INSTRUCTION MANUAL FOR PLFM-100A REPLACEMENT EXCITER PC BOARD JT COMMUNICATIONS 579 N.E. 44TH AVE. OCALA, FLA. 34470 352-236-0744 fax 352-236-5130 INTERNET EMAIL: jtcomm@atlantic.net TABLE OF CONTENTS: 1) INTRODUCTION 2) INSTALLATION 3) OPERATION 4) TROUBLESHOOTING 5) SCHEMATIC 6) PC BOARD LAYOUT 7) PARTS LIST 8) SWITCH PROGRAMMING CHART 1) INTRODUCTION NOTE- PLEASE READ THE ENTIRE CONTENTS OF THIS INSTRUCTION MANUAL BEFORE INSTALLING THIS UNIT. IF YOU HAVE ANY QUESTIONS CONCERNING THE OPERATION OR INSTALLATION OF THIS UNIT, PLEASE CONTACT THE FACTORY. The PLFM-100 Replacement Exciter P.C. Board is a universal replacement for the FM broadcast services. The PLFM-100 will retrofit older broadcast transmitter sections that are either unreliable or unrepairable. Many tube and early-model transmitters are operating beyond modern state-of-the-art standards. The PLFM-100 can replace portions of the older equipment, and will remain acceptable to F.C.C. broadcast standards under Title 47, parts 2.811, 2.904, 2.932, and part 73: 73.1670, 73.1690(e). THEORY OF OPERATION The PLFM-100 utilizes a phase locked direct FM modulated oscillator. Referring to the schematic, Q1 is a low-noise RF oscillator, tuned by the combination of L1 and varactor CR2. The capacitance of CR2 is biased at 2V by the AFC voltage from U2. The modulation and AFC voltage component connects to CR2. The RF signal is buffered and amplified by Q2, Q3 and Q5. Q4 is a 3W power transistor operating at a reduced rating. The RF signal at the output of Q3 routes into U1, a divide-by-40 prescaler. The output of the prescaler connects into U2, a parallel load PLL. Y1 is a 2.56 Mhz crystal internally divided in the PLL to a low frequency reference. The output (AFC Voltage) is a 2500 Hz pulse. The pulse duration is dependent upon the phase difference between the reference frequency and the incoming signal from the prescaler. As Q1 varies in frequency due to temperature and time, the correction voltage also varies directly to the frequency. The AFC voltage becomes filtered and routed to CR2. The characteristics of the loop filter are such that the modulating audio frequencies have small effects on the PLL loop stress. It would take a deviation of +/- 150 kHz at 10 Hz square wave to begin to interfere with the loop. Selection of the DIP switches changes the binary PLL number. This changes the AFC voltage, and the operating frequency. A large change in frequency requires readjustment of L1. L1 contains an aluminum slug. The aluminum has a superior characteristic at RF and a lower distortion than ferrite material. Also the aluminum slug INCREASES in frequency when the slug becomes inserted into the coil stock. 