Acom 600S User manual

HF + 6 m LINEAR AMPLIFIER
OPERATING MANUAL

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ACOM 600S
HF + 6 m SOLID STATE LINEAR AMPLIFIER
OPERATING MANUAL
CONTENTS
1. GENERAL INFORMATION....................................................................................................................... 2
1-1. Inroduction and description..................................................................................................... 2
1-2. Owner assistance ................................................................................................................... 2
1-3. Equipment supplied and options ............................................................................................. 2
1-4. Features ................................................................................................................................. 2
1-5. Safety considerations, explicit definitions................................................................................ 3
2. INSTALLATION ........................................................................................................................................ 4
2-1. Unpacking and Initial Inspection ............................................................................................. 4
2-2. Amplifier location selection; cooling. ....................................................................................... 4
2-3. Connecting the amplifier within the shack ............................................................................... 5
2-4. Installing options and connecting to external devices (transceiver, computer etc) .................. 7
3. INITIAL POWER ON AND SETTING INTO OPERATION ........................................................................ 9
3-1. Low-energy (waiting) mode of the power supply ..................................................................... 9
3-2. Front panel - controls and indication ....................................................................................... 9
3-3. Initial turning on – activation of the main power supply ......................................................... 10
3-4. Basic screen ......................................................................................................................... 10
3-5. Control system – buttons and menus.................................................................................... 12
3-6. Test transmission.................................................................................................................. 12
4. OPERATION WITH THE AMPLIFIER..................................................................................................... 16
4-1. Change of modes RX / TX and Operate / Stand-by; option AUTO OPERATE...................... 16
4-2. Band change, standard and expanded frequency coverage ................................................. 17
4-3. Change of antennas and operation with an external antenna tuner ...................................... 18
4-4. Cooling and fans operation; modes with increased heat loading........................................... 18
4-5. Monitoring the amplifier operating regime ............................................................................. 18
4-6. Automatic protection system................................................................................................. 18
5. MENUS – USEFUL INSTRUMENTS AND OPTIONS............................................................................. 20
5-1. Menu “Measurements in the amplifier” – AMP MEASURE.................................................... 21
5-2. Menu “Service functions in the amplifier” – AMP SERVICE. ................................................. 21
5-3. Menu “Selection of CAT/AUX interface” – CAT/AUX SETTINGS.......................................... 22
5-4. Menu “USER PREFERENCES”............................................................................................ 23
5-5. Reading the FAULTS LOG ................................................................................................... 24
5-6. Menu "RESTORE DEFAULT SETTINGS" ............................................................................ 25
6. REMOTE MONITORING AND CONTROL ............................................................................................. 26
6-1. General information .............................................................................................................. 26
6-2. Commands set...................................................................................................................... 26
7. MAINTENANCE ..................................................................................................................................... 27
7-1. Periodic maintenance; general checks and cleaning ............................................................ 27
7-2. Replacement of fuses ........................................................................................................... 27
7-3. Simplified schematic diagram; theory of operation................................................................ 28
7-4. Using the fault codes (signatures) for diagnostics................................................................. 31
7-5. FIRMWARE UPDATES ........................................................................................................ 32
8. SPECIFICATIONS.................................................................................................................................. 32
8-1. Parameters ........................................................................................................................... 32
8-2. Functions .............................................................................................................................. 33
8-3. Storage and shipment........................................................................................................... 33
9. DISCLAIMER of LIABILITY .................................................................................................................... 33

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1. GENERAL INFORMATION
1-1. Inroduction and description
This manual describes the installation, operation, and maintenance of the HF+6m solid-state linear power
amplifier ACOM 600S.
ACOM 600S is a state-of-the art linear amplifier which covers all amateur bands from 1.8 through 54MHz and
provides more than 600 W output power (PEP or continuous carrier) with less than 30W of drive. The working
parameters of the amplifier are indicated on a multi-functional, high resolution color display. The amplifier control
is performed with only six buttons from the front panel, directly by CAT interface from the transceiver or remotely
– by RS232 interface.
