The PA220 is part of the Eclipse range of modular base station equipment. It is a power
amplifier capable of deliver ing 100 Watts in the VHF frequency range. It is designed
to complement the T220 transmitter, and mounts in a standard Eclipse sub-rack.
1.1Installation
There are no front panel controls. In normal circumstances no alignment or setup is
required. If mounted in a sub-rack that has not previously been wired for a power
amplifier, the rack connector must be wired according to the guidelines in section 1.1.1
below.
1.1.1Sub-rack Wir i ng Guidel ine s
When installing an Eclipse Power Amplifier in an Eclipse sub-rack, observe the
following guidelines for sub-rack installation:
•
The sub-rack power supply must be capable of delivering the full current
requirements for all modules fitted in the sub-rack, typically 20 Amperes for a 100W
transmitter/amplifier.
•
Owing to the current drain, power supply lines should be cabled to the power
amplifier separately and using heavy gauge wire to minimise voltage drop and
interference via the power supply of other modules in the rack.
•
The ALC line from the power amplifier must be connected to the ALC input of the
exciter. If this connection is not correctly made, no control of the output power
level will be possible. This can result in excessive RF output power, and
consequent breach of licensing authority regulations, or possible overload of the
unit.
With an Eclipse T500, join pin 8 on the exciter and the amplifier.
1.2Front Panel Indicators
PWR LED
RFO LED
Page 4RF Technology PA220
The power (PWR) LED shows that the dc supply is connected to the
transmitter.
The RF output (RFO) LED indicates that the amplifier is being driven
and that the forward output power is above a preset level. This preset indication
level is generally set 1 - 3 dB below the preset out put power level. The presetting
potentiometer RV2 is not accessible without removal of the cover plate.
1OPERATING INSTRUCTIONS
13. Internal Adjustments
TEMP LED
amplifier's internal temperature become too high. The RF power is automatically
reduced if the internal temperature rises above safe limits.
The temperature (TEMP) LED indicates illuminates should the
1.3Internal Adjustments
All interna l adjustments are factory set and should not need to be changed under normal
conditions. A possible exception to this is the RF output power level which may need to
be changed to comply with local licensing requirements. The low forward power
warning circuit should be set at the same time as the forward power level.
WARNING
Ensure that the power setting complies with the
requirements of your licensing authority. Failure to do
so may result in penalties being imposed by the
licensing authority.
Output Power
(+50dBm), but may be set to any value between 20 and 100 Watts depending upon
local regulations in the destination country. RV2 determines the threshold
affecting the ALC voltage that is fed back to the transmitter module to regulate RF
output power.
RF Level Detector
the amplifier front panel is set by RV3. This is nominally set at half to threequarters of the preset output power.
The output power is set by R V2. This is nominally set to 100 W att s
The forward RF power threshold associated with the RFO LED on
1.4Amp lifier I/O Connections
The PA220 has three connectors on the rear panel.
1.4.1RF Input
The RF drive is delivered via a BNC connector. The absolute maximum power that
should be applied to this connector is 25 Watts.
1.4.2RF Output
The RF output signal is available from an N-type connector.
RF Technology PA220
Table 1: Pin connections for the 25 pin “D” connector on the rear panel
Note: The a mplifier is ca pable of delive ring as much as 120 Watts cont inuously.
In certain conditions1 an RF power of 130 Watt s or more can be available via this
connect or. This corresponds to pea k voltages in excess of 100 while current s in
excess of 2 Amperes may flow. Appropriate care should be ta ken when working
on the PA220 to avoid making or breaking connections when the amplifier is
operating, and to avoid RF burns through close proximity to live connections, etc.
1.4.325 Pin Connector
The 25-pin ``D'' connector provides connection to ground and dc power, and from the
automatic level control (ALC) circuit. The pin connections are given in table 1. The
ALC line floats high to approximately 7Vdc. Pulling this line low
will reduce output power. Voltages below 0.5V will reduce the output by more than
20dB. A pull-down current of approximately 1mA is required.
2Circuit Description
The following descriptions should be read as an aid to understanding the block and
schematic diagrams shown in figures 1 - 4.
