AMERITRON ALS-500M Operation manual
ALS-500M Instruction Manual
TABLE OF CONTENTS
ALS-500M Features........................................................................................................ 1
General Information ........................................................................................................ 2
Load Fault Circuit ...............................................................................................2
Bias Control Circuits........................................................................................... 2
Drive Power......................................................................................................... 2
Supply Voltage.................................................................................................... 3
SWR Considerations ........................................................................................... 3
Periodic Maintenance.......................................................................................... 3
Technical Assistance ........................................................................................... 3
Export Modifications........................................................................................... 4
Installation....................................................................................................................... 4
Location............................................................................................................... 4
Power Requirements ........................................................................................... 4
Fuse Holder Installation ...................................................................................... 5
Auxiliary Battery Installation.............................................................................. 5
Grounding........................................................................................................................ 6
Unibody Vehicles................................................................................................ 6
Frame-Type Vehicles .......................................................................................... 6
Interconnections Diagram ............................................................................................... 7
Interconnections .............................................................................................................. 8
Operation......................................................................................................................... 9
ALS-500M Parts List ...................................................................................................... 10
Combiner Board Parts List.................................................................................. 10
Power Amplifier Board Parts List....................................................................... 11
Output Filter Board .............................................................................................13
Bias Board Parts List........................................................................................... 15
Chassis Components Parts List ........................................................................... 17
ALS-500M Instruction Manual
ALS-500M FEATURES
1. Rugged devices.
The ALS-500M uses four rugged linear RF power devices.
2. Fast warm-up time.
The ALS-500M has no vacuum tubes to warm-up.
3. No tune operation.
Tuning adjustments are not necessary. A simple one knob selector switch permits operation on
frequencies between 1.5 and 21.6 MHz.
4. Load Fault Protection
The PA load impedance is monitored and the amplifier is bypassed if the bandswitch setting or
the external load is incorrect.
5. Current meter.
The ALS-500M has a DC current meter to monitor collector current.
6. Off/On switch.
This switch allows the amplifier to be by-passed for "bare-foot" operation without disconnecting
the high current leads.
7. Remote Off/On control.
A separate connection on the power connector allows low current control of the amplifier Off/On
function for remote mounting.
8. Remote A and B.
Ports A and B are for connecting the ALS-500RC. The ALS-500RC is a remote control head
that allows the amplifier to be located away from the operating station and still have access of the
front panel controls.
9. Compact size.
The ALS-500M weighs only 7.5 pounds and measures 3 3/4"H x 9"W x 15 1/2"D .
1
ALS-500M Instruction Manual
GENERAL INFORMATION
Load Fault Circuit
The ALS-500M features a load fault trip circuit that bypasses the amplifier if the amplifier frequency
switch is set to a lower frequency range than the exciter or if the load reflected power exceeds 70-100
watts. This circuit virtually eliminates the danger of component failures due to operating errors.
The Combiner circuit board near the PA contains the components that sense the reflected power at the
input of the low-pass filters used in the output circuit. Selecting a filter that has a cut off frequency
below the operating frequency or operating into loads with reflected power levels that exceed 70-100
watts will trip the overload and bypass the amplifier. SCR (Q5) on the Bias board keeps the amplifier
"locked out" until the POWER (ON/OFF) switch is cycled off and on.
Bias Control Circuits
The Bias board contains the temperature and bias control circuitry. The output transistor temperature is
monitored with diodes D1 and D2 on the PA module. The voltage drop across the diodes decreases as
the PA transistor temperature rises. The reduction in diode voltage with increasing temperature causes
IC 1c/d to reduce the PA base bias current supplied by Q2/3. Diodes D1/2 on the bias board limit the
available bias voltage if a failure in the bias circuit occurs.
IC 1a compares the voltage from the Power Amplifier temperature diodes to the reference voltage from
the temperature sensitivity control R28. If the temperature becomes too high (voltage too low) IC 1a
switches high and Q4 turns the cooling fan on. If the temperature continues to increase IC 1b will
eventually pull low and the voltage for the transmit relay and the bias voltage will be removed. The
THERMAL OVERLOAD LED is illuminated when the output of IC 1b is low. This circuit
automatically resets when the temperature drops to a safe operating range.
