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1. Terminology NOTE For detailed explanations of the following terms see various publications including the latest American Radio Relay League ARRL Handbook A AB1 Modulation class AB1 Class that provides good linearity in a push pull configuration AC Alternating current Electric current whose magnitude and direction vary with time ALC Automatic Level Control Technology that automatically controls output power C CW Continuous wave Electromagnetic wave of constant amplitude and frequency D dB Decibel Logarithmic unit of measure of the power of sound relative to a reference level E EBS Electronic bias switching A form of switching that increases negative grid 1 voltage in pauses in speech or between Morse code elements resulting in reduced standing bias on the tube DOCNUMBER 8406 Document Issue 1 0 February 2014 ampere Unit of electric current ARRL American Radio Relay League US national organization of amateur radio operators For more information go to www arrl org AWG American wire gauge Standard method of denoting wire diameter exciter Radio that provides RF drive for the amplifier to operate The transmitter portion of the transceiver Page Term 1 Alpha 8406 Linear Amplifier User Manual Page Terminology F FCC Federal Communications Commission For more information go to www fec gov FM Frequency modulation Modulati
2. DOCNUMBER 8406 Document Issue 1 0 Page vi February 2014 1 Introduction IMPORTANT 1 1 Product Description 1 1 1 2 Product Capabilities 1 2 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 Before operating your amplifier for the first time it is important that you study this manual carefully in particular the preparation setup and operation instructions Failure to perform procedures properly may result in electric shock fire hazard or serious damage that is not covered under warranty 1 1 Product Description DOCNUMBER 8406 Document Issue 1 0 February 2014 The Alpha 8406 see Figure 1 1 is a self contained manual tune very high frequency VHF linear power amplifier Page 1 1 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Introduction Figure 1 1 Alpha 8406 RF OUTPUT KW eS 2 2 RU KY o EFFICIENCY o o 50 wao IPA o FAULT iS AMIN 5 a 4 g A Wo p WW A EFFICIENCY j it Jf 2 8 1 2 Product Capabilities Product capabilities are as follows e Continuous radio frequency RF output The Alpha 8406 is capable of 1 5 kW continuous RF output with no time limit on any authorized amateur frequen
3. One or more connectors may be loose Check that all of the transformer connectors are securely attached that the 3x3 molex connector at the back of the amplifier is fully engaged and that the two connectors between the transformer and the HV power supply boards are firmly inserted Fuse F1 F3 may be open or missing Check fuses with an ohmmeter Replace any blown fuses with fuses of the same size The step start resistor may be open Check the resistor If it is damaged replace it The multimeter selector switch may be in the wrong position example Ip Set the switch to the correct position The transformer may be plugged into the power supply incorrectly Check the power supply wiring and connectors to ensure that the input and output connectors and the voltage taps are set properly An HV circuit fault may exist Check the line voltage The HV sampling resistor in the power supply may be damaged Contact RF Concepts technical support DOCNUMBER 8406 Document Issue 1 0 February 2014 RF Concepts LLC Amplifier turns on but HV reading is low as indicated on the multimeter bargraph Amplifier turns on but time delay does not complete and WAIT LED does not turn off Amplifier turns on and time delay completes but amplifier does not transmit Amplifier operates properly then turns off completely Amplifier transmits but red grid LED lights often When switching from STBY to OPR mode receive sig
4. damage Procedure 4 2 Connect the transformer Step 1 Remove the amplifier cover and set it aside The cover is attached with 31 6 32 screws 10 on each side of the amplifier and 11 on the top Step 2 Position the amplifier on a flat surface at or near where it is to be used with plenty of room for you to work The amplifier chassis is designed for the mechanical loads experienced when the amplifier is on a flat surface with the tilt bail up or down Installing the amplifier on a tilt so far that the transformer is cantilevered or hangs out to any degree can cause the chassis to distort Step 3 Pick the transformer up by the handle and move it onto the lip at the edge of the chassis about half way into the amplifier Step 4 Connect the transformer 4a Connect the transformer s 9 pin white Molex connector to the matching 3x3 Molex connector on the back of the amplifier s back wall Use the handle to move the transformer all the way into the amplifier and push it toward the center 4b Connect the transformer s 8 pin orange connector to the matching pins on the amplifier s mains board the upper of the two boards 4c Connect the transformer s 6 pin yellow connector to the matching pins on the amplifier s HV board the lower of the two boards routing it to the left of the white post between the boards 4d Ensure that all connector pins on these three connectors engage fully and correctly DOCNUMBER 8406 Docum
5. 4 Tube and Tube Deck DOCNUMBER 8406 Document Issue 1 0 February 2014 The Alpha 8406 uses a 4CX1500B tetrode vacuum tube The tube is operated in Class AB1 with the following voltages e Plate voltage 3500 V nominal e Grid 1 voltage 50 to 60 V e Grid 2 voltage 230 V Electronic bias switching EBS increases the negative grid 1 voltage during pauses in speech or between Morse code elements This reduces the standing bias on the tube resulting in less waste heat longer tube life and higher overall amplifier efficiency The artifacts of EBS are not noticeable under normal communications conditions The tube is operated as a swamped grid tetrode design The tube grid is tied at RF to a 50 ohm swamping resistor that absorbs most of the input drive power The RF voltage across this resistor is added to the grid 1 DC bias to provide the net low impedance tube grid 1 bias The RF Page 2 7 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Amplifier Components and Specifications Page 2 8 NOTE impedance represented by grid 1 and its capacitance are compensated for by a series inductance to provide SWR lt 2 1 across the full 6 m band at the amplifier s input The tube deck is a mechanical assembly enclosing the tube socket and the tube deck board The tube socket contains the integral screen grid grid 2 RF bypass capacitors as well as contacts for the screen heater and filament of the tube The
6. Concepts LLC 2 5 Specifications DOCNUMBER 8406 Document Issue 1 0 February 2014 Alpha 8406 Linear Amplifier User Manual Amplifier Components and 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 1500 W SWR tolerance 3 1 Duty cycle 100 Tube 4CX1500B Intermodulation level 34 dB two tone typical Harmonics 72 dBc Mode of operation AM CW SSB FM RTTY JT 65 Input AC voltage 100 120 200 220 240 selectable AC current lt 15 amps 240 VAC 1500 W Input impedance 50 ohms Output impedance 50 ohms RF connectors N female Cooling Forced air Size 17 3 W x 7 H x 19 5 D including muffin fan Weight 70 Ib 31 8 kg T R relay Vacuum QSK Tuning Manual Display Bargraph LED Interface USB Protection Against all common faults RF bypass level lt 300 W Page 2 9 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Amplifier Components and Specifications DOCNUMBER 8406 Document Issue 1 0 Page 2 10 February 2014 3 Preparing Your Station 3 1 Prepare Your Station 3 1 3 2 Understand the Limitations of Operation at Nonstandard Line Voltages 3 4 3 1 Prepare Your Station The Alpha 8406 is capable of dramatically improving the performance of your amateur station It i
7. Products Other products available to enhance your use of the Alpha 8406 include e Alpha 2000 dummy load e Alpha 4510A standing wave ratio SWR meters and wattmeters For more information go to rfconcepts com or call 303 473 9232 1 5 Assistance Technical assistance from RF Concepts is available from several sources e Go to our website at rfeoncepts com and click Support On this site you can get the following assistance Alpha Forum FAQs Legacy equipment information Manuals Repair information Software downloads Tech tips Technical support e E mail us by completing a support request at rfconcepts com e Fax us at 303 473 9660 e Phone us at 303 473 9232 DOCNUMBER 8406 Document Issue 1 0 Page 1 4 February 2014 2 Amplifier Components and Specifications DOCNUMBER 8406 Document Issue 1 0 February 2014 2 1 Boards 2 3 2 2 Controls and Display 2 6 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 The control circuit uses a microprocessor in the loop to monitor and control amplifier operation There are eight circuit boards in the amplifier e Center partition board e Control