2.1Amplifiers
The RF power amplificat ion is provided by two single transistor amplifiers, Q1 and Q2.
Each amplifier is rated at 50 watts output. The input and output impedances of the
transistors is matched to 50Ω by broad band microstrip matching networks.
Trimmer capacitors C10 a nd C24 are used on the input networks to optimize the input
match at center of the desired frequency range. Similarly C58 and C59 on the output
networks are used to optimize the output efficiency.
Since the design of the amplifiers allows them to be very broad band, they will not
usually require re-adjustment unless changing frequency from one end of the band to the
other.
___
_________________
1
Excessive powers may be available, for example, in the event of a failure of the ALC loop,
such as may arise if the ALC feedback connection is broken.
Page 6RF Technology PA220
2CIRCUIT DESCRIPTION
The dc supply is fed to the a mplif iers through resistors R27 and R28. This allows the
collector current of each amplifier to be measured at the test socket.
2.2 Power Splitter/C ombiners
2.2Power Splitter/Combiners
In the 100W models, zero-degree hybrid power splitter/combiners are used to parallel
the two amplif ier stages. The hybrids consist of quarte r-wave 70Ω transmission l ines
and 100Ω RF resistors CX1-4, R9 and R10. This configuration provides wider
bandwidth and better balance than lower cost 90-degree hybrids.
2.3Directional Coupler
The forward and reverse power components are measured through a coupled line
directional c oupler. The output of t he coupled line is frequency c ompensated by R13,
R14, C29 and C30 before being detected by D1 and D2.
The output of the detectors is proportional to the forward and reflected voltage
components.
2.4 Low Pass Filter
A low pa ss filter consist in g of L12 - 14 and C39 - 42 reduc es the harmonic components
to less than -80dBc. The filter uses a combination of lumped elements and printed
microstrips to obtain the required harmonic attenuation.
2.5Power Control Circuits
The forward and reverse voltages from the directional coupler are amplified and
inverted by U1a and U1b. The amplified voltages are combined before connecting to
the input of error amplifier U1d.
Error amplifier U1d compares the detected voltage with the dc reference voltage from
output power trimpot RV1. The amplified difference at the output of U1d is supplied to
the rear panel system connector for connection to the T220 ALC input.
Equipment TypeKey Specifications
Power Supply13.8Vdc, 15A
RF Source25 Watt (eg. T220 exciter)
RF Load / Attenuator
RF Power Metereg. HP437B or calibrated detector and voltmeter
50Ω, 50/100W, SWR<1.2:1
Table 2: Standard test equipment for the PA220 Power Amplifier
RF Technology PA220
Page 7
2.6 RF Output Indicator
3 FIELD ALIGNMENT PROCEDURE
2.6RF Output Indicator
The forward power voltage is compared with the pre-set dc reference voltage from RV2
by U1c. The output of U1c is used to turn on the RFO LED and provide an output
power logic signal to the test connector.
RV2 is normally set so that the RFO LED comes ON 1 - 3db below the nominal power
output level.
2.7Over Temperature Protection
Thermistor RT1 is mounted to the case of output transistor Q1. If the transistor case
temperature rises above 90 Celcius the resistance of RT1 increases and Q5 is turned
ON.
This causes the TEMP LED to come on and also reduces the dc reference voltage to the
output power error amplifier U1d. The input power will then be reduced by the
transmitter ALC circuits and the output transistor is kept within safe operating limits.
3Field Alignment Procedures
3.1Output Power Level
1. Set the unit up on a bench with the standard test equipment listed in table 2.
2. Set RV1 and RV2 both fully counter-clockwise.
3. Set the exciter to the desired operating frequency.
4. Adjust R V1 to set the output power on t he meter to the level at which you want the
RFO LED to illuminate.
5. Adjust RV2 until the RFO LED just goes out.
6. Adjust RV1 for the desired output power.
Page 8RF Technology PA220
4 SPECIFICATIONS3.2 Tuning Procedure
3.2Tuning Proc e dur e
Adjustment of the matching circuits is carried out with the aim of
•
ensuring that the specified power is available
•
balancing the load reasonably equally between the power transistors, and
•
obtaining acceptable efficiency in the power transistors.
