Daniels MT-3 User manual

MT-3 /MT-4 RADIO SYSTEMS
UHF AMPLIFIER
INSTRUCTION MANUAL
UT-3 / UT-4
406 - 470 MHz
Covers models: UT-3/400 Amplifier
UT-4/400 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.
DE™ is a registered trademark of Daniels Electronic Ltd. registered in the United States Patent and
Trademark Office.
Issue: Peliminary Previous Issue: N/A
Issue Date: October 98 Previous Issue Date: N/A Daniels Electronics Ltd.
Printing Date: October 98 Victoria, B.C.
Part No.: IM23D-UT 34400AMP PRINTED IN CANADA

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ii UHF Amplifier Instr uction Manual UT-3 406 - 512 MHz
Reviewed By:
Quality Assurance:
Larry Freeman _________________
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.

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UHF Amplifier Instruction Manual UT-3/UT-4 406 - 512 MHz iii
TABLE OF CONTENTS
Page
1 GENERAL.......................................................................................1-1
1.1 Introduction .............................................................................1-1
1.2 Perf ormance Specification ............................................................1-1
2 THEORY OF OPERATION ...................................................................2-1
2.1 Amplifier Operation ....................................................................2-1
2.2 Power Requirements ...................................................................2-2
2.3 RF Circuitry ............................................................................2-2
2.3.1 UT-3/400 Lowpass Filter ....................................................2-2
2.4 Power Control Circuitry ...............................................................2-3
2.5 Power Sensing Circuitry ..............................................................2-3
2.5.1 Output Power Sense..........................................................2-3
2.5.2 VSWRSense..................................................................2-4
2.5.3 VSWR Overload ..............................................................2-4
3 UT-3/400 AMPLIFIER ALIGNMENT ......................................................3-1
3.1 General..................................................................................3-1
3.2 RepairNote.............................................................................3-1
3.3 Recommended Test Equipment List.................................................3-1
3.4 Printed Circuitboard Numbering Convention .......................................3-2
3.5 Standard Factory Settings and Jumper Configuration............................. 3-2
3.6 UT-3/400 Amplifier Alignment .......................................................3-2
3.6.1 General.........................................................................3-2
3.6.2 UT-3/400 Amplifier Adjustment ............................................3-3
3.6.2.1 GeneralSet-Up.......................................................3-3
3.6.2.2 Output Power Alarm (Forward Power) ...........................3-4
3.6.2.3 Output Power.........................................................3-5
3.6.2.4 Antenna VSWR Alarm (ReversePower)..........................3-5
3.6.2.5 Antenna VSWR Overload ...........................................3-6
3.6.2.6 Procedure Verification ...............................................3-6
4 ILLUSTRATIONS AND SCHEMATIC DIAGRAMS ....................................4-1
4.1 UT-3/400 UHF Amplifier Component Layout.....................................4-2
4.2 UT-3/400 UHF Amplifier Schematic Diagram .....................................4-3
4.3 UT-3/400 UHF Lowpass Filter Component Layout...............................4-5
4.4 UT-3/400 UHF Lowpass Filter Schematic Diagram ...............................4-5

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iv UHF Amplifier Instr uction Manual UT-3 406 - 512 MHz
5 PARTSLISTS...................................................................................5-1
5.1 UT-4/400 UHF Amplifier Electrical PartsList......................................5-1
5.2 UT-4/400 UHF Amplifier Mechanical PartsList...................................5-4
5.3 UT-3/400 UHF Low Pass Filter Electrical PartsList..............................5-4
6 REVISION HISTORY ..........................................................................6-1

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UHF Amplifier Instruction Manual UT-3 406 - 512 MHz 1-1
1 GENERAL
1.1 Introduction
The UT-3/400 Amplifier provides the final stage of RF amplification and filtering for the entire
UHF Transmitter UT-3 406 -512 MHz family. The amplifier has four distinct frequency ranges:
406 to 430 MHz, 450 to 470 MHz, 470 to 490 MHz and 490 to 512 MHz as well as two distinct
output power ranges: 0.5 to 2.0 Wattsand 2.0 to 8.0 Watts. The UT-3/400 Amplifier is housed in
a machined aluminum case thatensures optimum RF shielding, provides a good ground, and also
acts as a heatsink.
Additionally, the UT-3/400 Amplifier is equipped with output power and VSWR sensing lines
which can be individually configured as open collector or linear outputs. The internal VSWR
sensor protects the amplifier from high antenna VSWR by approximately halving the amplifier's
RF gain when a VSWR overload condition is present.
Output filtering for the UT-3/400 Amplifier is provided by the UT-3/400 Lowpass Filter Board.
The lowpass filter assembly is mountedin a separate compartment of the amplifier case in order to
provided maximum attenuation of harmonic and other spurious signals.
Refer to Section 4 for the UT-3 406 - 512 MHz UHF amplifier and lowpass filter component
layouts and schematic diagrams
1.2 Performance Specification
Type: MT-3series UHF Amplifier module.
Compatibility: MT-3series Transmitter Main Board.
Frequency Range: 406 to 430 MHz, 450 to 470 MHz, 470 to 490 MHz or
490 to 512 MHz.
RF Power Output: adjustable 0.5 to 2.0 Wattsor 2.0 to 8.0 Watts
RF power Input: nominal level adjustable from +4 dBm to +10 dBm,
held within +/- 2 dB of nominal.
Ouput Impedance and VSWR: 50 Ω, Type N connector; 3:1 max. VSWR.
Input /Output Isolation: > 60 dB
Duty Cycle: 100%: Continuous operation from -40˚ C to +60˚C.

