Quartzlock A5-24 Operation manual

Model A5-24 Operation And Service Manual
A5-24 Manual 20 March 2002 Page 1 of 10
MODEL A5-24
24 Way Distribution Amplifier
USER’S HANDBOOK
Quartzlock UK Ltd
Gothic,
Plymouth Road,
Totnes,
Devon
TQ9 5LH,
England.
Tel: [phone]
Fax: [phone]
Web: www.quartzlock.com
E-mail: [email protected]

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Contents
Safety Considerations..........................................................................................................3
Voltage, Frequency and Power Characteristics...................................................................4
Environmental Conditions....................................................................................................4
Replaceable Fusing Characteristics.....................................................................................4
Cleaning Instructions ...........................................................................................................4
Distribution Amplifier A5-24 .................................................................................................5
Operating Procedure........................................................................................................5
Output Amplifier............................................................................................................6
Mother Board................................................................................................................6
Performance Verification..................................................................................................6
Equipment Required.....................................................................................................6
Procedures...................................................................................................................7
Specification.....................................................................................................................9
Appendix............................................................................................................................10

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Safety Considerations
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.
Before Applying Power
Verify that the product is set to match the available line voltage and the correct fuse is installed.
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.
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.
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.

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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.
Voltage, Frequency and Power Characteristics
Voltage 220-240V AC
Frequency 40-50Hz
Power characteristics 500mA Max
Environmental Conditions
Temperature
Operating (ambient) -10°C to +55°C (-65 to +65 op)
Storage -40°C to +85°C
Magnetic Field
Sensitivity ≤2x10-11/ Gauss
Atmospheric Pressure -60m to 4000m
<1x10-13/ mbar
Replaceable Fusing Characteristics
800mA time-lag HBC
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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Distribution Amplifier A5-24
Operating Procedure
Introduction
The Quartzlock model A5-24 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.
Input
One input is provided. This has input impedance of 50Ω. The input level should be between 0 and
+13 dBm.
Outputs
Twenty-four 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.
Power Supply
This unit operates from its own mains driven power supply, set at the factory to operate from 240V
ac. An internal switch on the power supply enables operation from 120V ac if required. The mains
fuse may need increasing in rating at 120V mains supply.

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Circuit Descriptions
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 AC voltage gain of the amplifier is set by the load network,
T2, R19, L1. T2 is a wide band choke, and L1 provides high frequency compensation. The output
stages of the amplifier are common collector stages TR1 and TR6. R1 and R3 set a 100Ω output
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 -6dB when the amplifier is loaded with 50W. The
voltage gain of the entire amplifier is about 12dB, and it is capable of an output power of about 17
dBm into 50W. At the nominal output power of 13dBm, 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. The
output may be floated by 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.
Mother Board
The main boards include the input amplifier, the 2 x 12 way splitter, the power supply, and 12
output amplifier modules. The circuit of the main board is given on drawing no TBD. The input
amplifier is very similar to an output amplifier module, except variable gain is provided. The gain
controls on the VR1’s, which vary the transconductance of TR6 and TR7. C12 provides high
frequency compensation. The 50Ω output impedance of the input amplifier provides a good match
to the passive splitter. The main board is supplied from the internal 24V DC power supply. A
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 circuits comprise RN1, D1 to D6, and TR11. If any of the output present transistors in the
output amplifiers are off, TR11 will turn on.
Performance Verification
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.

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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.
Procedures
Frequency Response
Connect the tracking source to the input of the Model A5-24, 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 A5-24 gain control (VR1) to give an output level of 13
dBm at 10 MHz.
Measure the frequency response and verify against the specifications.
Harmonic Distortion
Connect the 10 MHz signal source to the Model A5-24 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 A5-24 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.
Output to Output Isolation
Set the tracking generator to +10dBm output level, and connect to any output of the A5-24.
Terminate the A5-24 input with a 50Ω load. Connect the spectrum analyser to any other output of
the A5-24, 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-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.
Output to Input Isolation
Connect the tracking generator to any output, and the spectrum analyser to the input of the A5-24
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..
Maximum Output
Connect the 10 MHz signal source to the input of the A5-24, 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.
Spurious Outputs and Wideband Noise.
With the gain of the A5-24 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

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analysers’ noise figure, correct for measurement bandwidth, log amplifier, and detector.
Alternatively use a noise figure meter.
Input and Output SWR
Measure using a reflection bridge or network analyser
Setting Up
The only user adjustment required is to set the output levels. To do this proceed as follows:
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.
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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Specification
1. No of outputs: 24
2. No of inputs: 1 or 2
3. Input Characteristics:
a. Impedance: 50 Ωnominal
b. Level: 0 dBm to +13 dBm adjustable, sine wave
c. Input SWR: <1.2: 1 at 10 MHz <1.5: 1 at 100MHz
4. Output Characteristics:
a. Impedance: 50 Ωnominal
b. Level: 13 dBm nominal into 50 Ω(1 volt RMS)
c. Output SWR: <1.2:1
d. Maximum output: 16 dBm at 10 MHz typical
14 dBm at 100 MHz typical
5. Frequency Response:
a. 2 MHz to 100 MHz ±1.5dB
b. 500 kHz to 100 MHz ±3dB
6. Harmonics: (at nominal output, 10 MHz)
(Source harmonics less than -60dBc)
a. Second harmonic < -50dBc
b. Third harmonic < -40dBc
7. Isolation:
a. Output to output >90dB (adjacent outputs) at 10 MHz
>70dB (adjacent outputs) at 100 MHz
Typically >110 dB at 10 MHz and >90 dB at 100 MHz
b. Output to input >110dB at 10 MHz
>90 dB at 100 MHz
8. Phase Noise: (10MHz)
Offset From Carrier Phase Noise, dBc
a. 1 Hz -140
b. 10 Hz -150
c. >100 Hz -165
9. Spurious Outputs:
< -110 dBc (above 1 MHz) (typically <-120 dBc)*
10.Broadband Noise:
< -150 dBm/Hz
11.Delay Match Between Outputs
< 1ns
12.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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Appendix