8. current was detected when the amplifier was warming up or was unkeyed States 1 3 The threshold for this fault is one third of the value for a soft Ip trip or 533 mA 1 After the amplifier shuts off wait at least 20 seconds then use the ON OFF switch to turn the amplifier back on IMPORTANT When the amplifier trips out DO NOT repeatedly press the ON OFF switch to attempt to turn Page 7 3 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Diagnosing Faults and Troubleshooting 2 3 4 the amplifier back on Doing so is likely to result in severe damage to amplifier components Ifthe 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 Fix any problems in the bias control circuitry When you are certain that you have taken care of the problem that caused the fault turn the amplifier back on 7 2 Troubleshoot Problems Amplifier does not turn on nothing happens when the ON switch is pushed Amplifier turns on but no HV is indicated by the multimeter Page 7 4 LED bargraph 1 l External AC wiring a fuse or a circuit breaker may be open Check and correct wiring replace fuse or reset circuit breaker The amplifier cover may not be in place or properly secured or the cover safety interlock may be open Ensure that the cover is in place and all screws are securely inserted
9. lead to amplifier damage Such damage is not covered under warranty Damage to other station equipment may also result If the amplifier faults during operation do not turn it off To clear a fault For a gain fault wait for the amplifier to reset itself For all other faults resolve the fault as described in Chapter 7 Diagnosing Faults and Troubleshooting Then put the amplifier back into operation 5 1 Start Up the Amplifier Procedure 5 1 Start up the amplifier i Step1 Setup the amplifier as described in Chapter 4 Setting Up the Amplifier Step 2 Set the multimeter selector switch to HV Step 3 Press the POWER ON switch The following occur e The fan and internal blower begin to operate Within 5 seconds the blower increases to high speed and then drops back to idling speed If there is no air flow from the amplifier and no sound of blower operation immediately turn the amplifier off and investigate e Within 2 seconds the HV display moves all the way to the right certainly to gt 3000 V If it is lower than this investigate further the primary taps may not be correctly set DOCNUMBER 8406 Document Issue 1 0 February 2014 Page 5 1 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Operating the Amplifier Step 4 Step 5 Step 6 5 2 Tune the Amplifier Page 5 2 e The red LED representing 1800 W output power lights up indicating the start of a built in 1 80 second
10. moving the amplifier consider installing two outlets 1d Ask your contractor for two or three matching plugs during installation There are many styles of power plugs some of which are country specific A NEMA 6 20 plug is installed at the factory 1e Ask your contractor to measure the voltage and record it for reference If possible have the contractor measure the line voltage with a 10 A current draw and use this value for setting the transformer tap Provide proper airflow 2a Maintain at least 3 inches of clearance around the amplifier and at least 4 inches of clearance around the air intake and exhaust areas to allow for unobstructed airflow at all times Ensure that exhausted air cannot recirculate back into the amplifier air intake We recommend that you do not stack equipment on top of the amplifier 2b Ifyou are mounting the amplifier in a console ensure that the exhaust air is properly and fully removed from the console If outlet air is drawn back into the amplifier air intake and recirculated the amplifier gets hotter and hotter resulting in degraded performance or even failure If you are designing your own console consider putting in additional fans and or ducting to deal with waste heat 2c Ensure that equipment or other objects are not stacked on top of the amplifier 2d Minimize the possibility of dust or other contamination getting drawn into or falling on the amplifier Plan to periodically at least annually
11. 1 5 1 Start Up the Amplifier 5 1 5 2 Tune the Amplifier 5 2 5 3 Operate the Amplifier 5 5 5 4 Optional Operate the Amplifier Remotely 5 6 6 Maintaining the Amplifier aoaaa a 6 1 6 1 Clean the Amplifier Chassis 6 1 6 2 Replace the Tube and or Fuses 6 2 7 Diagnosing Faults and Troubleshooting 0 05222 eee 7 1 7 1 Diagnose Faults 7 1 7 2 Troubleshoot Problems 7 4 Terminology Term 1 Schematics Schem 1 DOCNUMBER 8406 Y Document Issue 1 0 February 2014 Page iii Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Contents DOCNUMBER 8406 Document Issue 1 0 Page iv February 2014 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 4 6 Procedure 5 1 Start up the amplifier page 5 1 Procedure 5 2 Tune the amplifier page 5 4 Procedure 5 3 Operate the amplifier page 5 5 Procedure 6 1 Clean the amplifier chassis page 6 1 Procedure 6 2 Replace the tube and or fuses page 6 2 DOCNUMBER 8406 Document Issue 1 0 February 2014 Page v Alpha 8406 Linear Amplifier User Manual RF Concepts LLC List of Procedures
12. Manual RF Concepts LLC Page Schematics DOCNUMBER 8406 Document Issue 1 0 Page Schem 2 February 2014
13. RF Concepts Alpha 8406 Linear Amplifier User Manual rfconcepts com Document Issue 1 0 February 2014 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Page ii Alpha 8406 Linear Amplifier User Manual RF Concepts LLC 634 S Sunset St Longmont CO 80501 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 February 2014 Contents Contents APUG dU Oa e E E eens ae mere e ey ter ae Soyer an eae nee Tree Te 1 1 1 1 Product Description 1 1 1 2 Product Capabilities 1 2 1 3 Safety Considerations 1 3 1 4 Related Products 1 4 1 5 Assistance 1 4 2 Amplifier Components and Specifications 84 5 2 1 2 1 Boards 2 3 2 2 Controls and Display 2 6 2 3 Output Tank Circuit 2 6 2 4 Tube and Tube Deck 2 7 2 5 Specifications 2 9 3 Preparing Your Station 2 2 aa a 3 1 3 1 Prepare Your Station 3 1 3 2 Understand the Limitations of Operation at Nonstandard Line Voltages 3 4 4 Setting Up the Amplifier 2 020 eee ee ees 4 1 4 1 Unpack the Amplifier and Transformer 4 1 4 2 Connect the Transformer 4 2 4 3 Adjust the Tube and Exhaust Chimney 4 3 4 4 Connect the Cables 4 3 4 5 Set the Input Drive Power 4 6 5 Operating the Amplifier 0002 ee eee ee ee ee 5
14. RF Concepts LLC Resolution Fault type 4 LED behavior Cause Resolution Fault type 5 LED behavior Cause Resolution Fault type 6 LED behavior Cause Resolution DOCNUMBER 8406 Document Issue 1 0 February 2014 Alpha 8406 Linear Amplifier User Manual Diagnosing Faults and Troubleshooting 1 Check the output coaxial cable and connectors replace or reconnect 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 Make adjustments as needed Neither Ip nor HV LED is blinking both are dark Input drive power is too high The amplifier behaves as follows at various input drive power levels e When power is below 75 W the amplifier operates normally e When power spikes above 75 W a 500 ms timer starts during which time the power threshold is reduced from 75 to 65 W If you do not reduce the power to below the threshold at the end of 500 ms Fault 4 results e When power exceeds 100 W the absolute maximum value at which the amplifier can operate an immediate Fault 4 results Decrease the input drive power The amplifier shuts off and goes to State 0 A hard fault has occurred because input drive power exceeded 125 W causing plate current to exceed 2 5 A Ip gt 2 5 A Decrease the input drive power The amplifier shuts off and goes to State 0 A hard fault has occurred because significant plate
