Alpha Power ALPHA 6 User manual

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ALPHA/POWER
by CrossLink, Inc. RF
Power for Communications and Industry
6185 Arapahoe Road,
Boulder, Colorado 80303-1401
[phone] * FAX [phone]

ALPHA POWER PRODUCTS
ALPHA 6
Operating Manual
DISCLAIMER
Information in this document is subject to change
without notice. Information provided by CrossLink
Inc.® is believed to be correct and reliable. However,
no responsibility is assumed by CrossLink Inc., unless
otherwise expressly taken. Companies, names, and
data used as examples are fictitious, unless otherwise
noted.
No part of this document may be reproduced or
transmitted in any form or by any means, graphic,
electronic, or mechanical, for any purpose without the
express permission of CrossLink, Inc. CrossLink, Inc.
may have patents or pending patents, trademarks,
copyrights, or other property rights covering the
subject matter in this document. The furnishings of
this document does not give you license to these
patents, trademarks, copyrights, or other intellectual
property, except as expressly written in any license
agreement form
CrossLink Inc.
6185 Arapahoe Road • Boulder, CO 80303
Phone [phone] • Fax [phone]
Read this entire manual and all other publications
pertaining to the work to be performed before you
install, operate, or maintain this equipment. Practice
all product safety instructions and precautions.
CrossLink, Inc. provides information on its products
and associated hazards, but it assumes no
responsibility for the after-sale operation of the
equipment or the safety practices of the Owner or
User. See Warranty and Notices Appendix.
©Copyright 2001 by CrossLink Inc.
All rights reserved.

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Table of Contents
OWNER ASSISTANCE.................................................................................................................................4
EQUIPMENT SHIPPED.................................................................................................................................4
SAFETY: INSTALLATION AND OPERATION ...............................................................................................5
BEFORE INSTALLING YOUR ALPHA 6........................................................................................................6
AC POWER SOURCE..................................................................................................................................7
ANTENNA..................................................................................................................................................7
COAX AND CONNECTORS..........................................................................................................................8
AIR FLOW.................................................................................................................................................. 8
RF SAF ETY................................................................................................................................................8
TRANSFORMER INSTALLATION (SEE FIGURES 2-4) ................................................................................... 9
INSPECTION OF TUBE & CHIMN EY ............................................................................................................9
AC PRIMARY CONNECTIONS & AMPLIFIER GRO UNDING .......................................................................10
POWER CORD CONNECTIONS — WARNING!..................................................................................... 10
RF GROUNDING ......................................................................................................................................11
COAXIAL CABLE TYPES & CONNECTORS ............................................................................................... 13
T/R CONTROL CABLE .............................................................................................................................13
FIGURE 5: ALPHA 6 REAR PAN EL ........................................................................................................ 14
4.1 Control Functions.........................................................................................................................15
4.2 Tune-up.........................................................................................................................................15
Grid Current .......................................................................................................................................16
ALC .....................................................................................................................................................16
Tune-up Procedure.............................................................................................................................16
4.3 Reflected Power Protection ...................................................................................................17
4.4 Automatic Level Control (ALC) .............................................................................................18
FIGURE 6 – INSIDE TOP VIEW ................................................................................................................. 19
FIGURE 7 – FRONT PAN EL LOWERED...................................................................................................... 20
FIGURE 8 - INSIDE FRONT PANEL...........................................................................................................21
OPERATING AND MAINTENANCE NOTES...................................................................................22
TUBES.................................................................................................................................................22
INTERLOCKS.....................................................................................................................................22
FUSES.................................................................................................................................................23
PLATE OVERCURRENT RELAY.......................................................................................................23
FIGURE 9 - REAR PANEL CONNECTIONS .................................................................................................25
TROUBLESHOOTING HINTS ............................................................................................................26
DESIGN AND CIRCUIT OVERVIEW................................................................................................28
RF Amplifier Section (See Figure 6, 13).............................................................................................28
Power Supplies (Figures 6, 9, 12)......................................................................................................28
SAFETY.................................................................................................................................................29
ALPHA PRODUCTS WARRANTY.....................................................................................................30