Note that the factory alignment procedure is complicated, but allows a given unit to
operate across a full 10% bandwidth, without further adjustment. Alignment without
appropriate equipment can leave the amplifier unstable or otherwise unable to meet
specification. However, the procedure below will usually provide adequate
performance.
1. Disconnect the ALC line.
2. Set the RF source to deliver 15W at the highest frequency in the band over which
the PA is specified.
3. Measuring the RF output power, adjust C10, C24, C102, C112, C58, C59, C104 and
C114 to obtain maximum output.
4. Measuring the collector currents of Q1 and Q2 at the test socket, adjust C58 and C59
to reduce and balance the currents, but keeping the power above the required level.
5. Proceed to carry out the power setting procedure in section 3.1.
4Specifications
4.1Description
The PA220 power amplifiers are designed for use with the T220 series tra nsmitters to
provide 100 Watts of RF output. Output power is regulated by connecting the ALC
output to the ALC input of the driving exciter. The drive from the transmitter module is
then automatically adjusted to maintain the required output.
The regulated power level can be preset over a wide guaranteed range from 25 to 100
Watts or more, depending on the available input power and the model.
Sensing circuits are provided to protect the output transistors from excessive
temperature. If the heat sink temperature rises to 80C, the input drive will be reduced to
prevent damage.
RF Technology PA220
Page 9
4.2 Physical Configuration
4 SPECIFICATIONS
4.2Physical Configuration
The power amplifier is designed to fit in an RF Technology sub-rack within a 19" rack
frame. The installed height is 4 Rack Units (RU), or 178mm, and the depth is 350mm.
The ampl ifier is 95.25 mm or three E clipse units wide. The ampl ifie r uses an extruded
aluminium heat sink with vertical fin s. Heatsink temperature rise is typically 20C at
50W output.
4.3Front Panel Indicators and Test Points
4.3.1Indicators
Power:
RF Power:
Over Temperature:
4.3.2Test Points
Forward Power:
Reverse Power:
Collector Currents:
1).
Green LED
Yellow LED
Red LED
Voltage to ground, 0 - 4V, uncalibrated (pin 4 - gnd)
Voltage to ground, 0 - 4V, uncalibrated (pin 3 - gnd)
Voltage to positive supply, across 0.1Ω, ±10% (p ins 7 - 1 and 8 -
4.4Electrical Specifications
4.4.1Power Requirements
Operating Voltage:
Current Drain:
100mA ma ximum standby
Polarity:
4.4.2Frequency Range
ModelFrequency Range
PA220215-240MHz
Page 10RF Technology PA220
Negative Ground
10.5 - 16 Volts, with output power reduced below 12.5V
16 Amperes maximum (14 typical) at 100 Watts and 13.5 Volts,
4SPECIFICATIONS
4.5 Antenna Impedance
4.5Antenna Impedance
Nominal load impedance is 50Ω SWR 1.5:1 or better. The PA350/500 will operate with
a VSWR of 2:1 at all phase angles. The forward power will reduce as reverse power
rises above acceptable limits, typically at an SWR of about 2.5:1.
4.6Output Power
Nominally 100 Watts, preset adjustable from 25 to 100. Gain is typically >5dB.
4.6.1Transmit Duty Cycle
The transmitte r is rated for 100% dut y cycle (continuous operation) at 50W output for
air temperature below 40C. Derate linearly above 40C to 50% at 60C.
The transmitter is rated for 50% duty cycle at 100W output for air temperature below
40C. Derate linearly above 40C to 5% at 70C.
4.7Spurious and Harmonics
Less than 1uW at any harmonic of the transmit frequency.
4.8Heatsink Temperature
The heatsink temperature can rise to 80C without affecting operation, except for
derating ba sed on air-temperature a s noted in section 4.6.1 above. Shutdown will occur
at heatsink temperatures exceeding approximately 90C.
4.9ALC Output
The AL C is intended for conne ction to the T500. It supplies a voltage which decreases
with increasin g power or temperature. Voltages below 6V should reduce drive power,
at a rate of approximately 6~dB/Volt, w ith voltages below 1V producing a minimum of
25~dB attenuation.
