Acom ACOM2100 User manual

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Outstanding HF Power Products
HF + 6 m LINEAR AMPLIFIER
ACOM2100
OPERATING MANUAL

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Table of Contents
I. GENERAL INFORMATION ..........................................…3
1-1.Introduction and Description ......................................... 3
1-2. Owner Assistance ................................................. 3
1-3. Equipment Supplied ............................................... 3
1-4. Features ........................................................ 3
1-5. Safety Considerations, Explicit Denitions .............................. 4
2. INSTALLATION .................................................... 6
2-1. Unpacking and Initial Inspection ...................................... 6
2-2. Mains Voltage Selection ............................................ 6
2-3.Transformer Installation ............................................. 6
2-4. Amplier Location Selection ......................................... 6
2-5. Connections ..................................................... 7
2-6. Installation of External Fan .......................................... 8
3. POWER ON, CONTROLS AND INDICATORS ............................ 9
4. OPERATION ..................................................... 11
4-1. Turning ON and OFF ............................................. 11
4-2. Changing Operate and Standby Modes ............................... 11
4-3. Antenna change ..................................................12
4-4. Tuning ......................................................... 12
4-5. Continuous carrier modes.......................................... 14
4-6. ON LINE Information Screens and Control Functions .................... 15
4-7. Auto-Protection System ........................................... 15
5. OFF LINE MODE .................................................. 16
5-1. Auto-Operate enabling and disabling ................................. 16
5-2. Antenna output assignment ........................................ 16
5-3. Reading Auto-protection Signatures .................................. 16
6. MAINTENANCE................................................... 17
6-1. Cleaning ....................................................... 17
6-2. Fuse Replacement ............................................... 17
6-3. Tube Replacement ............................................... 17
6-4. The ACOM2100 Simplied Schematic Diagram ..........................17
6-5. Troubleshooting ................................................. 18
7. SPECIFICATIONS ................................................. 20
7-1. Parameters ..................................................... 20
7-2. Functions ...................................................... 20
7-3. Storage and Shipment ............................................ 21
APENDIX A ........................................................ 22

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1. GENERAL INFORMATION
1-1. Introduction and Description
This manual explains the installation, operation, and maintenance of the ACOM2100 HF+6 meter linear
amplier.
The ACOM2100 is a complete and self-contained linear amplier that covers all amateur bands from 1.8
through 54 MHz and provides over 1500W PEP or continuous carrier output power with less than 85W
exciter drive. Antenna VSWR up to 3:1 is acceptable with 1500W forward power. Tuning is substantially
simplied by a plate-load True Resistance Indicator (TRI) and by an automatically controlled input
attenuator. Operating parameters are displayed by a multi-functional high brightness and contrast OLED
display. Full break-in transmit/receive switching (QSK) is standard.
1-2. Owner Assistance
If assistance is needed, you should contact your local dealer rst. If you still have an issue you need to
discuss with one of ACOM's specialists, the contact information is as follows: fax + 359 2 920 96 56, tel.
+ 359 2 920 97 80, e-mail [email protected], [email protected], WEB: www.acom-bg.com or
by mail: ACOM OOD, Blvd. Nikola Mushanov 151, 1330 Soa, Bulgaria.
1-3. Equipment Supplied
The ACOM2100 amplier and this manual are shipped in two cardboard cartons. One carton contains
the power transformer; the second carton contains the amplier.
1-4. Features
• Easy to operate. The TRI is a powerful tuning aid that, together with the 2:1 TUNE and LOAD caps
verniers and the automatically controlled input attenuator, helps the operator to quickly and precisely
match the antenna impedance to the optimum tube load impedance (5-10 seconds typically). The auto-
operate function (when enabled) maintains the amplier in the OPERATE mode for you, thus avoiding
unnecessary manual operations.
• No heavy outboard antenna tuners required for antenna VSWRs up to about 3:1. Your amplier will
enable you to change antennas virtually instantaneously and allow you to use your antennas over wider
frequency ranges.
• An amplier that is both user-friendly and that looks after itself. It is designed to safely withstand up
to 400W reected power, up to 100 milliseconds duration of drive spikes, drive RF "tails" after a PTT
or KEY release, operator's inadvertent tuning errors etc. The amplier also will not cease to function
with a "soft" AC mains and will deliver more than half power at only 85% of nominal mains voltage. It
can withstand voltage drops (down to zero Volts) for up to 10 milliseconds and can tolerate 15% mains
voltage spikes, which is especially important on Field Day, during DXpeditions, and at portable operating
events where emergency power is relied upon.
• OLED information display. All amplier status indications are explained via detailed text displayed on
the dot matrix, high brightness and contrast OLED display. The upper line on the OLED always reads
peak forward power. LED indicators are provided for: OPERATE mode, attenuation-on (ATT), transmit
(TX), selected antenna output (1, 2, or 3), and ON/OFF conditions.
• Antenna selection. Three antenna outputs are selectable using a push-button on the front panel.
• Easy maintenance. Data regarding amplier internal status is stored in a nonvolatile memory for 7 of
the most recent auto protection trips. This information can be forwarded to your dealer for diagnostics.
Using an Excel application, available from ACOM or your dealer free of charge, and a PC you can decode
the status data by yourself.

