J1000 Frequency Change Procedure

Transcription

1 J000 Frequency Change Procedure IS0402 Original Issue 5 July 2004 Nautel Limited 0089 Peggy's Cove Road, Hackett's Cove, NS, Canada B3Z 3J4 T F info@nautel.com U.S. customers please contact: Nautel Maine, Inc. 20 Target Industrial Circle, Bangor ME 0440 T F info@nautel.com support@nautel.com Copyright 2003 NAUTEL. All rights reserved.

2 IS0402 J000 Frequency Change Procedure INFORMATION SHEET INTRODUCTION The J000 transmitter is a broadband amplifier with frequency sensitive elements in the RF drive stage and the RF output filter. The selection of frequency sensitive components and adjustment of variable inductors used in these tuned circuits is typically carried out at the factory for the transmitter's assigned carrier frequency. Due to the nature of solid state transmitters, re-tuning of these elements is not normally required during the lifetime of the transmitter. In the event an RF carrier frequency change is required, the following procedures outline how to change the RF carrier frequency and realign the appropriate frequency sensitive components. Please read all instructions before starting.. Transmitter Shutdown Before proceeding, the transmitter MUST BE completely shut down. Switch off the ac power source at the service entrance and remove the ac connector from the rear of the transmitter.2 Frequency Sensitive Assemblies The following assemblies in the J000 transmitter contain components that are sensitive to the transmitter carrier frequency: (a) (b) (c) (d) Synthesizer RF Filter System Control Exciter Interface PWB.3 Test Equipment Table provides a list of test equipment required to perform the frequency change. Table Test Equipment Description Example Model Oscilloscope Tektronix Model T922 Frequency counter Agilent 538 Rf Signal Generator Logometrics Model 920B Rf Current Probe Delta TCA-5/0-EXR Dummy Load 50 ohms, 2 kw, VSWR<.: Resistor 000 ohms, ½ watt Table 2 Frequency Change Kit Description Part Number Quantity Low Band Parts List Capacitor 2000pF CC22 2 Capacitor 6000pF Capacitor 3000pF CCC33 2 High Band Parts List Capacitor 000pF CYP39 2 Capacitor 3000pF J000 Frequency Change Procedure Page of 8 IS0402 Issue.0

3 A2L3 A2L2 A2L A2L4 A2A3C2&C3 A2A4C3 A2A3C Figure RF Filter/Combiner Page 2 of 8 Issue.0 J000 Frequency Change Procedure IS0402

4 2 FREQUENCY CHANGE PROCEDURE 2. Frequency Synthesizer PWB If the transmitter is fitted with two synthesizers, repeat this procedure for frequency synthesizer PWBs in both Exciter A and Exciter B. 2.. Set the rotary dip switches S through S4 to the new frequency. S represents thousands of kilohertz, S2 is hundreds of kilohertz, S3 is tens of kilohertz, and S4 is ones of kilohertz. For a frequency of 323 khz the switches would be set as follows: S = (000 khz), S2 = 3 (300 khz), S3 = 2 (20 khz) and S4 = 3 (3 khz). 2.2 RF Filter 2.2. Terminate the reject load connector with a 50-ohm dummy load that has a VSWR less than : Locate the RF filter components as shown in Figure. To determine the correct components for the new frequency, refer to Table 3 for capacitor selection and Table 4 for inductor settings. If the correct components are not already installed, obtain the appropriate components from the transmitter frequency change kit identified in Table 2. Jumpers on PWBs A2A3 and A2A4 are used to set inductors A2L and A2L4 to either low or high band. On the RF filter input PWB A2A3, set the jumper between E3 and E4 for high band or between E3 and E5 for low band. On the forward/reflected power probe PWB A2A4, set the jumper between A and E6 for high band or between A and E4 for low band. Disconnect wire from A2A3B and reconnect it to ground. For example, if the new frequency is set at 200 khz, the capacitor selections from Table 3 would be as follows: A2A3C CYP39 A2A3C2&C A2A4C3 CYP39 From Table 4, the inductor A2L/L4 would be set at high. Table 3 RF Filter Capacitor Selection Frequency (khz) A2A3C A2A3C2&C3 A2A4C3 Nautel Part Number Capacitor Value Nautel Part Number Capacitor Value Nautel Part Number Capacitor Value CCC pf pf CCC pf CC pf pf CC pf CYP pf pf CYP pf Table 4 RF Filter Inductor Tap Selection Frequency (khz) Inductor A2L/L4 Setting Low High J000 Frequency Change Procedure Page 3 of 8 IS0402 Issue.0

5 2.2.3 Set the signal generator at three times the carrier frequency and at an amplitude of 2.0 V peak-to-peak. Monitor the output of the signal generator with an oscilloscope. 200 khz, the oscilloscope should be as shown in Figure 2. amplitude of 2.0 V peak-to-peak. Connect the signal generator output to Terminal B of the RF filter input PWB through a,000 ohm resistor. Monitor Terminal B with an oscilloscope. 200 khz, the oscilloscope should be as shown in Figure 4. Figure 2 Example Signal Generator Output Components A2A3C2/C3 and A2L2 form a series tuned circuit at the third harmonic of the carrier frequency. Adjust the inductance of A2L2 by unsoldering its tap and sliding it until the signal on the oscilloscope is minimized. 200 khz, the oscilloscope should be as shown in Figure 3. Figure 4 Example Terminal B Output Components A2A3C2/C3 and A2L2 in parallel with A2L3 form a parallel resonant circuit at the carrier frequency. Adjust the inductance of A2L3 by unsoldering its tap and sliding it until the signal on the oscilloscope is maximized. 200 khz, the oscilloscope should be as shown in Figure 5. Figure 3 Example Tuned Circuit Output Set the signal generator at the transmitter carrier frequency and at an Figure 5 Example Parallel Resonant Circuit Output Page 4 of 8 Issue.0 J000 Frequency Change Procedure IS0402

