Quartzlock A5-12 Installation and operating instructions

Model A5-12 Operation & Service Manual
A5-12 Manual A5 21 January 2005 Page 1
A5-12
12 Way Distribution Amplifier
OPERATION & SERVICE
MANUAL

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Contents
1Safety Considerations.......................................................3
1.1 General......................................................................3
1.1.1 Before Applying Power.......................................3
1.1.2 Before Cleaning..................................................3
1.1.3 This equipment must be earthed........................3
1.2 Voltage, Frequency and Power Characteristics.........4
1.3 Environmental Conditions..........................................4
1.3.1 Temperature.......................................................4
1.3.2 Magnetic Field....................................................5
1.4 Replaceable Fusing Characteristics ..........................5
1.5 Cleaning Instructions .................................................5
2Operating Procedure.........................................................6
2.1 Introduction................................................................6
2.2 Input...........................................................................6
2.3 Outputs......................................................................6
3Circuit Descriptions...........................................................7
3.1 Output Amplifier.........................................................7
3.2 Mother Board.............................................................7
4Performance Verification...................................................9
4.1 Equipment Required..................................................9
4.2 Procedures ................................................................9
4.2.1 Frequency Response..........................................9
4.2.2 Harmonic Distortion............................................9
4.2.3 Output to Output Isolation...................................9
4.2.4 Output to Input Isolation ...................................10
4.2.5 Maximum Output..............................................10
4.2.6 Spurious Outputs and Wideband Noise............10
4.2.7 Input and Output SWR .....................................10
4.2.8 Setting Up.........................................................10
4.2.9 Note:.................................................................11
5Specification....................................................................12

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1 Safety Considerations
1.1 General
This product and related documentation must be reviewed for familiarisation
before operation. If the equipment is used in a manner not specified by the
manufacturer, the protection provided by the instrument may be impaired.
1.1.1 Before Applying Power
Verify that the product is set to match the available line voltage and the correct
fuse is installed.
1.1.2 Before Cleaning
Disconnect the product from operating power before cleaning.
WARNING
Bodily injury or death may result from failure to heed a
warning. Do not proceed beyond a warning until the
indicated conditions are fully understood and met.
CAUTION
Damage to equipment, or incorrect measurement data, may
result from failure to heed a caution. Do not proceed beyond
a caution until the indicated conditions are fully understood
and met.
1.1.3 This equipment must be earthed
An uninterruptible safety earth ground must be maintained from the mains power
source to the product’s ground circuitry.
WARNING
When measuring power line signals, be extremely careful
and use a step down isolation transformer whose output is
compatible with the input measurement capabilities of this
product. The product’s front and rear panels are typically at
earth ground. Thus, never try to measure AC power line
signals without an isolation transformer.

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WARNING
Instructions for adjustments when covers are removed and
for servicing are for use by service-trained personnel only.
To avoid dangerous electrical shock, do not perform such
adjustments or servicing unless qualified to do so.
WARNING
Any interruption of the protective grounding conductor
(inside or outside the instrument) or disconnecting of the
protective earth terminal will cause a potential shock hazard
that could result in personal injury. Grounding one
conductor of a two conductor out-let is not sufficient
protection.
Whenever it is likely that the protection has been impaired, the instrument must be
made inoperative and be secured against any unintended operation.
If the instrument is to be energised via an autotransformer (for voltage reduction)
make sure the common terminal is connected to the earthed pole terminal (neutral)
of the power source.
Instructions for adjustments while the covers are removed and for servicing are for
use by service-trained personnel only. To avoid dangerous electrical shock, do not
perform such adjustments or servicing unless qualified to do so.
For continued protections against fire, replace the line fuse(s) with fuses of the
same current rating and type (for example, normal blow time delay). Do not use
repaired fuses of short-circuited fuse holders.
1.2 Voltage, Frequency and Power Characteristics
Voltage 220-240V AC
Frequency 40-50Hz
Power characteristics 500mA Max
1.3 Environmental Conditions
1.3.1 Temperature
Operating (ambient) -10°C to +55°C (-65 to +65 op)
Storage -40°C to +85°C

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1.3.2 Magnetic Field
Sensitivity ≤2x10-11/ Gauss
Atmospheric Pressure -60m to 4000m
<1x10-13/ mbar
1.4 Replaceable Fusing Characteristics
800mA time-lag HBC
1.5 Cleaning Instructions
To ensure long and trouble operation, keep the unit free from dust and use care
with liquids around the unit.
Be careful not to spill liquids onto the unit. If the unit does get wet, turn the power
off immediately and let the unit dry completely before turning it on again.
Clean with a damp (with water) cloth.
Never spray cleaner directly onto the unit or let liquid run into any part of it. Never
use harsh or caustic products to clean the unit.