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• Less noise in the shack. The input bypassing and vacuum antenna relays are virtually silent even in
the CW QSK mode thanks to specially designed mounting hardware.
• Less QRM and improved Electro Magnetic Compatibility during tuning. Amplier tuning can be achieved
in less than 10 seconds at a quarter of nominal output power.
• Operates without special signals from the transceiver. "Ground on TX" (PTT) and 85W RF drive power
are sufcient.
• Broadband input matching circuit design provides excellent transceiver loading over the entire spectrum,
from 1.8 MHz up to 54 MHz.
• Uses a single 4CX1000A/8168 ceramic and metal radial beam tetrode with plate dissipation of 1000W
(forced air cooled, grid-driven), which is specically designed for class AB1 RF linear amplier operation.
• Permanent monitoring includes protection of plate and grid voltages and currents, as well as exhaust
air temperature. The Bias Optimizer decreases the heat dissipated from the tube, and there is automatic
protection against overheating in accordance with specications of the tube manufacturer.
• Output RF arc protection is employed. This important feature safeguards the amplier, antenna,
antenna selector, and tuner against severe damage in case of possible breakdown.
• High voltage power supply inrush current limitation. This feature reduces the risk to sensitive devices
connected to the same mains circuit (important when used portable) when the amplier is turned on.
The amplier can be congured for 8 nominal mains voltages: 100, 110, 120, 200, 210, 220, 230, and
240VAC, 50 or 60Hz.
• Continuous monitoring and/or selectable measurement of the 12 most important parameters of the
amplier, exciter, and the selected antenna via the OLED.
1-5. Safety Considerations, Explicit Denitions
The ACOM2100 HF + 6 meters Linear Amplier is a Safety Class I unit. The third grounding lead of its
mains cord (colored yellow with two green stripes) and the ground stud on the rear panel of the amplier
(marked GND) should be connected to the station's grounding system for safe operation.
The amplier is designed to meet international safety standards and complies with UL and CE safety and
electromagnetic compatibility requirements, as well as FCC regulations.
This operating manual contains information, precautions, indications for cautions and warnings that must
be followed by the user to assure safe operation and to keep the ACOM2100 operating properly.
PRECAUTIONS:
The EXPLICIT DEFINITIONS described below apply to this operating manual:
W A R N I N G notes call attention to a procedure which, if not correctly performed, could result in
personal injury, re hazard or electric shock.
C A U T I O N notes call attention to a procedure which, if not correctly performed, could result in
equipment damage, not only in the amplier.
N O T E notes call attention to a procedure which, if not correctly performed, could result in inconvenience.

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W A R N I N G HIGH VOLTAGE!
The amplier works with high voltages above 3000V, which are LETHAL! Also,
for your safety, pull the amplier power plug out of the mains wall outlet and
WAIT AT LEAST 30 minutes EACH TIME BEFORE you remove the cover of the
amplier. Do not touch any part inside while the amplier is open because some
residual voltages may still be present.
W A R N I N G HIGH VOLTAGE!
NEVER ALLOW ANYONE, ESPECIALLY CHILDREN, to push anything into holes
in the case - this will cause electric shock. NEVER TOUCH AN ANTENNA during
transmission - this may result in an electric shock or burn. NEVER EXPOSE the
amplier to rain, snow or any liquids. AVOID placing the amplier in excessively
dusty environments or in direct sunlight. DO NOT OBSTRUCT AIR INTAKE
(rear panel) and EXHAUST (top cover) areas of the amplier. Keep a minimum
distance of 10cm (4 inches) to the intake and 50cm (20 inches) to the exhaust
openings.
W A R N I N G
Do not undertake your own repairs or changes in hardware or software of the
amplier. Doing so will endanger your or others' health or life or damage the
amplier and the equipment connected to it. Such repairs or changes are not
covered by warranty and may void the warranty. The manufacturer is not liable
for any such repairs or changes. Any such repairs or changes are strictly the
responsibility of the person or persons engaging therein.
C A U T I O N
To avoid damage (not covered under warranty) read the Installation - Section 2 of
this operating manual carefully. If you have any doubts or questions regarding the
installation, operation or safety of the amplier, please consult your dealer immediately.

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2. INSTALLATION
2-1. Unpacking and Initial Inspection
N O T E
Before you install your amplier, thoroughly read this manual. First, carefully inspect
the cardboard carton and its contents for physical damage. If damage is evident,
notify your dealer immediately. Delay may void the carrier's warranty. Keep all packing
materials for possible future amplier shipment.
2-2. Mains Voltage Selection
C A U T I O N
To avoid damage, which will not be covered under your warranty, check carefully to
be certain that the voltage for which the amplier is set corresponds to your mains
nominal voltage
Normally, the amplier is supplied set for a nominal mains voltage of 240V. If your mains voltage is not
240V, you must contact your dealer for instructions on how to change the voltage selector inside the
amplier. The only exception to this is if the unit has been custom ordered, in which case the voltage
selection will be noted in the Table of Individual Data (Table 2-1, below).
AMP s/n
Tube s/n
Table 2-1. ACOM 2100 Individual Data
C A U T I O N
The current consumed by the amplier from the mains supply should not exceed 16A
from 200/240VAC and 20A from 100/120VAC. You will have to reduce the output power
to about 1000W PEP if the amplier is operated at 120V or lower mains supply voltage.
2-3. Tranformer Installation
HV Tranformer Installaion is described in APPENDIX A.
2-3. Amplier Location Selection
C A U T I O N
The weight of the unit is about 29.3kg (64.6 Lbs), which should be handled by two
persons.
Position the amplier near where it will be used. You will need an easy access to the command knobs
and indicator's area, as well as to the rear panel cabling.
No magnetic-eld sensitive devices (such as microphones) should be located next to the right side of the
amplier because its power transformer is located there. It is advisable to position the amplier to the
right of your transceiver. No temperature-sensitive devices should be located above the exhaust hot air
area. Do not locate the amplier under a shelf, for example. DO NOT UNDER ANY CIRCUMSTANCES
OBSTRUCT the AIR INTAKE (rear panel) or EXHAUST (top cover) areas of the amplier. Keep a minimum
clearance distance of 10cm (4 inches) from the intake and 50cm (20 inches) from the exhaust openings.