6 2.2.7 Remove the signal generator, oscilloscope, and resistor and then solder the taps on A2L2 and A2L3 in place Set the signal generator at the transmitter carrier frequency and at an amplitude of 2.0 V peak-to-peak. Connect the signal generator output at the RF filter input connectors J4- and J5-. Place a low inductance jumper between Terminal B and ground. Monitor the output of the signal generator with an oscilloscope Set the signal generator at the transmitter carrier frequency and at an amplitude of 2.0 V peak-to-peak. Connect the signal generator at the RF filter output connector J. Monitor the output of the signal generator with an oscilloscope. 200 khz, the oscilloscope should be as shown in Figure 8. Figure 6 Example Terminal B Output 200 khz, the oscilloscope should be as shown in Figure Components A2A4Cand A2L form a series tuned circuit at the carrier frequency. Adjust the inductance of A2L by sliding the ferrite in/out of A2L until a null is observed on the oscilloscope. Lock A2L ferrite in place and remove the signal generator, jumper and oscilloscope. 200 khz, the oscilloscope should be as shown in Figure 7. Figure 8 Example Terminal A Output 2.2. Components A2A4C and A2L4 form a series tuned circuit at the carrier frequency. Adjust the inductance of A2L4 by sliding the ferrite in or out of A2L4 until a null is observed on the oscilloscope. Lock A2L4 ferrite in place and remove the signal generator, oscilloscope, and short circuit. Remove the wire from ground and reconnect it to A2A3B. 200 khz, the oscilloscope should be as shown in Figure 9. Figure 7 Example Series Tuned Circuit Output Figure 9 Example Series Tuned Circuit Output J000 Frequency Change Procedure Page 5 of 8 IS0402 Issue.0

7 3 TESTING AND CALIBRATION 3. Terminate the antenna and reject load connectors with a 50-ohm dummy load that has a VSWR less than : RF Drive Symmetry Measure the symmetry of the RF drive being applied from the active RF synthesizer PWB to the RF power modules as follows: (a) Select Exciter A as the active exciter. (b) Turn the transmitter on. Set the transmitter s RF output power to 50 watts. (c) Connect an oscilloscope between TP7 on Exciter A s RF synthesizer PWB and ground (TP4). Figure 0 shows the assembly for the exciter interface and synthesizer PWBs. (d) The oscilloscope should indicate a symmetrical (50% duty cycle) square wave with a nominal amplitude of 5 V peak-to-peak. (e) Adjust Exciter A s RF synthesizer PWB SYMMETRY potentiometer (R32) to obtain a 50% duty cycle. (f) If necessary, adjust the RF drive source to obtain a symmetrical square wave. NOTE If an external RF generator is producing the RF drive, verify its output waveform is symmetrical. If necessary, make adjustments as directed in the RF generator maintenance manual. (g) For dual exciter transmitters, select Exciter B as the active exciter. Repeat steps (c) through (f) for Exciter B. (h) Turn the transmitter off and disconnect the oscilloscope from TP7 and ground of the active RF synthesizer PWB. (i) Connect the oscilloscope between C5 or C6 and ground on RF power module A s power amplifier (A2AA5) (see Figure ). (j) Turn the transmitter on and set RF output power to 50 watts. (k) The oscilloscope should indicate a symmetrical (50% duty cycle) square wave with a nominal amplitude of 30 V peak-to-peak. (l) Adjust the exciter interface PWB SYMM (A) potentiometer (R9) to obtain a 50% duty cycle. Refer to Figure 0 for location of the symmetry potentiometer. (m) Turn the transmitter off and disconnect the oscilloscope from RF power module A s power amplifier. Repeat steps (i) through (m) for RF power module B (A2A2) by adjusting the exciter interface PWB SYMM (B) potentiometer (R0). Page 6 of 8 Issue.0 J000 Frequency Change Procedure IS0402

8 J CR2 R3 C2 R4 R34 R33 C2 U2 C4 CR5 J2 J4 C C E E B B C C E E J8 J9 J0 R3 R36 R35 C0 B Q3 B Q4 TP R8 R2 Q6 Q5 C J6 TP2 L L2 L3 L4 C3 + C3 + C4 + C5 + C6 C7 R7 R U CR4 Symmetry Potentiometer(s) SYMM(B) SYMM(A) R9 R4 R5 R6 R0 C8 R8 R2 R5 TP4 GND R25 R30 C8 C2 TP3 J3 R26 R Q Q8 R22 R R2 R9 R38 4 K2 3 R37 Q2 R32 R24 IPM GAIN R29 U3 C7 R28 C20 C6 R27 R20 R7 R23 IPM GAIN GRID K A B C D E F 0 7 CR TP5 GRID A B C D E F NAUTEL ASSY EXCITER INTERFACE NAPI SER. J7 R6 C9 Q7 R R3 GND J5 Figure 0 Exciter Interface/Synthesizer J000 Frequency Change Procedure Page 7 of 8 IS0402 Issue.0

9 Figure Power Amplifier C5/C6 Page 8 of 8 Issue.0 J000 Frequency Change Procedure IS0402