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2 Operating Procedure
2.1 Introduction
The Quartzlock model A5-12 is a linear distribution amplifier designed for
standard frequency distribution between 1 MHz and 100 MHz. The circuit is based
on a number of balanced linear amplifiers with high reverse isolation and low
phase noise. Twelve of these amplifiers are used to drive the twelve 50Ωoutputs.
They are called the output amplifiers in the following description. A modified
version of the output amplifier with a gain control, called the input amplifier,
drives a twelve way passive power splitter. This divides the signal with an
insertion loss of about 12 dB, and provides isolation of about 20 dB. The output
amplifiers each have an output signal monitor circuit, which is used as part of the
output fail monitoring.
2.2 Input
One input is provided. This has input impedance of 50Ω. The input level should be
between 0 and +13 dBm.
2.3 Outputs
Up to twelve outputs are provided. These have source impedance of 50Ω, and will
provide 13 dBm nominal into a 50Ωload. Maximum output is up to 16 dBm.

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3 Circuit Descriptions
3.1 Output Amplifier
The output amplifier is a differential amplifier based on a common emitter,
common base, and common collector cascade circuit. TR7 and TR8 are the
common emitter input stages. The emitter resistors R11 and R23, and R12 set the
transconductance. A feedback circuit comprising TR4/TR5 and TR9/TR10 sets the
DC collector current in each transistor. The voltage across the emitter resistors is
set equal to a 2.5V reference voltage fed to the amplifier from the "BIAS" pin. The
active control of DC current also reduces the current fluctuations due to 1/f noise
in the transistors. This reduces the phase noise.
TR2 and TR3 are the common base stages. These provide most of the reverse
isolation in the amplifier.
The load network, T2, R19, L1, sets the AC voltage gain of the amplifier. T2 is a
wide band choke, and L1 provides high frequency compensation.
The output stage of the amplifier is common collector stages TR1 and TR6. R1 and
R3 set 100Ωoutput impedance for each transistor. When combined in T1, a 50Ω
output impedance results. Due to the output impedance, the gain of the output
stages is –6 dB when the amplifier is loaded with 50Ω.
The voltage gain of the entire amplifier is about 12 dB, and it is capable of an
output power of about 17 dBm into 50Ω. At the nominal output power of 13 dBm,
the second harmonic distortion is less than -60 dBc due to the differential design.
Third harmonic distortion is less than -40 dBc. The bandwidth is +/-1 dB from 2
MHz to 100 MHz. The gain falls by a further 1 dB at 1 MHz.
A tuned version of the output amplifier is possible by replacing T2 by a tuned
transformer T4, and by adding C21. This reduces harmonic distortion further, and
also reduces integrated wide band noise.
Cutting a track, enabling an isolated output option to be available on some
products. The network associated with D1 rectifies a sample of the AC output and
turns on TR11. This provides an output monitor point on J2. The amplifier is
powered from +18V DC and +12V DC supplies. The power consumption is about
100 mA at 1 V and 40 mA at 12V.
3.2 Mother Board
The main board includes the input amplifier, the 12-way splitter, the power supply,
and 12 output amplifier modules.

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The input amplifier is very similar to an output amplifier module, except variable
gain is provided. The gain control is VR1, which varies the transconductance of
TR6 and TR7. C12 provides high frequency compensation. The 50Ωoutput
impedance of the input amplifier provides a good match to the passive splitter,
PS1.
The main board is supplied from a 24V DC supply. An off board regulator
provides 18V. R41 and R42 set the voltage of the 18V supply.
U3 is the 12V regulator. U1 provides the 2.5V bias supply for the input amplifier
and all the output amplifiers.
The output fail circuit comprises RN1, D1 to D6, and TR11. If any of the output
present transistors in the output amplifiers are off, TR11 will turn on.

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4 Performance Verification
4.1 Equipment Required
a) Spectrum analyser and tracking generator, 1 MHz to 100
MHz.
b) Sine wave signal generator or function generator, 10 MHz
c) RF Power meter
d) Low pass filter, Mini-circuits BLP 10.7
e) 50ΩBNC load
In addition, if input and output load and source impedance’s are to be checked, a
network analyser will be required.
Verification of the phase noise levels can be extremely difficult, requiring a cross
correlation type of phase noise test set, with a noise floor below -150dBc at 1Hz
and -160dBc at 10 Hz offset.
4.2 Procedures
4.2.1 Frequency Response
Connect the tracking source to the input of the Model A5-12, and the spectrum
analyser to any output. Set the tracking generator output level to 10 dBm, and the
spectrum analyser to sweep between 1 MHz and 100 MHz. Adjust the A5-12 gain
control (VR1) to give an output level of 13 dBm at 10 MHz.
Measure the frequency response and verify against the specifications.
4.2.2 Harmonic Distortion
Connect the 10 MHz signal source to the Model A5-12 input using the low pass
filter to remove source harmonics to less than -60 dBc. Set the output level to +10
dBm. Connect the spectrum analyser to any output and adjust the A5-12 gain
control to give +13 dBm output. Use the spectrum analyser to measure the
harmonic distortion, and verify against the specifications. Repeat for other outputs
if desired. Take care that the spectrum analyser is not generating harmonics so as
to affect the measurement.
4.2.3 Output to Output Isolation
Set the tracking generator to +10dBm output level, and connect to any output of
the A5-12. Terminate the A5-12 input with a 50Ω load. Connect the spectrum
analyser to any other output of the A5-12, and adjust for maximum sensitivity.

