J1000 Frequency Change Procedure

Transcription

1 J1000 Frequency Change Procedure for Release 3 (NARA40B) and Release 4 (NARA40C) transmitters IS06004C Issue October 010 Nautel Limited Peggy's Cove Road, Hackett's Cove, NS, Canada B3Z 3J4 T nautel (68835) or F info@nautel.com U.S. customers please contact: Nautel Inc. 01 Target Industrial Circle, Bangor ME T nautel (68835) or F info@nautel.com support@nautel.com Copyright 010 NAUTEL. All rights reserved.

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3 IS06004C J1000 Frequency Change Procedure INFORMATION SHEET 1 INTRODUCTION The J1000 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, retuning 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. 1.1 Transmitter Shutdown Before proceeding, the transmitter MUST BE completely shut down. Switch off ac power at the service entrance and remove the ac connector from the rear of the transmitter. 1. Frequency Sensitive Assemblies The following assemblies in the J1000 transmitter contain components that are sensitive to the transmitter carrier frequency: RF synthesizer PWB RF filter System control PWB Exciter interface PWB 1.3 Test Equipment and Tools Table 1 lists the test equipment and tools required to perform the frequency change. Table 1: Test Equipment and Tools Description Example Model Oscilloscope ** see NOTE below Tektronix Model T9 Frequency counter Agilent RF Signal Generator ** see NOTE below Logometrics Model 90B Dummy Load 50 Ω, kw, VSWR<1.1:1 Resistor 1000 Ω, ½ W Soldering iron** - NOTE If you are using a more sensitive piece of equipment (e.g., spectrum analyzer) in place of the oscilloscope and signal generator, the recommended signal amplitudes in the Frequency Change Procedure (paragraph ) do not apply. Table : Frequency Change Kits Kit, Band, Nautel Part # Capacitor Part # and Value Quantity Low Band ( khz) Nautel Part # (5600 pf) CCC33 (3000 pf) Medium Band ( khz) Nautel Part # High Band ( khz) Nautel Part # (5600 pf) (700 pf) CC (000 pf) (700 pf) CYP39 (1000 pf) 1 1 J1000 Frequency Change Procedure Page 1 of 7 IS06004C Issue 1.0

4 AL3 AL AL1 AL4 AA3C&C3 AA4C3 AA3C1 Fig. 1: RF Filter/Combiner FREQUENCY CHANGE PROCEDURE.1 RF Synthesizer PWB If the transmitter has two RF synthesizer PWBs, perform this procedure for both RF synthesizer PWBs (exciters A and B)..1.1 Set the rotary dip switches S1 through S4 to the new frequency, noting: S1 is 1000 x khz S is 100 x khz S3 is 10 x khz S4 is 1 x khz. S5 is 0.1 x khz Example: For a frequency of 133 khz, set the switches as follows: S1 = 1 (1000 khz), S = 3 (300 khz), S3 = (0 khz), S4 = 3 (3 khz), S5 = 0. Page of 7 Issue 1.0 J1000 Frequency Change Procedure IS06004C

5 . RF Filter..1 Ensure the reject load connector is terminated with a 50 Ω dummy load that has a VSWR less than 1:1.1. This should have already been connected... Locate the RF filter components as shown in Fig. 1. To determine the correct components for the new frequency, use Table 3 for capacitor selection, inductor tap selection and AA4-B jumper position. If the correct capacitors are not installed, obtain the appropriate components from the frequency change kit identified by part number and value in Table. Screw terminations on PWBs AA3 and AA4 are used to set inductors AL1 and AL4 to low, medium or high band. On RF filter input PWB AA3, connect wire L1- to E1 and L1-3 to E for high band or L1- to E and L1-3 to E1 for low or medium band. On forward/reflected power probe PWB AA4, connect wire L4- to E1 and L4-3 to E for high band or L4- to E and L4-3 to E1 for low or medium band. Disconnect wire from AA3E5 and reconnect the wire to ground. For NARA40C transmitters only: The B jumper on forward/reflected power probe PWB AA4 is used to configure the PWB s input capacitors to low, medium or high band. Connect the B jumper to to E5 for low or medium band or to E6 for high band. Example: if the new frequency is set at 100 khz, use the information in the third row (high band) of Table 3 to determine: Capacitor selections (part numbers from Table ): AA3C pf (Part # CYP39 AA3C and AA3C3 700 pf (Part # ) AA4C pf (Part # CYP39) Inductor AL1/L4 tap selections: Connect AL1- to AA3E1 Connect AL1-3 to AA3E Connect AL4- to AA4E1 Connect AL4-3 to AA4E AA4-B jumper position (applicable to NARA40C transmitters only): AA4E6 NOTE The following steps may require an inductance adjustment of AL and AL3. In some transmitters, the tap connections for these coils are soldered. In other transmitters, the tap connections are made using a clip. Table 3: RF Filter Capacitor Selection, Inductor Tap Selection and AA4-B Jumper Setting Frequency (khz) RF Filter Capacitor Selection Inductor Tap Selection (Low Band) (Med Band) (High Band) AA3C1 (pf) AA3C (pf) AA3C3 (pf) AA4C3 (pf) AL1- AL1-3 AL4- AL4-3 **AA4-B Jumper Setting AA3E AE3E1 AA4E AA4E1 AA4E AA3E AE3E1 AA4E AA4E1 AA4E AA3E1 AE3E AA4E1 AA4E AA4E6 ** Denotes AA4-B jumper is applicable to NARA40C transmitter variations only. J1000 Frequency Change Procedure Page 3 of 7 IS06004C Issue 1.0

