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RF Concepts Alpha 8406 User Manual

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RF Concepts
Alpha 8406 Linear Amplifier

User Manual

rfconcepts.com
Document Issue 1.0
February 2014

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Summary of Contents for RF Concepts Alpha 8406

  • Page 1: User Manual

    RF Concepts Alpha 8406 Linear Amplifier User Manual rfconcepts.com Document Issue 1.0 February 2014...

  • Page 2: Docnumber 8406 Document Issue

    303-473-9232 Prepared for RF Concepts by MH/GP/LW. To reach technical support or obtain copies of this document, go to rfconcepts.com. Copyright © 2014 RF Concepts LLC. All rights reserved. Specifications subject to change without notice. DOCNUMBER 8406 Document Issue 1.0...

  • Page 3: Table Of Contents

    Contents Contents 1. Introduction ........1-1 1.1 Product Description 1-1 1.2 Product Capabilities 1-2 1.3 Safety Considerations 1-3...
  • Page 4 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Contents DOCNUMBER 8406 Document Issue 1.0 Page iv February 2014...
  • Page 5 List of Procedures List of Procedures Procedure 3-1, “Prepare your station,” page 3–1 Procedure 4-1, “Unpack the amplifier and transformer,” page 4–1 Procedure 4-2, “Connect the transformer,” page 4–2 Procedure 4-3, “Adjust the tube and exhaust chimney,” page 4–3 Procedure 4-4, “Connect the cables,” page 4–3 Procedure 4-5, “Set the input-drive power,”...
  • Page 6 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC List of Procedures DOCNUMBER 8406 Document Issue 1.0 Page vi February 2014...

  • Page 7: Introduction

    1.3 Safety Considerations 1–3 1.4 Related Products 1–4 1.5 Assistance 1–4 Congratulations on your purchase of a professional-quality Alpha 8406 linear amplifier. This manual contains information that you must follow, and cautions and warnings that you must heed, to ensure safe installation and operation.

  • Page 8: Product Capabilities

    — Single sideband (SSB) — Slow-scan television (SSTV) • Compatibility with popular amateur transceivers and exciters. The Alpha 8406 requires ~50–65-W peak RF drive for 1.5-kW output. • Capability of full CW break-in (QSK) when used with any appropriate transceiver.

  • Page 9: Safety Considerations

    ~70 pounds. — Use proper lifting techniques and two people. • Remember that, although the Alpha 8406 meets international safety standards and US Federal Communications Commission (FCC) regulations, it works with high voltages that can be LETHAL. •...

  • Page 10: Related Products

    • For questions regarding engineering your amplifier into your amateur radio station, go to rfconcepts.com and click Support. 1.4 Related Products Other products available to enhance your use of the Alpha 8406 include: • Alpha 2000 dummy load • Alpha 4510A standing-wave-ratio (SWR) meters and wattmeters For more information, go to rfconcepts.com or call 303-473-9232.

  • Page 11: Amplifier Components And Specifications

    2.3 Output-Tank Circuit 2–6 2.4 Tube and Tube Deck 2–7 2.5 Specifications 2–9 The Alpha 8406 uses a ceramic-and-metal forced-air-cooled tetrode vacuum tube for amplification. The main power supply is an unregulated transformer/rectifier/capacitor power supply for the high-voltage (HV) and heater circuits. All other power supplies are regulated.
  • Page 12 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Amplifier Components and Specifications Figure 2-1 Amplifier front Figure 2-2 Amplifier back DOCNUMBER 8406 Document Issue 1.0 Page 2–2 February 2014...

  • Page 13: Boards

    RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Amplifier Components and Specifications Figure 2-3 Amplifier interior 2.1 Boards The following amplifier boards are described below in alphabetical order: • Center-partition board • Control board • Display board • HV board •...

  • Page 14: Control Board

    Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Amplifier Components and Specifications IMPORTANT Do not defeat this safety circuit. It is placed there for your protection. Control Board The control board is the heart of the amplifier. It is based on a PIC microcontroller.
  • Page 15 RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Amplifier Components and Specifications All power-supply filter capacitors on this board have bleeder resistors that discharge the capacitors in less than 60 seconds. If you must work on this board, confirm the discharged condition with a voltmeter, due to the remote possibility of bleeder resistor failure.

  • Page 16: Controls And Display

    For more information on the tube deck, see Section 2.4, “Tube and Tube Deck,” page 2–7. 2.2 Controls and Display The Alpha 8406 controls enable you to adjust and monitor the amplifier as needed (see Table 2-1). Table 2-1 Amplifier controls...

  • Page 17: Tube And Tube Deck

    TO OUTPUT FILTER TUBE ANODE TUNE CAP RF CHOKE 2.4 Tube and Tube Deck The Alpha 8406 uses a 4CX1500B tetrode vacuum tube. The tube is operated in Class AB1, with the following voltages: • Plate voltage: 3500 V nominal •...
  • Page 18 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Amplifier Components and Specifications impedance represented by grid 1 and its capacitance are compensated for by a series inductance to provide SWR <2:1 across the full 6-m band at the amplifier’s input.

