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1. SSTV Slow scan television STBY Standby SWR Standing Wave Ratio A measure of antenna and feed line efficiency T R Transmit Receive UHF Ultra High Frequency 300 3 000 Mhz 45 US United States VAC Volts of alternating current VDC Volts of direct current VSWR Voltage Standing Wave Ratio 46
2. V xI 2 3 For example if the Alpha 8406 operates from a circuit that is capable of delivering 120 V AC at a maximum current of 20A with no other loads connected to the circuit maximum peak RF output possible without tripping the 20A breaker or fuse is approximately Po max 120V x 20A 2 3 2400 2 3 1043 W If the same circuit also supplies a transceiver drawing peak line current of 5A and a lamp drawing 1A only 20 5 1 14A is available for the amplifier and maximum possible output is about Po max 120V x 14A 2 3 1680 2 3 730W Below are some considerations at the high end and the low end of this voltage range that are rarely encountered Low Voltage vs Power Output At the low end of the voltage range do not expect to be able to get 1 500 watts output if your line voltage is below 120 volts If your line voltage is between 110 and 130 volts then 1 500 watts PEP operation CW or SSB may be possible if your AC line service has sufficient current capacity 30 amp circuit recommended However 1 500 watts continuous should not be expected If your line voltage is between 90 120 volts then power outputs above 1 000 watts should not be expected from the amplifier Tune adjust the amplifier for no more than 1 000 watts output and simultaneously for maximum efficiency Place where normal air flow is not restricted because the cord could overheat If other equipment is drawing current from the same circuit as the Alp
3. These interlocks are designed to protect against dangerous electric shock resulting from accidental contact with the lethal voltages inside the amplifier WARNING ALWAYS DISCONNECT THE AC LINE CORD FROM THE POWER SOURCE BEFORE REMOVING THE TOP COVER FROM THE 8406 FOR ANY REASON Cover interlocks are intended only as back up protection against accidents Never depend on them Always disconnect the power cord from the AC mains before removing the cover Interlock switches should not be disabled for any reason 6 4 3 Fuses Never replace any fuse with one of a different type or greater current rating 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 USE ONLY 20 AMP 250 VOLT RATED FUSES for 190 220 VAC service 38 25 amp fuses may be used with caution for line voltages of 90 130 V The slow blow fuses Fe located below the primary line fuses may prevent damage to the stop start resistors and HV rectifiers in the event of abnormal turn on conditions or HV faults If the AC interlock is defeated and primary power is applied while the HV crowbar is close the step start fuses will normally blow CAUTION DAMAGE RESULTING FROM USE OF A FUSE OF INCORRECT SIZE OR TYPE WILL NOT BE COVERED UNDER WARRANTY AND MAY VOID THE WARRANTY 6 4 4 Plate Over Current Relay This relay will quickly turn off
4. additional RF power loss of an antenna tuner can be avoided by tuning the 8406 into the slight mismatch There is no advantage to using a tuner to tweak the last bit of SWR in fact you will lose power this way 6 1 4 Operating at Less Than 1 5 kW Requires Retuning If you tune the amplifier for maximum power output and then decide to operate the 8406 at a power output much different from 1 5 kW it must be re tuned for efficient and RF clean operation Under such lightly loaded conditions the green grid LED will probably be fully lit Note that if you tune the amplifier at 1 500 watts and then simply reduce power to 1 000 watts the tubes are actually going to run hotter than at 1 500 watts It is better to tune the amplifier with close to 50 watts of power but reduce the loading control to get 1 000 watts 6 1 5 Lightning Protection Induced energy from nearby electrical storms or other power transients may damage components in the amplifier Such damage is not covered under warranty It is important to use a good lightning arrestor however the only lightning proof solution available is to disconnect antenna feed lines and AC power when the equipment is not in use 6 1 6 Operating in Bypass Mode Whenever the 8406 is in line either off in standby STBY or in warm up with the WAIT LED lighted the amplifier is bypassed and the exciter is connected directly to the antenna The throughput limit in all cases is 200 watts when op
5. amplifier case without unplugging the unit from the wall outlet e Always resist the temptation to immediately hit the ON button after the amplifier faults to power off e Never touch an antenna during transmission e Never attempt to turn on the amplifier without the cover securely in place all attachment screws reinserted e Never turn the amplifier back on after a hard fault without waiting at least 20 seconds e Never allow liquids to enter the amplifier through the cover holes e Never stick objects into holes in the case Warnings posted in this manual should be read and thoroughly understood by users Failure to perform procedures properly may result in amplifier damage fire hazard or electric shock 1 5 Owner Assistance Technical Assistance from RF Concepts is available from several sources 6 e The RF Concepts web site is www rfconcepts com Click on Support and follow the instructions Many typical problems and their solutions are listed on this site On this site you can get the following assistance Technical Support Repair Information Software Downloads Manuals Tech Tips Legacy Equipment Information FAQ s Alpha Forum You can email us for customer support by filling in the support request at www rfconcepts com or you can send your request by fax to 303 473 9660 or call us at 303 473 9232 2 Quick Start Information 2 1 Overview This section explains in brief the items you need to consider when se
6. grid 1 and its capacitance is compensated for by a series inductance to provide less than 2 1 SWR on each band at the amplifier s input 5 5 Mains Board The power supply functions are split between the mains board and the high voltage HV board The mains board mostly deals 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 primary One of 5 tap options is selected by using a 5 way jumper field See section 4 3 for more details on how to set the jumper 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 When initially turned on the tap relays operate from a voltage derived from resistors from the AC line They hold via contacts on the trip relay on the HV board The regulated minus 12 volt and minus 124 volt supplies are also located on this board Many of the important voltages for the amplifier are brought to test points on this board 5 5 High Voltage Board The main high voltage for the amplifier is created on this 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 the other in the negative return which goes to ground The combination