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Introduction
IMPORTANT
Critical precaution during installation of your Alpha 6:
While the cover is removed to install the power transformer, make sure that the tube
is properly installed as described below. Failure to do this may cause severe
damage or destruction of the tube. Such damage is not covered under warranty.
General Description of the ALPHA 6 Amplifier
The ALPHA 6 is a self-contained 6m VHF Linear power amplifier capable of continuous
operation at 1500 watts peak power output on SSB, keyed CW, SSTV, RTTY, digital
modes or FM, with no time limit. If periods of “continuous-key-down” carrier operation
will exceed 5 minutes, or if the amplifier is to be operated from 50 Hz mains, the optional
auxiliary cooling fan available from CrossLink must be installed to avoid possible damage
not covered by the warranty.
All shipped, units delivered within the USA and its territories are manually tunable to cover
the entire 6m amateur band from 50-54 MHz.
Specifications, ALPHA 6
Frequency Coverage: Amateur band 50-54 MHz.
Power Output: 1500 watts peak all modes, including SSB, CW and continuous or
modulated carrier. Carrier operation (e.g., A0, RTTY or FM) for more than 5 minutes at or
near maximum rated power requires use of the auxiliary cooling fan accessory.
Drive Power: 50 to 60 watts nominal for rated output.
Power Gain: Nominally 14 dB, a power increase of 25 times.
Input Impedance: 50 ohms nominal, unbalanced; VSWR <2:1.This manual provides all
information necessary to install and operate the ALPHA 6. Schematic diagrams are
available on request, at no charge to owners.
Section
1

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Output Impedance: 50 ohms unbalanced.
MaximumLoad VSWR: 2:1 at full rated power output.
VSWR Trip: Automatic standby when reflected power >250
watts.
Intermodulation Distortion: 30 dB below rated output.
Harmonic Output: <-60 dBc.
Tubes: One Svetlana 4CX1600B ceramic-metal tetrode.
Cooling: Full-cabinet, ducted forced air using cushion-
mounted centrifugal blower.
Automatic Level Control (ALC): Negative from 0, adjustable.
Primary Power: 190-250 or 90-130 VAC nominal, 50-60 Hz,
fused at 20 amperes.
Power Transformer: 3+ kVA with strip-wound Hipersil core.
Protective Functions: Grid and screen current limiting; trip to standby
(automatic reset) for excessive VSWR or
average plate current, RF arc, severe mistuning;
AC off trip for HV fault; primary and step-start
fuses; cover AC interlock and HV crowbar
switches; AC inrush-current limiting (Step-
start).
Status Indicators: STANDBY, WAIT (initial turn-on time delay),
OPERATE and FAULT LEDs.
Metering: Dedicated, full-time LED bargraphs display
forward and reflected rf power; grid current
LEDs; LED bargraph selectable among plate
voltage, plate current, and tune-up functions.
Size: 7.5” H x 17” W x 16.5” D (19x43x39cm)
excluding controls, feet, and connectors.
Weight: 66lb. (30kg) net, 75lb (34kg) ship; two cartons.
Note: CrossLink reserves the right to change design and/or specifications without prior
notice or obligation.
Owner Assistance
Assistance is available from CrossLink Alpha Technical Support at 303.473.9232 x.141,
by fax at 303.473.9660, or by email at [e-mail].
Equipment Shipped
The Alpha 6 ships in two heavy-duty cardboard cartons. One carton holds the power
transformer and weighs 43 pounds; the second carton contains the amplifier and weighs 42
pounds.

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Safety: Installation and Operation
The Alpha 6 is designed to meet international safety standards and FCC regulations.
However, one should always remember that the equipment works with high voltages that
are LETHAL!
This operating manual holds information, cautions and warnings that must be followed to
ensure safe installation and operation. Read Section 1 before attempting to unpack or
operate the amplifier. Failure to perform procedures properly may result in amplifier
damage, fire hazard, or electric shock.
Warnings:
!Never open the amplifier case without unplugging the unit from the wall outlet.
!Never stick objects into holes in the case.
!Never touch an antenna during transmission.
CAUTION
CAUTIONCAUTION
CAUTION –
––
– READ THE MANUAL CAREFULLY BEFORE INSTALLING
YOUR 6.
The ALPHA 6 is extremely easy to install and operate, but failure to carry out each
procedure exactly as described in the manual is likely to lead to amplifier damage
which is not covered under warranty. Damage to other station equipment may also
result.

