RF Concepts PA06 User Manual Preliminary

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Document Description	Preliminary User Manual
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Date Submitted	2002-01-11 00:00:00
Date Available	2002-03-12 00:00:00
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Document Title	Preliminary User Manual

ALPHA 6
OPERATING MANUAL
PRELIMINARY DRAFT
ALPHA/POWER
by CrossLink, Inc. RF
Power for Communications and Industry
6185 Arapahoe Road,
Boulder, Colorado 80303-1401
(303) 473-9232 * FAX (303) 473-9660
INTERIM MANUAL
Page i
Alpha 6 User Manual Rev X
ALPHA 6
Operating Manual
ALPH A POWER PR ODUCTS
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 303.473.9232 • Fax 303.473.9660
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.
Table of Contents
OWNER ASSISTANCE .................................................................................................................................4
EQUIPMENT S HIPPED.................................................................................................................................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 SAFETY................................................................................................................................................8
TRANSFORMER INSTALLATION (SEE FIGURES 2-4) ...................................................................................9
INSPECTION OF TUBE & C HIMNEY ............................................................................................................9
AC P RIMARY CONNECTIONS & AMPLIFIER GROUNDING .......................................................................10
POWER CORD CONNECTIONS — WARNING! .....................................................................................10
RF GROUNDING ......................................................................................................................................11
COAXIAL C ABLE T YPES & CONNECTORS ...............................................................................................13
T/R CONTROL CABLE .............................................................................................................................13
FIGURE 5: ALPHA 6 REAR PANEL ........................................................................................................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 – F RONT PANEL LOWERED......................................................................................................20
FIGURE 8 - INSIDE FRONT P ANEL...........................................................................................................21
OPERATING AND MAINTENANCE NOTES...................................................................................22
TUBES.................................................................................................................................................22
INTERLOCKS .....................................................................................................................................22
FUSES.................................................................................................................................................23
PLATE OVERCURRENT RELAY .......................................................................................................23
FIGURE 9 - R EAR P ANEL 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
Page 2
Revision 1.0
1
Section
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.
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Alpha 6 User Manual Rev X
Output Impedance:
Maximum Load VSWR:
VSWR Trip:
Intermodulation Distortion:
Harmonic Output:
Tubes:
Cooling:
Automatic Level Control (ALC):
Primary Power:
Power Transformer:
Protective Functions:
Status Indicators:
Metering:
Size:
Weight:
50 ohms unbalanced.
2:1 at full rated power output.
Automatic standby when reflected power >250
watts.
30 dB below rated output.
<-60 dBc.
One Svetlana 4CX1600B ceramic-metal tetrode.
Full-cabinet, ducted forced air using cushionmounted centrifugal blower.
Negative from 0, adjustable.
190-250 or 90-130 VAC nominal, 50-60 Hz,
fused at 20 amperes.
3+ kVA with strip-wound Hipersil core.
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 (Stepstart).
STANDBY, WAIT (initial turn-on time delay),
OPERATE and FAULT LEDs.
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.
7.5” H x 17” W x 16.5” D (19x43x39cm)
excluding controls, feet, and connectors.
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 alpha-service@crosslinkinc.com.
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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Alpha 6 User Manual Rev X
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 – 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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Alpha 6 User Manual Rev X
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.
7. Never install cover screws 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.
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.
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Alpha 6 User Manual Rev X
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
inspection prior to full power operation. If any insulators are cracked or show signs of
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Alpha 6 User Manual Rev X
“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.
Coax and 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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Revision X
2
Section
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.
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Alpha 6 User Manual Rev X
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
230-250V
210-230V
190-210V
110-130V
90-110V
“A” Terminal
4 **
“B” Terminal
2**
4&7
Blower*
4 & 2**
4&3
4&3
4&7
1-3
Jumpers
Not used
for 190 - 250V
operation
1 - 2, 6 - 7
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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Alpha 6 User Manual Rev X
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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Alpha 6 User Manual Rev X
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
Interim Manual
ALPHA 6 Transformer Installation to be added here.
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Alpha 6 User Manual Rev X
3
Section
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 510mA 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.
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Figure 5: ALPHA 6 Rear Panel
To be labeled
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4
Section
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
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Alpha 6 User Manual Rev X
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 peakresponding.