7. heavy and must be moved with due caution using only the lifting handle CAUTION PROCEED SLOWLY to avoid bumping and damaging adjacent wires connectors or components While the top cover is removed make the tube is firmly seated in its socket rubber exhaust chimney is fully and correctly installed and anode connector is tightly clamped 19 to the tube The silicone rubber chimney installed on the 4CX1500B tube is a critical part of the cooling system Make sure the chimney is straight and fully installed so the bottom of the chimney is firmly against the tube deck and completely covers the airflow openings in the deck Make sure that the silicone rubber chimney is 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 Failure to ensure proper cooling airflow may result in tube damage or destruction which is not covered under warranty 4 2 2 Connecting the Transformer Power Plugs e Connect the 9 pin white Molex connector to the matching plug mounted on the back wall of the amplifier e Connect the 8 pin orange connector to the matching pins on the upper Mains PCB e Connect the 6 pin yellow connector to the matching pins on the lower HV PCB e Check to ensure that all connector pins on these three connectors engage fully and correctly 4 2 3 Power Cord Connections WARNING To avoid the hazard of a potent
8. is well protected and these adjustments tend to be less critical than in many other amplifiers Grid bias is stabilized against grid current fluctuations 6 3 4 ALC The 8406 grid current limiting circuits provide substantial tube protection against possible damage therefore no ALC control is necessary It is only necessary to set the drive power from the radio as detailed in this manual 6 3 5 Turning On The Amplifier Please Note Every time the ALPHA 8406 is powered up there is a built in 180 second warm up wait 1 Place the OPR STBY switch to STBY standby 2 Rotate the multimeter selector switch to HV 3 Depress the POWER ON switch The fan and blower should immediately begin to operate If there is no air flow from the amplifier and no sound of blower operation immediately turn the amplifier off and investigate 4 Within two seconds the HV display should be all the way to the right certainly above 2 500 Volts If it is lower than this investigate further perhaps the primary taps are not correctly set 5 At this time the red LED representing 1800 W output power is illuminated indicating 180 seconds countdown remaining 1800 10 180 seconds As the timer counts down the remaining time will be indicated by the currently illuminated LED on the power output bar graph moving to the left 6 Move the multimeter switch to the Ip position There should be no current indicated and this should be true during the entire period t
9. of these two 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 This voltage is also used to generate the hard fault condition When the power supply current exceeds about 2 to 2 5 Amps a relay operates to open the coil circuit of the mains tap relays on the mains board When these relays release the amplifier goes to the power off state This hard fault circuit operates independently of 28 microprocessor control The regulated screen supply is also located on this board All power supply filter capacitors on this board have bleeder resistors which will discharge the capacitors in less than 60 seconds If it is necessary to work on this board it is nevertheless recommended that the discharged condition be confirmed with a voltmeter due to the remote possibility of bleeder resistor failure 5 7 Control Board The control board is the heart of the amplifier It is based around a PIC microcontroller This microcontroller has a built in multi channel analog to digital converter which is used to monitor all the 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 is provided for remote monitoring and is found on the back of the Alp
10. that this be done for any installation both fixed and at an expedition or contest site If you have any questions regarding engineering your 8406 into your amateur radio station please visit our online technical support website at www rfconcepts com The below calculations are taken with the RF Exposure calculator located at http hintlink com power_density php Three representative calculations are presented below Two safe distances are represented The first is a controlled area A controlled area is where a person knows the radiation levels and exactly how long they can be in the area before having to leave the area for a specific period of time The second is an uncontrolled area An uncontrolled area is generally where pedestrians may not know they are in an exposure area and as a result this area the radiation levels must be below a point where a person may remain indefinitely 14 Wave Vertical Antenna 14 Interpretation of Results 1 The power value entered into these calculations should be the average power seen at the antenna and not Peak Envelope Power PEP You should also consider feedline loss in calculating your average power at the antenna 2 If you wish to estimate the power density at a point below the main lobe of a directional antenna and if the antenna s vertical pattern is known recalculate using the antenna s gain in the relevant direction 3 Please also consult FCC OET Bulletin 65 Supplement B
11. the amplifier in the event of grossly excessive plate current or fault in the high voltage circuitry The relay will not prevent tube or other damage due to either short or long term overdrive or improper tuning It is the operator s responsibility to ensure safe tuning drive and general operating conditions Should the over current relay trip remove AC power from the amplifier then determine and correct the cause of the trip before turning the 8406 on again This hard fault trip circuit does not rely on the microcontroller for it s operation and will protect the amplifier even if the processor has been damaged or is malfunctioning 6 4 5 Idling Plate Current and Electronic Bias Control EBS Idling plate current of the ALPHA 8406 is approximately 350 to 400 mA during full power transmission A detector senses RF drive and reduces plate current to 30 50 mA during pauses in speech and key up intervals thus substantially reducing average power supply loading heat generation and wasted energy 6 4 6 RF and Mistuning Protection The ALPHA 8406 s exclusive circuit senses the beginning of any RF arc in for example a TUNE or LOAD variable capacitor and automatically switches the amplifier to standby within a few milliseconds This system has virtually eliminated RF arc damage in current ALPHA amplifiers The system similarly detects severe miss tuning of the 8406 and if drive exceeds about 25 W switches the amplifier to standby The