2) INSTALLATION MOUNTING The PLFM100 has four #4 standoffs located 1/4 inch from each corner of the PC board. It is recommended that the PLFM100 be mounted to a metallic surface for minimized RF interference; the entire PC board would operate more reliable if the entire board is shielded in a separate enclosure. POWER The PLFM-100 connects to a single-ended +12VDC power source. The available current should be 0.2 amps. The Red wire is the +12v connection. A standard 7812 regulator circuit is recommended using conventional design techniques. RF CONNECTION The PLFM-100 connects to a standard 10-15W transmitters PA stage. There is sufficient drive to provide full output from the transmitter. Application notes on specific exciters are available from factory and/or Internet at no charge. The PLFM100 connects between the Modulated Oscillator section, and the next available stage that will accept an RF input of +20 dBm re. 50 ohms. The PLFM100 is a direct FM oscillator; no mixing or multiplying is required. Specific exciters make it necessary to remove multiplier/mixer sections of your exciter; locate the last multiplier stage of your exciter and connect to this point. AUDIO CONNECTIONS The PLFM-100 has a composite (flat) and a 75 us pre-emphasis input. A operating level of 0 dB re.0.7Vrms should be sufficient for full deviation. Both inputs are unbalanced. The composite input (green wire) has an impedance of 500 ohms resistive and should be connected from a low-impedance composite source. The pre-emphasized (white) connection is about 7.5 K resistive, and should also be driven from a low-impedance source. This input is frequency sensitive and the caution should be observed when using this input. 3) OPERATION A) FREQUENCY SET- COARSE The PLFM-100 has been factory set to 102.3 Mhz. Changing the frequency requires a DVM with 50000 ohms/volt, and a non-ferrous screwdriver. Please find the enclosed DIP switch setting chart. You will notice that the binary number for the desired frequency is also the operating frequency (102.3 Mhz=1023). First determine the operating frequency. Set the dip switches to the corresponding frequency, then connect the positive lead of the DVM to TP1 (on the pc layout) and the negative lead to