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
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
50
TBD
51
TBD
52
TBD
53
TBD
54
TBD
Load
TBD
TBD
TBD
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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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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Figure 6 – Inside Top View
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Figure 7 – Front Panel
Lowered
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Figure 8 - Inside Front
Panel
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5
Section
OPERATING AND MAINTENANCE NOTES
TUBES
The 4CX1600B tube used in the ALPHA 6 is very rugged and normally operates with a
large margin of safety. It should provide outstanding service for many years if not damaged
by abuse - especially overdrive or blockage of cooling airflow. Allow at least twelve inches
(31 cm) unobstructed clearance around the air intake and exhaust areas. Stacking
equipment is not recommended.
Never allow key-down plate current to exceed 1.5 amperes 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 tube life. It’s better to leave equipment in
standby for several hours than to cycle power repeatedly on-off-on-off over the same
period.
INTERLOCKS
The ALPHA 6 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. These interlocks are designed to protect against dangerous electric shock
resulting from accidental contact with potentially lethal voltages inside the amplifier.
WARNING!
WARNING!
WARNING!
WARNING!
WARNING!
ALWAYS DISCONNECT THE AC LINE CORD FROM THE POWER
SOURCE BEFORE REMOVING THE TOP COVER FROM THE 6 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 never be disabled for any reason except by a skilled and
experienced technician.
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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.
Slow-blow fuses F3 and F4, located above the primary line fuses, may prevent damage to
the step-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 closed, the step-start fuses normally will blow.
DAMAGE RESULTING FROM USE OF A FUSE OF INCORRECT SIZE OR TYPE
WILL NOT BE COVERED UNDER WARRANTY AND MAY VOID THE
WARRANTY.
PLATE OVERCURRENT RELAY
This relay will quickly turn off 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 overcurrent relay
trip and remove AC power from the amplifier, determine and correct the cause of the trip
before turning the 6 on again.
IDLING PLATE CURRENT AND ELECTRONIC BIAS CONTROL (EBS)
Idling plate current of the ALPHA 6 is approximately 350 to 400 mA during 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.
ARC & MISTUNING PROTECTION
ALPHA/POWER’s exclusive circuit senses the beginning of any RF arc in, for example, a
TUNE or LOAD variable capacitor and automatically switches the 6 to standby within a
few milliseconds. This system has virtually eliminated RF arc damage in current ALPHA
amplifiers. The system similarly detects severe mis-tuning of the 6, and if drive exceeds
about 25 watts switches the amplifier to standby. The 25 watt input trip threshold permits
safe tuneup at low power levels using the TUNE indicator, without aggravating and
unnecessary trip-outs.
PREVENTIVE MAINTENANCE
The amplifier interior, particularly high voltage areas, 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. The ALPHA accessory
cooling fan also should be installed to insure adequate cooling airflow.
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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 6 may be cleaned with a mild
household liquid detergent such as Formula 409 or Fantastik. Do not use chemical solvents,
as these may severely damage the front panel or cabinet finish. Never use an abrasive
cleaner.
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Figure 9 - Rear Panel Connections
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6
Section
TROUBLESHOOTING HINTS
A)
1)
2)
3)
4)
6 will not turn on; nothing happens when ON switch is pushed.
External AC wiring, fuse or circuit breaker may be open.
Amplifier cover not in place; cover safety interlock open.
Fuse F1-F4 open or missing; check fuses with an ohmmeter.
Step-start resistor R4 or R5 open.
B)
1)
2)
3)
4)
Amplifier turns on but no HV is indicated by the multimeter LED bargraph.
Multimeter selector switch in wrong position, e.g., Ip.
Possible HV circuit fault.
HV sampling resistor in power supply damaged.
Transformer plugged into power supply incorrectly.
C)
Amplifier turns on but no multimeter indications; other LED bargraphs are
operative.
Low voltage power supply problem.
Defect or damage on control board.
1)
2)
D)
1)
Amplifier turns on but time delay will not complete; WAIT LED does not
turn off.
Defect or damage in timing circuitry on control board.
E)
1)
Amplifier turns on, time delay completes but amplifier will not transmit.
Open T/R control line from transceiver to RELAY jack.
F)
1)
Amplifier transmits but red GRID LED often lights.