1-2. Owner assistance
If technical or operating assistance is needed, please contact your local dealer first. In the unlikely event you
need further information, you may get in touch with ACOM as follows: fax: + 359 2 920 96 56, telephone +359
2 920 96 55, e-mail: [email protected], [email protected].bg or by mail to: blvd. Nikola Mushanov 151, 1330
Sofia, Bulgaria. The ACOM Internet page is: www.acom-bg.com.
1-3. Equipment supplied and options
The amplifier is supplied in single box, which includes:
- the amplifier ACOM 600S;
- this manual with a CE declaration of compliance;
- four pieces of spare fuses;
Directly from ACOM or from your dealer you can also buy some of the following options:
- CAT interface cables for connecting the supported transceiver models (please specify the wanted one);
- Technical compact disk (CD), containing complete schematic diagrams, graphic information and parts
layouts of the printed circuit boards, as well as a list of commands set and the rules for remote control of
the ACOM 600S amplifier.
1-4. Features
5" (108x65mm) high resolution color display, 800x480 pixels, and 24-bits colors.
The final stage uses field effect (MOSFET) transistors type MRFE6VP6300H, which, according to their
manufacturer - Freescale Semiconductor - are designed to withstand high mismatch (SWR) at the output
and are intended for operation in aerospace, industrial, mobile, and radio broadcast applications.
Compatible with all transceiver models available on the market - does not need any special signals:
"ground on transmit" (PTT) and 30W of RF drive power is sufficient.
Broadband input circuit providing a perfect transceiver load with SWR below 1.2:1 (typically 1.1:1),
without retuning throughout the whole frequency range from 1.8 to 54MHz.
The overall operation of ACOM 600S is extremely simplified: the screen menus are intuitive and easy to
follow and no special skill is required from the operator when changing frequency bands.
Possibility of automatic control – when connected to a transceiver with a CAT interface, the amplifier
monitors constantly, duly follows the operating frequency, and changes the bands accordingly.
Even if not connected with CAT interface, the amplifier monitors the frequency of the input signal through
the built-in frequency counter and automatically switches over the bands.

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Remotely controlled by RS232 interface.
Takes care of itself during operation due to the continuously working protection circuits in all modes.
The operator can monitor digitally more than 10 parameters concerning the working regime of the
amplifier.
Easy maintenance – detailed data (55 parameters) about each of the last 28 hard-fault protection trips is
stored in the amplifier’s nonvolatile memory.
Convenient for expeditions and field operation: extremely compact and light construction, extended
mains voltage range (85-132VAC and 170-265VAC through changing only the main fuses - no internal
switching), limited inrush current and purely sinusoidal consumed mains current, automatic Power Factor
Correction (PFC) – all significant parameters in operation from unstable mains, generators etc. features
achieved thanks to the built-in switching-mode power supply (SMPS).
Perfect electromagnetic compatibility (EMC) both with the highly sensitive as well as with the powerful
appliances in the radio station (receivers, computers, more amplifiers) exceeding the standard EMC
requirements due to the use of PFC and the built-in additional radio-frequency filters.
1-5. Safety considerations, explicit definitions
The linear amplifier ACOM 600S is apparatus Class I of protection against electric shock, i.e. the third grounding
lead of its mains cord (colored yellow with two green stripes) and the grounding stud on the rear panel, marked
GND (Fig. 2-1), must be connected to the grounding system of the shack for safe operation.
The ACOM 600S amplifier is designed to meet international safety standards and complies with CE safety and
electromagnetic compatibility requirements, as well as FCC regulations.
This operating manual contains an assortment of precautions, indications for cautions, and warnings that MUST
BE FOLLOWED by the user to ensure safe operation and always maintain the ACOM 600S amplifier in a safe
working condition.
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, fire hazard or electric shock or lightning.
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 ACOM 600S amplifier.