15. W The maximum possible RF output power for any particular primary AC voltage and current capacity is Po max V D 2 3 DOCNUMBER 8406 Document Issue 1 0 Page 3 4 February 2014 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 connected to the circuit the maximum peak RF output possible without tripping the 20 A breaker fuse is Po max 120 V x 20 A 2 3 1043 W If the same circuit also supplies a transceiver drawing peak line current of 5 A and a lamp drawing 1 A only 20 5 1 14 A is available for the amplifier reducing the maximum possible power to Po max 730 W For expected behaviors at nonstandard line voltages see Table 3 1 Table 3 1 Amplifier behavior at nonstandard line voltages Line voltage Expected behavior Low 90 130 V For a line voltage of lt 120 V do not expect to get 1500 W output For maximum efficiency tune the amplifier for no more than 1000 W output For a line voltage of 110 130 V 1500 W peak envelope power PEP operation CW or SSB may be possible if your AC line service has sufficient current capacity 30 A circuit recommended However do not expect to get continuous 1500 W output High gt 250 V Tube lifetime may be reduced Try the following e Ask your utility company
16. amage to the amplifier and other equipment e NEVER operate the amplifier with the cover removed e ALWAYS use an AC plug that is appropriate for the amplifier s primary mains voltage current rating and configuration e ALWAYS use grounding type AC connectors that conform to local codes e NEVER use 120 VAC plugs and power receptacles for 190 250 V circuits e ALWAYS connect ALL station equipment to a good common ground Failure to do so may allow RF feedback to leak into the transceiver and cause severe signal distortion DOCNUMBER 8406 Document Issue 1 0 Page 4 4 February 2014 RF Concepts LLC Step 3 Step 4 Step 5 Step 6 Step 7 DOCNUMBER 8406 Document Issue 1 0 February 2014 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 2b Connect the black and white wires in the amplifier power cord to the two hot wires of the AC source Either wire may be connected to either side of the line For best results use a dedicated 200 240 V branch circuit of 10 AWG copper wire or equivalent rated at 20 A to feed the amplifier Replace the amplifier cover and all attachment screws Use only the 6 32 screws supplied with the amplifier Do not tighten any of the screws until all a
17. be Replace fuses as needed For 190 210 VAC service use only 20 A 250 V rated fuses For 90 130 VAC service you may optionally use 25 A fuses with caution IMPORTANT Never replace a fuse with one of a different type or greater current rating Damage resulting from DOCNUMBER 8406 Document Issue 1 0 February 2014 RF Concepts LLC Step 5 DOCNUMBER 8406 Document Issue 1 0 February 2014 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 Replace the cover and reconnect the AC line cord to the power source Page 6 3 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Maintaining the Amplifier DOCNUMBER 8406 Document Issue 1 0 Page 6 4 February 2014 7 Diagnosing Faults and Troubleshooting 7 1 Diagnose Faults DOCNUMBER 8406 Document Issue 1 0 February 2014 7 1 Diagnose Faults 7 1 7 2 Troubleshoot Problems 7 4 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 direct
18. board e Display board e HV board e Low pass filter board e Mains board e Transmit receive T R board e Tube deck board In addition to these the tube tank circuit assembly and transformer complete the main sections of the amplifier These major blocks are described below The amplifier includes a 5 V power supply mounted behind the front panel Whenever the amplifier is plugged into the mains power this supply is active and there is power to the microcontroller on the main control board This feature enables the amplifier to be turned on or off remotely It also enables remote monitoring and debugging via a USB cable connected to a computer The amplifier front back and interior are shown below see Figure 2 1 Figure 2 2 and Figure 2 3 Amplifier components are listed alphabetically and described below Page 2 1 Page 2 2 Alpha 8406 Linear Amplifier User Manual Amplifier Components and Specifications Figure 2 1 Amplifier front 60 AAW N yy W MN 0 0 Uum ly e S ww MN 8 i EFFICIENCY nw RF Concepts LLC DOCNUMBER 8406 Document Issue 1 0 February 2014 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 e Center partition board e Control board e Display board e HV board e Low pass filte
19. cessive amplifier grid current e Operation at lower power results in decreased amplifier efficiency Recommended Practice We recommend that you tune first into a dummy load or artificial antenna then connect the antenna and make any slight final adjustments that may be needed DOCNUMBER 8406 Document Issue 1 0 February 2014 RF Concepts LLC DOCNUMBER 8406 Document Issue 1 0 February 2014 Alpha 8406 Linear Amplifier User Manual Operating the Amplifier High SWR Considerations For any frequency where antenna VSWR gt 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 Nevertheless at SWR lt 2 1 the additional RF power loss of an antenna tuner can be avoided by tuning the amplifier into the slight mismatch There is no advantage to using a tuner to tweak the last bit of SWR in fact you lose power this way RF and Mistuning Protection The amplifier senses the beginning of any RF arc in for example a TUNE or LOAD variable capacitor and automatically switches the amplifier to standby mode within a few milliseconds This system has virtually eliminated RF arc damage in current Alpha amplifiers The system similarly detects severe mistuning and if drive exceeds 20 W switches the amplifier to standby mode The 20 W input trip threshold permits safe tuning at low pow
20. cket 4a Use good quality low loss coaxial cable 4b Ensure that the cables have a solid ground shield in place CAUTION When using any high power amplifier failure to connect ALL station equipment to a good common ground may allow RF feedback to leak into the transceiver and cause severe signal distortion 4c Use new clean connectors and install them according to manufacturer recommendations After soldering the connectors and before mating them with the amplifier clean the connectors Remove any excess solder braid fragments and the like 4d Support the coax frequently using noncompressive clips so that it does not hang or stretch under its own weight Avoid sharp or kinked bends most manufacturers specify a minimum bend radius for their product 4e Ensure that the connection from feed line to antenna is waterproof 4f Provide for disconnection of the feed line when it is not in use This protects against damage caused by static charges and lightning strikes IMPORTANT Damage from static charges and lightning strikes is not covered under warranty DOCNUMBER 8406 Document Issue 1 0 February 2014 Page 3 3 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 We strongly reco
21. clean the dust out of the amplifier paying particular attention to the tube fins For more information see Section 6 1 Clean the Amplifier Chassis page 6 1 Ready the antenna 3a Ensure that the antenna is rated for 1500 W and that it is carefully tuned and installed for minimum voltage SWR Many antennas that are suitable for general use are unsuited for operation at full 1500 W power At this power level in a 50 ohm circuit the RMS current is 5 5 A and the peak RF voltage is 387 V For SWR 2 1 these values double to 11 A and 775 V The actual voltage and current at various points in or on your antenna may be many times these values DOCNUMBER 8406 Document Issue 1 0 February 2014 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 IMPORTANT The importance of a well constructed feed line system cannot be overstated The purpose of the amplifier is to provide approximately 2 S units 12 dB of improvement in your radiated signal Cheap poor or underrated cables and connectors can degrade performance by at least one S unit This means that you could have bought a 375 W amplifier and achieved the same radiated signal by buying good quality feed line components Never use old coax which may have had moisture penetrate under the ja
22. 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 Set the multimeter selector switch to Ip plate current and leave it there while the warmup countdown proceeds No current should be indicated during the entire warmup period The WAIT and STBY LEDs blink about twice per second indicating that warmup is still in progress The FAULT and OPER LEDs remain unlit Ensure that exhaust air is detectable from the exit vent holes above the tube If exhaust air is NOT detectable TURN OFF the amplifier immediately ensure that the exhaust chimney is properly positioned over the tube and power up the amplifier again When the WAIT LED goes out and the OPR or STBY lights stop blinking indicating that warmup is complete move the OPR STBY switch to OPR Each amplifier ships from the factory with a performance data sheet showing the tune and load settings that we used to achieve full output power on that particular amplifier into an Alpha 2000 50 ohm dummy load You can find this data sheet inside the amplifier in the space where the transformer normally goes Your goal in tuning the amplifier is to optimize efficiency and linearity at a specific output power Operation at higher or lower power results in the following e Operation at higher power without appropriate readjustment results in flat topping also known as splatter and usually ex
