DANIELS ELECTRONICS LTD. ® MT-3 RADIO SYSTEMS VHF AMPLIFIER INSTRUCTION MANUAL VT-3 132 - 174 MHz Covers models: VT-3/150 Amplifier Copyright © 1998 Daniels Electronics Ltd. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written consent of Daniels Electronics Ltd. Issue: Issue Date: Printing Date: Part No.
Reviewed By: Quality Assurance: Name Signature _________________ Date NOTE: The user's authority to operate this equipment could be revoked through any changes or modifications not expressly approved by Daniels Electronics Ltd. The design of this equipment is subject to change due to continuous development. This equipment may incorporate minor changes in detail from the information contained in this manual.
TABLE OF CONTENTS Page 1 GENERAL....................................................................................... 1-1 1.1 Introduction............................................................................. 1-1 1.2 Performance Specification ............................................................ 1-1 2 THEORY OF OPERATION................................................................... 2-1 2.1 Amplifier Operation.................................................................... 2-1 2.
5 PARTS LISTS...................................................................................5-1 5.1 VT-3/150 Amplifier Electrical Parts List.............................................5-1 5.2 VT-3/150 Low Pass Filter Electrical Parts List .....................................5-3 5.3 VT-3/150 Amplifier Mechanical Parts List ..........................................5-3 6 REVISION HISTORY..........................................................................
1 GENERAL 1.1 Introduction The VT-3/150 Amplifier provides the final stage of RF amplification and filtering for the entire VHF Transmitter VT-3 132 - 174 MHz family. The amplifier has two distinct frequency ranges: 132 to 150 MHz, and 150 to 174 MHz with continuously adjustable 2.0 to 8.0 Watts output power. The VT-3/150 Amplifier is housed in a machined aluminum case that ensures optimum RF shielding, provides a good ground, and also acts as a heatsink.
Transmitter Mismatch Protection: 20:1 VSWR at all phase angles. Transmitter Alarm: Forward power sense and reverse VSWR; - open collector output (separate or 'OR'ed configuration); -linear output (separate lines only). Operating Temperature Range: -30˚ C to +60˚ C, optional -40˚ C temperature test. Operating Humidity: 95% RH (non-condensing) at +25˚ C. Operating Voltage: +13.8 Vdc Nominal (range +11 to +16 Vdc), +9.5 Vdc Regulated. Transmit Current: 0.7 Amp typical; 1.
2 THEORY OF OPERATION 2.1 Amplifier Operation A power control circuit monitors the RF output power of amplifier U4 and keeps the power constant. The output power from the high power amplifier will change as the unregulated +13.8 Vdc supply varies. Note that the frequency band does not change how the amplifier operates; it only changes a few component values in the RF circuitry. Power for the VT-3/150 Amplifier is provided from the MT-3 Transmitter Board. The +13.
2.3 RF Circuitry The RF circuitry consists of several blocks: a 7 dB input pad (R1, R2, and R3), an RF amplifier module (U4), an output power boosting transistor (Q7), three directional couplers (TL1, TL3, and TL4), and the VT-3/150 Lowpass Filter. The heart of the VT-3/150 Amplifier is RF amplifier module U4. The output of U4 is further amplified by Q1 to a maximum of 8.0 Watts at the antenna connector.
2.5 Power Sensing Circuitry The VT-3/150 Amplifier is equipped with output power and VSWR sensing lines which can be individually configured as open collector or linear outputs. In open collector configuration, the output is active low, that is, when a fail condition is detected (not enough output power or too high antenna VSWR) the open collector transistor is turned on. In linear configuration, a voltage proportional to the sensed output power or antenna VSWR is output.
2.5.3 VSWR Overload The VSWR overload circuit protects the VT-3/150 Amplifier from excessive antenna VSWR by reducing the amplifier's gain (output power) when an overload condition occurs. The VSWR overload circuit (R14, R37, R39, R40, U2a, and Q6) is an extension of the VSWR sense circuit and operates the same as the VSWR sense open collector circuit. The VSWR Overload Adjust potentiometer (R37) reduces the voltage level of the VSWR Alarm Setpoint.