12. 25 watt input trip threshold permits safe tune up at low power levels without aggravating and unnecessary trip outs 6 5 Standard Maintenance Tasks 39 The amplifier interior particularly the high voltage area should be cleaned with a vacuum cleaner and a soft bristle brush frequently enough to prevent visible accumulation of dust In extremely dusty conditions it may be advisable to secure a thin air filter of the type used for window air conditioners across the air intake on the rear panel There are no user accessible lubrication points in the amplifier Do not apply oil or grease to any of the components The exterior of the ALPHA 8406 may be cleaned with a mild household liquid detergent Do not use chemical solvents as these may severely damage the front panel or cabinet finish Never use an abrasive cleaner The amplifier should be cleaned at least once a year and all dust should be removed This includes blowing out the cooling fins in the 4CX150SOB Tetrode 40 7 Troubleshooting Hints 7 1 Normal Troubleshooting Amplifier must be plugged in to the AC mains for 5 seconds before turning on the front panel AC switch 8406 will not turn on nothing happens when ON switch is pushed 1 External AC wiring fuse or circuit Check amp correct wiring replace fuse or breaker may be open reset circuit breaker 2 Amplifier cover is not in place or properly secured cover safety interlock is open 3 Fuse F1 F4 open or mi
13. ERATE mode unless the OPER STBY switch has been placed in the STBY position This 4 second period can be shortened by toggling the OPER STBY switch 31 While the FAULT LED is flashing the Ip and HV LED s are used to indicate which of the four fault conditions caused the amplifier to enter fault mode Fault type 1 Neither Ip nor HV LED s are lit Output relay did not close This fault will rarely be encountered but if it is it must be investigated further immediately as continued operation with this fault could cause additional damage to the amplifier Fault type 2 Ip LED is blinking This indicates that the plate current in the tubes exceeded 1 5 amps This could be caused by the amplifier being mistuned or by overdriving the amplifier If neither of the above is the case then a problem in the bias control circuitry may be indicated Fault type 3 Both Ip and HV LED s are blinking This indicates that the gain of the amplifier has fallen below 10 dB This is an important safety feature of the amplifier as many different problems in the amplifier or with its operation can be detected as a drop in gain To avoid this fault occurring while the amplifier is being tuned up the gain fault detection is disabled when drive power to the amplifier is below approximately 20 watts This allows correct initial amplifier tuning to be achieved before going to full power Fault type 4 HV LED is blinking This indicates a reflected power fau
14. Preliminary ALPHA 8406 6 Meter VHF LINEAR AMPLIFIER OPERATING MANUAL eer 70 ty My TUNE wo o ssl BRS mN Fy a HF LINEAR AMPLIFIER aiy Men Ze 20 hy 2 wily S T p lt 2010 RF Concepts Inc 634 S Sunset St Longmont Colorado 80501 Phone 303 4739232 All rights reserved Specifications subject to change without notice Rev 1 2 December 2010 Index Specifications Introduction Quick Start Information Station Engineering Considerations Unpacking and Preparation Theory of Operation Operations and Maintenance Trouble Shooting Hints Glossary 2 31 41 45 Specifications 8406 6 Meter Amplifier Frequency Input drive Level Power Output SWR Tolerance Duty Cycle Tubes Inter Modulation Level Harmonics Mode of Operation Input AC Voltage AC Current Input Impedance Output Impedance RF Connectors Cooling Size Weight T R Relay Tuning Display Interface Protection RF Bypass Level 50 54 MHz 50 Watts Nominal 1500 watts 3 1 100 4CX1500B 34 dB minimum Two Exciter 72 dBc CW SSB FM 100 240 Selectable lt 13 5mps 240 VAC 1500 watts 50 Ohms 50 Ohms N Female Forced Air 17 3 W x 7 H x 21 0 D Including Fan Space 70 Ibs 31 8 kg Vacuum QSK Manual Bargraph LED USB Against all common faults Less than 200 watts This amplifier meets or exceeds all technical specifications listed ab
15. citer Drive Correctly Set Section 6 1 1 __ Amplifier Tuned to Antenna System Section 6 3 6 10 3 Station Engineering Considerations 3 1 Overview 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 This section provides a few hints for important operational considerations but it is recommended that the user also consult a good source of general information such as The Radio Amateur s Handbook by the ARRL especially if this is the first high power amplifier you have used 3 2 AC Power Source This amplifier runs best when powered by a 200V 240V AC circuit If you do not have a 240V AC outlet in your shack you will need to get a licensed electrical contractor to install one A minimum of a 20 amp capacity is required A 20 amp breaker on your 240V circuit is sufficient There are many styles of plugs some of which are country specific For this reason the amplifier is not shipped with a power plug Select a location for the outlet as close as possible to where you expect to operate the 8406 If you are not sure or contemplate moving the amplifier you may choose to get a second outlet installed at the same time Ask your contractor for two or three matching plugs during installation as there are several styles of connector available Ask the contracto
16. d drive to maintain 1 500 W is steadily increasing Problem Correction 1 If the amount of drive required to maintain 1 500 watts is steadily increasing this is an f tubes need replacing indication that the tubes are probably aging Contact Alpha Customer Support to see if 44 8 Glossary The following terms are used in this manual Detailed explanations may be found in various publications including the ARRL Handbook AB1 Modulation class AB1 Provides good linearity in push pull configuration AC Alternating current ALC Automatic Level Control ampere Current measurement ARRL American Radio Relay League AWG American Wire Gauge CW Continuous wave dB Decibel EBS Electronic bias switching Exciter The radio that provides RF drive for the 8406 to operate FCC Federal Communications Commission FM Frequency modulation FSK Frequency shift keying HF High frequency 3 to 30 MHz HV High voltage Hz Hertz Ip Idling plate current kV Kilovolts kVA Kilovolts ampere kVA 0 8 kilowatts kW Kilowatt LED Light emitting diode LV Low voltage mA milliAmpere MHz Megahertz OPR Operate PSK Phase shift keying A digital modulation scheme QSK Quick shift keying In this CW transmitting mode the transmitter is only on for the duration of each dot or dash and switches to receive between each RCA Radio Corporation of America Also a type of interconnecting plug RTTY Radio teletype SSB single side band