4.10 Connectors
4.10.1RF Input
The RF drive is delivered via a BNC connector. The maximu m power that should be
applied to this connector is 32 Watts.
RF Technology PA220
Page 11
A ENGINEERING DIAGRAMS
4.10.2RF Output
The RF output signal is available from an N-type connector.
4.10.325-Pin Connector
A 25-pin, D-shell (``D'') connector is mounted on the rear panel. It provides power
connections and a connection from the automatic level control (ALC) circuit. The pin
connections are given in table 1.
4.10.49-Pin Connector
A front-panel, 9-pin, D-shell connector provides analogue voltages for testing purposes.
AEngineering Diagrams
A.1 Block Diagram
Figure 1 show s the block signal flow diagram of the PA220 amplifier. Figure 2 shows
the chassis wiring diagram of the PA220 amplifier.
A.2 Circuit Diagrams
Figure 3 shows the detailed circuit diagram of the amplifier with component numbers
and values.
A.3 Component Overlay Diagrams
Figure 5 shows the PCB overlay guides for the amplifier with component positions.
Page 12RF Technology PA220
AENGINEERING DIAGRAMS
A.1 wiring and block diagrams
Figure 1: The block circuit diagram of the PA220 Amplifier
RF Technology PA220
Page 13
A.1Wiring and block Diagrams
A ENGINEERING DIAGRAMS
Figure 2: The chassis wiring diagram of the PA220 Amplifier.
Page 14RF Technology PA220
AENGINEERING DIAGRAMSA.2 Circuit Diagrams
Figure 4: The component circuit diagram of the power amplifier.
RF Technology PA220
Page 15
AENGINEERING DIAGRAMS
A.3 Component Overlay Diagrams
Figure 5: The component overlay diagram of the PA220 amplifier.
PCB PA LED30/9106/0001
D1Diode LED Green T1 3/421/1011/LEDG
D2Diode LED Red T1 3/421/1011/LEDR
D3Diode LED Yellow T1 3/421/1011/LEDY
End of assembly
Start assembly 12/0004/ 0001
Connector 16 w ay IDC35/2512/0016
Cable 16 way 26GA .05 ID36/1000/0016
Connector DB9F IDC35/5020/009F
End of assembly
Connector DB25M solder35/5020/ 025M
Spacer M3x1073/ M 3SP/H010
Screw M 3x6 CSK PD BZNK70/M 315/0006
Nut M3 Steel BZNK72/M315/ 0001
Washer M3 Shakeproof St eel BZ NK71/M325/ 0001
Scre w M 3 x6 TT PNHD PD BZNK70/M 355/0006
Scre w M 3 x10 TT PNHD PD BZNK7 0 /M355/0010
Spacer Al 5Dx3L M3 Clear73/M3SP/0003
Start assembly 12/0005/ 0075
Connector N type flange mount35/50NA/0001
Cable coax RG31635/0030/0316
End of assembly
RF Technology PA220
Page 19
Start assembly 12/0006/ 0320
Connector B NC crimp35/50BA/0001
Cable coax RG321636/0030/ 0316
End of assembly
Start assembly 12/0007/ R370
Wire 50x.25 T/C PVC Red36/ 50X2/ RED
QC 6.35 F Crimp35/1635/0001
End of assembly
Start assembly 12/0007/ B340
Wire 50x.25 T/C PVC Black36/50X2/BLK
QC 6.35 F Crimp35/1635/0001
End of assembly
Bottom, Pow er amp80/9127/0001
Top, Power amp80/9126/0001
Rear panel, Power amp80/9125/0001
Front sub panel, Power amp80/9128/0001
Front panel, Power amp80/9129/0001
Heat Sink, Power amp80/9130/0001
Cover plain module80/9101/0001
Pawl latch, DIUS DP109SAC76/0001/0001
Handle 3.076/0002/300B
Handle ferrule .156 blk76/0003/156B
Screw 4- 40x6 CSK PD BZNK70/4415/ 0006
Label, PA Front panel81/ 9105/ 0001
Label, S/W and SMA81/9100/PA220
Gnd lug M3 Utilux H25439/ M 301/ H254
Page 20RF Technology PA220
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