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Before Installing Your Alpha 6
1. Be careful not to twist or warp the
chassis when handling the amplifier
with its cover removed. Never lift
the chassis by a corner, especially
when the transformer is in place.
Never apply A-C power without the
transformer properly and fully
installed.
2. When installing or removing the
transformer, move carefully and
follow the instructions in this manual
exactly. Insure that all connectors
are properly mated and fully seated.
Don’t force them! Tuck the lifting
handle out of the way so the
interlock can close.
3. Insure that the tube is solidly seated
in its socket with the red silicone
rubber chimney firmly seated against
the chassis.
4. Connect the green conductor in the
Alpha 6 power cord only to the
power source neutral or ground.
Connecting the green wire to a
“hot” line is almost certain to cause
immediate damage. Triple check
your wiring before plugging in!
5. Make sure the primary power tap is
connected to the tap closest to your
actual AC voltage. See manual
section 4.
6. Solidly bond all station equipment
chassis together. Heavy braid, such
as the outer conductor of RG-8/U
coaxial cable, is recommended for
the purpose. This is important for
personal and equipment safety as
well as to avoid RF feedback.
7. Neverinstallcoverscrews longer
than ¼”. Longer screws may
penetrate internal boards or wiring
and cause severe damage. Make
sure each screw hole in the cover is
aligned with its corresponding
captive nut in the chassis before
inserting screws.

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Station Engineering
Considerations
The 6 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 gives a few hints for important things to look
for, 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.
AC Power Source
If you do not have a 220V 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. Select a location for
the outlet as close as possible to where you expect to operate the 6. If you are not sure, or
contemplate moving the amplifier, it may be cheaper to get a second outlet installed at the
same time. Ask your contractor for two or three matching plugs while he is there, as there
are several styles of connector available. Ask the contractor to measure the voltage and
record it, so you can set the line voltage tap on the Alpha 6 appropriately. If he can, ask him
to tell you the line voltage with a 10 Amp current draw, and use this value for setting the
transformer tap.
Antenna
Many antennas which are suitable for general use are unsuited for operation with a full 1500
watts 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: 11 Amps and 775
Volts. The voltage and current at various points in or on your antenna can actually be many
times these values.
On a simple dipole with sharp wire ends, corona (localized ionization) can easily occur.
Corona can (and has!) lead 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 up for a long period of time, it may be worth taking it down for
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“tracking”, replace them. Doubling-up on insulators is also easy to do, and may save
problems. If there is any chance of people or objects coming close to the antenna, take steps
to move it higher, or place barriers so that this cannot happen.
Check the SWR of your antenna. If you have a favorite part of any band you use most often,
consider adjusting the antenna for minimum SWR in this part of the band.
Coaxand Connectors
The importance of a well constructed feedline system cannot be overstated. After all, the
purpose of the amplifier is to provide (coax and connectors continued) approximately 2 S
units (12+ dB) of improvement in your radiated signal. All too often installations are
encountered where cheap/poor/under-rated/old coax and connectors are probably
responsible for one S unit of degradation. This means you could have bought a 375 Watt
amplifier and achieved the same radiated signal by buying good quality feedline
components! Use the lowest loss 50 Ohm coaxial cable you can get your hands on. Use
new, clean connectors installed per the manufacturers recommendations. Clean the
connectors after soldering them, and before mating them with the amplifier. Make sure any
excess solder is removed from the connector, likewise any fragments of braid etc. Never use
old coax, which may have had moisture penetrate under the jacket. Run the coax in straight
lines as much as possible. Support it frequently using non-compressive clips so it does not
hang and stretch under its own weight. Avoid sharp bends (most manufacturers will specify
a minimum bend radius for their product). Make sure the transition from feedline to antenna
is waterproof. Provide for disconnection of the feedline when not in use.
Air Flow
It is critical that the 6 air flow is unrestricted in any way. 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. Poorly designed consoles can
result in outlet air being drawn back into the amplifier air intake and recirculated, getting
hotter and hotter, 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.
RF Safety
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. CrossLink strongly recommends that this be done for any
installation, both fixed and at an expedition or contest site.
If you have any questions regarding engineering your 6 into your amateur radio station, do
not hesitate to call CrossLink Alpha Technical Support.