17. erating into a 1 1 SWR This power level should be reduced accordingly for a higher SWR Any power level more than this may damage the RF switching relays in the 8406 33 6 2 Transceiver Connections The Alpha 8406 relay jack has approximately 12 V on it When pulled all the way to ground a current of 10 mA flows Consult your transceiver manual for additional information on how to connect to an external amplifier 6 3 Initial Setup and Tuning 6 3 1 Control Functions The following chart shows the controls that allow you to adjust and monitor the amplifier BAND Used to select amateur band desired in MHz Sets output tank circuit to resonance within each band Higher frequencies tend to tune toward the 0 end of the dial scale while lower frequencies tend to tune further toward the 100 end Sets amplifier plate loading and determines the power level at which best efficiency and linearity are achieved In general loading is heavier at greater scale settings Higher frequencies tend to load more toward the 100 end of the dial scale and lower frequencies toward the 0 end 6 3 2 Tune Up The objective of tune up is to adjust the amplifier and the drive applied to it to obtain optimum efficiency and linearity at the desired output power Any linear amplifier must be adjusted for optimum efficiency and linearity at each specific power level If operation at higher power is then attempted without appro
18. ha 8406 The USB driver for the amplifier is provided on the CD shipped with the unit or can be found on the Alpha website at www rfconcepts com 5 8 Display Board The display board uses a MAX7219 LED driver chip It receives data from the controller via an SPI interface It contains a regulator to drop the 12 V to 5 V for the display 5 9 T R Board The T R board contains the input and output relays as well as the input power detection and output directional wattmeter The voltages from the detector are connected to the control board There is a trimmer capacitor on this board that is adjusted with the amplifier operating into a good 50 ohm dummy load The capacitor is rotated to minimize the reflected power voltage The board also has a static protection inductor on the RF output for 50 54 MHz operation This is located between the PCB and the flange of the output connector 5 10 Center Partition Board This contains the RF decoupling circuit on the B line as well as the crowbar safety circuit This safety device consists of a piece of spring metal which shorts out the B line when the top cover of the amplifier is removed Do not defeat this safety circuit It is placed there for your protection 29 30 6 Operation amp Maintenance The ALPHA 8406 is extremely easy to operate but failure to carry out each procedure exactly as described in this manual is likely to lead to amplifier damage which is not covered unde
19. ha 8406 then the considerations in section 4 2 3 should be taken into account High Voltage and Tube Life At the high end sometimes encountered when using poorly regulated generators the plate voltage and tube heater voltage may be too high If voltages above 250 volts are applied for any length of time the lifetime of the tubes may be reduced If this is your situation the first line of defense is to contact your utility company and ask if they can reduce your line voltage If this is not possible you may 21 want to consider placing your own step down transformer in line between the AC outlet and the amplifier If this is necessary a transformer with at least 4 kVA rating is required due to the nature of the current waveform in the primary Another choice for voltage control a ferro resonant voltage regulator is an expensive solution but is a good way to stabilize primary voltage Note If you intend to operate the amplifier on any of the 90 130V settings the two lower 2 amp fuses on the rear panel will have to be changed to 5 Amp to allow for the increased in rush current RF Input FIGURE 4 2 1 Amplifier Interior Output Tank Circuit 4CX1500B Tube Deck Shielding Output RF Connector Cooling Fan Low Pass Filter Input RF Connector HV Safety Switch AC Transformer Molex Air Inlet Input AC safety Switch HV AC Transformer Transformer Relay and AC tap PCB 22 Chassis AC Fuses AC Cord USB Input Grou
20. he amplifier is warming up Leave the switch in the Ip position during amplifier warm up The Wait LED will be blinking about twice per second indicating that warm up is still in progress The FAULT OPER and STBY LED s should not be illuminated 35 CAUTION EXHAUST AIR MUST BE DETECTABLE FROM TOP VENT If exhaust air is not coming from the top vents TURN OFF the amplifier immediately and verify that the exhaust chimneys are properly positioned over the tubes When the warm up delay is complete the WAIT LED will extinguish and the OPR or STBY lights will stop blinking Put the OPR STBY switch to OPR and the Alpha 8406 is now ready Frequency TUNE LOAD 50 20 25 51 28 10 52 40 5 53 99 58 0 Each ALPHA 8406 shipped from our factory will include an individual table showing the tune and load settings we used to achieve full output power on that amplifier into an AP 2100 a 50 ohm dummy load These settings will vary from those in the manual depending on your station setup CAUTION If at any time in the following procedure the amplifier fails to respond as described remove drive immediately and turn the OPR STBY switch to STBY Verify all connections and cables turn the amplifier switch to OPR and proceed with the tuning procedure Alpha Amplifiers recommended tune up procedure Tune for Maximum Efficiency Your Alpha 8406 is most easily tuned with the multimeter switch in the efficienc
21. he amplifier or its power tubes In most cases when one of the protective functions is tripped the amplifier will go to Standby 1 3 Shipping Information The Alpha 8406 amplifier ships in two heavy duty double cardboard cartons One carton 5 holds the power transformer and weighs 43 1b 20 kg and the second carton contains the amplifier and weighs 50 1b 17 kg Alpha recommends that you retain the cartons after installation in the unlikely situation that you need to ship the unit later Contact RF Concepts at 303 473 9232 for shipping advice and assistance 1 4 Safety Information Installation and Operation e Make sure the Alpha 8406 is located where there is good air circulation all around and on top of the cabinet The unit may become hot during operation e The Alpha 8406 weighs approximately 70 pounds when the transformer is installed Use proper lifting techniques and two people when moving the amplifier Note that amplifier should NEVER be transported with the transformer in place e The Alpha 8406 is designed to meet international safety standards and FCC regulations However one should always remember that the equipment works with high voltages that can be LETHAL This operating manual holds information cautions and warnings that must be followed to ensure safe installation and operation Read Chapter 1 before attempting to unpack or operate the Alpha 8406 amplifier Warnings What Not to Do e Never open the