If the band switch is in the wrong position, the antenna SWR is high, or the amplifier is being driven
into non-linear operation a "load fault" will occur. When a load fault occurs gate voltage is applied to
SCR Q5. This causes Q5 to latch in a conducting state. Q5 will remain in this condition and the
amplifier's relay line will be disabled until the OFF/ON switch is cycled off and on. The LOAD
FAULT LED on the front panel is illuminated whenever SCR Q5 is in conduction and the amplifier is
bypassed from a load fault.
Drive Power
The ALS-500M normally requires much less than 100 watts of drive to produce full output power.
This drive power varies considerably with the gain of the transistors used in the amplifier and the
power supply voltage. As a general rule, exceeding 100 watts of drive for long periods of time may
cause component failures. Exceeding 70 watts of peak drive power may cause distortion and increase
the bandwidth of the transmitted signal.
2
ALS-500M Instruction Manual
Supply Voltage
Low voltage solid state amplifiers are very sensitive to power supply voltage changes. For maximum
performance, the voltage should be maintained as high as possible consistent with component life. The
devices used in this amplifier have demonstrated excellent life with supply voltages up to 16 volts, and
will produce the rated output power at 14 volts dc. The output power will decrease by approximately
85 watts per volt as the supply voltage is lowered from 14 to 12 volts.
SWR Considerations
SWR (Standing Wave Ratio) causes higher voltages and/or currents to appear at the output connector
of the amplifier. This problem occurs with all amplifiers regardless of whether tubes or
semiconductors are used in the output stage.
The devices used in the ALS-500M have very good overload tolerance. The low pass output network
in the ALS-500M not extremely sensitive to load impedance changes. This makes the ALS-500M less
sensitive to frequency and SWR changes than many other similar amplifiers. The multiple section
output network and push-pull output configuration used in the ALS-500M also offers excellent
harmonic suppression.
The only danger presented by a high SWR is that the current and power dissipation in the output
devices may exceed safe limits. This can result in heat damage and failure of the amplifying devices.
If the SWR exceeds 2:1 the power level should be reduced until the reflected power is 60 watts or less.
At approximately 70 watts of reflected power the internal safety circuitry will disable the amplifier.
Periodic Maintenance
The lack of high voltage in this unit eliminates the chance of dirt and dust causing high voltage arcing
in this unit. The only deleterious effect of dust and dirt is a reduction in cooling efficiency. The
primary maintenance requirement is to monitor the amount of dirt and dust in the amplifier, and
remove the dust and dirt before cooling problems begin. Low pressure compressed air can be used to
blow the dust out of this amplifier whenever a noticeable accumulation of dust builds up.
A soft bristled brush and a small amount of alcohol can be used to clean stubborn dust from the fan or
the other components. Be careful not to get any cleaning compounds on relay contacts or in switches.
If it becomes necessary to perform maintenance on any switch or relay contact Ameritron. Ameritron
has free technical support for customers that wish to service their own equipment.
Technical Assistance
Ameritron has free technical information bulletins that provide assistance with the most common
operational problems. Technical assistance is also available by calling (662) 323-8211 or FAX (662)
323-6551 during our normal business hours (8:00 to 4:30 Central Time on weekdays) for questions
that are not properly addressed by the technical bulletins. Ameritron's policy is to provide complete
technical support to our customers. Before calling, please have the following information available:
1. The model and serial number the unit.
2. The date of purchase and the dealer.
3. A brief description of the station equipment and antenna system.
4. A complete description of the problem along with all meter readings.
3
ALS-500M Instruction Manual
Written assistance is also available. Due to time delays in processing mail, please allow a minimum of
three weeks for a written reply. Send questions to: Ameritron, 116 Willow Road, Starkville, MS
39759
Export Modifications
A simple modification will allow operation on frequencies above 22 MHz. A parts kit to make this
modification is available by sending a written request for an MOD-10M export modification kit along
with a copy of your valid amateur license to the Ameritron. There is a charge for this kit. Export
models are shipped with this modification installed and have an "X" following the serial number.
INSTALLATION
Location
Do not locate this amplifier in excessively warm locations, near heater vents, or in unventilated areas
with ambient temperatures exceeding 120 degrees Fahrenheit. Be sure that air can circulate freely
around and through the amplifier cabinet. Do not obstruct the air inlet at the right front side of the
amplifier or the outlet air holes on the lower left side of the amplifier.