ground. Set the DVM to 10V DC scale. While observing the DVM, rotate L1. If the desired frequency is less than the factory set, rotate the coil counterclockwise. If the desired frequency is more than the factory set frequency, rotate the coil clockwise. Continue turning slowly until the DVM reads 2VDC. The PLL is now "locked" to the desired frequency. The out of lock LED should also go off. Disconnect then re-connect the power source, and observe the LED. It will come on, then go out after approx. 1 second. This verifies that the PLFM100 is phase locked to the desired frequency. To change the frequency again, repeat the above procedure. The greater you deviate from the present frequency, the further you will need to rotate L1. Remember to set the coil so that you obtain the 2VDC on the DVM. This will keep the PLFM-100 at highest linearity and guarantee optimum lock performance. PLEASE NOTE-IT WILL BE NECESSARY TO RETUNE TRIMMER CAPS TC1 & TC2 IF A LARGE DEVIATION FROM THE SELECTED FREQUENCY TO THE FACTORY PRESET FREQUENCY. It is best to observe the output on an oscilloscope with 150mHz bandwidth or an external RF voltmeter. A spectrum analyzer would reveal best results when tuning trimmers for minimum harmonics & maximum output. FREQUENCY SET- FINE If it becomes necessary to change the fine (within 5 kHz) frequency, connect a frequency counter to the RF output. Rotate the trimmer capacitor located near the reference crystal Y1 until the desired frequency is obtained. 4) TROUBLESHOOTING IF A PROBLEM EXISTS IN THE OPERATION OF THIS UNIT, PLEASE REFER TO THIS CHART. PROBLEM SOLUTION(S) No output 1 Unit will not lock (led will not extinguish) 2,3,6,8 Audio distortion 4,5 Unit locks randomly 5,6,8 Tuning voltage not at 2.0 V @ T.P. 1 2,3,5,6 Tuning voltage jumps from below 2V to above 2V 7 Unit will not lock on desired frequency 2 Low output or excess harmonics 9 Unit not within +/- 2kHz frequency 10 SOLUTIONS 1) Check power supply. 2) Dip switches not properly set, see instructions. 3) L1 coil out of lock range. 4) Excessive audio input. 5) L1 coil at end of lock range. 6) L1 coil not properly adjusted, see instructions. 7) Turning L1 too rapidly. 8) Unit not properly shielded, see instructions. 9) TC1 and/or TC2 not properly tuned. 