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PREPARING THE ALPHA 6 FOR
OPERATION
Transformer Installation (See Figures 2-4)
Remove the amplifier top cover to install the transformer. Only one possible transformer
orientation allows mating all its connectors without straining leads. Lift the transformer high
enough to clear the right side chassis lip and move it sideways into the chassis. USE
CAUTION--PROCEED SLOWLY to avoid damaging wires or components. From
underneath, insert the supplied bolts with washers through the clearance holes in the chassis
and into the nuts in the transformer base. CAUTION! Mate transformer connectors
carefully and gently to insure that all connector pins engage correctly and fully.
Inspection of Tube & Chimney
While the top cover is removed, make sure tube is firmly seated in its socket, rubber exhaust
chimney is fully and correctly installed, and anode connector is tightly clamped to tube.
The silicone rubber chimney installed on the 4CX1600B tube is an absolutely essential part
of the cooling system. Make sure the chimney is straight and fully installed so that the
bottom of the chimney is firmly against the tube deck and completely covers the airflow
openings in the deck. Tube cooling air 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.
Section
2

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AC Primary Connections & Amplifier Grounding
Primary voltage taps are selected at the terminal strip numbered “1” to “7” and located on
the mains board mounted on the chassis center divider, left of the transformer. Terminal
number 1 is closest to the rear panel of the amplifier. Connect the two wires labeled “A”
and “B” for the line voltage to be used, as shown in the following table. The two short
jumper wires supplied are not used on 190-250V, but must be connected as shown for
operation on 90-130V mains.
PRIMARY “A” Terminal “B” Terminal Blower* Jumpers
230-250V 4 ** 2** 4 & 2** Not used
210-230V 4 3 4 & 3 for 190 - 250V
190-210V 5 3 4 & 3 operation
110-130V 4 6 4 & 7 1 - 2, 6 - 7
90-110V 5 6 4 & 7 1 - 3 6 - 7
* The blower wires are the 2 black wires marked “4” and “x”, (4 to terminal4, X to 2, 3,
or 7 per table). Optional external muffin fan has 2 black wires, one is connected with
blower wire 4 and the other to the same terminal as blower wire X (2,3,or 7 per table)
** Factory settings.
NOTE: If you intend to operate the amplifier on any of the 90 - 130V settings, the two
lower fuses on the rear panel (2 amp) will have to be changed to 5 amp to allow for the
increased in-rush current.
NOTE: Do not operate amplifier without all cover screws installed. Do not operate
amplifier without a good RF ground connection on the rear panel ground terminal.
Power Cord Connections — WARNING!
To avoid the hazard of a potentially fatal electric shock and/or severe damage to the
ALPHA 6 and other equipment, always use an AC plug which 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 6 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).

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The green conductor in the power cord is wired to the ALPHA 6 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 200-240V branch circuit of #10
AWG copper wire or equivalent, rated at 20A, to feed the amplifier.
Important information concerning operation from 90-130V mains
Electrical power equipment will draw twice as much primary current from 120V
mains as from 240V mains. Therefore, operating the ALPHA 6 on a typical
120V/20A household circuit without exceeding the 20A circuit rating will limit
maximum peak power output to about 600-1000 watts. Maximum possible RF
output power for any particular primary AC voltage and current capacity may be
estimated as:
Po max = (Vline x Iline) / 2.3.
For example, if the Alpha 6 operates from a circuit which is capable of delivering
115V 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 = (115V x 20A) / 2.3 = 2300/2.3 = 1000 watts.
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 = (115V x 14A) /2.3 = 1610/2.3 = 700W.
RF Grounding
A ground stud with wing nut is provided on the rear of the chassis. Connection should be
made from this stud to a good RF earth ground, such as a copper water pipe or driven rod,
via heavy copper braid or strap. 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.
Replacing the Amplifier Cover
Use only the 6-32 screws supplied with the amplifier and do not tighten any of the screws
until all are started.
Blower
Remove blower motor shipping hardware from rear chassis wall. Save the two 10-32 bolts,

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fiber washers, and rubber shim; reinstall this hardware whenever the chassis is transported.
NOTE: For heavy-duty use or 50 Hz operation, the optional auxiliary fan must be installed.
Figures 2 – 4 ALPHA 6 Transformer Installation to be added here.