22. ially fatal electric shock and or severe damage to the ALPHA 8406 and other equipment always use an AC plug that is appropriate for the primary mains voltage current rating and configuration NEVER use 120V type plugs and power receptacles for 190 250V circuits ALWAYS use grounding type AC connectors which conform to local codes and ensure that the green wire in the Alpha 8406 power cable is wired only to the AC mains safety ground or to neutral as may be necessary with a 240V circuit configured 120V N 120V without a separate ground commonly found in the US The green conductor in the power cord is wired to the ALPHA 8406 chassis It MUST be connected only to the power source safety ground or neutral The black and white power cord wires connect 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 4 2 4 Important Information about Operation from 90 130V AC 20 Electrical power equipment will draw twice as much primary current from 120 V mains as from 240 V mains Therefore operating the ALPHA 8406 on a typical 120 V 20 Amp household circuit without exceeding the 20 A circuit rating will limit maximum peak power output to about 600 1000 W Maximum possible RF output power for any particular primary AC voltage and current capacity may be estimated as P max
23. k 24 into the transceiver and cause severe signal distortion 4 4 2 Replacing the Amplifier Cover Replace all attachment screws Use only the 6 32 screws supplied with the amplifier and do not tighten any of the screws until all are started Do not attempt to operate the amplifier with the cover removed or only placed back on the unit without the attachment screws This WILL cause damage to the Alpha 8406 and may also lead to injury or death to the operator 4 5 Amplifier Station Interconnections Once the power transformer is installed properly configured and the cover replaced place the amplifier in its operating position The amplifier with the transformer installed is heavy so you may need assistance to safely move it Make sure it is placed on a stable surface and that there is sufficient space to the rear sides and top to allow good air flow and safe placement of cables 4 5 1 Coaxial Cable Types amp Connectors Connect the transceiver RF output to the ALPHA 8406 RF INPUT connector with 50 ohm coaxial cable RG 58C U or equivalent Coaxial cable from the 8406 RF OUTPUT connector to the antenna should be RG 8A U RG 213 U or LMR 400 ALC cable is not interconnected when used with a modern transceiver 4 5 2 T R Control Cable The Alpha 8406 has a full break in vacuum relay QSK system requiring only the normal interconnection when used with a modern QSK transceiver The Alpha 8406 requires a contact closure short circuit
24. lt The 8406 is set up to trip when the reflected power exceeds approximately 250 watts At 1 500 watts output this would represent VSWR fault The fault type codes above are also reported in the amplifier telemetry data via the serial or USB ports on the rear of the amplifier If the tube current exceeds about 2 5 amps the amplifier is shut off completely that is the AC is shut off The ON OFF switch will need to be used to put the amplifier back on line To avoid problems wait at least 20 seconds after this occurs before attempting to put the amplifier back on line If the amplifier trips again immediately investigate and cure the problem before attempting to turn the amplifier on again Repeatedly hitting the ON switch when the amplifier trips out is likely to result in severe damage to components in the amplifier If a hard fault trips the amplifier all the way OFF wait at least 20 seconds before turning the amplifier power on again If you are certain that you have taken care of the problem that caused the fault you may turn the amplifier back to operate and proceed with use 32 6 1 3 High SWR Considerations On any frequency where your antenna VSWR exceeds 1 5 1 it s important to carefully tune the ALPHA 8406 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 output of the Alpha 8406 Nevertheless if the system SWR is below 2 1 the
25. nd FIGURE 4 2 2 Amplifier Rear 23 41 0 Eg J20 J21 J22 J23 Flying lead attachment points Figure 4 3 AC Power Setting Input AC tap settings can be made by moving the flying lead to the marked AC spade posts marked in the appropriate voltages The proper taps must be made before the AC power is applied When making changes make sure the amplifier is unplugged Never use a tap other than the proper voltage or damage to the tubes and amplifier will result With the top cover removed the primary voltage taps are located on the top of the Mains Board which is between the transformer and the front panel There is a row of 5 fast on connectors J1 through J5 and a flying jumper connector which mates with them See Figure 4 3 above There are 5 nominal primary voltages which cover all the line voltages normally encountered around the world Selecting the appropriate tap for your situation will optimize amplifier performance safety and lifetime The nominal mid range voltage for each tap is printed on the Mains Board circuit board These voltages are 100 120 200 220 and 240 Volts The acceptable line voltage for each tap is the center voltage plus or minus 10 Volts One of these taps is suitable for any of the nominal line voltages encountered worldwide CAUTION When using any high power amplifier failure to connect ALL station equipment to a good common ground may allow RF feedback to lea
26. nd antenna Correct 200 W impedance mismatches 3 Exciter output poorly controlled Consult exciter s User s Manual for assistance on controlling output 42 Receive signals disappear or are severely attenuated when switching from STBY to OPR 1 RELAY T R control cable from Check T R control cable to make sure it is transceiver is shorted switching properly Replace if needed 2 Transceiver locked in transmit Make sure transceiver is properly switching between transmit and receive See transceiver s User s Manual for assistance Plate current indicated when amplifier is in STBY or receive 1 4CX1500B tube heater to cathode Contact Alpha Customer Support leakage or short ae De MASSUER piasek Contact Alpha Customer Support 43 Distorted SSB signal Grid bias is unexpectedly decreasing 1 Excessive RF drive from transceiver Decrease drive from transceiver Re check and or insufficient amplifier loading amplifier tuning 2 Coaxial connector coax feed line antenna feed point balun tuner or antenna trap arcing on voice peaks 3 RF feedback from antenna into Make sure all power cords microphone and transceiver via the transceiver power cord key cables or other cables are properly microphone or key cable or other shielded and grounded unshielded station patch cables 4 Poor station RF ground Be sure the amplifier and transceiver have a proper RF ground Correct if necessary Require
