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Summary of Contents for RF Concepts Alpha 8406
- Page 1 Preliminary ALPHA 8406 6 Meter VHF LINEAR AMPLIFIER OPERATING MANUAL © 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...
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Page 2: Table Of Contents
Index Specifications Introduction Quick Start Information Station Engineering Considerations Unpacking and Preparation Theory of Operation Operations and Maintenance Trouble Shooting Hints Glossary... -
Page 3: Specifications
Specifications 8406 6 Meter Amplifier Frequency 50-54 MHz Input drive Level 50 Watts Nominal Power Output 1500 watts SWR Tolerance Duty Cycle 100 % Tubes (4CX1500B) Inter Modulation Level 34 dB minimum, Two Exciter Harmonics -72 dBc Mode of Operation CW, SSB, FM Input AC Voltage 100-240 Selectable... -
Page 5: Introduction
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. -
Page 6: Owner Assistance
1.4 Safety Information – Installation and Operation 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. ... - Page 7 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 ...
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Page 9: Quick Start Information
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. - Page 10 __ 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) __ Exciter Drive Correctly Set? (Section 6.1.1) __ Amplifier Tuned to Antenna System? (Section 6.3.6)
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Page 11: Station Engineering Considerations
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. - Page 12 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.
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Page 13: Coax And Connectors
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. - Page 14 RF fields. This information is available in ARRL publications, FCC printed rules, and on the web. RF Concepts strongly recommends that this be done for any installation, both fixed and at an expedition or contest site.
- Page 15 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.
- Page 16 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.
- Page 17 3 Element Beam at 35 feet Average Power at the Antenna 1400 watts 5 dBi Antenna Gain in dBi 100 feet Distance to the Area of Interest 30.48 metres Frequency of Operation 50 MHz Are Ground Reflections Calculated? 0.0613 mW/cm Estimated RF Power Density Controlled Uncontrolled...
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Page 19: Unpacking And Preparation
4 Unpacking & 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. -
Page 20: Power Cord Connections
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). - Page 21 P max = (V x I ) / 2.3 lineline 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: P o max = (120V x 20A) / 2.3 = 2400/2.3 = 1043 W...
- Page 22 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.
- Page 23 USB Input AC Fuses AC Cord Chassis Ground FIGURE 4-2-2 Amplifier Rear...
- Page 24 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.
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Page 25: Replacing The Amplifier Cover
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. - Page 26 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.
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Page 27: Theory Of Operation
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. - Page 28 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.
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Page 29: Control Board
A USB port is provided for remote monitoring and is found on the back of the Alpha 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... -
Page 31: Operations And Maintenance
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. - Page 32 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.
- Page 33 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 additional RF power loss of an antenna tuner can be avoided by tuning the 8406 into the slight mismatch.
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Page 34: Control Functions
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. -
Page 35: Turning On The Amplifier
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). - Page 36 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”.
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Page 37: Normal Use
“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. - Page 38 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.
- Page 39 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.
- Page 40 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.
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Page 41: Troubleshooting Hints
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. Problem Correction 1) External AC wiring, fuse or circuit Check &... - Page 42 Amplifier turns on but no multimeter indication; other LED bargraphs are operative. Problem Correction 1) Low voltage power supply problem. 2) Defect or damage on control board. 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...
- Page 43 Receive signals disappear or are severely attenuated when switching from STBY to OPR. Problem Correction 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.
- Page 44 Distorted SSB signal; Grid bias is unexpectedly decreasing. Problem Correction 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.
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Page 45: Glossary
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... - Page 46 US – United States. VAC – Volts of alternating current. VDC – Volts of direct current. VSWR – Voltage Standing Wave Ratio...
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