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Measure the output isolation at 10 MHz and 100 MHz. Note that it may be
necessary to fit ferrite sleeves to the spectrum analyser and/or tracking generator
cables to avoid common mode cross talk. The output-to-output isolation is defined
as the tracking generator level minus the level measured by the spectrum analyser.
Repeat for a number of combinations of outputs, choosing adjacent and remote
outputs, and verify against the specifications.
4.2.4 Output to Input Isolation
Connect the tracking generator to any output, and the spectrum analyser to the
input of the A5-12 and adjust for maximum sensitivity. Measure the output
isolation at 10 MHz and 100 MHz. Note that it may be necessary to fit ferrite
sleeves to the spectrum analyser and/or tracking generator cables to avoid common
mode cross talk. The output-to-input isolation is defined as the tracking generator
level minus the level measured by the spectrum analyser.
Repeat for a number of combinations of outputs, choosing adjacent and remote
outputs, and verify against the specifications..
4.2.5 Maximum Output
Connect the 10 MHz signal source to the input of the A5-12, and the spectrum
analyser to any output. Increase the input level until the third harmonic rises
abruptly, showing that clipping is occurring. Alternatively an oscilloscope may be
used to adjust to maximum output. Transfer the output to the RF power meter and
read the maximum output level. Repeat at 10 MHz if required.
4.2.6 Spurious Outputs and Wideband Noise.
With the gain of the A5-12 adjusted for 13 dBm output with 10 dBm input at 10
MHz, disconnect the signal source and terminate the input with the 50Ω load.
Connect the spectrum analyser to any input and search for discrete spurii.
Calculate their level in dBc related to the 13 dBm nominal output. Measure the
wideband noise, using a preamplifier if necessary to improve the spectrum
analysers’ noise figure, correct for measurement bandwidth, log amplifier, and
detector. Alternatively use a noise figure meter.
4.2.7 Input and Output SWR
Measure using a reflection bridge or network analyser
4.2.8 Setting Up
The only user adjustment required is to set the output levels. To do this proceed as
follows:

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1. Remove the lid.
2. Connect desired input between 0 and 13 dBm.
3. Connect a spectrum analyser, oscilloscope with 50Ωinput impedance, or RF
power meter to any output.
4. Adjust output level to 13dBm (1V RMS) using the pre-set (VR1) on the main
board.
5. Replace the lid.
4.2.9 Note:
All the amplifiers are class A linear amplifiers. The gain may be set to provide any
output level up to clipping if desired.

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5 Specification
Input Characteristics
No of inputs 1
Impedance 50Ωnominal
Level 0dBm to +13dBm adjustable, sine wave
Input SWR <1.2: 1 at 10 MHz
<1.5: 1 at 100MHz
Output Characteristics
No of outputs 12
Impedance 50Ωnominal
Level +13dBm nominal into 50Ω(1V RMS)
Output SWR <1.2:1
Maximum output 16dBm at 10 MHz typical
14dBm at 100 MHz typical
Frequency Response
2 MHz to 100 MHz ±1.5dB
500 kHz to 100 MHz ±3dB
Harmonics (10 MHz)
(Source harmonics less than -60dBc)
Second harmonic < -50dBc
Third harmonic < -40dBc
Isolation
Output to output >90dB (adjacent outputs) at 10 MHz
>70dB (adjacent outputs) at 100 MHz
Output to input >110dB at 10 MHz
>90 dB at 100 MHz
Phase Noise (10MHz)
Offset From Carrier Phase Noise, dBc
1 Hz -140
10 Hz -150
>100 Hz -165
Spurious Outputs

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< -110 dBc (above 1 MHz)
Broadband Noise
< -150 dBm/Hz
Delay Match Between Outputs
< 1ns
Temperature Stability of Delay
10ps/°C
Phase change at output due to open or short at any other output
(Calculated from isolation): <0.5ps (at 10MHz)
*Spurious outputs are exclusively from the switch mode power supply

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