27. on transmit from its RELAY jack center pin to chassis This function is supplied by the transceiver usually from a dedicated relay that is normally open in receive and closed in transmit Shielded wire should be used for the T R control cable The Alpha 8406 end must be fitted with a common phono RCA type plug and the other end with a connector suitable for the transceiver The T R relay contact must close before application of RF drive Modern transceivers have the proper time delay between key up and the start of the transmitted signal to allow the Alpha 8406 to follow the CW keying If a T R timing problem is suspected connect the CW keyer to the RELAY jack on the Alpha 8406 and connect a cable from KEY OUT on the amplifier to the keying input of the transmitter 25 4 5 3 ALC The Alpha 8406 does not generate or use ALC voltages to control an exciter For proper operation the exciter transceiver should have its power output set so as not to over drive the amplifier input Today s modern transceivers have very good power output limiting As a rule ALC is not needed if the transceiver is less than 15 years old Should your transceiver be older then the power output should be reduced so voice peaks will not overdrive the transmitter under any modulation condition 26 Theory of Operation 5 1 Theory of Operation Overview The Alpha 8406 uses a tetrode vacuum power grid tube 4CX1500B as the amplifying devices The main power suppl
28. or dust removal Too ensure adequate cooling make sure the top and rear of your amplifier have at least 3 of clearance to allow unobstructed airflow md Make sure the exhausted air OMZ Ti cannot be recirculated back PA S ALPHA 84 i TIRET ET i e A HRAL K wile me into the amplifier air intake on ow y RUU gy 12 3 4 Antennas Many antennas that are suitable for general use are unsuited for operation with a full 1500 W of power At this power level in a 50 ohm circuit the RMS current is 5 5 amps and the peak RF voltage is 387 volts With a 2 1 SWR these values double to 11 amps and 775 volts The actual voltage and current at various points in or on your antenna may actually be many times these values On a simple dipole with sharp wire ends corona localized ionization can easily occur Corona can and has led to fire in nearby objects Traps in beams and verticals can heat up significantly during high power operation Instances of melting or flashover of traps have occurred in many installations where insufficient thought has been given to their ratings If an antenna has been deployed for a long period of time it may be worth taking it down for inspection prior to full power operation 3 5 Coax and Connectors The importance of a well constructed feed line system cannot be overstated After all the purpose of the amplifier is to provide approximately 2 S units 12 dB of improvement in your radia
29. ove 1 Introduction 1 1 General Description Congratulations on your purchase of a professional quality Alpha 8406 amplifier With proper installation and care you can expect to enjoy your Amateur Radio hobby with this amplifier improving your signal for many years to come Please study this manual carefully before operating your amplifier for the first time The Alpha 8406 is a self contained manual tune VHF linear power amplifier capable of continuous operation at 1500 W peak power output on SSB keyed CW SSTV RTTY digital modes or FM with no time limit See our web site at www rfconcepts com or call 303 473 9232 for further information 1 2 Amplifier Capabilities CAUTION It is extremely important to thoroughly review the Installation and Operation sections of this manual before attempting to us the Alpha 8406 Failure to do so could result in serious damage that may not be covered under warranty e Continuous RF Output The 8406 is capable of 1 5 kW continuous RF output on all commonly used modes and on any authorized amateur frequency from 50 54 MHz e Compatibility with popular amateur transceivers and exciters The 8406 requires approximately 50 65 W peak RF drive for 1 5 kW output e Capable of full CW break in QSK and all digital modes when used with any appropriate transceiver e Protective functions are built in The control system incorporates protective functions that minimize the probability of accidental damage to t
30. priate readjustment the result will be flat topping also known as splatter and usually excessive amplifier grid current If operated at a much lower power level than it has been adjusted for the amplifier s efficiency decreases considerably Recommended practice is to tune first into a dummy load or artificial antenna then connect the antenna and make any slight final adjustments that may be needed 6 3 3 Grid Current Information The ALPHA 8406 operates in Class AB1 when delivering maximum output power consistent with excellent linearity A small amount of grid current flows and the green GRID MIN LED illuminates as drive approaches the optimum level The green GRID LED will flicker on SSB voice peaks and illuminate under CW SSTV RTTY carrier conditions 34 As overdrive approaches grid current increases rapidly and the red GRID MAX LED illuminates At maximum output and efficiency the red LED lights dimly full illumination of the red LED indicates overdrive and must be avoided If the red LED lights up before the desired value of plate current and or against grid current fluctuations On SSB optimum output consistent with good linearity occurs when the green forward LED s illuminates on most voice peaks and the red LED flickers dimly on only the highest peaks Excessive grid current results from overdrive and or inadequate loading The solution is to restrict drive and or increase amplifier loading The 8406 s 4CX1500B tube
31. r to measure the voltage and record it so you can set the line voltage tap on the 8406 appropriately If possible have the contractor measure the line voltage with a 10 amp current draw and use this value for setting the transformer tap The Alpha 8406 can run when connected to a 120V AC outlet However you WILL NOT achieve full legal limit output in this case If the amplifier is connected to a 120V AC outlet you should not expect more than 1000 W output 3 3 Air Flow 11 It is critical that airflow around the Alpha 8406 remain unimpeded at all times Keep the top of the amplifier clear of any restrictions If you are mounting the amplifier in a console make sure that the exhaust air is properly and fully removed from the console Figure 3 3 Minimum clearance for proper airflow e Keep top tube exhaust clear e Keep rear intake clear Poorly designed consoles can result in outlet air being drawn back into the amplifier air intake and recirculated thus getting hotter and hotter and resulting in degraded amplifier performance or even failure If you are designing your own console consider putting in additional fans and or ducting to deal with waste heat Try to minimize the possibility of dust or other contamination getting drawn into or falling on the amplifier It is also advisable to periodically at least annually clean the dust out of your amplifier for continued flawless operation RF Concepts recommends the use of compressed air f