N O T E notes call attention to a procedure which, if not correctly performed, could result in
inconvenience.
W A R N I N G HIGH VOLTAGE!
The mains power voltage plus a high DC voltage up to 500V inside the
ACOM 600S amplifier are LETHAL! For your safety, pull the amplifier
power plug out of the mains wall outlet and WAIT AT LEAST three
minutes EACH TIME BEFORE you remove the cover of the amplifier.
W A R N I N G HIGH VOLTAGE!
NEVER ALLOW, ESPECIALLY CHILDREN, to push anything into holes
in the case - this will cause ELECTRIC SHOCK! Never touch an
antenna or antenna isolators during transmission or tuning - this may
result in an electric shock or burn. Never expose the amplifier to rain,
snow or any liquids. Avoid placing the amplifier in excessively dusty
environments or in direct sunlight. DO NOT OBSTRUCT COOLING
AIR movement areas.
W A R N I N G

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Do not undertake your own repairs or changes in hardware or
firmware of your ACOM 600S amplifier. Doing so will endanger your
or others' health or life or damage the amplifier 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 by the warranty) please 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 ACOM 600S amplifier, please consult your dealer immediately.
2. INSTALLATION
2-1. Unpacking and Initial Inspection
C A U T I O N
Before you start any work on installing the ACOM 600S amplifier, please
thoroughly read through this manual. First carefully inspect the shipped
carton and Its contents as described below for anything missing from the
set (S. 1-3) or mechanical damages. If anything is missing or is obviously
damaged (scratched, bent, smashed or something is rattling inside or
moving freely when turning over, notify immediately your dealer! The
delay may Infringe the warranty conditions of the carrier.
N O T E
Keep the original packing for possible future transportation.
Take out and inspect carefully the contents of the cardboard carton for possible transportation damages. On the
amplifier check the chassis, the front panel, the display and the buttons below it and on the rear panel – all
connectors, the main power switch, the fuses, and the integrity of the power cable - especially at the area where
it comes out from the panel.
Check in the same way the options if such have been ordered.
2-2. Amplifier location selection; cooling.
Locate the amplifier close to the place where it will be used. You will need an easy access to the rear panel for
connecting cables, and of course, to the buttons and the screen on the front panel of the amplifier.
The ACOM 600S operates with forced air cooling. Locate the amplifier so that there are no objects or devices
closer than 10cm (4”). At an ambient temperature of 40ºC (104ºF) the exhaust air can reach 65ºC (150ºF), this is
why if nearby items are sensitive to heating from outside or use forced air cooling, increase the distances
accordingly.
C A U T I O N
Do not leave free papers, cloth or other light materials around and under
the amplifier. They may be drawn in by the cooling air stream and block
some ventilation apertures. Thus the amplifier will get easily and frequently
overheated which may age prematurely the materials in its construction
and lead to damages, not covered by the warranty.

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2-3. Connecting the amplifier within the shack
W A R N I N G
Before you connect the amplifier to external grounding, you should
advise with a licensed electrician and check-up whether such kind of
connection is allowed by the national and local electrical code, safety
rules, and regulations in force. Simultaneous connection to the earth
grounding and bonding may be inadmissible or may fall under special
requirements in some countries!
W A R N I N G
Never use the gas installation tubing as grounding. This can cause an
EXPLOSION!
W A R N I N G
Do not use the steam-heating or water-supply network tubing as
grounding! Thus, you may involuntarily expose to dangerous voltage
not only yourself but also other people using the same installation.
C A U T I O N
Have in mind that the grounding installation will have to withstand
emergency currents above 15A with minimal voltage drop on it thus it may
be necessary to improve its conductivity using heavier leads and lower-
resistive grounding path. The grounding lead should be at least 4mm2
(AWG 11 or SWG 13).