10) see FINE FREQUENCY adjustment section. --NOTICE-- IF YOU CANNOT FIND SOLUTION TO PROBLEM, CONTACT FACTORY FOR TECHNICAL ASSISTANCE. IF THE FAILURE IS DUE TO WORKMANSHIP OR PREMATURE COMPONENT FAILURE , THE PRODUCT WILL BE REPAIRED WITHIN ONE (1) YEAR OF DATE OF PURCHASE. YOU MUST CALL THE COMPANY DURING WORKING HOURS SO THAT A RETURN AUTHORIZATION CAN BE GENERATED. IN SOME CASES, A LOANER UNIT MAY BE AVAILABLE. AGAIN REQUEST THIS SERVICE WHEN CONTACTING FACTORY. 7) PARTS LIST DESCRIPTION QTY. CALLOUT(S) IC, PLL 1 U1 IC, PRESCALLER 1 U2 IC, VOLTAGE REG, .1A 5V MC78L05 1 U3 XSTR, NPN, RF LO-NOISE OSC/AMP 4 Q1,2,3,5 XSTR, NPN, RF AMP 2N5019 or MRF237 1 Q4 DIODE, SIL, 1N4001/2 2 CR1,3 DIODE, VARACTOR, MV209 1 CR2 COIL, VAR, .22UH, AL. SLUG 1 L1 COIL, FERRITE BEAD/10 ohm RES 2 L2,3 COIL, FIXED, #22, 1/4" 3.5" 4 L4,5,6,7 XTAL, 2.56 mHz, HC-33 1 Y1 CAP, DISC. .01uF, 50V 13 C1,2,6,7,23,25-27,29,32,33,37,38 CAP, POLY, 0.1UF ECQV1H104JZ (PANA) 5 C6, C12-15 CAP, POLY, 0.01UF ECQV1H103JZ (PANA) 1 C18 CAP, DISK 10PF, NPO 2 C19,C22 CAP, DISK 12PF, NPO 8 C28,30,31,35,36,36a,39,C\ CAP, DISK 15PF, NPO 1 C9 CAP, DISK 30PF, NPO 1 C8 CAP, DISK 43PF, NPO 3 C20,C34,C37 CAP, VAR. 3-12 PF NPO 1 C35 CAP, VAR. 5-15 PF N750 2 TC1,TC2 CAP, ELECT. 2.2UF/50V RADIAL 4 C4,C14,16,17 CAP, ELECT. 100UF/25V RADIAL 3 C5,11,24 RESISTOR, C.F. 100 1/4W 5% 2 R17,28 " " 470 " " 5 R11,12,19,21,30 " " 1K 5 R1-5,16 " " 2.2K " " 2 R26,27 " " 3K " " 1 R25 " " 4.7K " " 2 R9,10 " " 6.8K " " 1 R13 " " 10K " " 1 R15 " " 22K " " 4 R14,20,22,31 " " 100 1W 5% 1 R24 " " 316 1% 1 R6 " " 634 1% 2 R7,8 SWITCH, DIP 8 POS 2 SW1,2 (one may be 4 pos.) LED, RED T1-3/4 1 DS1 PC BOARD 1 STANDOFF F-F 4-40 x 1/2 4 SCREW, P.H. 4-40 x 1/4 4 8) SWITCH PROGRAMMING CHART SWITCH PROGRAMMING CHART ³ ³ n=not used ³ PLEASE REFER TO THE SWITCH LEGEND ³ NOTE THAT A LOGIC "0" IS CLOSED (ON) ³ÚÄÄÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄÄÄÄ¿ AND A LOGIC "1" IS OPEN (OFF) ³ nnnn123 4567891011 ³ ³ÀÄÄÄÄÄÄÄÄÄÙÀÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ dip switches ^ msb lsb pc board edge----^ 11 9 8 7 6 5 4 3 2 1 <---switch location on diagram above 0 1 1 0 1 1 1 0 0 0 0 88.0 0 1 1 0 1 1 1 0 0 0 1 88.1 0 1 1 0 1 1 1 0 0 1 0 88.2 0 1 1 0 1 1 1 0 0 1 1 88.3 0 1 1 0 1 1 1 0 1 0 0 88.4 0 1 1 0 1 1 1 0 1 0 1 88.5 0 1 1 0 1 1 1 0 1 1 0 88.6 0 1 1 0 1 1 1 0 1 1 1 88.7 0 1 1 0 1 1 1 1 0 0 0 88.8 0 1 1 0 1 1 1 1 0 0 1 88.9 0 1 1 0 1 1 1 1 0 1 0 89.0 0 1 1 0 1 1 1 1 0 1 1 89.1 0 1 1 0 1 1 1 1 1 0 0 89.2 0 1 1 0 1 1 1 1 1 0 1 89.3 0 1 1 0 1 1 1 1 1 1 0 89.4 0 1 1 0 1 1 1 1 1 1 1 89.5 0 1 1 1 0 0 0 0 0 0 0 89.6 0 1 1 1 0 0 0 0 0 0 1 89.7 0 1 1 1 0 0 0 0 0 1 0 89.8 0 1 1 1 0 0 0 0 0 1 1 89.9 0 1 1 1 0 0 0 