  • Page 19: Specifications

    RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Amplifier Components and Specifications 2.5 Specifications The amplifier’s specifications are as follows: Table 2-2 Alpha 8406 linear amplifier specifications Parameter Value Frequency coverage 50–54 MHz Input-drive level 50 W nominal Power output...
  • Page 20 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Amplifier Components and Specifications DOCNUMBER 8406 Document Issue 1.0 Page 2–10 February 2014...

  • Page 21: Preparing Your Station

    Voltages 3–4 3.1 Prepare Your Station The Alpha 8406 is capable of dramatically improving the performance of your amateur station. It is important that you observe good engineering practices to achieve all the benefits of such a station in a safe and reliable manner.
  • Page 22 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Preparing Your Station 1c Select a location for the outlet as close as possible to where you expect to operate the amplifier. If you are not sure or contemplate moving the amplifier, consider installing two outlets.
  • Page 23 RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Preparing Your Station 3b If an antenna has been deployed for a long period of time, take it down and inspect it before full-power operation. Step 4 Provide adequate RF cabling.

  • Page 24: Understand The Limitations Of Operation At Nonstandard Line Voltages

    Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Preparing Your Station NOTE: The FCC requires users to check their installations for compliance with published values for allowable exposure to RF fields. This information is available in ARRL publications, FCC printed rules, and on the web.
  • Page 25 RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Preparing Your Station For example, if the amplifier operates from a circuit that is capable of delivering 120 V AC at a maximum current of 20 A with no other loads...
  • Page 26 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Preparing Your Station DOCNUMBER 8406 Document Issue 1.0 Page 3–6 February 2014...

  • Page 27: Setting Up The Amplifier

    4.5 Set the Input-Drive Power 4–6 • IMPORTANT The Alpha 8406 is extremely easy to set up, operate, and maintain. However, failure to carry out each procedure exactly as described in this manual is likely to lead to amplifier damage.

  • Page 28: Connect The Transformer

    Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Setting Up the Amplifier 4.2 Connect the Transformer • IMPORTANT The transformer is very heavy. When moving it, use due caution and handle it only by the lifting handle. • Do not over-tighten the screws that hold the transformer in place, as doing so may cause excessive vibrations or noise.

  • Page 29: Adjust The Tube And Exhaust Chimney

    RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Setting Up the Amplifier Step 5 Secure the transformer into place from the bottom of the amplifier by inserting the supplied bolts (1/4/20 ½-inch hex bolts) with ¼-inch washers through the four clearance holes in the chassis and into the nuts in the transformer base.
  • Page 30 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Setting Up the Amplifier Figure 4-1 Amplifier voltage taps 1a Ensure that the amplifier is unplugged. 1b Connect the flying jumper connector to the terminal marked with the appropriate voltage. These five nominal primary voltages — 100, 120, 200, 220, and 240 V —...
  • Page 31 RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Setting Up the Amplifier 2a Connect the green wire in the amplifier power cord only to the AC mains safety ground (or to neutral, as may be necessary with a 240-V circuit configured 120V-N-120V without a separate ground, commonly found in the US).

  • Page 32: Set The Input-Drive Power

    Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Setting Up the Amplifier transmit on the amplifier’s RELAY jack center pin to the chassis. This function is supplied by the transceiver, usually from a dedicated relay that is normally open in RECEIVE mode and closed in TRANSMIT mode.
  • Page 33 RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Setting Up the Amplifier Step 2 Set the transceiver’s power output so as not to overdrive the amplifier input. For information on how to do so, see the manual for your particular transceiver.
  • Page 34 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Setting Up the Amplifier DOCNUMBER 8406 Document Issue 1.0 Page 4–8 February 2014...

  • Page 35: Operating The Amplifier

    5.4 (Optional) Operate the Amplifier Remotely 5–6 • IMPORTANT The Alpha 8406 is extremely easy to set up, operate, and maintain. However, failure to carry out each procedure exactly as described in this manual is likely to lead to amplifier damage.

  • Page 36: Tune The Amplifier

    Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Operating the Amplifier • The red LED representing 1800-W output power lights up, indicating the start of a built-in180-second countdown (1800/10 = 180 seconds). As the timer counts down, the remaining time is indicated by the currently lit LED on the power-output bargraph.
  • Page 37 For any frequency where antenna VSWR > 1.5:1, it is important to retune the amplifier for a proper match. The Alpha 8406 does not contain an antenna tuner. The SWR can be tuned via the antenna or an external tuner connected to the amplifier output.
  • Page 38 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Operating the Amplifier Following is our recommended procedure for tuning the amplifier. When the amplifier is tuned properly on 6 meters, you should see the parameters listed in Table 5-1. Table 5-1 Parameters indicating proper tuning...

  • Page 39: Operate The Amplifier

    RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Operating the Amplifier Step 5 Key the amplifier with 10-W drive and adjust the TUNE control so that the peak in RF out is at the same point as the dip in Ip.