For details and recommendation on the grounding and RF counterpoise system concerning the electromagnetic
compatibility see also S. 3-6(g).
a) GND stud - external grounding connection of the amplifier. After having made strictly all check-ups
described above, first connect the grounding stud of the amplifier (located on the rear panel and marked
GND – Fig. 2-1) to the grounding system of the shack.
b) KEY-IN jack - amplifier input for receive/transmit control from the transceiver.
The transceiver switches the amplifier from receive mode into transmit mode (RX/TX) via grounding of the KEY-
IN input.
Connect a shielded cable from the respective control output of your transceiver, providing “ground on transmit”
(PTT), to the KEY-IN input on the amplifier rear panel (RCA PHONO jack socket – Fig. 2-1). Use a standard
“RCA PHONO” jack plug for connection to the amplifier.
The manufacturers of transceivers give different names to this output, for example: TX-GND, SEND, T/R LINE,
RELAY, PTT, and others. At some transceivers “ground on transmit” output should be activated by a software
command, a menu or via changing a switch on the rear panel or inside the transceiver. See instructions in the
manual of your transceiver.
C A U T I O N
Before connecting the KEY-IN input verify the electrical specifications of
the transceiver control output (from its own manual) to make sure of their
compatability. The signal voltage applied by the amplifier KEY-IN jack to
the transceiver control output “ground on transmit” does not exceed +12.6V
against ground and its closed-circuit current is below 6mA. See also S. 8-
2(a).
N O T E
Your amplifier will not work if the KEY-IN input is not connected correctly. If
you experience any difficulty consult your dealer.

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Fig. 2-1 Rear panel connections
c) KEY-OUT jack - transmit-enabling control output from amplifier to the transceiver.
The KEY-OUT jack on the rear panel provides an additional control signal from amplifier toward transceiver. It
can be used for improving reliability of the receive/transmit (RX/TX) switching.
When the amplifier is not powered up, KEY-OUT is connected internally to KEY-IN through the contacts of a
relay inside the amplifier, thus always enabling transceiver transmission. Also, in Stand-by mode KEY OUT
unconditionally follows the state of the KEY-IN input. When in Operate mode however, KEY-OUT follows KEY- IN
only when all conditions for safe transmission have been found OK by the amplifier control circuit. At detection of
any risk, transmission is quickly disabled by means of opening the KEY-OUT circuit constrainedly.
C A U T I O N
KEY-OUT is a low-powered output, this is why make sure that the signal
voltage coming to it from the respective transceiver connection does not
exceed 50VDC (open circuit) and that its closed-circuit current is below
20mA.
If your transceiver has a suitable input, which disables transmission unless it is grounded externally, we
recommend that you connect it to the KEY-OUT jack of the amplifier. Use shielded cable terminated with а
standard “RCA PHONO” jack plug.
The manufacturers of transceivers give different names to this transceiver input, for example: TX-INHIBIT,
MUTE, LINEAR, and others. Check the manual of your transceiver. Approach your dealer for details. If your
transceiver has no such input, do not worry – ACOM 600S will operate normally without it as well – then KEY-
OUT jack can remain not connected.
d) RF INPUT – should be connected to the antenna input/output of the transceiver.
Connect a 50-Ohm coaxial cable with a connector type PL-259 from the transceiver output (antenna jack) to the
RF INPUT jack on the rear panel of the amplifier.
N O T E
When operating with the amplifier, do not turn on the transceiver built-in
antenna tuner (if present).
e) RF OUTPUT – should be connected to the antenna, antenna switch or tuner.
Connect a 50-Ohm coaxial cable with a connector type PL-259 from RF OUTPUT on the rear amplifier panel to
the antenna switch, tuner or antenna intended for the respective frequency band.

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C A U T I O N
If you use an amplifier for the first time in your shack, pay serious attention
to the size of coaxial cable from your amplifier output to the antenna. The
cable must be capable of handling the increased power safely, particularly
on the 10m and 6 m bands. This warning refers equally to the antenna
switch, tuner, and the whole antenna system, for example, for multi-band
antennas with resonance circuits (traps etc).