23. cy in the range 50 54 MHz and on all commonly used modes including the following All digital modes Frequency modulation FM Keyed continuous wave CW Radioteletype RTTY Single sideband SSB Slow scan television SSTV e Compatibility with popular amateur transceivers and exciters The Alpha 8406 requires 50 65 W peak RF drive for 1 5 kW output e Capability of full CW break in QSK when used with any appropriate transceiver e Built in protective functions The control system incorporates protective functions that minimize the probability of accidental damage to the amplifier or its tube In most cases when a protective function is tripped the amplifier goes to standby mode DOCNUMBER 8406 Document Issue 1 0 Page 1 2 February 2014 RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Introduction 1 3 Safety Considerations General Considerations For safe operation take the following precautions e Locate the amplifier where there is good air circulation all around and on top of the cabinet The unit may become hot during operation e Move the amplifier only with great caution being sure to do the following Remove the transformer and move it separately from the amplifier by means of its lifting handle Never transport the amplifier with the transformer in place as together they weigh 70 pounds Use proper lifting techniques and two people e Remember that although th
24. e Alpha 8406 meets international safety standards and US Federal Communications Commission FCC regulations it works with high voltages that can be LETHAL IMPORTANT e NEVER open the amplifier case without first unplugging the unit from the wall outlet e NEVER touch an antenna during transmission e NEVER turn on the amplifier without the cover securely in place and all attachment screws inserted e NEVER turn the amplifier back on after a hard fault that is a fault to power off without waiting at least 20 seconds e NEVER cover or obscure the exhaust holes in the amplifier cover Never stick objects into the holes or allow liquids to enter through the holes RF Exposure The FCC requires users to check their installations for compliance with published values for allowable exposure to RF fields This information is available in American Radio Relay League ARRL publications FCC printed rules and on the web We strongly recommend that you do this for any installation either fixed and at an expedition or contest site DOCNUMBER 8406 Document Issue 1 0 February 2014 Page 1 3 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Introduction SEE a e For information on RF exposure see FCC OET Bulletin 65 Supplement B at http www fcc gov encyclopedia oet bulletins line e For questions regarding engineering your amplifier into your amateur radio station go to rfconcepts com and click Support 1 4 Related
25. e caused by insufficient cooling airflow is not covered under warranty 4 4 Connect the Cables Procedure 4 4 Connect the cables Step1 _ Set the voltage tap A row of primary voltage taps is located on the top of the mains board between the transformer and the front panel The row contains five fast on terminals J22 to J26 and a flying jumper connector that mates with them see Figure 4 1 DOCNUMBER 8406 Document Issue 1 0 February 2014 Page 4 3 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 cover all the line voltages normally encountered around the world The nominal midrange voltage for each tap is printed on the mains board circuit board The acceptable line voltage for each tap is the center voltage plus or minus 10 V Important To prevent damage to the tube and amplifier never set a tap to other than the proper voltage We strongly recommend that you operate the amplifier on 240 VAC If you choose to do otherwise see Section 3 2 Understand the Limitations of Operation at Nonstandard Line Voltages page 3 4 Step 2 Connect the power cord WARNING To avoid the hazard of a potentially fatal electric shock and or severe d
26. ent Issue 1 0 Page 4 2 February 2014 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 12 inch hex bolts with inch washers through the four clearance holes in the chassis and into the nuts in the transformer base CAUTION Do not use the transformer s shipping bolts They are too long and will damage the transformer 4 3 Adjust the Tube and Exhaust Chimney With the amplifier cover removed adjust the tube and exhaust chimney Procedure 4 3 Adjust the tube and exhaust chimney Step 1 Ensure that the tube is firmly seated in its socket The 4CX1500B tube has a bayonet style base It is installed onto a central pin in the tube socket and then rotated clockwise into place so that the flanges on the tube line up with the connectors in the socket To remove the tube rotate it counter clockwise and then pull it up out of the socket Step 2 Ensure that the anode connector is tightly clamped to the tube Step 3 Ensure that the silicon rubber exhaust chimney is straight and that the bottom is firmly against the tube deck and completely covers the airflow opening in the deck The chimney should be flush with the top cover when it is placed back on the amplifier Tube cooling exhaust must exit only through the tube anode fins it must not be allowed to escape outside them IMPORTANT Damag
27. er levels without aggravating and unnecessary trip outs Retuning If you tune the amplifier for maximum power output and then decide to operate it at a power output much different from 1 5 kW you must retune it for clean and efficient operation CAUTION During tuning if the amplifier fails to respond as described do the following 1 Remove drive immediately 2 Turn the OPR STBY switch to STBY 3 Verify all connections and cables 4 Turn the amplifier switch to OPR 5 Proceed with the tuning procedure Page 5 3 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Operating the Amplifier Page 5 4 Step 1 Step 2 Step 3 Step 4 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 Parameter Value Ip In the range 0 9 1 1 A read on the 0 1 5 A scale for 1500 W output Input drive At or below 50 W Power output Full legal depending on voltage SWR e For SWR lt 2 0 1 1500 W with 40 50 W drive e For SWR gt 2 0 1 full power may not be possible but the other tuning indications are the same Grid current Green light flickers barely if at all normally 40 mA At gt 100 mA the system alarms Efficiency Approximately 60 During normal operation this is the most useful parameter to monitor on the multimete
28. her keydown mode monitor the efficiency display and use the tune and load controls as required to keep efficiency maximized Monitor grid current The green grid light normally flickers occasionally in any operating mode as RF is produced Whether you see this depends on your particular tube amplifier and current mode of operation You should not expect to see the green light come on full during normal operation The red grid light indicates excessive grid current resulting from overdrive and or inadequate loading Address this problem as soon as possible by reducing the drive and or increasing the load control 5 4 Optional Operate the Amplifier Remotely Page 5 6 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 DOCNUMBER 8406 Document Issue 1 0 February 2014 RF Concepts LLC DOCNUMBER 8406 Document Issue 1 0 February 2014 NOTE Alpha 8406 Linear Amplifier User Manual Operating the Amplifier Although you can operate the amplifier remotely you cannot adjust the tune and load controls via the USB interface remotely Nor do we at RF Concepts make our own software available