Amplifier overdriven or underloaded; reduce transceiver output and /or increase
amplifier loading.
Load VSWR (reflected power) exceeds 200W.
Exciter output poorly controlled. External ALC may help.
2)
3)
G)
Amplifier operates but green GRID LED will not light and plate current is
low; transceiver does not seem to be able to drive amplifier to its rated RF
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Alpha 6 User Manual Rev X
1)
2)
3)
H)
output power level.
External ALC control voltage to transceiver excessive (see section 4.4, Automatic
Level Control).
Input rf load resistor or bias circuitry damaged.
Possible damaged or defective tube(s).
1)
2)
Receive signals disappear or are severely attenuated when switching from
STBY to OPR.
RELAY (T/R) control cable from transceiver is shorted.
Transceiver locked in transmit
I)
1)
2)
Plate current indicated when amplifier is in STBY or receive.
4CX1600B tube heater-to-cathode leakage or short.
Tube bias supply or T/R bias switch faulty.
J)
1)
2)
Distorted SSB signal; possible severe television interference.
Excessive RF drive from transceiver and/or insufficient amplifier loading.
Coaxial connector, coax feedline, antenna feedpoint balun, tuner, or antenna trap
arcing on voice peaks.
RF feedback from antenna into transceiver via the transceiver power cord,
microphone or key cable, or other unshielded station patch cables.
Poor station RF ground.
3)
4)
K)
1)
2)
Low frequency audio hum on transmitted signal.
Defective microphone cord (especially, broken ground lead).
Dynamic (magnetic) microphone located within about two feet of 6 power
transformer. All dynamic microphones pick up some magnetically-coupled hum
from the external field of nearby power transformers. In cases where objectionable
hum is experienced while using the 6 and popular microphones such as the Heil
series, the problem usually can be resolved by keeping the microphone at least 18
to 24 inches from the front of the amplifier and ensuring that transceiver mike gain,
speech processing, and internal drive (ALC) levels are not adjusted to exceed 10
dB. In rare cases it may be necessary to use a ceramic or condenser type
microphone.
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7
Section
DESIGN AND CIRCUIT OVERVIEW
RF Amplifier Section (See Figure 6, 13)
Two 4CX800A/GU74b tubes are employed in a grounded-cathode, grid-driven circuit. Excellent
linearity is achieved by operating the tubes as tetrodes with normal control grid (G1), screen grid
(G2), and plate (anode) DC voltages. Drive voltage required under these conditions is low enough
to permit using an untuned input loaded by non-inductive 50 ohm resistor R1. A simple network
(C7, C8, K2, L1 in Figure 13) compensates for tube and wiring reactances on the highestfrequency bands, yielding extremely low input VSWR across the entire HF range.
RF negative feedback provided by un-bypassed cathode resistors R4 and R13 stabilizes amplifier
power gain at the desired level of about 14 dB and further enhances linearity. Protection of tubes
and other components against damage due to internal tube flash-over is provided by a gasdischarge surge suppressor, GT1, connected from the screen grids to ground, as well as D1 and R3
on the screen/filament board.
The Alpha 6 RF output network is a conventional pi-L except that plate RF choke L4 is switched
by a relay to optimize performance across all nine 1.8-29.7 MHz amateur bands. Two-section
TUNE and LOAD capacitors C22 and C32 are switched to provide an “electrical vernier” for
smooth, easy and accurately-resettable tuneup “by the numbers” on all bands.
Power Supplies (Figures 6, 9, 12)
Transformer T1 supplies all raw AC voltages required. Step-start resistors R4 and R5 in series
with the primary of T1 limit inrush current to a safe level and are shorted out by relay K2 shortly
after turn-on. NOTE: For heavy-duty use or 50 Hz operation, the optional auxiliary fan must be
installed.
The high voltage full-wave bridge rectifier (Figure 9) consists of a molded block HV rectifier
assembly. Bridge D1-D4 provides rectified DC for the screen grids, while D5-D8 and associated
components make up the regulated bias supply.
Figure 12 shows HV filter capacitor bank C2-C10 and the monitoring points for HV and IP. K1 is
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the plate overcurrent relay. MOSFET Q12 and associated components provide regulated screen
grid voltage for the tubes and also limit maximum screen current to a safe value. Q12 is mounted
on the rear of the 6 front subpanel for heat sinking.