We recommend that you use coaxial cable sized as a minimum similarly to the following types: RG8x, RG8MINI,
RK50-4-11, RK50-4-13 or better still - RG213 or RK50-7-11. Consult your local supplier of coaxial cables to make
the right choice.
f) Preparation of the mains outlet for the amplifier, requirements for the installation and the mains
voltage.
C A U T I O N
Before connecting your amplifier to the mains, check-up with a licensed
electrician if it is properly wired and if your mains is adequate for the
current which the amplifier can consume at an emergency (up to10A from
200/240VAC mains and up to 15A from 100/120VAC mains). Also, make
sure that the grounding lead is connected properly in the wall mains outlet
intended for the amplifier. If subsequently you connect the amplifier to a
different outlet, make sure about it as well.
It is preferable for the amplifier to use the closest mains outlet. Make sure that the respective fuses, the voltage,
and the frequency of your power mains match the ACOM 600S amplifier specifications (see S. 8-1(g)).
g) Mains cord – installation of mains plug and main fuses suitable for your nominal mains voltage.
C A U T I O N
If your amplifier has only one mounted mains fuse (Fig. 2-1 / S. 7-2), it is
suitable ONLY for power mains networks of the type 0-220/240VAC, which
are standard in the EU.
C A U T I O N
Make sure you check whether the main fuses installed in your amplifier
correspond to your mains nominal voltage and if necessary replace them
as described in Section 7-2!
Because of differences among standards in the different countries, the mains plug is supplied and mounted by
your dealer. He connects a standard mains plug for apparatus Class I of protection against electric shock
corresponding to the national and local electrical code, safety rules, and regulations in force in your country.
C A U T I O N
The lead colored in yellow with two green stripes in the mains cord is the
grounding, while the blue and brown leads are active. When the amplifier is
only fitted with one mains fuse, then the fuse is connected in series with
the brown lead, which must be the actve.
If you have any doubt if the mains-cord leads are connected correctly in your mains plug, please consult your
dealer immediately. Using a licensed electrician, the user must implement the checks mentioned above each
time the amplifier is to be connected to a mains network outside the country in which it was purchased.
2-4. Installing options and connecting to external devices (transceiver, computer
etc)
a) CAT/AUX interface - connecting and operation with various transceiver models (see table 2-1 below and
the respective menu in S. 5-3 and Fig. 5-3).
Most of the modern transceivers that provide output data of their working frequency by a serial or parallel port or
as an analogue signal (0 to 8V depending on the frequency) can be connected to the CAT/AUX interface

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connector of ACOM 600S. This will allow the amplifier to follow the changes of the frequency bands automatically
and without any transmission, while the operator is operating with the transceiver.
For control of the amplifier through the CAT/AUX interface you need a special cable between the transceiver and
CAT/AUX connector (type HD-15) on the rear panel of the amplifier – Fig. 2-1. Such a cable can be supplied as
an option along with the amplifier or you can buy it from your dealer additionally, but you can assemble it yourself
as well, using information from table 2-1 and your transceiver's manual.
Schematics of cables for connecting to many transceiver models are readily available in the Technical compact
disk (CD) – an option to the amplifier, as well as on the ACOM Internet page (S. 1-2).
Table 2-1 shows the signals and the pin out of the CAT/AUX connector - rear panel of the amplifier.
Table 2-1
CAT/AUX
interface PIN NO. PIN NAME DESCRIPTION SPECIFICATIONS
Rear panel
view
1 RxD Received Data TTL input
2 RxD Received Data RS232 input
3 TxD Transmitted Data RS232 output
4 TxD Transmitted Data TTL output
5 GND Ground 0 Volt
6 BAND
voltage Analogue input 0 to +8V
7 B. data 0 Bit 0 TTL input
8 B. data 1 Bit 1 TTL input
9 B. data 2 Bit 2 TTL input
10 B. data 3 Bit 3 TTL input
11 ON RMT Remote Pwr On +4.5 to +15V / 3mAmax
1 to 2 seconds pulse
12 Debug
mode CPU only Power Input +8 to + 15V / 0.4A
13 KEY-IN Transmit Request Rx/Tx control input
Less than +12.6V
Less than 6mA
14 KEY-OUT Transmit Enable O.C. output, 0 to +50V
20mA maximum
15 GND Ground 0 Volt
N O T E
Due to the variety of existing CAT protocols for different transceivers, the
amplifier response may be different for some transceiver models, as
described below.