6 ..3 Set the signal generator to three times the carrier frequency and for a minimum amplitude of.0 V p-p. Connect the signal generator, through a 1000 Ω resistor, to terminal E5 of the RF filter input PWB. Monitor E5 with an oscilloscope should be as shown in Fig....5 Set the signal generator to the transmitter carrier frequency and for a minimum amplitude of.0 V p-p. Connect the signal generator, through a 1,000 Ω resistor, to terminal E5 of the RF filter input PWB. Monitor E5 with an oscilloscope should be as shown in Fig. 4. Fig. : Example Signal Generator Output..4 Components AA3C/C3 and AL form a series tuned circuit at the third harmonic of the carrier frequency. Adjust the inductance of AL by loosening its tap and sliding it until the signal on the oscilloscope is minimized. oscilloscope should be as shown in Fig. 3. Fig. 4: Example Terminal B Output..6 Components AA3C/C3 and AL in parallel with AL3 form a parallel resonant circuit at the carrier frequency. Adjust the inductance of AL3 by loosening its tap and sliding it until the signal on the oscilloscope is maximized. oscilloscope should be as shown in Fig. 5. Fig. 3: Example Tuned Circuit Output Fig. 5: Example Parallel Resonant Circuit Output..7 Remove the signal generator, oscilloscope and resistor. Secure (solder or tighten) the tap connections on AL and AL3. Page 4 of 7 Issue 1.0 J1000 Frequency Change Procedure IS06004C

7 ..8 Set the signal generator to the transmitter carrier frequency and for a minimum amplitude of.0 V p-p. Connect the signal generator output, through a 1000 Ω resistor, to the RF filter input connectors J4-1 and J5-1 (link J4-1 and J5-1 together and connect signal generator ground to chassis ground). Place a low inductance jumper between terminal E4 and ground. Monitor the RF filter input (J4-1/J5-1) with an..10 Set the signal generator to the transmitter carrier frequency and for a minimum amplitude of.0 V p-p. Connect the signal generator, through a 1000 Ω resistor, to the RF filter output connector J1. Monitor the RF filter output (J1) with an oscilloscope should be as shown in Fig. 8. oscilloscope should be as shown in Fig. 6. Fig.8: Example Terminal A Output Fig. 6: Example RF Filter Input..9 Components AA3C1 and AL1 form a series tuned circuit at the carrier frequency. With the cover securely installed, Adjust the inductance of AL1 by sliding the ferrite in/out of AL1 to get a null on the Lock AL1 ferrite in place and remove the signal generator, oscilloscope, resistor and jumper. oscilloscope should be as shown in Fig Components AA4C3 and AL4 form a series tuned circuit at the carrier frequency. With the cover securely installed, adjust the inductance of AL4 by sliding the ferrite in or out of AL4 to get a null on the Lock AL4 ferrite in place and remove the signal generator, oscilloscope and resistor. Remove the wire from ground, added at step.., and reconnect it to AA3E5. Also, remove the low inductance jumper between terminal E4 and ground, added at step..8. oscilloscope should be as shown in Fig. 9. Fig.7: Example Series Tuned Circuit Output Fig.9: Example Series Tuned Circuit Output J1000 Frequency Change Procedure Page 5 of 7 IS06004C Issue 1.0

8 ..1 Set the signal generator to three times the transmitter carrier frequency and for a 10 V p-p amplitude. Connect the signal generator output to the RF filter input connectors J4-1 and J5-1 (link J4-1 and J5-1 together and connect signal generator ground to chassis ground). Terminate RF filter output J1 in 50 Ω. Monitor the RF filter output (J1) with an NOTE Setting the signal generator to 10 V p-p improves tuning resolution. If the signal generator is not capable of 10 V p-p, set its amplitude to maximum...13 Fine tune the third harmonic filter by loosening the tap on AL and sliding it to get a null on the When a null is achieved, secure (solder or tighten) the tap setting...14 Remove the signal generator and 3 TESTING AND CALIBRATION 3.1 Terminate the antenna and reject load connectors with a 50-ohm dummy load that has a VSWR less than 1.1:1. 3. 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) Remove RF power module A from the transmitter and remove its right-hand cover (as viewed from the front). (b) Connect the oscilloscope between C5-LHS or C6 and ground on RF power module A s power amplifier (AA1A5) (see Fig. 10). Reinstall the RF power module in the transmitter. (c) Turn the transmitter on and set RF output power to 50 W. (d) The oscilloscope should indicate a symmetrical (50% duty cycle) square wave with a nominal amplitude of 30 V p-p. (e) Adjust exciter A s RF synthesizer PWB SYMMETRY potentiometer (R3) to obtain 50% duty cycle. (f) For dual exciter transmitters, select exciter B as the active exciter. Adjust exciter B s RF synthesizer PWB SYMMETRY potentiometer (R3) to obtain 50% duty cycle. Page 6 of 7 Issue 1.0 J1000 Frequency Change Procedure IS06004C

9 Fig. 10: Power Amplifier C5/C6 J1000 Frequency Change Procedure Page 7 of 7 IS06004C Issue 1.0