0 1 0 0 90.0 0 1 1 1 0 0 0 0 1 0 1 90.1 0 1 1 1 0 0 0 0 1 1 0 90.2 0 1 1 1 0 0 0 0 1 1 1 90.3 0 1 1 1 0 0 0 1 0 0 0 90.4 0 1 1 1 0 0 0 1 0 0 1 90.5 0 1 1 1 0 0 0 1 0 1 0 90.6 0 1 1 1 0 0 0 1 0 1 1 90.7 0 1 1 1 0 0 0 1 1 0 0 90.8 0 1 1 1 0 0 0 1 1 0 1 90.9 0 1 1 1 0 0 0 1 1 1 0 91.0 0 1 1 1 0 0 0 1 1 1 1 91.1 0 1 1 1 0 0 1 0 0 0 0 91.2 0 1 1 1 0 0 1 0 0 0 1 91.3 0 1 1 1 0 0 1 0 0 1 0 91.4 0 1 1 1 0 0 1 0 0 1 1 91.5 0 1 1 1 0 0 1 0 1 0 0 91.6 0 1 1 1 0 0 1 0 1 0 1 91.7 0 1 1 1 0 0 1 0 1 1 0 91.8 0 1 1 1 0 0 1 0 1 1 1 91.9 0 1 1 1 0 0 1 1 0 0 0 92.0 0 1 1 1 0 0 1 1 0 0 1 92.1 0 1 1 1 0 0 1 1 0 1 0 92.2 0 1 1 1 0 0 1 1 0 1 1 92.3 0 1 1 1 0 0 1 1 1 0 0 92.4 0 1 1 1 0 0 1 1 1 0 1 92.5 0 1 1 1 0 0 1 1 1 1 0 92.6 0 1 1 1 0 0 1 1 1 1 1 92.7 0 1 1 1 0 1 0 0 0 0 0 92.8 0 1 1 1 0 1 0 0 0 0 1 92.9 0 1 1 1 0 1 0 0 0 1 0 93.0 0 1 1 1 0 1 0 0 0 1 1 93.1 0 1 1 1 0 1 0 0 1 0 0 93.2 0 1 1 1 0 1 0 0 1 0 1 93.3 0 1 1 1 0 1 0 0 1 1 0 93.4 0 1 1 1 0 1 0 0 1 1 1 93.5 0 1 1 1 0 1 0 1 0 0 0 93.6 0 1 1 1 0 1 0 1 0 0 1 93.7 0 1 1 1 0 1 0 1 0 1 0 93.8 0 1 1 1 0 1 0 1 0 1 1 93.9 0 1 1 1 0 1 0 1 1 0 0 94.0 0 1 1 1 0 1 0 1 1 0 1 94.1 0 1 1 1 0 1 0 1 1 1 0 94.2 0 1 1 1 0 1 0 1 1 1 1 94.3 0 1 1 1 0 1 1 0 0 0 0 94.4 0 1 1 1 0 1 1 0 0 0 1 94.5 0 1 1 1 0 1 1 0 0 1 0 94.6 0 1 1 1 0 1 1 0 0 1 1 94.7 0 1 1 1 0 1 1 0 1 0 0 94.8 0 1 1 1 0 1 1 0 1 0 1 94.9 0 1 1 1 0 1 1 0 1 1 0 95.0 0 1 1 1 0 1 1 0 1 1 1 95.1 0 1 1 1 0 1 1 1 0 0 0 95.2 0 1 1 1 0 1 1 1 0 0 1 95.3 0 1 1 1 0 1 1 1 0 1 0 95.4 0 1 1 1 0 1 1 1 0 1 1 95.5 0 1 1 1 0 1 1 1 1 0 0 95.6 0 1 1 1 0 1 1 1 1 0 1 95.7 0 1 1 1 0 1 1 1 1 1 0 95.8 0 1 1 1 0 1 1 1 1 1 1 95.9 0 1 1 1 1 0 0 0 0 0 0 96.0 0 1 1 1 1 0 0 0 0 0 1 96.1 0 1 1 1 1 0 0 0 0 1 0 96.2 0 1 1 1 1 0 0 0 0 1 1 96.3 0 1 1 1 1 0 0 0 1 0 0 96.4 0 1 1 1 1 0 0 0 1 0 1 96.5 0 1 1 1 1 0 0 0 1 1 0 96.6 0 1 1 1 1 0 0 0 1 1 1 96.7 0 1 1 1 1 0 0 1 0 0 0 96.8 0 1 1 1 1 0 0 1 0 0 1 96.9 0 1 1 1 1 0 0 1 0 1 0 97.0 0 1 1 1 1 0 0 1 0 1 1 97.1 0 1 1 1 1 0 0 1 1 0 0 97.2 0 1 1 1 1 0 0 1 1 0 1 97.3 0 1 1 1 1 0 0 1 1 1 0 97.4 0 1 1 1 1 0 0 1 1 1 1 97.5 0 1 1 1 1 0 1 0 0 0 0 97.6 0 1 1 1 1 0 1 0 0 0 1 97.7 0 1 1 1 1 0 1 0 0 1 0 97.8 0 1 1 1 1 0 1 0 0 1 1 97.9 0 1 1 1 1 0 1 0 1 0 0 98.0 0 1 1 1 1 0 1 0 1 0 1 98.1 0 1 1 1 1 0 1 0 1 1 0 98.2 0 1 1 1 1 0 1 0 1 1 1 98.3 0 1 1 1 1 0 1 1 0 0 0 98.4 0 1 1 1 1 0 1 1 0 0 1 98.5 0 1 1 1 1 0 1 1 0 1 0 98.6 0 1 1 1 1 0 1 1 0 1 1 98.7 0 1 1 1 1 0 1 1 1 0 0 98.8 0 1 1 1 1 0 1 1 1 0 1 98.9 0 1 1 1 1 0 1 1 1 1 0 99.0 0 1 1 1 1 0 1 1 1 1 1 99.1 0 1 1 