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N O T E
If the power transformer is not readily installed check the Transformer installation
leaet supplied with it.
2-4. Connections
Connection to your station must be accomplished in the order described below before you apply mains
voltage to the amplier.
W A R N I N G
Note that the grounding system may have to withstand currents over 20A with
minimal voltage drop. Therefore, it may be necessary to improve grounding
system conductivity with heavier conductors and a lower-resistance ground
path. The grounding conductor should be at least 8mm2 (AWG 8 or SWG 10).
Fig. 2-1 Connections
a) First, connect the ground stud of the amplier (on the rear panel, marked GND) to the station's
grounding system (Fig.2-1).
b) Connect a coaxial cable with a PL-259 plug from the transceiver output to the amplier rear panel
RF INPUT socket.
C A U T I O N
If this is the rst time you are using a power amplier in your station, pay close
attention to the coaxial cable type from the amplier's three outputs. The cable must
be capable of handling the increased power levels, particularly on the 10m and 6m
bands. We recommend that you use RG213 or better coaxial cables. Consult your
local cable supplier for the appropriate cable selection. This caution applies equally
to the antenna selector, tuner and antennas system as well.
c) Connect a suitable coaxial cable from your antennas to the appropriate amplier output on the rear
panel, marked ANTENNA 1, ANTENNA 2, and ANTENNA 3, using PL-259 plugs with PTFE insulation.
d) Run a cable terminated with a phono (RCA) connector from the transceiver socket providing a "ground
on transmit" (PTT) control signal to the amplier rear panel KEY-IN socket.

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N O T E
Your amplier will not work if KEY-IN is not connected properly.
Transceiver producers give different names to this output, such as TX-GND, SEND, T/R-LINE, PTT,
etc. Some transceivers require that "ground on transmit" be implemented via a software command,
or by changing the setting of a switch on the rear panel or in the interior of the transceiver. Check your
transceiver manual. Consult with your dealer if you are having difculty.
The switching voltage presented from amplier KEY-IN socket to the transceiver “ground on transmit”
output does not exceed 13V (positive to the ground). The closed-circuit current is below 5mA.
e) The KEY-OUT socket on the rear panel provides an extra control signal from the amplier to the
transceiver. It can be used to improve the transmit/receive switching safety. The rating on this output
is very low current, so be certain that the load will not exceed 50VDC when it is open circuit and 20mA
when it is closed.
If your transceiver has a suitable input that disables transmission, we recommend that you connect it
with a cable terminated in a phono (RCA) connector to the KEY-OUT socket of the amplier. Transceiver
producers give different names to this input and they are for instance TX-INHIBIT, MUTE, LINEAR, etc.
Check your transceiver manual.
Your amplier will function normally if the KEY-OUT remains unused.
f) Preparation of wall outlet for the amplier.
W A R N I N G
If your amplier is only tted with one mains fuse, it is suitable for the European
Union ONLY. Your dealer will check that your amplier is correctly fused before
it is shipped to you, based upon your indicated location. Customers should
check with a qualied electrician if the amplier is to be used outside the country
for which it was purchased.
Your dealer will t the correct mains plug for your country, and will check that the amplier is correctly set
for the mains network applying there. If the amplier is to be connected to the mains network in another
country, check with your dealer or a qualied local electrician before use there.
W A R N I N G
Before connecting the amplier to your mains supply, be sure that the supply is
correctly wired, and that it is adequate for the current drawn by the amplier - up
to 16A from 200/240V and 20A from 100/120V. Make certain that the grounding
lead is connected properly in the wall outlet used for the amplier.
It is preferable that you use a wall outlet close to the power source. The power cord leads and associated
wiring should be at least 2.5mm2 (AWG 13 or SWG 15). Check if the respective fuses can handle current
up to 16A (20A for 120VAC) as well, and whether the voltage corresponds to the voltage for which the
amplier is set (S.2-2). If you connect the amplier to a different mains outlet, be sure that you check it
as well.
Make sure the main Power Switch on the rear panel is in the OFF position and insert the amplier's mains
plug into the wall outlet prepared for it. The amplier remains switched off at this time.
2-5. Installation of External Fan
This fan (Fig. 2-1) is not necessary in SSB and CW modes, or in continuous carrier modes (RTTY, SSTV
etc.) with a maximum carrier-down time of 5 minutes and a subsequent pause of 3 minutes. For higher
duty cycles such as continuous broadcast or increased ambient temperatures the fan is recommended.
The auxiliary fan (92x92x25mm or 92x92x38mm) must be a brushless type, 2...5W/24VDC. It may be
installed by your dealer or by the manufacturer on request.