- Some older transceivers employ a rather slow protocol or send frequency data with a delay of several
seconds – then the amplifier response will be delayed respectively;
- In some cases, when the transceiver is powered on after the amplifier, you may need to press and hold
up for one second the button BAND of the amplifier, up or down (Fig. 3-2), to make the transceiver inform
the amplifier about its frequency; in other occasions, the transceiver transmits its frequency only on
changes and you may need to move slightly the main frequency dial knob or change it in another way in
order to announce it to the amplifier after an initial power turn on;
- in "split" operation, not all transceivers provide frequency data of VFO A and VFO B correctly; if your
receive and transmit frequencies fall in different frequency bands (Cross Band Operation) and the
amplifier unnecessarily switches between them at each transition receive/transmit (RX/TX), you may
deactivate the amplifier’s CAT/AUX interface control while operating "split" (S. 5-3 and Fig. 5-3).

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b) RS232 Interface. Table 2-2 shows signals and pin out of the RS232 connector on the rear panel of the
amplifier. Details about connecting and using the RS232 interface are given in the Technical compact
disk (CD) – option to the amplifier and / or in the respective control programs.
This connector can remain unconnected until you decide to use the amplifier with remote control.
Table 2-2
RS 232
interface PIN NO. PIN NAME DESCRIPTION SPECIFICATIONS
Rear panel
view
1 - Not connected -
2 TxD Transmitted Data RS232 level output
3 RxD Received Data RS232 level input
4 - Not connected -
5 GND Ground 0 Volt
6 DSR Data Set Ready RS232 level input
7 - Not connected -
8 CTS Clear To Send RS232 level input
9 - Not connected -
3. INITIAL POWER ON AND SETTING INTO OPERATION
C A U T I O N
Do not turn on the amplifier for at least two hours after it is unpacked and
installed in its operating position. Pay particular attention whenever the
amplifier is moved from a very cold place to a very warm one because
unseen condensation may develop and this could result in damage to the
high voltage circuits of the amplifier. Under these circumstanves, do not
turn on the amplifier for at least 4 hours. A similar effect could occur
following a rapid warming of the room, such as winter use of a powerful
electric heater.
After having mounted and connected the amplifier according to the instructions in Section 2 INSTALLATION and
have followed all requirements, check whether mains switch on the rear panel is in turned-off position – in Fig. 2-
1 the rocker of the POWER ON switch must be protruding from the side of the “ON” inscription. Afterwards insert
the mains plug of the amplifier into the mains outlet prepared for it. For now the amplifier remains turned off.
3-1. Low-energy (waiting) mode of the power supply
Now you can put the mains switch on the rear panel in a turned-on position, pushing its rocker so that it sinks
from the side of the “ON” inscription (Fig. 2-1). This will activate only the low-energy (waiting) mode of the power
supply and will illuminate the red LED above button ON/OFF on the front panel, while the main power supply is
still inactive and the display is dark.
3-2. Front panel - controls and indication
a) ON/OFF button – serves for manual (local) start up of the power supply from low-energy (waiting) mode
of the power supply (S. 3-1) into working mode, i.e. for activating of the main power supply and starting
operation with the amplifier. The same button is used also for main power supply deactivation – return
into the low-energy (waiting) mode of the power supply at ceasing operation with amplifier.
b) LED indicator above the ON/FF button. The red LED indicator glowing above the ON/OFF button at a
dark display shows that mains voltage is fed from the plug, the POWER ON switch on the rear panel
(Fig 2-1) is in a turned-on position, but the power supply is in its low-energy (waiting) mode (S. 3-1). In
this mode activation of the main power supply is expected to start operation with the amplifier.