  • Page 40: Optional) Operate The Amplifier Remotely

    You can operate the Alpha 8406 remotely, and therefore presumably unattended. Such remote/unattended operation is possible because tuning on the Alpha 8406 is broad, so there is often no need to readjust it once correct tuning has been established. Remote/unintended operation is advantageous in that it can enable you to put the amplifier close to the antenna, an important consideration on VHF.
  • Page 41 We offer no support for this, since setup requires intimate knowledge of the details of your network. Other users on the RF Concepts forums may be able to help. Other ways may be possible as well, such as via wifi-to-serial or Ethernet- to-serial converters.
  • Page 42 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Operating the Amplifier DOCNUMBER 8406 Document Issue 1.0 Page 5–8 February 2014...

  • Page 43: Maintaining The Amplifier

    6.2 Replace the Tube and/or Fuses 6–2 • IMPORTANT The Alpha 8406 is extremely easy to set up, operate, and maintain. However, failure to carry out each procedure exactly as described in this manual is likely to lead to amplifier damage, which is not covered under warranty.

  • Page 44: Replace The Tube And/Or Fuses

    Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Maintaining the Amplifier WARNING WARNING! Do not allow any liquids to enter the cover’s tube- exhaust holes. Step 3 Disconnect the AC line cord from the power source and remove the cover.

  • Page 45: Step 5

    RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Maintaining the Amplifier use of a fuse of incorrect size or type is not covered under and may void the warranty. Blowing of one or both primary-line fuses indicates that the maximum safe average power capability of the amplifier has been substantially exceeded or that an equipment failure has occurred.
  • Page 46 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Maintaining the Amplifier DOCNUMBER 8406 Document Issue 1.0 Page 6–4 February 2014...

  • Page 47: Diagnosing Faults And Troubleshooting

    Diagnosing Faults and Troubleshooting 7.1 Diagnose Faults 7–1 7.2 Troubleshoot Problems 7–4 7.1 Diagnose Faults If the amplifier encounters unsafe operating conditions, it enters a protective fault mode and faults into STBY or OFF. The OPR LED goes off and the FAULT and STBY LEDs go on. When this happens, the tube is biased off and the relays are placed in bypass mode, causing RF from the radio to go directly to the antenna.
  • Page 48 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Diagnosing Faults and Troubleshooting Fault type 1 Both Ip and HV LEDs are blinking. LED behavior Amplifier gain has fallen to <10 dB. Cause This is an important safety feature of the amplifier, as many different problems can be detected as a drop in gain.
  • Page 49 RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Diagnosing Faults and Troubleshooting 1. Check the output coaxial cable and connectors; replace or reconnect Resolution as needed. 2. Check the antenna SWR using an external wattmeter or by putting the amplifier in standby mode and using the SWR meter on your transceiver.

  • Page 50: Troubleshoot Problems

    Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Diagnosing Faults and Troubleshooting the amplifier back on. Doing so is likely to result in severe damage to amplifier components. 2. If the plate current again starts to rise while the amplifier is warming up, investigate and resolve the problem before attempting to turn the amplifier on again.

  • Page 51: Document Issue 1.0

    RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Diagnosing Faults and Troubleshooting The plate voltage to the power supply may be too low. Check the line Amplifier turns on but HV reading is low as indicated on voltage and confirm that the tap is set correctly.
  • Page 52 4. The station RF ground may be poor. Ensure that the amplifier and transceiver have a proper RF ground. The tube may be aging. Contact RF Concepts technical support to Required drive to maintain 1500 W is steadily increasing determine whether the tube needs to be replaced.
  • Page 53 Terminology Terminology NOTE: For detailed explanations of the following terms, see various publications including the latest American Radio Relay League (ARRL) Handbook. AB1 — ampere — Modulation class AB1. Class that provides Unit of electric current. good linearity in a push-pull configuration. ARRL —...
  • Page 54 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Page Terminology FCC — FSK — Federal Communications Commission. Frequency-shift keying. Type of For more information, go to www.fcc.gov. frequency modulation in which information is conveyed by shifts in the output frequency FM —...
  • Page 55 RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Terminology –6 mA — MHz — Milliampere. 10 Megahertz. 10 OPR — Operate. PCB — the modulation envelope under normal Printed circuit board. Board that operating conditions. mechanically supports and electrically connects electronic components.
  • Page 56 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Page Terminology STBY — SWR — Standby. Mode in which an electronic Standing-wave ratio. Ratio of the appliance is turned off but under power and amplitude of a partial standing wave at an ready to activate on command.
  • Page 57 Schematics Schematics NOTE: The following pages contain detailed schematics for the Alpha 8406 linear amplifier. DOCNUMBER 8406 Document Issue 1.0 February 2014 Page Schem–1...
  • Page 58 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Page Schematics DOCNUMBER 8406 Document Issue 1.0 Page Schem–2 February 2014...

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