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3. POWER ON, CONTROLS AND INDICATORS
C A U T I O N
Do not turn the amplier on for at least 2 hours after unpacking it in the room where it
will be used. Pay particular attention when you move it from a very cold into a warm
place - condensation is likely and this could result in damage to the high voltage
circuits. In such a case, wait at least 4 hours. A similar effect can occur after a rapid
warming of the operating room (for instance after switching on a powerful heater in
a cold shack).
C A U T I O N
To avoid damage (not covered under warranty) carefully check that the voltage for
which the amplier is set corresponds to your mains nominal voltage (see S.2- 2 and
table 2-1).
After following all instructions in S.2, you may turn ON the main power switch marked "LINE" on the rear
panel (Fig.2-1). The LED indicator above the red ON/OFF button located on the front panel must light
red and an inscription "ACOM1500" will appear on the display (Fig.3-1):
Fig. 3-1 ACOM2100 Display and Control
Note that the upper line of the OLED always reads the peak forward power, even in STBY mode. The
2400W scale resolution is 20W per bar. Note too that levels below 50W may be not detected.
In this position (called OFF LINE hereafter), only the micro-controller is operational, while the amplier
itself is still turned off (and the tube is not powered at all).
Control of the amplier is accessible during OFF LINE and ON LINE (OPERATION) states, each having
several information screens and control functions (see Fig. 3-2):

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Fig.3-2 Information Screens and Control Functions Structure
The OPER button changes operate and standby modes alternatively (S.4-2) while ON LINE. Please
note that Auto-Operate might be enabled (S.5-2). The same button activates signature list while OFF
LINE (S.5-3).
The PREV and NEXT buttons change information screens or select control functions (S. 4-6) for both
OFF LINE and ON LINE modes.
The ON/OFF button switches OFF LINE and ON LINE (OPERATION) states of the amplier alternatively.
You can proceed in one of two ways:
a) You may use the OFF LINE information screens and control functions. They refer to the auto-protection
signatures list, as well as the Auto-Operate feature and Antenna assignment. This is described in S5.
b) You may turn on the amplier and start the warm-up sequence. After 3 minutes you may tune and
begin operating the amplier and you can use the ON LINE (OPERATION) information screens or control
functions (see below).

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4. OPERATION
Operation of the amplier is simplied through use of the TRI tuning aid, Auto-Operate function, and
automatic protection system, so you may begin using the amplier immediately following installation.
However, to make full use of the amplier's potential and to fully congure it to your local conditions, we
recommend that you thoroughly read the following information.
There are 14 ON LINE information screens, which can be selected by pressing repeatedly the NEXT or
PREV buttons (see g.3-2). Their purposes and methods of use are described in the next 7 sections,
4-1 through 4-7.
4-1. Turning ON and OFF
In order to turn on the amplier while the Main Power Switch (located on the rear panel) is on, press the
red ON/OFF button (located under the red LED on the front panel right-bottom corner) and hold it on for
about one second. The OLED will light and the ON/OFF LED indicator above the button will change the
color from red to green. You will hear the blower and the optional external fan starting at high speed for
a second and then slowing down.
After successfully passing the initial amplier self-tests, the ON/OFF LED begins ashing green while
the following inscription on the OLED remains lit:
WARMING UP: nnn s
(nnn above is the number of seconds remaining to readiness for operation)
A tube warm-up period of 180 seconds (3 minutes) follows. During this time the amplier remains in
standby mode, so you can continue operating with the transceiver.
Pressing either the PREV or NEXT buttons during this period will result in changing the screen to one
of the 14 available information screens described in S.4-6 below. This will not inuence the warming-
up process, so you may pass through all information screens, to monitor the High Voltage value or the
Exhaust Air temperature, for example. You may also return to the earlier screen to see how many seconds
are still needed until the tube cathode reaches its operating temperature.
N O T E
When you intend to have a short operating break, it is better to leave the amplier in
standby mode instead of turning it off. Tube life is shortened by repeatedly turning on
and off the heater lament. However, if you unintentionally power-off the amplier, it
is best to switch it on again immediately. When the pause is short (up to one minute)
and the cathode is still warm, the warm-up period is shortened signicantly, which
reduces the waiting time and prolongs the tube's life.
After the indicated period expires, the ON/OFF button stops ashing and lights green constantly.
If the auto-operate function has been selected to ON (see S.5-2), the green OPER LED will
illuminate automatically. The last used (one out of 14) information screen appears on the display,
e.g., "WARMING UP: Ready.”
The bar-graph on the upper line always indicates the peak forward power (as well as during
OFF LINE).
In order to turn the amplier off, press the red ON/OFF button. If you intend to have a break
for a long time, it is best to turn it off using the Main Power Switch (on the rear panel) as well.
4-2. Changing Operate and Standby Modes
With the Auto-Operate function disabled (see S.5-2), the OPER button changes two modes
alternatively.
When Auto-Operate is enabled, the amplier will be maintained in operate mode by default, unless you use
the OPER button manually to go to standby (in which case the Auto-Operate is suppressed temporarily).
Pressing OPER again will restore the Auto-Operate feature.

