Ameritron 2WUALS13 User Manual
Ameritron ALS-1300
1200-watt
NO TUNE
TMOS-FET AMPLIFIER
The Ameritron ALS-1300 is 160 through 15-meter amateur radio band 1200-watt output solid-state amplifier. It
uses eight 50-volt conservatively rated linear RF MOSFETS. 50-volt linear FET’s designed for transmitting
service produce an exceptionally clean signal compared to other solid-state amplifiers. Fan speed is regulated by
temperature sensors; assuring conservative cooling with minimum noise.
Nominal driving power is 90 watts for 1200-watts output (approximately 11 dB gain) on most bands. The
compact 10” wide by 6-1/2” high amplifier package (depth only 18”) fits nearly any station configuration. The
attractive desk-top amplifier unit weighs only 22 pounds.
An external 50-volt 50-ampere regulated power supply powers the ALS-1300. The supply is wired for 230
VAC (200-260 VAC, 50-60 Hz, 15 amperes), but can be rewired for 120 VAC operation for lighter duty
operation.
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Table of Contents
TABLE OF CONTENTS .......................................................................................................................2
AMPLIFIER FEATURES ...................................................................................................................... 3
POWER SUPPLY .................................................................................................................................4
Power Line Requirements ..................................................................................................................................................................... 4
Power Supply Features..........................................................................................................................................................................4
Power Supply Location ......................................................................................................................................................................... 4
GENERAL INFORMATION ..................................................................................................................5
Amplifier...............................................................................................................................................................................................5
Power Supply ........................................................................................................................................................................................ 5
INSTALLATION....................................................................................................................................5
Airflow.................................................................................................................................................................................................. 6
INTERCONNECTION WIRING.............................................................................................................7
AMPLIFIER REAR PANEL .................................................................................................................. 8
FRONT PANEL ....................................................................................................................................9
OPERATION.......................................................................................................................................10
MARS OR CAP OPERATION ............................................................................................................ 10
INITIAL OPERATION ......................................................................................................................... 11
CIRCUIT BOARDS.............................................................................................................................12
CB-1.................................................................................................................................................................................................... 12
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Amplifier Features
This amplifier provides the following standard features:
Eight conservatively rated, very linear, 50-volt MOSFET transistors
Operational in a few seconds, no long filament warm-up time
Clean layout with easy-to-service modular construction
Front panel indicators including wrong band and other fault errors
Quiet variable-speed forced air cooling system
Power module balance metering
Power module current and voltage metering with LED illumination
PEP forward output power and PEP reflected output power metering
Reflected power protection
Bandswitch error protection
Standard negative going ALC output with front panel adjustment control
ALC metering and an ALC LED indicator
Fully regulated external power supply
Compact size 17.5” deep x 7” high x 10.5” wide
Weight amplifier section 23 pounds
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Power Supply
The power supply for the ALS-1300 is a voltage regulated current limited supply. It contains 14-volt positive
and negative supplies as well as dual 50-volt 25-ampere continuous (30-ampere peak) fully current limited
supplies. Each PA (power amplifier) module in the ALS-1300 operates from the separate 50-volt sources,
giving a total dc input power rating of 2500 watts to the power amplifier modules.
Power supply to amplifier interconnections are through a heavy-duty cable using a large Cinch Jones connector.
Power Line Requirements
This amplifier ships wired for 200-260 Vac. The maximum average power line current is 12 amperes at 240
volts. Two 250-volt 15-ampere fuses fuse the power line.
Note: 120-volt power mains operation is possible with a reduction in CW or RTTY power. Because average
power is very low, SSB operation is unaffected by 120 volt operation. Fuse size would be 25 amperes
maximum.
Power Supply Features
Efficient operation from 200-260 volts ac (12 amperes minimum) and 100-135 volts (20 amperes
minimum)
Wide range of power line frequencies, 40-400 Hz
Fully regulated current-limited outputs
Step-start to limit stress on power supply components
Exceptional filtering and RFI suppression
Compact light-weight design
Power Supply Location
Locate the power supply in a convenient ventilated area near the amplifier location. Do not place the power
supply next to sensitive equipment like audio processors, transceivers, or microphones. For safety ground the
wing nut stud on the supply rear to the station ground buss. The station ground buss should comply with
national electrical codes. These codes dictate that station grounds must be bonded to the power mains entrance
ground. A station ground that is not bonded to the mains ground does not offer lightning protection!