Control Circuits (Figure 7)
Control and monitoring circuits are grouped on the Control Board, which is physically located on
the front of the 6 subpanel. Generally, monitoring and protective functions are clustered on page 1
of the schematic; warm-up, status indicators, and keying/switching functions are on page 2.
Front Panel Displays (Figure 8)
The Display Board, located on the rear side of the 6 front panel, incorporates all indicator LEDs
and their associated driver chips. The RF forward (output) power bargraph is at top right, reflected
power bargraph center right, multimeter bottom right, and the individual indicator LEDs at bottom
left.
Output RF Wattmeter Detector Board - See Figure 14.
Multimeter Selector Switch Wiring - See Figure 11.
Switch Matrix Board - See Figure 10.
SAFETY
There are lethal voltages in the Alpha 6 amplifier. Special precautions must be taken to allow for the safe
completion of these modifications.
1) Always unplug the amplifier from the 240 vac mains before opening the case and doing any work on
your 6.
2) The high voltage crowbar activates when the cover is removed and should eliminate any residual high
voltage within the amplifier but it is always prudent to short the high voltage to ground in the area of the
tube plates or the plate RF choke with an insulated screw driver as an extra precaution.
3) Do not attempt to test the modifications with the cover removed since the built-in interlocks will not
allow the amplifier to be energized.
4) Do not defeat the interlocks as a means of testing the amplifier with the cover removed. Proper operation
of the amplifier requires that the cover be in place for shielding the digital circuitry from the radiated RF
signal.
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ALPHA Products Warranty
CROSSLINK INC. warrants as follows each new amateur radio product of its manufacure, sold and
used in the United States, Its Possessions, and Canada.
1.
Workmanship and all components except rf power tubes are warranted for FOUR Years from
date of original purchase if used exclusively in licensed amateur radio service. WARRANTY IS VOIDED
BY ILLEGAL SALE OR USE OF EQUIPMENT (e.g. US sale of export models).
2.
Eimac power tubes are warranted by their manufacturer, CrossLink Inc. will assist owners in securing
warranty service if requested.
Svetlana power tubes are warranted by CrossLink for one year from date of original purchase.
3.
Warranty does not apply to repair of damage resulting from improper maintenance or repair,
misuse, neglect, abuse, or improper installation, nor to units not operated in accordance with specifications
and instructions furnished by CrossLink, nor to units repaired or altered by persons not authorized by
CrossLink,, nor in cases where the serial number has been removed, altered, or defaced.
4.
If a malfunction is suspected, before attempting repairs or returning equipment to CrossLink or
the selling dealer for service, the owner shall contact CrossLink or the selling dealer factory service
department, providing model and serial number plus details of equipment hookup, accessory equipment
used, operating conditions, and abnormalities observed. CrossLink will furnish a new part in exchange for
any covered defective part or, if it is determined that factory service is required, will authorize return
tofactory. Equipment authorized for return shall be shipped to CrossLink fully prepaid and insured via
United Parcel Service or air express. USING ONLY FACTORY APPROVED PACKING; REMOVE
POWER TRANSFORMER BEFORE SHIPPING ANY UNIT WHICH WAS ORIGINALLY SHIPPED
FROM THE FACTORY WITH TRANSFORMER REMOVED. All shipping charges are the
responsibility of the owner.
5.
In order to receive service under this warranty, the owner must either (a) have returned a
completed warranty registration form to CrossLink within 30 days of original purchase OR (b) provide
proof of ownership as well as proof of the original date of sale by CrossLink or by an authorized CrossLink
dealer.
6.
No person is authorized to assume for CrossLink any liability in connection with our products,
other than as set forth in this warranty. CrossLink reserves the right to change its products as it deems
desirable, without obligating itself to make such changes available for previously manufactured products.
UNDER PROVISIONS OF THE FEDERAL MAGNUSON –MOSS WARRANTY ACT, THIS
WARRANTY POLICY IS CLASSIFIED AS A LIMITED WARRANTY.
CrossLink Inc.
303.473.9232 x. 151 Sales & Serivce
303.473.9660 fax
www.crosslinkinc.com
6185 Arapahoe Road, Boulder CO 80303
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