29. if needed Page 7 5 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Diagnosing Faults and Troubleshooting 2 The transceiver may be locked in transmit Ensure that the transceiver is properly switching between TRANSMIT and RECEIVE modes For assistance see the transceiver manual When amplifier is in STBY or The tube bias supply or T R bias switch may be faulty Contact RF RECEIVE mode plate current Concepts technical support is indicated Distorted SSB signal grid 1 The RF drive from the transceiver may be excessive and or amplifier bias is unexpectedly loading may be insufficient Decrease drive from the transceiver decreasing Recheck the amplifier tuning 2 The coaxial connector coax feed line antenna feed point balun tuner or antenna trap may be arcing on voice peaks Replace the faulty components 3 RF feedback may exist from the antenna into the transceiver via the transceiver power cord microphone or key cable or other unshielded station patch cables Ensure that all power cords microphone and key cables and other cables are properly shielded and grounded 4 The station RF ground may be poor Ensure that the amplifier and transceiver have a proper RF ground Required drive to maintain The tube may be aging Contact RF Concepts technical support to 1500 W is steadily increasing determine whether the tube needs to be replaced DOCNUMBER 8406 Document Issue 1 0 Page 7 6 February 2014 Terminology
30. insertion loss is 0 14 dB The inductor is made from wide silver plated strap material The capacitors are low loss porcelain types All joints are silver soldered Adequate cooling is ensured in two ways the board has slots to enable cooling from both sides and it is mounted in front of the inlet to the blower to enable exposure to copious air flow Mains Board Power supply functions are split between the mains board and the HV board The mains board deals mostly with the primary side of the transformer The various taps for the transformer primary are routed through this board and so is the AC line input Relays on the mains board connect the AC line to the appropriate taps on the transformer primary Also on the mains board is a step start circuit This circuit consists of a relay and a resistor which are time sequenced to limit the inrush current into the amplifier when it is first turned on The regulated 12 and 124 V supplies are also located on this board Many of the important voltages for the amplifier are brought to test points on this board The primary voltage taps are located on the top of the mains board between the transformer and the front panel There is a row of five fast on connectors J22 through J26 and a flying jumper connector that mates with them The amplifier is always shipped with the jumper sent to J22 the 240 V position T R Board The transmit receive T R board contains the input and output
31. k RF out with TUNE control Further increase the amplifier s drive to the desired power level and adjust settings to maximize amplifier efficiency 7a Set the multimeter selector switch to Efficiency and set the radio to RTTY or CW to transmit a steady carrier 7b Set the tune and load controls to the settings listed on the amplifier s performance data sheet as required to achieve 1500 W output in the lab key the amplifier with RF and adjust the tune and load controls for maximum efficiency the efficiency scale range is 50 to 70 7c Increase the drive power to the desired output power then readjust the tune and load controls for maximum efficiency After 30 seconds of keydown the internal blower is set automatically to medium speed 5 3 Operate the Amplifier DOCNUMBER 8406 Document Issue 1 0 February 2014 NOTE Step 1 Step 2 Step 3 If the amplifier faults during operation it usually resets itself after 4 seconds For information about faults see Chapter 7 Diagnosing Faults and Troubleshooting Procedure 5 3 Operate the amplifier Start up and tune the amplifier as described in Start Up the Amplifier page 5 1 and Tune the Amplifier page 5 2 Apply RF The amplifier requires only 50 W for full output Note that applying RF can cause the internal blower to change speed Any time the amplifier is keyed and producing RF for more than 30 seconds continuously blower speed is se
32. ly minor risk of electrical arcing DOCNUMBER 8406 Document Issue 1 0 February 2014 RF Concepts LLC mA Milliampere 10 A O OPR Operate P PCB Printed circuit board Board that mechanically supports and electrically connects electronic components PEP Peak envelope power Average power supplied to the antenna transmission line by a transmitter during one RF cycle at the crest of Q QSK Quick shift keying Digital modulation scheme in which the transmitter is on only for the duration of each dot or dash and switches to R RCA Radio Corporation of America Also a type of interconnecting plug RF Radio frequency Frequency within the range 3 Hz to 300 GHz RG x x Coaxial cable type S SSB Single sideband Modulation scheme that refines upon amplitude modulation DOCNUMBER 8406 Document Issue 1 0 February 2014 Alpha 8406 Linear Amplifier User Manual Terminology MHz Megahertz 10 Hz the modulation envelope under normal operating conditions PSK Phase shift keying Digital modulation scheme in which information is conveyed by changes or modulations in the phase of a reference signal RECEIVE mode between each dot or dash allowing the operator to hear any signal being sent RMS Root mean square Statistical measure of the magnitude of a varying quantity such as a wave RTTY Radio teletype Telecommunications system consisting of two o
33. ly to the antenna The FAULT LED on the front panel flashes on and off for 4 seconds After this period unless the OPER STBY switch has been placed in the STBY position the amplifier attempts to return to OPERATE mode You can shorten this 4 s period by toggling the OPER STBY switch While the FAULT LED is flashing the Ip and HV LEDs indicate which fault type caused the amplifier to enter fault mode Fault type codes are also reported in the amplifier telemetry data via the USB port on the rear of the amplifier These fault types are summarized in Table 7 1 and described in the following text Table 7 4 Fault types LED behavior Fault type Cause Ip LED HV LED Blinking Blinking Amplifier gain is below 10 dB 2 Dark Plate current in the tube exceeds 1 6 A Dark Blinking Reflected power is too high Dark Input drive power is too high 5 Plate current exceeds 2 5 A 6 Plate current was detected during warmup Faults 5 and 6 do not display on the front panel Rather they indicate only through telemetry via the USB port Page 7 1 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Diagnosing Faults and Troubleshooting Fault type 1 Fault type 2 Fault type 3 Page 7 2 LED behavior Cause Resolution LED behavior Cause Resolution LED behavior Cause Both Ip and HV LEDs are blinking Amplifier gain has fallen to lt 10 dB This is an important safet
34. ment Issue 1 0 Page 5 8 February 2014 6 Maintaining the Amplifier 6 1 6 2 IMPORTANT Clean the Amplifier Chassis 6 1 Replace the Tube and or Fuses 6 2 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 Damage to other station equipment may also result Do not apply oil or grease to any amplifier components There are no user accessible lubrication points in the amplifier The amplifier is equipped with a cover interlock switch that removes primary power from the amplifier and a crowbar that short circuits high voltage to the chassis when the cover is lifted These interlocks protect against electric shock resulting from accidental contact with the lethal voltages inside the amplifier The cover interlock is intended only as backup protection against accidents Never depend on it Always disconnect the power cord from the AC mains before removing the cover IMPORTANT Do not disable the interlock switch for any reason 6 1 Clean the Amplifier Chassis Perform this procedure at least once a year Procedure 6 1 Clean the amplifier chassis Step1 Power down the amplifier Step2 Clean the exterior with a mild liquid detergent Do not use chemical solvents as these may severely damage the front panel or cabinet finish Never use an abrasive clea
35. mmend that you do this for any installation both fixed and at an expedition or contest site e For information on RF exposure see Section 1 3 Safety Considerations page 1 3 e For questions regarding engineering your amplifier into your amateur radio station go to rfconcepts com and click Contact Us Step 5 Provide surge protection IMPORTANT Induced energy from nearby electrical storms or other power transients may damage amplifier components Such damage is not covered under warranty It is therefore important to use a good lightning arrestor However the only lightning proof solution available is to disconnect antenna feedlines and AC power when the equipment is not in use Whenever the amplifier is online either off in STBY mode or warming up with the WAIT LED lighted the amplifier is bypassed and the exciter is connected directly to the antenna e For SWR 1 1 the throughput limit in all cases is 300 W e For SWR gt 1 1 reduce the power level as necessary Any reflected power level higher than 100 W may damage the RF switching relays in the amplifier 3 2 Understand the Limitations of Operation at Nonstandard Line Voltages Electrical power equipment draws twice as much primary current from a 120 V mains as from a 240 V mains Therefore if you operate the amplifier on typical 120 V 20 A household circuit without exceeding the 20 A circuit rating you limit maximum peak power output to 600 1000