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General Information
Amplifier
The Ameritron ALS-1300 is a solid-state 1200-watt nominal RF output power 1.8-22 MHz amplifier. This
power is peak envelope power, which is the same as actual carrier power on CW. It uses eight exceptionally
very low distortion push-pull parallel MRF-150 or equivalent RF power TMOS transistors. The ALS-1300
meets or exceeds all FCC rules governing amateur radio external power amplifiers.
Two temperature sensors on each PA (power amplifier) module, with bias tracking FET temperature and fan
speed tracking heatsink temperature, control bias and fan speed.
Harmonic suppression comes from push-pull operation of linear devices, and a series of high quality 5-pole
low-pass filters. This amplifier exceeds all FCC mandated harmonic restrictions.
Antenna switching is through a sequenced pair of miniature relays on a plug in board. Relay switching time is
approximately five milliseconds. This amplifier’s “relay” jack sources 12 volts when open circuit, and the relay
jack current upon closure is less than 20 mA.
This amplifier includes two dual-movement cross-needle meters. This is the equivalent of having four panel
meters. The left hand meter is a dual power amplifier current meter. The right hand meter continuously displays
forward RF peak envelope power on one dedicated scale, while the second movement in the right hand meter
switches between reflected power, combiner mismatch voltage, ALC, and each power amplifier’s voltages.
While this amplifier will run more than 1200 watts PEP output, linearity will suffer. Ameritron recommends
running 1200 watts peak power for maximum linearity, at which point this amplifier will have comparable IM
performance to the best vacuum tube linear amplifiers. The characteristics of linear high-voltage FET’s are very
much like those of triode vacuum tubes.
Power Supply
The ALS-1300 has an external power supply. This power supply normally operates from 200-260 volts at 50400 Hz. It connects to the amplifier through a single cable. The power supply should be located in a cool spot
away from sensitive audio systems or cables.
Installation
Please look your amplifier and power supply over carefully. Observe the air inlet and outlet ventilation holes.
Locate the air inlet and outlet areas of the amplifier. Facing the amplifier front panel, the cooling air inlet is on
the right side. The warm air outlet is on the left side of the amplifier as viewed from the normal operating
position (front view). While the outlet air won’t be particularly warm, it is never a good idea to have it blow
into heat sensitive equipment such as transceivers or other power amplifiers. Have the same consideration for
your new amplifier and power supply. Be sure the air inlet temperature isn’t substantially above normal room
temperature. Ideally the air inlet should be kept below 32° C or 90° F, although temperatures up to 41° C or
106° F are permissible. If ambient temperatures exceed these limits it might become necessary to reduce duty
cycle or power.
Warning: Do not block cooling air inlets and outlets!
Never expose the amplifier to water or mist.
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Airflow
The amplifier must have a clear area to the sides and top for proper airflow, and to the rear for interconnection
wiring. It is especially important to avoid obstructions that block the air inlet on the top left and both lower
sides. Two inches clearance is normally adequate for full ventilation. Keep any papers or loose objects that
might impede airflow away from the air inlets and outlets.
Locate the amplifier and power supply away from sensitive equipment such as microphones, audio processing
equipment, or low level audio or radio frequency amplifiers. Generally the best location for the power supply is
below the operating desk and away from antenna feedlines. This will keep fan noise and any RF coupling to a
minimum.
The power supply is factory wired for 200-260 Vac. It uses a standard NEMA-6-15P 15-ampere 240-volt plug.
The round center pin is the safety ground. Do not remove the safety ground.
CAUTION! Before connecting the power supply to an electrical outlet, always be sure you have completed the
following four steps:
1. Insert the 15-ampere 250V fuses into the two black fuse caps.
2. Insert the fuse and cap assemblies into the power supply’s fuse holders. The fuses lock in place
with a slight turn.
3. Connect the power supply to the amplifier.
4. Be sure the amplifier power switch is turned off.
Caution! Fuses have both voltage and current ratings. Use only 250V rated
fuses in this device. The voltage rating generally is marked on fuses. DO NOT
use automotive-type low voltage fuses in any power line application. For 240volt operation 15-ampere fast blow fuses are required.
Warning: Never insert the power supply cord into the outlet unless the above
four steps have been completed!!
Position the amplifier at the desired location on your operating desk, position it so you have access to the rear
panel, and connect the rear panel cables. Do not connect the power mains at this time!
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