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Fig. 3-1 Front panel
During operation with the amplifier the display is illuminated and the red LED above the ON/OFF button indicates
the button location which can be very useful in case of fast switching off in poor light conditions.
c) Keyboard with 6 buttons for manual (local) control of the amplifier. The function of each button is
prompted on the display above it. Depending on the menu displayed, the buttons may have different
functions.
d) The color display shows all the relevant information about the status of the amplifier.
3-3. Initial turning on – activation of the main power supply
In order to activate the main power supply at starting amplifier operation, press and hold on the ON/OFF button
on the front panel for one or two seconds - аbout three seconds later the display will flash and show the basic
screen showing the amplifier status and operation - Fig. 3-2.
After turning on, the amplifier stands in Stand-by or Operate mode – it depends on whether the AUTO OPERATE
option has been activated – see S. 5-4 USER PREFERENCES.
3-4. Basic screen
There are 9 information areas on the basic screen as follows:
a) Information area for the frequency band – the borders of the currently selected BAND are displayed.
If at start up of the amplifier there is no information about the operating frequency (neither the CAT/AUX nor the
RS232 interface is connected) the last working frequency is taken, which has been stored in the nonvolatile
memory of the amplifier.

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Fig. 3-2 Basic screen
b) Information area for measurements or alarm messages.
Any two operator-chosen parameters will be normally displayed in this area on black background – see the list in
S. 5-1 Measurements in the amplifier – AMP MEASURE.
The alarm messages (either type WARNING or SOFT FAULT) appear with black font on yellow background on
the area for measurements and are flashing frequently in order to attract the operator's attention (Fig. 4-1).
The WARNING type of messages appear only temporarily (for about three seconds), afterwards the indication of
the measurements is restored automatically (S. 4-6(a)).
The SOFT FAULT type of messages appear in the same field (on the area for measurements) however they
remain and persist on the screen until the AUTO OPERATE time is elapsed (S.4-1(c)) or until the operator
presses any button, then the measurements indication is restored, too.
c) Indicator for the working mode - OPR, STB or AUTO OPER (S. 4-1).
d) Indicator RX/TX reflects the state of the request for transmit (KEY-IN input). The RX indication is green
and the TX is red. When a request is present but it could not be performed for any reason, the respective
indicator RX or TX is flashing frequently.
e) Bar-graph and digital indicator for forward power at the output. Reads the power fed from the amplifier to
the antenna.
f) Bar-graph and digital indicator for output reflected power. Entering the red zone is inadmissible.
g) Bar-graph and digital indicator for temperature of the final stage. Entering the red area is inadmissible.
h) Information label for activated CAT/AUX interface. When CAT/AUX is deactivated, this label is shaded.
i) Information label for activated REMOTE CONTROL – flashes after feeding one or more commands by
the RS232 interface. Dies out (remains shaded) after feeding one or more manual (local) commands
from the buttons or by the CAT/AUX interface from the transceiver.

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3-5. Control system – buttons and menus
a) The OPR/STB and the BAND (up and down) buttons are used for manual (local) control of the amplifier in
the basic screen (Fig. 3-2):
- the left-most button – OPR/STB is for alternative switching of the amplifier mode between Operate and
Stand-by;
- the next two buttons – BAND up and down arrows – serve for manual change of the frequency bands in
ascending or descending order; pressing and holding on either up or down arrow for one second will
refresh the information about the operating frequency on the CAT/AUX INTERFACE;
b) The right-most button – MENU (Fig. 3-2) – serves for access to the list of menus.
All necessary instruments, as well as the control and service options of the amplifier are structured in six menus.