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When the Auto Operate function is disabled, the amplier will shift and stay in STBY mode after each
protection trip. To restore operation, the OPER button must be depressed.
When the Auto Operate function is enabled (see S 5-2), the amplier will shift to the STBY mode on a
protection trip. It will return to the OPER mode after about four seconds automatically.
4-3. Antenna change
By pressing the ANT button, the amplier output can be switched between three antenna outputs. The
three lights above the button indicate the current antenna selection. Selection of any of the antenna
outputs can be disabled if not used - see S. 5-3 - Antenna output assignment. This prevents inadvertent
selection of antenna outputs, preventing no-load transmission and possible amplier damage.
C A U T I O N
To avoid damage (not covered under warranty) do not change antennas while
transmitting. Do not transmit into an antenna output (1, 2, or 3) if it is not connected
to an antenna or a dummy load.
4-4. Tuning
Tuning is possible only in operate mode, so you may need to press the OPER button in order to illuminate
the LED above it (unless Auto-Operate is active).
a) Preliminary information.
Tuning the amplier is a procedure of matching the impedance of the currently used antenna to the
optimum tube load resistance. This will ensure optimum plate efciency and RF gain at nominal output
power, with minimum resulting IMD.
Please note, that the REFLECTED POWER readings and the measured VSWR depend on the antenna
impedance only, and not on the amplier tuning. If the antenna impedance is different from 50-Ohm
pure resistive (nominal), the REFLECTED POWER reading will always indicate some reected power
(even with optimal tuning). Proper tuning will assure operation at maximum power without distortion or
danger to the amplier.
Note also that the real OUTPUT POWER in the load is equal to the difference between the FORWARD-
and REFLECTED- readings. For instance, at a reading of FORWARD 1500W and REFLECTED 250W,
the real OUTPUT POWER will be equal to their difference - 1250W (into a 2.4:1 VSWR load). At a very
high VSWR (no antenna or badly mismatched antenna), the FORWARD and REFLECTED readings will
be almost equal, while the real OUTPUT POWER (the difference between them) will be practically zero.
The amplier can operate safely if the following rule is obeyed: "REFLECTED POWER < 400W.” Matching
is assured for loads with VSWR up to 3:1. Nevertheless, for some loads and bands, matching is possible
at even higher VSWR gures. The maximum usable forward power at a VSWR of 3:1 is 1500W with
375W reected. For higher than 400W reected power a ** REFLECTED POWER ** soft-fault protection
trip will occur.
C A U T I O N
Using a coaxial cable with VSWR > 3:1 on HF, and particularly on the 10 and 6
meters bands, is not recommended. At such high values of VSWR, the high voltages,
high currents, and heat associated with line losses risk permanently damage to your
coaxial cable or antenna switch.
Adjust amplier tuning when you change the band or between CW and SSB segments within the same
band. Readjust it each time when you change the antenna, even in the same band, as well as periodically,
even though you may have not changed band or antenna. A signicant change in the environment, such
as rain, snow, ice, new or removed large metallic objects, alien wires nearby etc., can cause signicant
changes in the antenna impedance and an increased VSWR.

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N O T E
If you use more than one antenna per band, it is necessary that you select the proper
antenna BEFORE the next step. Retune after selecting a different antenna for the
same band, since the impedances may differ substantially (unless their VSWRs are
excellent, i.e., below 1.2:1 for both).
C A U T I O N
Do not switch the BAND switch knob while transmitting with the amplier! Such hot
switching will eventually destroy the band switch, and this is not covered by the
warranty!
C A U T I O N
When tuning, do not apply continuous drive longer than one minute and after that
pause 1-2 minutes for tube cooling.
We recommend that you tune-up at the center frequencies of the preferred frequency band. First, select
the band switch and the correct antenna number (never with RF applied!). Then, use table 4-1 in order
to achieve an approximate preset for both TUNE capacitor and LOAD capacitor knobs:
Band, MHz Tune Knob Dial Load Knob Dial
1.8 - 2
3.5 - 4
7 - 7.3
10.1 - 10.2
14 - 14.35
18 - 18.2
21 - 21.45
24.9 - 25
28 - 29.7
50 - 54
Table 4-1. Approximate tuning preset
b) Selecting the plate-load True Resistance Indicator (TRI) tuning aid.
You may select the TRI scale in three different ways:
- By briey pressing simultaneously the PREV+NEXT buttons. This will insert a 6dB attenuator between
the driver and the amplier's input (the ATT LED will light), removing the need to reduce the drive power
during tuning. Press PREV+NEXT buttons momentarily again to switch the attenuator out of the input
circuit and to return to the earlier screen. If you use any of PREV or NEXT buttons, the attenuator will
be switched off too, but the information screen will change.
- By pressing repeatedly either the PREV or NEXT button until you reach the TRI scale. This will not
insert the attenuator, so you must be careful to use less than 20W drive (unless the amplier is near
correct tuning); otherwise the next step will be executed automatically:
- By simply applying a normal (50-85W) drive level while the amplier is not yet tuned. This will
automatically invoke the TRI tuning aid and will insert the input attenuator (the ATT LED will light) after
one second. The attenuator will be switched off, and the old screen will be returned automatically, after
PTT is released. If near-optimal tuning is achieved, the attenuator will not be inserted again. If the old
screen was unchanged (TRI, selected manually earlier), it will be possible to precisely tune the amplier
at nominal power without changing drive at all. Use this approach to shorten the tuning process duration.
c) Tuning Procedure.
While a continuous carrier (CW key down, RTTY or FM) signal at the desired frequency is still applied:
- Look at the upper scale (forward power); obtain maximum power using the upper (TUNE) knob;