32. r to be in Compliance yes yes The above calculation represents a four element beam at 35 feet above the ground feed with 1400 watts of power At 100 feet most of the pattern gain is still over the person standing at 100 feet 17 4 Unpacking amp Preparation 4 1 Unpacking Inspect both boxes for physical damage Save all packing material for possible future use Contact 303 473 9232 if shipping damage is found Carefully unpack the amplifier and transformer Carefully remove the amplifier and place it on a workbench or table where you can install the power transformer 4 2 Installing the Power Transformer It is recommended that the power transformer be installed when the amp is at or near the place it is to be used The chassis of the 8406 is designed for the mechanical loads it experiences when the amplifier is on a flat surface with the tilt bail up or down If the amplifier is tilted too far such that the transformer is cantilevered or hanging out to any degree the chassis of the amplifier can distort If the amplifier is moved even if only from one site to another locally remove the transformer to avoid the possibility of damage CAUTION Do not operate amplifier without the cover in place and all cover screws installed Do not operate the amplifier without a good ground connection on the rear panel ground terminal Make sure all RF cables have a solid ground shield in place WARNING The transformer is very
33. r warranty Damage to other station equipment may also result 6 1 Before Operating Your Alpha 8406 6 1 1 Setting Input Drive You must set the transceiver output power properly Virtually all damage to has resulted directly from severe overdrive The ALPHA 8406 requires about 50 W drive for full rated output Damage caused by applying several times rated drive power to the ALPHA 8406 will not be covered under warranty Fortunately most modern transceivers maintain quite consistent output from band to band and mode to mode when set up properly CAUTION Setting only the transceiver POWER or RF PWR control IS NOT SUFFICIENT Several popular transceivers can generate RF spikes of 200 300 W Make sure your transceiver does not produce over wattage spikes Some transceivers are capable of 200 watts out Male sure the transceiver power output is adjusted correctly 6 1 2 Dealing with Faults The ALPHA 8406 faults into STBY or OFF when unsafe operating conditions occur This is shown when the amplifier changes from the OPR LED being ON to the Fault and STBY LED s If the 8406 encounters unsafe operating conditions it enters a protective Fault mode When this happens the tubes are biased off and the relays are placed in the bypass mode so that RF from the radio goes directly to the antenna The FAULT LED on the front panel will flash on and off for a period of about 4 seconds after which the amplifier will attempt to go back into OP
34. read on the 0 to 1 5A scale for 1500W output and input drive should not need to be more than about 70W Plate current Ip is the most useful parameter to monitor on the multimeter bargraph during normal operation of the amplifier 6 4 Normal Use 6 4 1 Tube 37 The 4CX1500B tube used in the Alpha 8406 is supplied as a selected and tested tube The tube is very rugged and normally operates with a large margin of safety The tube should provide outstanding service for many years if not damaged by abuse such as overdrive or blockage of cooling airflow Allow at least three to four inches 10 cm of unobstructed clearance around the air intake and exhaust areas Stacking equipment on top of the amplifier is not recommended Never allow key down plate current to exceed 1 5 A for more than one or two seconds If you do and a plate current trip occurs it will automatically reset in about 4 seconds if the amplifier is returned to receive key up Never allow the red GRID LED to stay brightly illuminated for more than a second Frequent on off AC power cycling may shorten the tubes life It is less stressful to leave equipment in standby for several hours than to cycle power repeatedly on off on off over the same period 6 4 2 Interlocks The ALPHA 8406 is equipped with a cover interlock switch intended to remove primary power from the amplifier and a crowbar to short circuit the high voltage to chassis whenever the cover is lifted
35. ssing Check Check and replace any blown fuses with fuses with an ohmmeter fuses of the same size 4 Step start resistor open Check resistor If damaged replace Make sure cover is replaced and all screws securely inserted Amplifier turns on but no HV is indicated by the multimeter LED bargraph Set Multimeter switch to the correct 1 Multimeter selector switch in wrong ws position position e g Ip 2 Possible HV circuit fault oS a 3 HV sampling resistor in power supply damaged Check power supply wiring and connectors 4 Transformer plugged into power supply to be sure input and output connectors are incorrectly set properly and the voltage taps have been set properly 41 Amplifier turns on but no multimeter indication other LED bargraphs are operative 1 Low voltage power supply problem Amplifier turns on but time delay will not complete WAIT LED does not turn off Problem Correction 1 Defect or damage in timing circuitry on Contact Alpha Customer Service control board Amplifier turns on time delay completes but amplifier will not transmit Problem Correction 1 Open T R control line from transceiver to Contact Alpha Customer Service RELAY jack Amplifier transmits but red GRID LED illuminates often 1 Amplifier overdriven or under loaded f Reduce transceiver output and or increase amplifier loading 2 Load VSWR reflected power exceeds Check output cabling a
36. tanding 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 5 3 Output Tank Circuit The output tank circuit of the Alpha 8406 is designed to provide reliable high efficiency low distortion performance in a very compact volume The basic topology is pi C which provides harmonic attenuation adequate to meet the requirements of all countries globally that permits power outputs of 1 500 watts The amplifier is designed to operate with only a single tube in order to reduce tube capacitance 27 5 4 Tube Deck The tube deck is a mechanical assembly built around the tube deck PCB The tube deck PCB has the tube socket mounted on it as well as those critical circuit elements that need to be in close proximity to the tubes The tube socket contains integral screen grid grid 2 RF bypass capacitors Also on this PCB is the input bypass relay This relay is under microprocessor control and in one position switches the input RF to the tube and in the other it switches the input RF to the tube matching circuit The tube is operated as a swamped grid tetrode design The tube grid is tied at RF to a 50 ohm swamping resistor which 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 impedance represented by
