Alpha 9500 Autotune Legal Limit

Alpha 9500 Autotune Full Legal Limit Linear Amplifier

  • Alpha 9500 Autotune Full Legal Limit Linear Amplifier
The Alpha 9500 is no ordinary linear amplifier. The Alpha 9500 is the culmination of over 40 years of design and engineering. The Alpha 9500 is an advanced technology, auto tuning, linear amplifier that effortlessly delivers 1500 watts of power with as little as 45 watts of drive. Price: $8,795.00bnbutton

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9500 amplifiers are available for immediate shipping.

Read the QST October 2010 9500 review.

Key Features

  • Fully automatic, legal limit plus headroom amplifier
  • Alpha’s low-drive, tube amplifier design delivers the cleanest possible signal
  • Operates on all Amateur Radio Bands 160M thru 10M
  • Single, easy to find, inexpensive 3CX1500A7 8877 type tube
  • Internal, automatic 4 port antenna switch capable of combining any 2 antenna ports
  • Alpha’s Legendary service and support
  • 4 year limited warranty on hardware, 1 year on tube
  • 1500W, 100% duty cycle, no time limitation, key down forever
  • Rugged construction built to last
  • Remotely controllable via RS232 or USB port
  • Designed, built, and serviced in the USA
  • Capable of passing 1500W through, in bypass
  • Protection against all common faults

It’s the Ultimate Amplifier

Experience the magic of almost instantaneous band switching and tuning with the Alpha 9500. Send a few dits and the 9500 quickly changes bands, tunes and loads, putting you right where you want to be, without flipping, twisting, and turning the knobs normally necessary on a manual tune amplifier.

Built Rock Solid, from the Chassis Up

We took all the best parts of the Alpha 87A and made them better. With the Alpha 9500, we start with a heavy duty, .080 , 5052 grade, iridite yellow chromate coated, aluminum chassis that resists both flex and corrosion. To it, we bolt the front panel assembly and a center partition, building a solid I beam structure that just doesn’t move. Add our custom made, time proven, transformer that weighs a massive 35 lb and is capable of delivering 3,500VA of power to the plate of the Alpha 9500’s tube. Every time the Alpha 9500 is powered on, circuitry in the amplifier reads the mains voltage and automatically selects the proper transformer input tap, so without manually strapping the primary, the Alpha 9500 can be moved from a 100V system to a 240V system without operator intervention.

Big Robust RF Deck and Tank Pi-L Network

The Alpha 9500 utilizes the same superbly designed RF deck found in its predecessor, the Alpha 87A, but instead of the two 3CX800s, our selection for this amplifier is the single 3CX1500A7 8877 high power triode. After careful thought and testing, we felt that this was a robust, fault tolerant, easy to find tube that should be available for many years to come. It’s the choice for many of the MRI amplifiers in use today, so there is little chance of being orphaned as so many of the tubes of the past. Multiple factories worldwide provide tens of thousands of these yearly.

Under microprocessor control, a heavy duty, four gang, commercially rated, ceramic switch assembly, connected to a beefy stepper motor simultaneously switches both the input matching circuitry and the output tank circuitry in tandem. Alpha 9500’s output tank is built to take a beating. With the famous heavy duty, silver plated, hand made, Alpha Pi-L matching network, the Alpha 9500 will operate into up to a 3:1 SWR without the need for an external antenna tuner.

Add two more high torque stepper motors one for each of the carefully chosen Tune and Load capacitors both conservatively rated so they will give years of smooth performance, and you ve got what it takes to switch bands, tune and load this amplifier automatically. The Alpha 9500 will sense the frequency, switch to the proper band and sub-band settings, and set the tune and load capacitors to their proper settings, all in less than one second.

Multiple Microprocessors Control This Amplifier

Rather than using a single microprocessor for control and processing, the Alpha 9500 uses five. This simplified the point to point wiring in the Alpha 9500 so, instead of a complex wiring harness with multiple connectors that are more prone to failure, the Alpha 9500 uses a simple 2 wire, I2C microcomputer bus to communicate among the subassemblies, vastly simplifying the interconnection scheme and increasing the reliability of the system. Separate microprocessors on many of the subassemblies have sole responsibility to control and monitor the health and performance of that single function, enabling the amplifiers ability to deliver high performance, high power, linear amplification, while protecting each subsystem from operating outside its safe operating envelope.