14
- Look at the lower (Load Cap) scale and turn the lower (LOAD) knob in order to center the triangle
marker at the "!" mark.
- Release the PTT briey in order to disable the attenuator, then repeat both steps at nominal power.
Always nish by peaking with the TUNE knob
.
N O T E
Appearance of an arrow on either left or right TRI scale edges means that the LOAD
knob position is far off. To correct this, turn the LOAD knob to the prompted direction
until the triangle marker appears inside the scale eld.
I
_____
!_____ IIII >____!_____ IIIIIIIIIII _____!____< IIIIIII _____!__v___ IIIIIIIIIIIIIIII _____v_____
no marker:
use TUNE knob for
max. P to get any
marker.
marker is a far left:
turn LOAD knob
pointer to right until
marker inside.
marker is a far right:
turn LOAD knob
pointer to left until
marker inside.
marker inside:
turn LOAD knob
slightly left to
center it.
LOAD is tuned:
turn TUNE knob to
peak Forward
Power & finish.
Fig. 4-1. Using TRI tuning aid
Please note that the TRI mark will not appear until at least 5W drive is applied, and at least 20W forward
power is achieved.
If, for some reason, matching cannot be accomplished successfully, check the BAND switch position and
proper antenna selection. Then check the antenna VSWR at the same drive frequency.
d) Tuning hints.
While turning the knobs, note that both tunings would be virtually independent. This is a benet of the
TRI. The plate-load resistance increases to the right and decreases to the left of the TRI center.
The scale center corresponds to the proper LOAD capacitor tuning, which presents an optimum load
resistance to the tube.
If you tune to the right, more gain will be obtained but less undistorted output power will be attainable.
You may prefer to use this tuning approach when your drive power is insufcient or when you need less
output but better efciency, for instance at heavy duty modes (RTTY, SSTV etc.) where less heat is
wanted (not only in the amplier but also in the transceiver).
Tuning to the left of the center would lead to the opposite: less gain and more power attainable. Of
course, this requires more drive power, more plate current, and more plate heat, which shortens the
tubes-expected life, as its cathode would be exhausted more quickly.
You might use the above off-center tuning hint also to compensate for mains voltage variations in order
to maintain tube efciency: tune to the right when mains is higher, or tune to the left if it is lower than the
nominal voltage. Please see S.2-2 (Mains Voltage Selection) for more than 5% deviation.
4-5. Continuous carrier modes
The maximum output power in continuous carrier modes such as RTTY etc. is 1500W. You may exceed
this limit for short periods (one minute or less), while adjusting the drive power for instance. Please have
in mind, however, that the mean output power should not exceed 1500W for longer periods.
For prolonged transmissions the amplier gain can drop between 5% and 10% during the rst minute
which is normal while temperature balance of the tube is achieved. You can easily compensate this by
increasing the drive power slightly. Once the drive power has been set, the output power remains stable
with the time for hours.
.

15
C A U T I O N
For transmissions longer than 15 minutes the external auxiliary fan must be installed
(see S.2-5).
4-6. ON LINE Information Screens and Control Functions
a) Besides the Warming Up and TRI (described above in S.4-1 and S.4-4), you have 12 more Information
screens available. They are as follows: Forward Power, Reected Power, Output Power (difference
between forward and reected), Antenna VSWR, Drive RF Power, RF Power Gain, Plate Current, High
Voltage, Plate RF Peak, Screen Current, DC Power Input (product of plate current and high voltage),
and Exhaust Air Temperature (Celsius and Fahrenheit scales). You can use them to monitor the technical
state of the amplier and associated parameters, in a digital form.
Selection is made by the PREV and NEXT buttons. You may change the information screens while the
amplier is used and controlled in operate and standby modes, changes transmit and receive, without
any inuence by the measurement process.
b) You can control the Auto-Operate feature and antenna output assignments while ON LINE. In order
to enter the control menu, press the PREV+NEXT buttons simultaneously and hold them for two seconds.
Further proceed as described for OFF LINE mode below - see S.5-1 and S.5-2 for details.
4-7. Auto-Protection System
When any abnormal condition is detected, the amplier will evaluate the risk and may use three different
degrees of protection, depending on the nature of the problem. Each event is accompanied by descriptive
text.
a) The rst degree of protection consists of a warning message only and does not interrupt transmission.
Examples include "Reduce Drive", "Plate Current", etc. You may continue to transmit under such conditions
but you are close to a trip threshold.
b) The second degree of protection is a trip to standby mode (Soft Fault). An example is ** GRID
CURRENT **. All Soft-Fault messages are marked with two asterisks on both screen edges. The
message remains on the display until any button is pressed or until the auto-operate function returns to
“operate mode” automatically. The Soft Faults permit correction by the user, such as by using less drive,
improving antenna VSWR, etc.
c) The third degree of protection is a trip to OFF LINE mode (Auto-Protection). See S.6-5 - Troubleshooting.
If it is not evident why the trip has occurred, you may try to turn the amplier on again. If the problem
persists, you will need to contact your dealer - see S.1-2.
N O T E
The 6dB input attenuator is automatically inserted about one second after faulty tuning
is detected at drive levels above 20W. It is also switched off at every PTT release
(unless inserted manually).