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Amplifier/Station Interconnections
(See fig. 5)
Coaxial Cable Types & Connectors
Connect the transceiver RF output to the ALPHA 6 RF INPUT with 50 ohm coaxial cable- RG-58C/U or
equivalent. A 6 ft. cable is supplied for this purpose. Coaxial cable from the 6 RF OUTPUT to antenna
should be RG-8A/U, RG-213/U, or equivalent high quality type with a type N male plug on the amplifier
end. RG8X cable is not recommended.
T/R Control Cable
The Alpha 6 has a full break-in vacuum relay QSK system requiring only the normal interconnection
when used with a modern QSK transceiver. The Alpha 6 requires a contact closure (short circuit) 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 6 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. The Alpha 6 protection circuitry prevents “hot-switching” with RF drive applied.
Modern transceivers have the proper time delay between keyup and the start of the transmitted signal to
allow the Alpha 6 to follow the CW keying. If a T/R timing problem is suspected, connect the CW keyer
to the RELAY jack on the Alpha 6, and connect a cable from KEY OUT on the amplifier to the keying
input of the transmitter.
ALC
The use of external ALC is not normally needed or recommended when the ALPHA 6 is used with
modern transceivers. However, the Alpha 6 does generate a negative-going ALC control voltage that can
be fed back to most transceivers if required, to minimize the possibility of overdriving the amplifier. This
external ALC voltage is available at the amplifier’s rear panel ALC jack via a common phono connector.
Alpha 6 grid current exceeding about 1mA will initiate ALC and light the green GRID LED. About 5-
10mA yields full ALC output-nominally -10 Vdc - and the red GRID LED lights. If the exciter requires a
lower ALC voltage, the Alpha 6 ALC potentiometer may be set accordingly. While driving the amplifier,
adjust the ALC pot to limit maximum transceiver output as desired. We recommend contacting CrossLink
customer service before attempting to use external ALC with the Alpha 6.
Section
3

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Figure 5: ALPHA 6 Rear Panel
To be labeled

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Operation
(Refer to Figures. )
4.1 Control Functions
(See front cover photo)
TUNE - Sets output tank circuit to resonance. Higher frequencies tend to tune toward the
“0” end of the dial scale, while lower frequencies tend to tune further toward the “100” end.
LOAD - 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.
POWER - Press ON to apply primary AC power to the amplifier or to reset power if the
plate overcurrent relay has tripped. Press OFF to remove primary AC power.
OPR/STBY- Operate places the amplifier in-line. With the Alpha 6 off, in StandBy, or in
warm-up with the WAIT LED lighted, the amplifier is bypassed and the exciter is
connected directly to the antenna.
Metering LEDs & Bargraphs - Separate bargraphs provide instantaneous full-time display
of peak values.
RF OUTPUT and REFLECTED POWER: Red and green “GRID” LEDs indicate,
respectively, that normal peak drive has been reached and the onset of overdrive and
flattopping.
A switch-selected bargraph monitors three additional functions:
TUNE: Permits a simple and safe tune-up procedure to be performed at low output power.
See section 4.2 below.
IP: Plate current, 1.5 amperes full scale (approximately 75 mA per segment).
HV: Plate voltage, 3000 VDC full scale (150 V per segment).
4.2 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 a specific power level. If operation at
higher power is then attempted without appropriate readjustment, the result will be
flattopping, “splatter,” and (usually) excessive amplifier grid current. If operated at a much
Section
4

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lower power level than it has been adjusted for, the amplifier’s efficiency decreases
considerably.
Grid Current
The ALPHA 6 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 lights as drive approaches the optimum level. The green GRID LED should flicker on
some SSB voice peaks, and light under CW/SSTV/RTTY carrier conditions. As overdrive
approaches, grid current increases rapidly and the red GRID MAX LED lights. 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 before the desired value of
plate current and/or power output is reached, readjust amplifier loading before continuing.
On SSB, optimum output consistent with good linearity occurs when the green GRID LED
lights on most voice peaks and the red LED flickers dimly only on the highest peaks.
Excessive grid current results from overdrive and/or inadequate loading. The solution is to
reduce drive, and/or increase amplifier loading. The 6’s 4CX800A/GU74b tubes are well
protected and these adjustments tend to be less critical than in many other amplifiers.
ALC
The Alpha 6 grid current limiting circuits provide substantial tube protection against
possible damage. The ALC voltage generated by the Alpha 6 cannot control the amplifier
itself and is not applied internally. If ALC control is required, a connection must be made
from the Alpha 6 to the transceiver ALC input. (See Sections 3 and 4.4)
Tune-up Procedure
NOTE: The forward and reflected power LED bargraphs and GRID LEDs are peak-
responding.
BEFORE INITIAL TUNE-UP, MAKE SURE A SUITABLE ANTENNA OR 50 OHM
DUMMY LOAD IS CONNECTED TO THE ALPHA 6. Leave the amplifier off or in
standby and apply exciter power to make a forward vs. reflected power check. If reflected
power is less than ten percent of forward power, the VSWR is lower than 2:1 and it is safe
to proceed with tuneup.
1. Turning on the amplifier.
∙Place the OPR-STBY switch in STBY (standby).
∙Rotate the multimeter selector switch to HV.
∙Depress POWER/ON.
If any of the following does NOT occur, depress POWER/OFF switch immediately and
investigate before proceeding:
∙The blower starts (note air exhausting above tubes).
∙The multimeter bargraph automatically displays HV; it should indicate approximately
2.8 KV.
∙The WAIT LED is lighted