The computing platform in the Alpha 9500 is responsible for system configuration, mains voltage selection, frequency counting, SWR computations, input matching, cathode bias selection, band switching, auto tuning, and antenna relay switching. It monitors low voltage power supplies, plate voltage, plate current, grid current, amplifier gain, tube bias, primary or mains voltage, and RF power in both directions simultaneously.

Accurate power and SWR measurements are made with the separately powered, internal wattmeter, which uses a variant of the “Bruene” bridge to provide amazing accuracy across a wide range of frequency and power. Unlike other amplifiers that use inaccurate simple diodes, the 9500 uses two high quality log detectors to accurately measure the forward and reverse power simultaneously.

If the computing platform senses a problem with any of the 10 performance measurements it watches, it takes itself off-line and resets itself. If the Alpha 9500 senses a condition that could damage the tube, it trips off line, bypassing the amplifier to instantly to protect itself.  Correct the problem, press the amplifier power on switch to acknowledge the fault, and press the online button and you’re instantly back online at full power.

Interested in connecting your computer to the Alpha 9500?  Both RS232 and USB ports are provided for remote control and diagnostics, and with its simple operating control command language, integrating it into a fully automatic, remotely controlled station is a reality.

Simple Installation

Besides the AC power (mains) connection, there are only two required inputs to the Alpha 9500 – the amp key line from the radio (KEY IN), and the RF IN. All RF connectors on the Alpha 9500 are BIRD type quick change SO-239, for ultimate reliability and flexibility. Need N-type connectors in any of the positions? Remove 4 screws surrounding the SO-239 connector, remove it, plug in the N-type quick change connector, reinstall the 4 screws and the job is done.

No need for ALC input like lesser amplifiers. The micro computing platform assures you don’t damage the tube by overdriving it. Separate input match circuits for each Amateur band guarantees a proper match with any standard 50 ohm output from your transceiver.

RF output is delivered through the amplifiers own 4 port automatic antenna switch. Latching relays control each of 4 antenna ports, so the last antenna you chose, stays selected – even without power to the amplifier.

Proudly Handcrafted in the USA

This amplifier is as rugged and reliable as anything we’ve created.  We buy the best components available for the Alpha 9500. Our stringent selection of even the simplest components demonstrates the commitment that we have to deliver the best, most reliable amplifier in the world.

The Alpha 9500 is finely handcrafted and is designed and built in Colorado, USA, comes with an industry leading 4-year warranty on the amplifier, and 1-year warranty on the tube, and is supported by our friendly and knowledgeable staff.  We build them by hand, tune them by hand, and burn them in overnight at full power so we know that when you get your Alpha 9500, you’ll have an amplifier that is the most rugged, best built in the world. It’s shipped in two separate double boxes with the transformer packed separately so there’s little chance of anything happening to it on its way from the factory to its new operating position in your shack .


  • Frequency coverage: All amateur frequencies from 1.8-29.7 MHz
  • Power output: 1500 Watts minimum on all served bands
  • 3rd Order IM: <-30 dBc
  • SWR tolerance: 3:1
  • Drive power: 45 – 60 Watts nominal for full power out
  • Tube: single 3CX1500/8877 type high performance power triode with a plate dissipation of 1500 watts provides key down performance on all frequency bands, all modes, and all duty cycles.
  • Cooling: Forced air from two blowers
  • Antenna outputs: comes standard with 4 x SO-239 BIRD connectors, but can be changed to Type N easily from the back panel by removing 4 screws.
  • Antenna selection:  Internal 4 port antenna switch with 1 or 2 outputs per band/segment
  • Calibrated Wattmeter: The Bruene type wattmeter accurately simultaneously measures both forward and reverse power and displays this information on the easy to read bar graph meters on the front panel.  It also uses the information to simultaneously monitor the gain of the amplifier.
  • Protection Mechanisms: HV Interlock and Power Interlock.
  • Bypass mode: There are two power “ON” buttons on the Alpha 9500. “ON1” activates the Wattmeter and antenna selector without powering the amplifier itself, and sets the amplifier into “bypass” mode. The Amplifier is powered with the “ON2” button.
  • Input: Comes standard with an SO-239 BIRD connector, but can be changed to BIRD N Type easily from the back panel – order JCX-X130
  • Tuning/Band switching: Automatic plus manual override
  • Power: 100,120,200,220,240 VAC, 50/60 Hz, selection Automatic. At 240 VAC requires 20 Amps.  Power cord is 8 feet long.  Note – Although the amplifier will operate at 100V, the mains will have to be able to deliver upwards of 35 amps.
  • Interface: Serial port and USB. Full remote control capability.
  • Protection: Protected against all common faults.
  • Display: Bar graphs display Power, SWR, Grid Current, Plate Current, Plate Voltage, and Gain – all simultaneously.  Digital Panel Meter can display Forward Power, Plate Current, Plate Voltage, Grid Current, SWR, Filament Voltage, and PEP Output.
  • T/R switching: Two Gigavac brand vacuum relays enabling QSK (full break-in) at QRO (full power).  KEY IN jack 12 vdc / 12 ma.
  • Bypass capability: 1500 Watts.
  • Shipping Weight: 95 lb, Assembled weight 82 lb
  • Product Size:  17.5″w x 7.5″h x 19.75″d
  • Standard Shipping Packaging: We ship the amplifier in a double box, and the  transformer in a separate box.