16
5. OFF LINE MODE
There are two control functions and 14 information screens available in the Off Line Mode of the amplier.
You may enable/disable the Auto-Operate feature and assign the antenna outputs. You may also list
the auto-protection signatures. The tube is not powered at all (only the micro-controller is active) during
these operations.
5-1. Auto-Operate enabling and disabling
When enabled, this function will maintain the amplier in OPER MODE automatically - see S.4-2. The
OPER button will be still functional, so you can change to STANDBY and return to OPERATE manually
at any time. The auto-operate function will be disabled temporarily when you enter the STANDBY mode
but it will be restored after you return to OPERATE by depressing the OPER button.
After having selected the display brightness (see the previous S.5-1), you may continue depressing the
PREV+NEXT buttons in order to enable or disable the Auto-Operate feature. The "Auto Operate = ..."
screen will appear on the bottom line. Use the PREV button to select OFF or the NEXT button to select ON.
Briey press the PREV+NEXT buttons again in order to reach the last control function – the antenna
outputs assignment (see the next S. 5-3). Alternatively, you may leave the buttons unused for 20 seconds.
In any case, the selections made so far will be retained in the amplier’s memory.
5-2. Antenna output assignment
If there is no antenna connected to an antenna output then the output should be disabled. This will make
the switching between two available antennas easier and, more important, it will prevent potentially
damaging the amplier by no-load transmissions.
In order to enable or disable an antenna output, briey press PREV+NEXT buttons successively until the
“Ant:(1-…) 2-…3-…” screen appears. Using the ANT button, move the brackets to enclose the antenna
output you want to disable or enable. Press the PREV button to disable or NEXT to enable it. Press
PREV+NEXT briey again to conrm the antenna output assignments and then leave the menu.
N O T E
All selections you make are stored in the amplier nonvolatile memory. If no button
is pressed for 20 seconds, the selections made so far are accepted and the control
function is left automatically.
5-3. Reading Auto-protection Signatures
On every Hard Fault protection trip of the amplier, signature information is stored in its nonvolatile
memory. The 7 most recent auto-protection trip signatures are stored there, which may be forwarded to
your dealer for diagnostics.
In order to read the trip signatures, press the OPER button while OFF LINE. The display will illuminate
at full brightness and the beginning of the signatures list will appear. Use NEXT and PREV buttons
to navigate through the 7 pairs of screens. For each auto-protection trip there is a pair of information
screens, beginning with nA... and nB... where:
- "n" is the successive number of the event (nr.1 is the latest, nr.7 is the oldest one);
- A and B mark the rst and second parts of an information screen pair.
Two lines, three groups by six symbols (36 symbols in total) are to be copied concerning every one of
the 7 memorized events, from 1A-1B through 7A-7B.
To decode the signatures please see S.6-5 (Troubleshooting).

17
N O T E
After every signature listing the tube warm-up time is reset to 180 seconds regardless
of time in the OFF LINE state.
6. MAINTENANCE
6-1. Cleaning
W A R N I N G
Do not use solvents for cleaning - they may be dangerous both for you and for
the amplier paint or plastics.
Do not open the amplier. Cleaning of the amplier outer surface can be done with a piece of soft cotton
cloth lightly moistened with clean water.
6-2. Fuse Replacement
If it is necessary to replace the mains fuses, use only standard ones.
The Primary Mains Fuse(s) of the amplier are located on the rear panel (Fig. 2-1). They are of the fast
(quick blow) type, 1-1/4 x 1/4 inch Cartridge Fuses, Size "0". Use 20A for 100-120VAC operation. Use
16A for 200-240VAC operation (15A standard is also acceptable).
Besides the primary fuses, on the MAINS PCB (inside the amplier) there are three small glass fuses
(5x20mm European size): one 100mA 250VAC normal blow and two 2A 250VAC slow-blow. These
fuses should not be replaced by the user. Should one of these fuses be blown, it may be indicative of a
serious fault. A fault of this type will not occur under normal operating circumstances. Replacing these
fuses involves special skills and is inherently dangerous. For these reasons, we recommend this work
be carried out by a trained service technician.
6-3. Tube Replacement
A single 4CX1000A/8168 ceramic and metal tetrode is employed in the amplier. Replacement is a
complex and potentially dangerous procedure. For this reason, we recommend this work be carried out
by a trained service technician. Check with your dealer before attempting to replace your tube.
6-4. The ACOM1500 Simplied Schematic Diagram
See Fig.6-1 ACOM2100 Simplied Schematic Diagram. The 4CX1000A/8168 ceramic and metal radial
beam tetrode (V1) is grid-driven. It can dissipate up to 1000W when forced air cooled and is specically
designed for class AB1 RF linear ampliers.
The input signal from the RF INPUT jack is passed through a broadband input matching circuit, which
consists of components in the INPUT PCB and Rsw. This circuit tunes out the tube input capacitance.
The swamping resistor Rsw is a termination load for this circuit and can dissipate up to 100W of RF
drive power.
Cathode resistors labeled Rc create DC and RF negative feedback, thus stabilizing the gain and equalizing
the frequency response. The varistor VSsg, in the screen grid circuit protects the tube and the screen
grid voltage regulator in the event of an internal tube ashover.
The combination noted as Lp1-Rp1 in the plate circuit is a VHF/UHF parasitic suppressor. DC plate
voltage is fed through chokes RFC1-RFC2 and the capacitor Cb3 blocks it from the output. The output
circuit consists of LP1, LP2, LL, CP1-CP3, and CL1-CL3, which form a classic Pi-L network to suppress
any harmonic frequency emissions. This tank is switched and tuned by S1A-S1C and the air variable
capacitors CP1, 2 and CL1, 2. The output signal is fed through an additional VHF low-pass lter for
frequencies above 55 MHz (Lf1, Lf2 and Cf). Then it is passed through the vacuum antenna relay K1,