37. ted signal All too often installation problems are encountered where cheap poor or under rated coax and connectors are used These often are responsible for at least one S unit of degradation This means you could have bought a 375 W amplifier and achieved the same radiated signal by buying good quality feed line components Use the lowest loss 50 ohm coaxial cable you can obtain Use new clean connectors installed according to the manufacturer s recommendation Clean the connectors after soldering them and before mating them with the amplifier Make sure any excess solder is removed from the connector likewise remove any fragments of braid etc Never use old coax which may have had moisture penetrate under the jacket Support the coax frequently using non compressive clips so that it does not hang or stretch under its own weight Avoid sharp or kinked bends most manufacturers will specify a minimum bend radius for their product Make sure the connection from feed line to antenna is waterproof Provide for disconnection of the feed line when it is not in use this protects against damage caused by power surges and lightning strikes which are not covered under the amplifier warranty 3 6 RF Safety 13 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 RF Concepts strongly recommends
38. the Amateur Radio supplement to FCC OET Bulletin 65 It contains a thorough discussion of the RF Safety regulations as they apply to amateur stations and contains numerous charts tables worksheets and other data to help determine station compliance The above calculation is for a vertical ground plane antenna at 20 feet elevation feed with a short piece of coax with the station located just below the antenna Minimum safe distance is represented in Red The antenna is located at ten feet above ground 6 Element Beam at 100 Feet 15 The above calculation represents a 1400 watt RF signal feed into a 6 element yagi located 100 feet above the ground As a result the down ward lobe 100 feet from the base of the tower is at a 45 degree angle The RF measured is out of the main lobe and as a result the antenna has a negative 10 dB of gain over the normal 12 dBi gain if the person was standing in the main pattern lobe 16 3 Element Beam at 35 feet Average Power at the Antenna 1400 watts Antenna Gain in dBi 5 dBi 100 feet Distance to the Area of Interest 86 AS meres Frequency of Operation 50 MHz Yes Are Ground Reflections Calculated Estimated RF Power Density 0 0613 mW em Controlled Uncontrolled Environment Environment Maximum Permissible 1 005 0 205 Exposure MPE mW cm mW cm 55 3913 feet Distance to Compliance 24 7994 feet 16 8833 From Centre of Antenna 77 5589 meters ant r Does the Area of Interest Appea
39. tting up your Alpha 8406 amplifier If you already have a well designed shack and have used an amplifier before please review the items below to make sure you have considered all the critical items for proper installation and operation If you are using an amplifier for the first time please skip this section and go to sections 3 4 and 5 for a more detailed explanation of how to set up your shack for maximum safety and operating enjoyment If you have installation questions do not hesitate to contact Customer Support We much prefer to address questions prior to power up 2 2 Station Engineering Considerations Checklist Make sure you have properly addressed the following concerns Section 2 3 below before installation of your Alpha 8406 amplifier If you are unsure of any of these items please read the noted sections carefully 2 3 Preparation _ 240V AC Power in shack Section 3 2 __ Amplifier placed with proper airflow Section 3 3 __ Antenna ready for 1 500W Section 3 4 __ Adequate RF cabling Section 3 5 __ RF Exposure Safety Section 3 6 2 4 Unpacking Unit Checked for Damage __ Transformer Installed Section 4 2 1 4 2 2 __ Power Cord Connector Attached Section 4 2 3 __ AC Primary Voltage Set Section 4 3 6 ___ Amplifier Grounded Properly Section 4 4 1 __ Amplifier Cover Replaced and Secured Section 4 3 6 2 5 Operation __ All Exciter Interconnections Set Section 6 2 __ Ex
40. y position Efficiency should be in the 55 59 range the efficiency scale ranges from 50 to 70 You should watch the efficiency reading during long transmissions and peak it for best performance 36 Dip and Load Method Tuning up for Operation at 1 500 W RF Output Preset BAND TUNE and LOAD controls to the nominal positions given in your amp s specific tune up table or Table 6 3 Note Final TUNE and LOAD settings will vary with the operating frequency antenna characteristics and power level 1 Please limit the transceiver drive to about 60W for tuning up and operating the amp Set multimeter to Ip Plate Current Set TUNE and LOAD controls to numbers indicated in the tune up sheet originally included with the amplifier Key radio with 10W drive and adjust TUNE control for a peak in RF out which should be at the same point as a dip in Ip Increase drive to get 500W output going back and forth between the TUNE and LOAD to peak the RF output If more output is desired increase drive from radio slightly increase LOAD for a peak in RF out then peak RF out with TUNE control Increase drive to get 1000W output going back and forth between the TUNE and LOAD to peak the RF output If more output is desired increase drive from radio slightly increase LOAD for a peak in RF out then peak RF out with TUNE control When the amplifier is tuned correctly on 6 Meters the Ip should range between 0 9A and 1 1 A
41. y 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 7 circuit cards in the amplifier 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 8406 amplifier includes a 5 V power supply that is mounted behind the front panel Any time the amplifier is plugged into the mains power this 5 V supply is active and there is power to the micro controller on the main control board This feature allows the amplifier to be turned on or off remotely as well as remote monitoring and debugging though a USB cable connected to a computer 5 2 Tubes The amplifier is designed to use the 4CX1500B tetrode tube The amplifier design uses this tube well within ratings The tube is operated in Class AB1 with a plate voltage of 3 400V nominal full output key down a grid 1 voltage of 50 to 60 volts and a grid 2 voltage of 230 volts The tube has an inductance resistor in series with the cathode This resistor stabilizes the tube bias and provides negative feedback which improves linearity and hence IMD performance Electronic bias switching EBS increases the negative grid 1 voltage in pauses in speech or between Morse code elements This reduces the s

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