36. most modern transceivers maintain quite consistent output from band to band and mode to mode when set up properly Procedure 4 5 Set the input drive power Consult your amplifier s specific performance data sheet to determine the drive requirements and the tune and load settings required to deliver 1500 W This data sheet is placed inside the amplifier in the space where the transformer goes at the factory before shipping DOCNUMBER 8406 Document Issue 1 0 February 2014 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 Step 3 Ifthe transceiver is more than 15 years old reduce the power output so that voice peaks do not overdrive the transmitter under any modulation condition DOCNUMBER 8406 Document Issue 1 0 February 2014 Page 4 7 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Setting Up the Amplifier DOCNUMBER 8406 Document Issue 1 0 Page 4 8 February 2014 5 Operating the Amplifier 5 1 Start Up the Amplifier 5 1 5 2 Tune the Amplifier 5 2 5 3 Operate the Amplifier 5 5 5 4 Optional Operate the Amplifier Remotely 5 6 IMPORTANT e 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
37. nals disappear or are severely attenuated DOCNUMBER 8406 Document Issue 1 0 February 2014 Alpha 8406 Linear Amplifier User Manual Diagnosing Faults and Troubleshooting The plate voltage to the power supply may be too low Check the line voltage and confirm that the tap is set correctly The timing circuitry on the control board may be damaged or defective Contact RF Concepts technical support The T R control line key line connection to the amplifier may be faulty 1 Confirm that the key line is inserted into the correct jack on the back of the amplifier 2 Confirm that the key line is connected to the correct port on the transceiver and that amplifier keying is enabled 3 If the tube current has exceeded 2 5 A follow the resolution instructions for Fault type 2 page 7 2 and Fault type 5 page 7 3 4 Confirm that the cable is good 5 Confirm with the multimeter switch in the Ip position and the amplifier keyed with no RF that plate current is drawn The tube current may exceed 2 5 A See the resolution instructions for Fault type 4 page 7 3 The amplifier may be overdriven or incorrectly tuned most likely the load control is set too low Reduce the transceiver output and adjust the tune and load controls to maximize efficiency with minimum grid lights 1 The RELAY T R control cable from the transceiver may be shorted Check the cable to ensure that it is switching properly Replace it
38. nd higher frequencies toward the 100 end of the dial scale 2 3 Output Tank Circuit Page 2 6 The output tank circuit provides reliable high efficiency low distortion performance in a very compact volume In any VHF amplifier the most critical design decision is the output tank network topology We considered a transmission line design but rejected it as being difficult and expensive to build Likewise we considered and DOCNUMBER 8406 Document Issue 1 0 February 2014 RF Concepts LLC Alpha 8406 Linear Amplifier User Manual Amplifier Components and Specifications rejected the standard pi L configuration that is used so widely at HF because of tough FCC harmonic requirements and the difficulty of achieving full output over the entire band The topology that we chose see Figure 2 4 is the pi C configuration which provides harmonic attenuation adequate to meet the requirements of all countries globally that permit power outputs of 1500 W In this configuration the anode capacitance of the tube forms the input capacitance of the pi network This network allows full coverage of the band with two rugged air variable capacitors A single large silver plated inductor completes the tank arrangement it is made from half inch copper tubing that is formed to shape then silver plated The single tube design reduces tube capacitance and facilitates control of stray inductances in the circuit Figure 2 4 Output tank circuit 2
39. ner DOCNUMBER 8406 Document Issue 1 0 February 2014 Page 6 1 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Maintaining the Amplifier Step 3 Step 4 Step 5 Step 6 WARNING Do not allow any liquids to enter the cover s tube exhaust holes Disconnect the AC line cord from the power source and remove the cover WARNING Before lifting the cover for any reason disconnect the AC line cord from the power source Clean the interior particularly high voltage areas with a vacuum cleaner and a soft bristle brush frequently enough to prevent visible accumulation of dust Optimally remove the plate under the tube deck attached with 4 screws and use compressed air to blow out the cooling fins in the tube If conditions are extremely dusty secure a thin air filter of the type used for window air conditioners across the air intake on the rear panel Replace the cover and reconnect the AC line cord to the power source 6 2 Replace the Tube and or Fuses Page 6 2 Step 1 Step 2 Step 3 Step 4 Perform this procedure only as needed Procedure 6 2 Replace the tube and or fuses Power down the amplifier Disconnect the AC line cord from the power source and remove the cover WARNING Disconnect the AC line cord from the power source before lifting the cover for any reason Replace the tube as needed Ensure that cooling airflow to the tube is sufficient Use a high quality 4CX1500B tu
40. on scheme in which information is conveyed over a carrier wave by variations in frequency H HF High frequency Radio frequency within the range 3 30 MHz Ip Idling plate current in amperes Plate current measured when the amplifier is keyed and RF is not present K key Signal from the radio to the amplifier that instructs the amplifier to switch from RECEIVE to TRANSMIT mode because the radio is ready to generate RF power The programmable delay between keydown and RF out is generally 8 12 ms When the amplifier is keyed it is in State 5 L LED Light emitting diode Semiconductor diode that emits incoherent narrow spectrum light providing a form of electroluminescence Page Term 2 RF Concepts LLC FSK Frequency shift keying Type of frequency modulation in which information is conveyed by shifts in the output frequency between predetermined values HV High voltage Electrical circuit in which the voltage used presents risk of both electric shock and electrical arcing Hz Hertz One periodic event per second kV kilovolt 1000 V kVA kilovolt ampere Unit of electrical power equal to 1000 volt amperes where 1 volt ampere is the power dissipated when 1 volt produces a current of 1 ampere 1000 W capability kVA 0 8 kilowatts kW Kilowatt 1000 W LV Low voltage Electrical circuit in which the voltage used presents risk of electric shock but on
41. or to drop voltage from 12 V to 5 V for the display HV Board The main high voltage for the amplifier is created on the HV board using a full wave bridge rectifier and a bank of capacitors This power supply has two 10 ohm resistors one in the positive B lead and one in the negative return that goes to ground This combination of resistors limits the surge current in the case of a B arc The voltage across the resistor in the negative return is used to monitor tube plate current in the control board It is also used to generate a hard fault condition When the power supply current exceeds 2 5 A a relay opens the coil circuit of the mains tap relays on the mains board causing the amplifier to go to the power off state This hard fault circuit operates independently of microprocessor control The regulated screen supply is also located on this board DOCNUMBER 8406 Document Issue 1 0 February 2014 RF Concepts LLC DOCNUMBER 8406 Document Issue 1 0 February 2014 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 Low Pass Filter Board The output low pass filter is a single stage unit optimized for low loss at 6 m The measured