18
wattmeter current transformer TA1, and a high-pass lter RFCasw-Casw for frequencies below 100kHz,
to the antenna switch and the three outputs. The chokes RFC3 and RFCasw keep track of the antenna
relay contacts and together with Casw prevent the plate supply voltage from reaching the antenna. The
RF choke RFCasw shunts the high voltage to ground should the DC blocking capacitor Cb3 fail. The
resistor Rasw protects Casw from electro-static voltage build-up from the antenna.
The PLATE CAPACITIVE DIVIDER and RF WATTMETER are the main sources of information for the
control circuit of the amplier during the antenna impedance matching process. The control circuit is
based on the 80C552 micro-controller from Philips.
All supply voltages are delivered from the MAINS&LOW VOLTAGE and HIGH VOLTAGE SUPPLY PCBs.
The control grid, screen grid, and plate currents, plate cooling airow temperature, reected power, etc.
are continuously monitored by the micro-controller. Many software-derived protections are based on
this information.
* Detailed electrical schematic diagrams are available from ACOM or from your dealer on request.
6-5. Troubleshooting
See S.5-3 for the method of reading the auto-protection signatures. You can decode them using
the information below.*
The signatures are structured in two lines, three groups by six symbols for every one event of
auto- protection trip. The last event is numbered as 1A-1B pair of lines, and the oldest one is
7A-7B.
The meaning of the rst group is as follows:
a) nA - the number of the trip;
b) Next three symbols mean the following:
PN0 - tests made during Power-On procedure, before HV is ON;
PN2 - tests made during Power-On procedure, after HV is ON and one second after step-
start relay is closed;
SB0 - tests made in Stand-By, during the warm-up period or while entering Stand By (from
Operate);
SB2 - tests made during Stand-By, after the warm-up period;
PR0 - tests made while entering Operate;
PR2 - tests made during Operate;
TR0 - antenna relay tests made while changing from Tx to Rx (during Operate)
TR2 - antenna relay tests made while changing from Rx to Tx (during Operate)
TR4 - antenna relay tests made during Tx (Operate mode)
TR6 - antenna relay tests made during Rx (Operate mode)
c) The last symbol of the rst group designates the kind of the input parameter that caused the
protection circuit to trip. The abbreviations in brackets below are the signal names/designations
according to the CONTROL PCB electrical schematic diagram and signal type:
1 - peak forward power (pfwd, analogue)
2 - reected power (r, analogue)

19
3 - input (drive) power (inp, analogue)
4 - peak anode alternate voltage (paav, analogue)
5 - screen grid current (g2c, analogue)
6 - plate current (ipm, analogue)
7 - high voltage (hvm, analogue)
8 - exhaust air temperature (temp, analogue)
9 - drive power exists (*GRIDRF, logic)
A - antenna power exists (*PANT, logic)
B - output relay closed (ORC, logic)
C - RF arc fault (ARCF, logic)
D - control grid current too high (G1C, logic)
E - +24VDC power supply error (PSE, logic)
F - low airow (LAIR, logic)
For instance, "1ATR4B" in the rst group would mean that the last auto-protection (1A) tripped
by the antenna relay tests made during the Tx - Operate mode (TR4), and the "output relay
closed - ORC" signal was failing (B).
The next ve groups of symbols carry information about the analogue and logic values as
measured by the micro-controller at the moment of auto-protection trip.
* Additional information is available from ACOM or from your dealer on how to interpret these
values. Using an Excel application available from ACOM or your dealer free of charge, and a
PC, you can decode these signatures.
In case it is necessary to ship the amplier please see S.7-3.

20
7. SPECIFICATIONS
7-1. Parameters
a) Frequency Coverage: All amateur bands 1.8-54 MHz, extensions and/or changes on request.
b) Power Output: 1500 W PEP or continuous carrier, no mode limit.
In continuous carrier modes (RTTY etc.) for transmissions longer than 5 minutes (up to several hours
depending on ambient temperature), the external auxiliary fan must be installed.
c) Intermodulation Distortion: Better than 32dB below PEP rated output.
d) Hum and noise: Better than 40dB below rated output.
e) Harmonic Output Suppression:
1.8-21.5 MHz - better than 50 dB below rated output, 24-54 MHz - better than 66dB below rated output.
f) Input and Output Impedances:
- Nominal value: 50 Ohm unbalanced, UHF (SO239A) type connectors;
- Input circuit: broadband, VSWR less than 1.3:1, 1.8-54 MHz continuously (no tunings, no switching);
- Bypass path VSWR less than 1.1:1, 1.8-54 MHz continuously;
- Output (antenna) impedance matching capability: VSWR up to 3:1 or higher.
g) RF Gain: 13.5dB typically, frequency response less than 1dB (50-85W drive power for rated output).
h) Primary Power: 100-264 V (100, 110,120, 200, 210, 220, 230 & 240V nominal taps, +I0% -15% tol.),
50-60 Hz, single phase, 3500 VA consumption at rated output.
i) Complies with CE safety and electromagnetic compatibility requirements as well as FCC-regulations.
j) Size & Weight (operating): W445 mm x D375 mm x H205 mm, 29.3 kg (17.5x14.8x8.1 inches, 64.6 Lbs)
k) Operating environments:
- Temperature range: 0...+50 degs. Celsius;
- Humidity: up to 95% @ +35 degs. Celsius.
- Height: up to 3000m (10 000ft) above sea level without output deterioration.
7-2. Functions
a) Antenna Impedance Matching Process: plate-load True Resistance Indicator (TRI) aided.
b) Three antenna outputs selectable by a button on the front panel.
c) T/R System: QSK operation with quiet, built-in vacuum RF antenna relay.
d) Protections:
- Cover interlock for operator's safety;
- Inrush power-on current is limited;
- High voltage, control grid, screen grid, and plate currents;
- Exhaust air temperature;
- T/R sequencing;
- Antenna relay contacts, including RF power induced in antenna from another nearby transmitter;
- Antenna matching quality;
- Reected power;
- RF arcs, including in antenna system;
- Overdrive.