When not using the ALS-500M remote control head the best location for this amplifier is one that
allows the meter to be easily read and the controls accessed during operation. The length of each 13.8
volt high current cable is very important. Every consideration should be given to keeping the high
current battery lead lengths as short as practical. This includes the ground leads to the battery and the
ground lead to the vehicle's chassis.
The lengths of the remaining low current power and control cables are not critical. The relay control
lead can be made from any good quality two wire cable. Low level audio type cables sold for stereo
and VCR use are ideal for the relay connection. The RF cables should be kept as short as practical.
Power Requirements
This amplifier requires 11-18 volts positive at low current (less than 4 amperes) for the control and
bias circuits. This is a non-critical voltage. The voltage applied to the low current control line will not
affect the performance of the amplifier if it is within the specified range. The control line is the small
red wire that connects between pin 10 of the power connector and the 5 ampere fuse.
The heavy RED conductors and the black battery return and chassis ground conductors must carry the
full peak current of the amplifier. This current can reach 80 amperes on voice peaks or 40 amperes of
average current. This large current is split between the two large RED wires leaving pins 3 and 4 of the
power connector. The ground connections from pins 11 and 12 must also carry this current. It is
extremely important to minimize the voltage drop across these conductors. For maximum performance,
all of the high current leads (including the ground leads) must be kept as short as possible.
The following chart gives the approximate peak voltage drop in volts per foot of a single supply wire
with 40 amperes of current. Remember the ground wires also carry high current. This chart assumes
that the chassis ground of the vehicle has negligible resistance, and that the negative lead to the battery
is the same wire gauge as the positive supply leads. The chart on page 5 indicates the maximum length
of each individual wire for full performance:
4
ALS-500M Instruction Manual
AWG
(single conductor)
10 gauge 0.04 V/ft 5 ft.
8 gauge 0.025 V/ft 8 ft.
6 gauge 0.015 V/ft 12 ft.
4 gauge 0.01 V/ft 20 ft.
For best performance the voltage drop at maximum power in the high current power and ground leads
should be limited to a 0.2 volt maximum. Refer to the Interconnections section for information on the
wiring and fuse requirements of this amplifier.
Fuse Holder Installation
Included in the wire harness bag are 3 fuses and fuse holders. Install these fuse holders at the battery
or electrical system voltage source after the power harness wires have been routed to their final
destinations.
The cartridge type low current fuse holder is for the red low current power lead. Use 3AG type
(automotive glass) 5 ampere fast blow fuses for this lead. This holder is usually shipped with the lead
connected to both sides of the holder. Cut the lead in the middle and remove 1/2 inch of insulation.
Connect the short side of the holder (without a spring) to the lead from the amplifier. If a remote
on/off switch other than the ALS-500RC is used it should be installed between this fuse and the
amplifer. Connect the long side of the holder to an ignition key switched source or to a positive
battery lead. A switched source can usually be obtained from a fuse in the fuse box (radio or
accessory) or a convenient wire under the dash. Use wire nuts or solder and tape all connections.
The plug-in fuse holders and 30 ampere fuses are for the red high current power leads. Do not insert
any fuses until wiring is complete. These holders have Teflon coated 12 gauge leads. They can be
used for any size of power lead because their length is short. Solder one lead of each holder to one of
the lugs supplied. Install the lugs over the starter solenoid post that connects to the battery or over the
bolt that secures the positive battery terminal. Use a separate nut to secure the lugs to avoid disturbing
battery connections if possible.
Connect the other lead of each 30 ampere fuse holders to the heavy gauge power leads by stripping,
twisting, and then soldering the leads together. Bare wires should be wrapped with several layers of
electrical tape. Be sure to dress all amplifier leads so that they are not exposed to sharp edges, high
temperatures, or moving parts. After wiring is completed install the fuses.
Voltage Drop
at 40 amps
Maximum Length For
Full Performance
Auxiliary Battery Installation
If possible, avoid the use of an auxiliary storage battery. Ameritron does not assume any liability and
does not recommend the use of an auxiliary battery. The individual installation is left entirely up to
the installer. The following suggestions will increase the safety of the installation.
The positive lead that connects the auxiliary battery to the main battery should be fused at both ends
with automotive type fuse links rated at 75 to 100 amperes. The positive power cable that connects the
5
Loading...