42. quipment may also result e Proceed slowly throughout these procedures to avoid bumping and damaging adjacent wires connectors and components 4 1 Unpack the Amplifier and Transformer Step 1 Step 2 Step 3 DOCNUMBER 8406 Document Issue 1 0 February 2014 Procedure 4 1 Unpack the amplifier and transformer Prepare your station as described in Chapter 3 Preparing Your Station Remove the amplifier and transformer from their cartons The Alpha 8406 ships in two heavy duty double wall cardboard boxes The carton containing the amplifier weighs 50 Ib 23 kg the carton containing the transformer weighs 43 1b 20 kg 2a Inspect the boxes for shipping damage 2b Unpack the boxes and place the contents on a workbench or table 2c Retain the boxes and all packing material in case you need to ship the unit later Inspect the amplifier and transformer for shipping damage If you find damage contact RF Concepts technical support Page 4 1 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Setting Up the Amplifier 4 2 Connect the Transformer IMPORTANT e The transformer is very heavy When moving it use due caution and handle it only by the lifting handle e Do not over tighten the screws that hold the transformer in place as doing so may cause excessive vibrations or noise e If you move the amplifier even if only from one site to another locally remove the transformer first to avoid the possibility of
43. r bargraph The range of the efficiency scale on the amplifier s front panel is from 50 to 70 As the amplifier s output power level decreases efficiency also decreases below about kW it falls to lt 50 at which point the efficiency display is not usable However efficiency is still calculated on the control board and the data are available via the USB port Plate current In the green zone 1 A at 1500 W At gt 1 6 A the system alarms Procedure 5 2 Tune the amplifier Start up the amplifier as described in Start Up the Amplifier page 5 1 Set the TUNE and LOAD controls to the values given in your amplifier s specific performance data sheet Note that final TUNE and LOAD settings will vary with operating frequency antenna characteristics and power level Limit the transceiver drive to lt 50 W for tuning and operating the amplifier Set the multimeter selector switch to Ip plate current DOCNUMBER 8406 Document Issue 1 0 February 2014 RF Concepts LLC Step 5 Step 6 Step 7 Alpha 8406 Linear Amplifier User Manual Operating the Amplifier 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 Increase the amplifier s drive to 500 W output going back and forth between TUNE and LOAD to peak the RF output To increase output increase the drive slightly increase LOAD for a peak in RF out then pea
44. r board e Mains board e Transmit receive T R board e Tube deck board Center Partition Board The center partition board contains the RF decoupling circuit on the B line as well as the crowbar safety circuit When you remove the top cover of the amplifier the spring metal of this safety device shorts out the B line DOCNUMBER 8406 Document Issue 1 0 February 2014 Page 2 3 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Amplifier Components and Specifications IMPORTANT Page 2 4 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 This microcontroller has a built in multichannel analog to digital converter that monitors all critical voltages and currents in the amplifier as well as the input power and output forward and reflected power It uses these converted values to control the amplifier s operation and to drive the display board on the front panel A USB port on the back of the amplifier is provided for remote monitoring The USB driver for the amplifier is provided on the CD that ships with the amplifier or is available from the company website Display Board The display board uses a MAX7219 multiboard LED display driver chip The chip receives data from the control board via a serial peripheral interface SPI this data determines which LEDs to light The board contains a regulat
45. r more teleprinters using radio as the transmission medium SSTV Slow scan television Picture transmission method for transmitting and receiving static pictures via radio Page Term 3 Alpha 8406 Linear Amplifier User Manual Page Terminology STBY Standby Mode in which an electronic appliance is turned off but under power and ready to activate on command T T R Transmit receive U UHF Ultra high frequency Radio frequency within the range 300 3000 MHz 3 GHz V VAC Volts of alternating current VDC Volts of direct current VHF Very high frequency Radio frequency within the range 30 300 MHz Page Term 4 RF Concepts LLC SWR Standing wave ratio Ratio of the amplitude of a partial standing wave at an antinode maximum to the amplitude at an adjacent node minimum Measure of antenna and feedline efficiency transceiver Device that has both a transmitter and a receiver within the same circuitry or chassis US United States VSWR Voltage standing wave ratio Example If VSWR 1 2 1 the maximum standing wave amplitude is 1 2 times greater than the minimum standing wave amplitude DOCNUMBER 8406 Document Issue 1 0 February 2014 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 Alpha 8406 Linear Amplifier User
46. re started WARNING Do not attempt to operate the amplifier with the cover removed or placed on the unit without the attachment screws Doing so damages the amplifier and may also cause injury or death to the operator Place the amplifier in its operating position on a stable surface with sufficient space to the rear sides and top to allow good air flow and safe placement of cables It is important to maintain at least 3 inches of clear space above the amplifier for the warm exhaust air from the tube and to ensure that this warm air is not drawn into the back of the amplifier again Connect the amplifier s RF INPUT to the transceiver s RF OUTPUT Use 50 ohm coaxial cable RG 58C U or equivalent Connect the amplifier s RF OUTPUT to the antenna Use RG 213 U LMR 400 or LMR 600 cable Connect the transceiver s control T R cable to the amplifier s KEY IN input The amplifier s relay jack has 12 V on it When pulled all the way to ground a current of 10 mA flows For information on how to connect to an external amplifier see your transceiver manual The amplifier has a full break in vacuum relay QSK system that requires only the normal interconnection when used with a modern QSK transceiver The amplifier requires a contact closure short circuit on Page 4 5 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 Thi
47. relays as well as the input power detection and output directional wattmeter Voltages from the detector are connected to the control board A trimmer capacitor on this board is adjusted at the factory You should not touch it Page 2 5 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Amplifier Components and Specifications The board also has a safety inductor on the RF output for 50 54 MHz operation located between the PCB and the rear chassis Tube Deck Board The tube deck board is located in the tube deck below the tube socket It contains critical circuit elements that need to be in close proximity to the tube The tube heater bias and screen connections are all located on this board The tube deck temperature sensor and the input match for the tube complete this board 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 Control Purpose LOAD Controls the load capacitor Sets the amplifier plate loading and determines the power level for best efficiency and linearity Heavier loading is toward the 100 end and lighter loading is toward the 0 end of the dial scale TUNE Controls the tune capacitor Sets the output tank circuit to resonance at each frequency Lower frequencies tend to tune toward the 0 end a
48. s function is supplied by the transceiver usually from a dedicated relay that is normally open in RECEIVE mode and closed in TRANSMIT mode 7a Use shielded wire for the T R control cable Fit the amplifier end with a common phono RCA type plug and the transceiver end with a suitable connector 7b Ensure that the T R relay contact closes Modern transceivers have the proper time delay between key up and the start of the transmitted signal to allow the amplifier to follow the CW keying 4 5 Set the Input Drive Power Page 4 6 IMPORTANT Step 1 The amplifier s grid current limiting circuits provide substantial protection against possible tube damage Therefore the amplifier does not generate or use Automatic Level Control ALC voltages to control an exciter You need only set the input drive power as described in this section e The amplifier requires up to 50 W drive for full rated output e You must set the transceiver output power properly It is not sufficient to set only the transceiver POWER or RF PWR control Virtually all damage to date has resulted directly from severe overdrive e Several popular transceivers can generate RF spikes of 200 300 W Adjust your transceiver so that it does not produce over wattage spikes For more information see the manual for your particular transceiver e Damage caused by application to the amplifier of several times rated drive power is not covered under warranty Fortunately
