPLY 110~240V AC POWERFUL LOW PASS FILTERS. 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)XLR AUDIO IN, CONNECTED TO AUDIO-MIXER OR RADIO LINK. 4 PTT. WHEN GROUNDED THE UNIT SWITCHES TO TRANSMISSION LIKE WITH THE FRONT PANEL ST.BY-TX SWITCH 5) REMOTE. 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 TWO FUSE HOLDERS AT THE REAR PANEL 8) FUSES. TOP FUSE:6A BOTTOM FUSE:1.5A AT 230V & 3A AT 110VAC.
ANTENNAS & TUNERS
MATCHING CIRCUITS TO DRIVE TUBE AMPLIFIERS 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.
ADJUSTMENT AND TUNING 1) CONNECT THE POWER CABLE, THE MODULATION COAXIAL XLR CABLE, THE GND WIRE & THE ANTENNA COAXIAL CABLE. 2) SET AUDIO POTENTIOMETER TO MINIMUM. 3) SET THE POWER-TUNE SWITCH TO TUNE POSITION. 4) LEFT SWITCH (TX-ST.BY) AT ST.BY POSITION. 5) RIGHT SWITCH (ON-OFF) AT ON POSITION. 6) PUSH THE UNLOCK AND ONE OF OTHER TWO PUSH BUTTONS TO GO THE OPERATION FREQUENCY 7) SET SWITCH (TX-ST.BY)TO TX POSITION. 8) TUNE THE ANTENNA TUNER (CAPACITORS AND COILS) TO GET THE LOWER SWR LOOKING THE SWR LED BAR (IDEAL 1:1) IF NOT POSSIBLE, CHANGE FREQUENCY AND RESTART THE TUNING PROCESS OR CHANGE THE ANTENNA WIRE LENGTH. 9) NOW SET THE POWER-TUNE SWITCH TO POWER POSITION AND ROTATE THE POWER POTENTIOMETER TO MAXIMUM. 10) DO A FINE TUNING SWR. 11) NOW YOU ARE READY TO DRIVE WITH AUDIO LEVEL. ROTATE THE AUDIO POTENTIOMETER AND DO NOT EXCEED THE 0 DB & SET THE EQUALIZER FOR BEST SOUND. ENJOY.
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 50 OHM. ATTENTION! WIRE RESISTORS ARE NOT SUITABLE CONSTRUCTION: FOR A 80 WATT TRANSMITTER WE NEED 164 RESISTORS 8Κ2 2W CONNECTED IN PARALLEL. 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:((300/1,665MHZ)/2) Χ 0,97=87,38 METERS IF WE FEED THIS ANTENNA IN THE MIDDLE WITH 50OHM COAXIAL CABLE WE HAVE A 50 OHM 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 5-6CM 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.
TERMS OF WARRANTY & PROPER OPERATION ATTENTION THE DEVICE IS COVERED BY FULL ONE-YEAR GUARANTEE OF GOOD OPERATION AND AGAINST DEFECTIVE COMPONENT AND EXTENDED TO THE REPAIR OF REPLACEMENT OF DEFECTIVE COMPONENT IN OUR LABS WITHOUT ANY COST. EXCEPTIONS OF WARRANTY OUTPUT TRANSISTORS THAT THEY CAN BE DESTROYED DUE TO: 1A) THUNDERS OR STATICS THROUGH THE ANTENNA OR POWER LINES. 1B) OSCILLATING OR ARCING OF RF POWER AMPLIFIERS FED BACK TO THE DDS EXCITER. 1C) AUDIO CONNECTION TO THE WRONG DEVICES. 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: WEB http://www.pll.gr E-MAIL info@pll.gr TEL: 210-2824273 MOBILE 697 38 33000 THANKS FOR YOUR PREFERENCE, ALWAYS AT YOUR SERVICE. ANASTASIOS TOURIS RF & ELECTRONIC ENGINEER SV1EDT