3 VT-3/150 AMPLIFIER ALIGNMENT 3.1 General Connections to the power supply, alarm and transmit enable lines (ENA), are clearly marked on the amplifier case. The amplifier is enabled when the enable line (ENA) is grounded. If the amplifier is installed in the transmitter, alignment is simplified by using an SR-3 Subrack, SM-3 System Monitor, and RF extender cable to provide transmitter power and signal interconnection (see the Transmitter Main Board Manual for details).
It is recommended that the radio communications test set be frequency locked to an external reference (WWVH, GPS, Loran C) so that the high stability oscillator may be accurately set to within its ±1 ppm frequency tolerance. 3.4 Printed Circuitboard Numbering Convention To ease troubleshooting and maintenance procedures, Daniels Electronics Limited has adopted a printed circuitboard (PCB) numbering convention in which the last two digits of the circuitboard number represent the circuitboard version.
3.6.2 VT-3/150 Amplifier Adjustment The Amplifier alignment consists of two adjustment procedures; (i) a general set up (section 3.6.2.1) procedure which sets up the proper bias conditions for the RF transistors and (ii) the RF threshold adjustments which set up the desired alarm threshold levels as well as the RF output power. The general alignment procedure is required following major repair operations, changes in RF input levels or large changes in operating frequency (greater than ± 1.0 MHz).
4. Monitor the +9.5 Vdc and 13.8 Vdc supply current and adjust R7, the output power adjustment, so that approximately 1 Amp is being drawn on the +9.5 Vdc line and 1.3 Amps or less is being drawn on the 13.8 Vdc line. This should produce approximately 8 Watts. 5. If only a 6 or 7 watt output is obtained, adjust the low pass filter coil pairs L2/L3 and L1/L4 to obtain 8 watts. 3.6.2.
3.6.2.3 1. Output Power Turn R7, the output power adjustment, clockwise to the desired transmitter output power. 3.6.2.4 Antenna VSWR Alarm (Reverse Power) Open Collector Output * note: the antenna VSWR alarm output is factory configured as an open collector output so a pull-up resistor may be required on transmitter pin Z26 if one is not already present. The output power alarm must be set first before the antenna VSWR alarm can be set. 1.
3.6.2.5 Antenna VSWR Overload 1. Disconnect the radio communications test set and so that the amplifier is terminated with an open circuit. 2. Monitor the current from the +9.5 Vdc supply. 3. Adjust R37, the VSWR overload adjustment, clockwise until a noticeable drop in the +9.5 Vdc current occurs. 4. Reconnect the radio communications test set and, the +9.5 Vdc current should return to the previous level. 3.6.2.6 Procedure Verification 1. Verify that the current drawn from the +13.
4 ILLUSTRATIONS AND SCHEMATIC DIAGRAMS This Page Intentionally Left Blank DANIELS DE ELECTRONICS 4-1 VHF Amplifier Instruction Manual VT-3 132 - 174 MHz
4.1 VT-3/150 VHF Amplifier Component Layout MBZ5233B R37 50K JU3 R21 50K JU4 R36 50K R38 Q5 PZT2222A 1K JU1 R7 50K R25 1K JU2 R6 27K4 R14 10K R4 D1 R5 4K53 C13 100n R8 3K48 10n C14 MMBD701 D7 Q6 10K R41 Q1 IRF9540 R10 10K C12 10nF 27K4 U1 R28 R29 Q3 MC 10K 33172 PZT2222A R9 Q4 R31 10K C17 10n 10K 49K9 BC817-25 C15 10n R11 R12 10K R27 49K9 R30 JU5 49K9 R26 49K9 C39 2.2nF TL5 R39 1K 49K9 C25 150p L2 0.