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1-2 UHF Amplifier Instruction Manual UT-3 406 - 512 MHz
HarmonicEmissions: Less than -80 dBc.
Transmitter Mismatch Protection: 20:1 VSWR at allphase 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 VdcNominal(range +11 to +16 Vdc),
+9.5 VdcRegulated.
Transmit Current: 0.7 Amp typical ; 1.1 Amp maximum
Amplifier Standby Current: less than 0.5 mA.
Amplifier Enable: Active to ground.
Amplifier Enable Response: typically overdamped, rising to within 90% of full power
within 5 msec; maximum (underdamped) overshoot of 30%.

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UHF Amplifier Instruction Manual UT-3 406 - 512 MHz 2-1
2 THEORY OF OPERATION
2.1 Amplifier Operation
The operation of the UT-3/400 Amplifier varies slightly according to whether the amplifier is a low
power (0.5-2.0 W) or a high power (2.0-8.0 W) version. The low power amplifier does not use
transistor Q1 to boost the output power; consequently, it does not require the +13.8 Vdc supply.
In both versions the power control circuitry monitors the RF output power of amplifier U4 and
keeps the power constant. Therefore, the output power from the high power amplifier will change
as the unregulated +13.8 Vdcsupply varies. Note thatthe frequencyband does not changehow the
amplifier operates; it only changes a few component values in the RF circuitry.
Power for the UT-3/400 Amplifier is provided from the MT-3 Transmitter Board. The +13.8 Vdc
supply (if required) is continuously connected to the amplifier; whereas, the +9.5 Vdc supply is
always switched by the transmitter's PTT circuitry. The UT-3/400 Amplifier will not consume any
power from the +13.8 Vdc supply until +9.5 Vdc is switched on for the amplifier's circuitry and
an RF input signal is present. The synthesizer or crystal control module controls the +9.5 Vdc to
the amplifier's circuitry; switching it on by grounding the amplifier's input enable line. The
synthesizer will ground the input enable line only when the synthesizer's RF signal is phase
locked. This prevents unwanted spurious emissions during transmitter start-up. A typical start-up
sequenceis listed below:
1) +13.8 Vdcis always present
2) the transmitter is keyed on
3) +9.5 Vdcis switched on by the PTT circuitry and the synthesizer
or crystalcontrolmodulePTT lineis pulledlow
4) an RF signal is output to the amplifier
5) the amplifier's input enable lineis activated
6) the amplifier outputs RF power

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2-2 UHF Amplifier Instruction Manual UT-3 406 - 512 MHz
2.2 Power Requirements
Typical current requirements for the UT-3/400 Amplifier at different power levels are given in the
Table 2-1 below. The current drawn from the +9.5 Vdc supply should never exceed 1.2 Amps
and the currentdrawn from the +13.8 Vdcsupply should never exceed 1.5 Amps.
Table 2-1 UT- 3/400 Amplifier Current Consumption
0.5 to 2.0 Watt Amplifier 2.0 to 8.0 Watt Amplifier
Output +9.5 Vdc Output +9.5 Vdc +13.8 Vdc
Power Supply Current Power
Supply Current
Supply Current
0.5 W 0.65 A 2.0 W 0.64 A 0.51 A
1.0 W 0.87 A 4.0 W 0.79 A 0.75 A
1.5 W 1.02 A 6.0 W 0.89 A 0.93 A
2.0 W 1.17 A 8.0 W 1.04 A 1.10 A
Note: Current consumption measured at 470 MHz
2.3 RF Circuitry
The RF circuitry consists of several blocks: a 5 dB input pad (R1, R2, and R3), an RF amplifier
module (U4), an output power boosting transistor (Q1), three directional couplers (TL1, TL3, and
TL4), and the UT-3/400 Lowpass Filter. The heart of the UT-3/400 Amplifier is RF amplifier
module U4. This module amplifies a 1 mW signal up to a maximum of 2.0 W, at the antenna
connector, for a low power unit. In high power units, the output of U4 is further amplified by Q1
to a maximum of 8.0 Watts at the antenna connector. Capacitors C17 and C24 provide tuning for
transistor Q1's input and output match. Although the input match and the output match for Q1 are
tunable, the networks have been made broadband so that the high power amplifiers will operate
over the same frequencyrange as the low power amplifiers. The frequency band of the UT-3/400
Amplifier is determined by the operating frequency range of the RF amplifier module U4.
Directional couplers (TL1, TL3, and TL4) are used to sample forward and reverse power. The
sampled power is used by the sensing and power control circuits to control the amplifier's
operation. The finalstep in the RF path is output filtering and, as mentioned earlier, this is done by
the UT-3/400 Lowpass Filter.
2.3.1 UT-3/400 Lowpass Filter
The UT-3/400 Lowpass Filter is a 50 ohm, 9 pole, reciprocal filter with a 3 dB cutoff frequency of
approximately 512 MHz. The lowpass filter assembly attenuates the desired signal's harmonics as
well as any other out-of-band emissions so that a 'clean' RF signal is output to the antenna
connector.