Keying Cable for Kenwood radios – Order HERE !

Keying Cable for Yaesu radios – Order HERE !

Keying Cable for Elecraft, Flexradio, Icom, Ten Tec and Yaesu FTdx-3000 radios – Order HERE !


Alpha 9500 User Manual, Version 1.3 (12/2017) Alpha9500_R1.3_121916_manual
Alpha 9500 Fault Codes,  Fault Resolutions, and other operating notes – Updated 01 Dec 2015 9500 Faults01
Alpha 9500 User Manual, Version 1.2 (6/2015) Alpha9500_R1.2_062215_manual
Contact Alpha for latest version firmware files (3.03c is latest version)
Alpha 9500 firmware 3.03 Notes 9500 3.03 Firmware Notes
Alpha 9500 firmware 2.27 Notes Alpha_9500_2.27_Errata
9500 Tube Operating Bias Adjustment 9500 Tube Bias Adjust Procedure
Alpha 9500 Remote Software 1.4 Alpha9500_remote_1_4
Alpha 9500 Remote 1.4 README A9500_remote_notes
Alpha 9500 Schematics with RF Section (Main Controller Rev A, HVPS Rev A, AC Mains Rev A) 9500_schematics_with_rf_section
Alpha 9500 Main Controller Schematics Rev B BCX-X421_SCH_REV_B
Alpha 9500 HVPS Schematics Rev C BCX-X419_SCH_REV_C
Alpha 9500 AC Mains Schematics Rev B BCX-X420_SCH_REV_B
Alpha 9500 Parts List, with HVPS Rev A and C, and Main Controller Rev A and B A9500 BOM All
Alpha 9500 Parts List, Zipped file of PDF docs 9500
Alpha 9500 Commands & Returns  9500_keyboard_commands_and_return_strings
Alpha 9500 Remote Operation Programming Alpha 9500 Remote Operation
Alpha 9500 Installing Replacement Blower Motor On Original Bracket Dayton_4M070_motor_on_original_bracket1
Alpha 9500 Blower Replacement Procedure  replacing-9500-blower
Alpha 9500 Fuse Addition To 40v Supply 40V Fuse Addition
Alpha 9500 Power Supply Removal Removing 9500 PS stack
Amplifier Keying Specs (RELAY or KEY IN jack) Amp_Keying_Specs
USB / Serial COM port (FTDI) drivers CDM21216_Setup_1
Hyperterminal hyperterminal
Maintenance Remote
Alpha Colt Bootloader Alpha_Colt_Bootloader_1_1
QST October 2010 review of 9500 9500_prod_rev_october2010

2 Replies to “Alpha 9500 Autotune Legal Limit”

    • Glenn Pladsen

      The Alpha 9500 Autotune function is not that of an antenna tuner.
      It will constantly monitor the input power, output power, and grid
      current and tune the motorized TUNE and LOAD capacitors for best
      efficiency. The optimum settings will change as you move across the
      band or if the drive power is changed.
      The amplifier measures the frequency of the drive signal and changes
      bands within one second when the radio is keyed on a new frequency. It
      goes to saved settings in memory, and retunes if it is needed.

      The 9500 has high reflected power protection, tripping to standby if it
      exceeds about 250w. This is almost 3:1 VSWR at 1500w output. This is to
      protect the vacuum relay in the T/R circuit from excessive voltages.
      Reducing the output power will allow transmitting into a higher VSWR.

      An antenna tuner capable of really handling 1500w under a wide variety
      of loads is almost the same size as the amplifier (like a Nye-Viking, Ten
      Tec or Pal-Star tuner). If the antenna has a VSWR of over 3:1 on some
      bands, a heavy-duty antenna tuner would be required to match the load


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