5
General Information
Amplifier
The Ameritron ALS-1300 is a solid-state 1200-watt nominal RF output power 1.8-22 MHz amplifier (1.8-30
MHz with optional MOD-10MK). This power is peak envelope power, which is the same as actual carrier
power on CW. The ALS-1300 uses eight exceptionally 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 track FET and heatsink temperatures and
provide fan speed control for heatsink cooling as well as FET bias control.
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 requirements.
Antenna switching is through a sequenced pair of miniature relays on a plug in board. Relay switching time is
approximately five milliseconds. The ALS-1300 “relay” jack sources 12 volts when open circuit, and the relay
jack current upon closure is less than 20 mA. Note: Five milliseconds is fast enough for QSK operation. Due to
mechanic relays and relay noise, Ameritron still recommends the Ameritron QSK-5 T/R Switch for QSK
operation. The QSK-5 uses Pin Diodes that switch much faster and quieter than relays.
This amplifier includes two dual-movement cross-needle meters. This is the equivalent to 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 is switch selected
between reflected power, combiner mismatch voltage, ALC, and the drain voltage of each power amplifier.
While this amplifier will run more than 1200 watts PEP output, linearity will suffer. Ameritron recommends
running no more than 1200 watts peak power for maximum linearity, where 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 external power supply normally operates from 200-260 volts at 50-400 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. Locate the air inlet and outlet areas of the
amplifier. The cooling air inlet is on the right side as viewed from the normal operating position (front view).
The warm air outlet is on the left side of the amplifier. While the outlet air won’t be noticeably 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 the ALS-1300 amplifier and power supply. Be sure the air inlet temperature is not
substantially above normal room temperature. Ideally the air inlet temperature should be kept below 32° C or
90° F, although inlet 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.