4.2 VT-3/150 VHF Amplifier Schematic Diagram +13.8 VDC LOW / HIGH BAND FIL5* +13.8 VDC LPF +13.8 VDC C1 1nF R1 30R1 R2 178R R3 178R 2 3 C4 18nF C2 18nF TO ALL SWITCHED +9.5V FIL2 +9.5 VDC LPF S R4 49k9 AMPLIFIER ENABLE I/P C27 100nF FB3* L8 19nH R45 10R 6 5 + L4 150nH L3 180nH R15 49R9 TL2 Q7 MRF262 C33 68pF LB/51pF HB C35 SELECT LB = LOW BAND HB = HIGH BAND FB1 C8 1nF C7 100nF C9 18nF Q1 IRF9540 C10 10nF R7 50k D5 MMBD701 C12 10nF C39 2.
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4.3 VT-3/150 VHF Lowpass Filter Component Layout 4.
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5 PARTS LISTS 5.1 VT-3/150 Amplifier Electrical Parts List Ref Desig Description Part No. C1 C2-C5 C6 C7 C8 C9 C10 C11 C12 C13 C14, C15 C16 C17 C18 C19 C20 C21-C23 C24 C25 C26 C27 C28 C29 C30 C31 C31 C32 C32 C33 C33 C34 C34 C35 C35 C36 C36 C37 C37 C38 C38 C39 CAP., SM, 1nF CER, 1206, C0G CAP., SM, 18nF CER, 1206, X7R CAP., SM, 4.7µF TANT., 10%, 16V CAP., SM, 100nF CER, 1206, X7R CAP., SM, 1nF CER, 1206, C0G CAP., SM, 18nF CER, 1206, X7R CAP., SM, 10nF CER, 1206, X7R CAP.
Ref Desig Description Part No. FB1 FB2, FB3 FIL1-FIL5 FERRITE BEAD, SM, 43 MIX 1812 PKG FERRITE BEAD, 64MIX 3X3.5mm OD FILTER, EMI PI/5500pF, 8-32 UNC 1213-43181200 1210-64030350 1302-P552D10D J1 J2 CONNECTOR, SMB, JACK,2 HOLE FLANGE CONNECTOR, N JACK PANEL MNT, C/SNK 5120-J2SC01BG 5184-10923011 L1-L3 L4 L5 L6, L7 L8 L9 L10 L11 LPF1 INDUCTOR, SM., 180nH 20%, 1812 CHOKE, RF/MOULD., 150nH 10%, .37 INDUCTOR, SM, 1.5µH 10%, 1812 INDUCTOR, SM, 1.5µH 10%, 1812 COIL, 1.5 TURNS, 18AWG, 3.
Ref Desig Description Part No. R38, R39 R40 R41 R42 R43 R44 R45 RES., SM, 1k00 1206, 1%, 100ppm RES., SM, 221k 1206, 1%, 100ppm RES., SM, 10k0 1206, 1%, 100ppm RES., SM, 1k00 1206, 1%, 100ppm RES., SM, 27k4 1206, 1%, 100ppm RES., SM, 10k0 1206, 1%, 100ppm RES., 10R METAL FILM, 5%, 0.5W 1150-3B1001FP 1150-5B2213FP 1150-4B1002FP 1150-3B1001FP 1150-4B2742FP 1150-4B1002FP 1101-1A0100JP TL1 TL2, TL3 TL5 COAX, DIRECTIONAL COUPLER 0.5" COAX, DIRECTIONAL COUPLER 0.5" COAX, CONFORMABLE 31.5mm, 50 OHM, 0.
Description Part No. Qty. SCREW, M3 X 8, CAP SOCK-M2.5, S/S SCREW, M3 X 8, CAP SOCK-M2.5, S/S SET SCREW, M3 X 3, HEX SOCKET, A2 SHOULDER WASHER, M3 0.24" OD, NYLON 5812-3M0SA08S 5812-3M0SA08S 5817-3M0AC03S 5674-120N2440 3 2 1 1 TUBING, TFE-260C, 22AWG,Thin 5mm TURRET TERMINAL, 4-40 0.
6 REVISION HISTORY ISSUE DATE REVISION 1 Jul 97 First Issue.
ISSUE DATE REVISION DANIELS DEELECTRONICS 6-2 VHF Amplifier Instruction Manual VT-3 132 - 174 MHz