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Alpha 6 User Manual Rev X
Interim Manual
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IMPORTANT: EXHAUST AIR MUST BE DETECTABLE FROM THE TOP
VENTS: If it is not, TURN OFF the amplifier immediately and verify that the exhaust
chimneys are properly positioned over the tubes. When the warm up delay is complete
(about 150 seconds), the WAIT LED will extinguish. The ALPHA 6 is now “ready”.
2. Tuning Up for Operation at 1,500 Watts RF Output
Preset TUNE, and LOAD controls to the nominal positions given in TABLE I, below.
TABLE I - Preliminary Tuneup Settings
Frequency (MHz) Tune Load
50 TBD TBD
51 TBD TBD
52 TBD TBD
53 TBD TBD
54 TBD TBD
NOTE: Final TUNE and LOAD settings will vary with the operating frequency,
antenna characteristics, and power level.
3. Reduce transceiver carrier output control to ZERO.
4. Press OPR (operate) on OPR-STBY switch. OPR LED should light.
5. Select TUNE function of the multimeter bargragh.
IF AT ANY TIME IN THE FOLLOWING PROCEDURE THE AMPLIFIER FAILS
TO RESPOND AS DESCRIBED, REMOVE DRIVE IMMEDIATELY!
6. Switch transceiver to CW and increase its carrier output to approximately 15 watts
(6 output approx. 300-500 watts).
NOTE! If more than about 25 W drive is applied while the 6 is substantially mistuned,
the 6 will switch to STBY. If the amplifier is returned to receive (key-up) it will
automatically reset to OPR in about 4 seconds.
7. Adjust TUNE control to deflect the TUNE LED maximum leftward.
8. Adjust LOAD control to place the illuminated TUNE LED below the “V” mark on
the TUNE scale.
9. Repeat steps 6 and 7 above.
10. Increase excitation until 6 output is about 1500 watts.
11. Repeat steps 6 and 7 at least twice.
12. Touch up TUNE for maximum power output.
The ALPHA 6 is now correctly tuned to deliver 1500 watts RF output on SSB, CW,
FSK, SSTV and FM. The TUNE LED normally fluctuates during modulation or
keying. Illumination of the first red LED on the RF OUTPUT bargraph indicates
output has exceeded 1500 watts.
To operate at reduced power in any mode, simply decrease drive (i.e., transceiver
power out put).
4.3 Reflected Power Protection
While operating, check the bargraph to ensure that reflected power remains below about
165 watts peak (2:1 VSWR when amplifier output is 1,500 watts). Fluctuating reflected
power may indicate a problem in the feedline or antenna. If reflected power exceeds 250
watts the 6 will automatically switch to standby. The FAULT LED will illuminate,

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Alpha 6 User Manual Rev X
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indicating that the 6 protection system has tripped it to STBY. Such faults reset
automatically if the transceiver is returned to receive for approximately 4 seconds.
4.4 Automatic Level Control (ALC)
If external ALC is used, amplifier grid current peaks greater than approximately 3mA will
initiate ALC. At grid current of 5-10 mA, ALC output is nominally -10V. If the transceiver
requires less ALC voltage, adjust the rear panel ALC potentiometer counterclockwise until
smooth ALC action results. Increase the exciter RF output until the red GRID LED just
illuminates on voice peaks.
A VOM can be used to measure ALC voltage while the pot is adjusted for suitable peak
ALC voltage. Many Kenwood and Yaesu transceivers work well with -8 and -10 VDC
maximum. Icom transceivers generally require lower peak voltage, typically -2 to -3 VDC.

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Alpha 6 User Manual Rev X
Figure 6 – Inside Top View