1 1 1 0 0 0 0 0 99.2 0 1 1 1 1 1 0 0 0 0 1 99.3 0 1 1 1 1 1 0 0 0 1 0 99.4 0 1 1 1 1 1 0 0 0 1 1 99.5 0 1 1 1 1 1 0 0 1 0 0 99.6 0 1 1 1 1 1 0 0 1 0 1 99.7 0 1 1 1 1 1 0 0 1 1 0 99.8 0 1 1 1 1 1 0 0 1 1 1 99.9 0 1 1 1 1 1 0 1 0 0 0 100.0 0 1 1 1 1 1 0 1 0 0 1 100.1 0 1 1 1 1 1 0 1 0 1 0 100.2 0 1 1 1 1 1 0 1 0 1 1 100.3 0 1 1 1 1 1 0 1 1 0 0 100.4 0 1 1 1 1 1 0 1 1 0 1 100.5 0 1 1 1 1 1 0 1 1 1 0 100.6 0 1 1 1 1 1 0 1 1 1 1 100.7 0 1 1 1 1 1 1 0 0 0 0 100.8 0 1 1 1 1 1 1 0 0 0 1 100.9 0 1 1 1 1 1 1 0 0 1 0 101.0 0 1 1 1 1 1 1 0 0 1 1 101.1 0 1 1 1 1 1 1 0 1 0 0 101.2 0 1 1 1 1 1 1 0 1 0 1 101.3 0 1 1 1 1 1 1 0 1 1 0 101.4 0 1 1 1 1 1 1 0 1 1 1 101.5 0 1 1 1 1 1 1 1 0 0 0 101.6 0 1 1 1 1 1 1 1 0 0 1 101.7 0 1 1 1 1 1 1 1 0 1 0 101.8 0 1 1 1 1 1 1 1 0 1 1 101.9 0 1 1 1 1 1 1 1 1 0 0 102.0 0 1 1 1 1 1 1 1 1 0 1 102.1 0 1 1 1 1 1 1 1 1 1 0 102.2 0 1 1 1 1 1 1 1 1 1 1 102.3 1 0 0 0 0 0 0 0 0 0 0 102.4 1 0 0 0 0 0 0 0 0 0 1 102.5 1 0 0 0 0 0 0 0 0 1 0 102.6 1 0 0 0 0 0 0 0 0 1 1 102.7 1 0 0 0 0 0 0 0 1 0 0 102.8 1 0 0 0 0 0 0 0 1 0 1 102.9 1 0 0 0 0 0 0 0 1 1 0 103.0 1 0 0 0 0 0 0 0 1 1 1 103.1 1 0 0 0 0 0 0 1 0 0 0 103.2 1 0 0 0 0 0 0 1 0 0 1 103.3 1 0 0 0 0 0 0 1 0 1 0 103.4 1 0 0 0 0 0 0 1 0 1 1 103.5 1 0 0 0 0 0 0 1 1 0 0 103.6 1 0 0 0 0 0 0 1 1 0 1 103.7 1 0 0 0 0 0 0 1 1 1 0 103.8 1 0 0 0 0 0 0 1 1 1 1 103.9 1 0 0 0 0 0 1 0 0 0 0 104.0 1 0 0 0 0 0 1 0 0 0 1 104.1 1 0 0 0 0 0 1 0 0 1 0 104.2 1 0 0 0 0 0 1 0 0 1 1 104.3 1 0 0 0 0 0 1 0 1 0 0 104.4 1 0 0 0 0 0 1 0 1 0 1 104.5 1 0 0 0 0 0 1 0 1 1 0 104.6 1 0 0 0 0 0 1 0 1 1 1 104.7 1 0 0 0 0 0 1 1 0 0 0 104.8 1 0 0 0 0 0 1 1 0 0 1 104.9 1 0 0 0 0 0 1 1 0 1 0 105.0 1 0 0 0 0 0 1 1 0 1 1 105.1 1 0 0 0 0 0 1 1 1 0 0 105.2 1 0 0 0 0 0 1 1 1 0 1 105.3 1 0 0 0 0 0 1 1 1 1 0 105.4 1 0 0 0 0 0 1 1 1 1 1 105.5 1 0 0 0 0 1 0 0 0 0 0 105.6 1 0 0 0 0 1 0 0 0 0 1 105.7 1 0 0 0 0 1 0 0 0 1 0 105.8 1 0 0 0 0 1 0 0 0 1 1 105.9 1 0 0 0 0 1 0 0 1 0 0 106.0 1 0 0 0 0 1 0 0 1 0 1 106.1 1 0 0 0 0 1 0 0 1 1 0 106.2 1 0 0 0 0 1 0 0 1 1 1 106.3 1 0 0 0 0 1 0 1 0 0 0 106.4 1 0 0 0 0 1 0 1 0 0 1 106.5 1 0 0 0 0 1 0 1 0 1 0 106.6 1 0 0 0 0 1 0 1 0 1 1 106.7 1 0 0 0 0 1 0 1 1 0 0 106.8 1 0 0 0 0 1 0 1 1 0 1 106.9 1 0 0 0 0 1 0 1 1 1 0 107.0 1 0 0 0 0 1 0 1 1 1 1 107.1 1 0 0 0 0 1 1 0 0 0 0 107.2 1 0 0 0 0 1 1 0 0 0 1 107.3 1 0 0 0 0 1 1 0 0 1 0 107.4 1 0 0 0 0 1 1 0 0 1 1 107.5 1 0 0 0 0 1 1 0 1 0 0 107.6 1 0 0 0 0 1 1 0 1 0 1 107.7 1 0 0 0 0 1 1 0 1 1 0 107.8 1 0 0 0 0 1 1 0 1 1 1 107.9 1 0 0 0 0 1 1 1 0 0 0 108.0