49. s important that you observe good engineering practices to achieve all the benefits of such a station in a safe and reliable manner SEE In addition to reading this chapter we recommend that you consult a IZZ good source of general information such as the latest Amateur Radio Relay League ARRL Handbook for Radio Amateurs especially if this is your first high power amplifier Procedure 3 1 Prepare your station Step1 Provide 220 VAC power 1a Ifyou do not have a 220 VAC outlet in your station have a licensed electrical contractor install one The amplifier runs best when powered by a 200 240 VAC circuit A minimum of a 20 A capacity is required A 20 A breaker on your 220 V circuit is sufficient IMPORTANT Although the amplifier can run when connected to a 120 VAC outlet it will give you lt 1000 W output much lower than the full legal limit For information on the use of nonstandard line voltages see Section 3 2 Understand the Limitations of Operation at Nonstandard Line Voltages page 3 4 1b When sizing the circuit be sure to include the current drawn by other equipment that may be on the same circuit DOCNUMBER 8406 Document Issue 1 0 February 2014 Page 3 1 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Preparing Your Station Page 3 2 Step 2 Step 3 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
50. t to medium after 60 seconds it is set to high When operating primarily in CW or SSB mode monitor plate current Page 5 5 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Operating the Amplifier Step 4 Step 5 e Idling plate current for the Alpha 8406 is 350 400 mA during full power transmission A detector senses RF drive and during pauses in speech and key up intervals reduces plate current to 30 50 mA substantially reducing average power supply loading heat generation and wasted energy Do not allow key down plate current to exceed 1 5 A for more than a second or two If you do and the overcurrent plate current trip occurs after you return the amplifier to RECEIVE mode key up it automatically resets in 4 seconds If the plate current becomes excessive or the high voltage circuitry faults the plate current relay quickly turns the amplifier off However the relay does not prevent tube or other damage due to either short term or long term overdrive or improper tuning It is your responsibility to ensure safe tuning drive and general operating conditions If the overcurrent relay trips remove AC power from the amplifier then determine and correct the cause of the trip before turning the amplifier back on This hard fault trip circuit does not rely on the microcontroller for its operation and protects the amplifier even if the processor is damaged or malfunctioning When operating in JT 65 or anot
51. temperature sensor on the tube deck board sends data to the amplifier s control board This information is used to control the speed of the DC squirrel cage blower that exhausts into the tube deck Cool air is drawn into the amplifier by the muffin fan at the rear of the amplifier and over the transformer and the high voltage section The air then flows through the amplifier s center partition and is pulled in by the blower and forced through the tube fins to keep the tube within the correct operating temperature range The blower has three speeds low medium and high The amplifier s control board determines which speed to set based on the temperature that is measured in the tube deck Any time the amplifier is keyed and producing RF for more than 30 seconds continuously the blower speed is set to medium speed After 60 seconds it is set to high speed e The amplifier s grid current limiting circuits provide substantial protection against possible tube damage Therefore the amplifier does not generate or use Automatic Level Control ALC voltages to control an exciter You need only set the input drive power as explained in Section 4 5 Set the Input Drive Power page 4 6 e To prolong tube life refrain from cycling AC power on off on off repeatedly It is less stressful to leave equipment on and in standby mode for several hours than to cycle it on and off repeatedly DOCNUMBER 8406 Document Issue 1 0 February 2014 RF
52. to reduce your line voltage e Place your own step down transformer in line between the AC outlet and the amplifier A transformer with at least 4 kVA rating is required due to the nature of the current waveform in the primary e Use a ferroresonant voltage regulator This is an expensive but effective way to stabilize primary voltage IMPORTANT If you intend to operate the amplifier at 90 130 V or if other equipment draws current from the same circuit as the amplifier do the following 1 Ensure that the AC cord is not coiled too tightly or placed where normal air flow is restricted and can cause it to overheat 2 Change the bottom 2 A slow blow fuse on the rear panel to a 5 A slow blow fuse to allow for the increased in rush current DOCNUMBER 8406 Document Issue 1 0 February 2014 Page 3 5 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Preparing Your Station DOCNUMBER 8406 Document Issue 1 0 Page 3 6 February 2014 4 Setting Up the Amplifier IMPORTANT 4 1 Unpack the Amplifier and Transformer 4 1 4 2 Connect the Transformer 4 2 4 3 Adjust the Tube and Exhaust Chimney 4 3 4 4 Connect the Cables 4 3 4 5 Set the Input Drive Power 4 6 e 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 Such damage is not covered under warranty Damage to other station e
53. to you for this purpose However an excellent control program is available from Dan Greil AE9K on his website at www ae9k com There are three ways to operate the amplifier remotely 1 Via direct USB connection from a PC at the operating position using one or more USB cables and hubs The length of a single USB hop is limited to 5 m about 16 ft You can extend this length by using USB hubs 2 Via a dedicated PC remote to the operator and adjacent to the amplifier connected to the amplifier by a single USB cable The remote control program runs on the PC and you connect to it using remote desktop software such as Remote Desktop LoMein or GoToMyPC 3 Via a PC or other computer example Linux on a Raspberry Pi board adjacent to the operator and remote from the amplifier connected to the amplifier by some form of serial port redirection such as serial over IP to create a virtual COM port on the PC This is the trickiest to set up and requires that you have a good knowledge of computers and networking 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 Such implementations are the responsibility of the user Page 5 7 Alpha 8406 Linear Amplifier User Manual RF Concepts LLC Operating the Amplifier DOCNUMBER 8406 Docu
54. y feature of the amplifier as many different problems can be detected as a drop in gain So that this fault does not occur while the amplifier is being tuned gain fault detection is disabled when drive power to the amplifier is below 20 W This allows correct initial amplifier tuning to be achieved before going to full power 1 Reduce the input drive power 2 Retune the amplifier Ip LED is blinking Plate current in the tube has exceeded 1 6 A If the current exceeds 2 5 A AC select relays are de energized and the amplifier shuts off completely 1 Retune the amplifier 2 Ensure that the amplifier is not overdriven 3 Fix any problems in the bias control circuitry 4 If the amplifier has shut off wait at least 20 seconds then use the ON OFF switch to turn the amplifier back on 5 If the amplifier trips again immediately investigate and resolve the problem before attempting to turn the amplifier on again DO NOT repeatedly hit the ON switch when the amplifier trips out Doing so is likely to result in severe damage to amplifier components When you are certain that you have taken care of the problem that caused the fault you may turn the amplifier back on HV LED is blinking Reflected power is too high The amplifier trips when reflected power exceeds 250 W At 1500 W output this represents a voltage standing wave ratio VSWR fault exceeding 3 1 DOCNUMBER 8406 Document Issue 1 0 February 2014

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