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UHF Amplifier Instruction Manual UT-3 406 - 512 MHz 2-3
2.4 Power Control Circuitry
The UT-3/400 Amplifier employs a closed loop power controlwhich uses a sample of the forward
RF power to controlthe gain of RF amplifier U4. Op-amp U1b compares the sampled RF voltage
to the output power setpoint and generates an error signal which Q3 uses to control the voltage on
U4's gain controlpin. The output power setpoint is determined by R7, the Output Power Adjust
potentiometer.
In low power amplifiers jumper JU5 is installed and the forward power is sampled by TL3, D6,
C27, R18, L11, R19, and C28. In high power amplifiers jumper JU5 is not installed and the
forward power is sampled by TL1, D5, C14, R13, L6, R12, and C15. In both high power and
low power amplifiers, the power control circuitry keeps the output power of U4 constant.
Therefore, in high power amplifiers, the amplifier's output power will fluctuate with variations in
the +13.8 Vdcsupply voltage.
2.5 Power Sensing Circuitry
The UT-3/400 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, thatis, 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.
Both the Output Power Alarm setpoint and the VSWR Alarm setpoint are individually adjustable;
however, the Output Power Alarm setpoint must always be adjusted before the VSWR Alarm
setpoint. This is because the Output Power Alarm setpoint is used as a reference by the VSWR
Alarm circuitry.
2.5.1 Output Power Sense
The output power sense circuitry uses directional coupler TL3 to sample some of the forward
power. The sampled power is rectified by diode D6 and capacitor C27 and then amplified by
op-amp U3b. Op-amp U3b's amplification is controlled by R21, the output power alarm adjust
potentiometer. The amplified voltage is then output directly in linear operation (JU1 installed, JU2
not installed) or compared to +6.3 Vdc by op-amp U1a which then drives transistors Q5 and Q6
for open collector operatio n (JU1 not installed, JU2 installed).
In open collector configuration, Q6 (the open collector output transistor) is turned on when an
alarm condition occurs. The adjustment range for the output power alarm can vary depending on
the setting of R21 (the Output Power Alarm Adjust potentiometer).

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2-4 UHF Amplifier Instruction Manual UT-3 406 - 512 MHz
2.5.2 VSWR Sense
The VSWR sense circuitry uses directional coupler TL4 to sample some of the power reflected
from the antenna terminal. The reflected power is rectified by diode D7 and capacitor C33 and then
amplified by op-amp U2b. Op-amp U2b's amplification is controlled by R36, the VSWR Alarm
Adjust potentiometer. The amplified voltage is then output directly in linear operation (JU4
installed, JU3 not installed) or compared to the output power alarm setpoint by op-amp U3a which
then drives transistor Q7 for open collector operation (JU4 not installed, JU3 installed).
In open collector configuration, Q7 (the open collector output transistor) is turned on when an
alarm condition occurs. The adjustment range for the VSWR Alarm can depending on the setting
of R36 (the VSWR Alarm Adjust potentiometer).
2.5.3 VSWR Overload
The VSWR overload circuit protects the UT-3/400 Amplifier from excessive antenna VSWR by
reducing the amplifier's gain (output power) when an overload condition occurs. The VSWR
overload circuit (R38 to R41, R8, U2a, and Q4) is an extension of the VSWR sense circuit and
operates the same as the VSWR sense open collector circuit. The VSWR Overload Adjust
potentiometer (R38) reduces the voltage level of the VSWR Alarm Setpoint. The voltage set by
R38 is the compared to the output power alarm setpoint by op-amp U2a which then drives
transistor Q4. When transistor Q4 turns on, signaling an overload condition, resistor R8 is
grounded which reduces the output power setpoint. Reducingthe output power setpoint lowers the
UT-3/400 Amplifier's gain and protects the amplifiers from excessive current draw resulting from
high antenna VSWR.
The VSWR overload circuit's range of adjustment depends on the setting of the VSWR Alarm
Adjust potentiometer (R36). The VSWR overloadtransistor Q4 can be activated at the same point
at which the VSWR alarm becomes active or the VSWR overload circuit can be disabled by turning
R38 completely counterclockwise.