Each of them has only one hierarchical level (menu depth) – Section 5 and Fig. 5. This simplified structure gives
the operator maximum clarity and possibility of easy navigation. More handiness is provided by the uniform
approach to the different menus:
- in each screen (the menu list and all tools in them) the left-most button is always HELP and the right-
most – always EXIT;
- the HELP button can be used at any time for obtaining of auxiliary information concerning the currently
activated screen (context sensitive help);
- the currently chosen menu title (for example AMP MEASURE) is always present at the top of the menu;
- the EXIT button can be used at any time to leave the currently used menu or the menu list for possibly
easiest and fastest “return” to the basic screen (Fig. 3-2).
For more details on the control system and use of the menus see Section 5. MENUS – USEFUL INSTRUMENTS
AND OPTIONS.
3-6. Test transmission
To make sure that you have installed the amplifier correctly, before you put it in operation, make a test
transmission as described below. Repeat these tests for each new band and antenna, as well as after installing a
new or repaired antenna, antenna switch, tuner, and / or connecting cables.
a) Check of RF by-pass path at non-driven amplifier.
For this check the amplifier must be completely installed and connected withing the shack according to Section 2,
but not powered by the mains, i.e. the mains power plug must be pulled out from the mains outlet or the POWER
ON switch on the rear panel must be in turned off position. In any case the LED above ON/OFF button must be
dark for this test.
First, check if the transceiver reception is normal. If you observe a significant worsening of reception, search for
the problem first in the coaxial connections to the amplifier (S. 2-3(d),(e)).
If reception is normal, prepare the transceiver regime as follows:
- select a continuous carrier mode (CW, RTTY, FM or some digital mode);
- switch the microphone off (decrease the mic gain), ban the FSK respectively;
- reduce the output power control to a minimum;
- select a suitable indication so that you can watch the RF power and SWR at the transceiver output;
- if the transceiver has an incorporated antenna tuner – switch it off.
Now in receive mode select a frequency which is not occupied at the moment and press shortly the transmit
actuator (the PTT or the TX button) while observing the output power and the SWR indicators. If the power or the

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SWR at the transceiver output are too high (over 5W or SWR over 2:1) immediately release the actuator and
search for the reason as follows:
- check again whether the output control is set at minimum;
- check whether the frequency on which you are transmitting is within the operating range of the selected
antenna;
- check the good working order of the connecting coaxial cables, connectors, and feed lines from the
transceiver antenna jack through the amplifier, the antenna switch or external tuner (if there is such) to
the BALUN transformer, and the antenna itself (S. 2-3(e)).
In case of difficulty use antenna measurement instruments or contact your dealer.
If the power and SWR are as expected, then go transmitting again and while watching the power and the SWR
indicators, increase transceiver power gradually from minimum to maximum (but not more than 200W, in order not
to overload the RF by-pass circuit of the amplifier).
If SWR remains below 2:1 (preferably below 1.5:1) at the last test, decrease the power from the transceiver to
minimum again and continue with the next check. Otherwise you will have to make corrections on the antenna and
/ or feed-line matching or use an external tuner for this antenna. The tuner should handle the maximum output
power of the amplifier (S. 8-1(b)) at the respective antenna SWR.
b) Check in Stand-by mode.
After a successful check-up with non-powered amplifier, item (a), turn on its mains power supply and run it to the
basic screen, as described in Sections 3-1 to 3-4 (Fig. 3-2).
For this check it is necessary that the amplifier is in the Stand-by mode. If the AUTO OPER option has been
activated at any previous switching on of the amplifier, it will automatically start in the AUTO OPER mode (Fig. 3-2
and S. 5-4) immediately after turning power on. In such a case, press once the OPR/STB button to return the
amplifier manually to the Stand-by mode.
In this state repeat the receive and transmit tests with the transceiver through the amplifier RF by-pass path, as it
was described in the preceding item (a). During these tests note also whether the bar-graphs and digital indicators
for forward and reflected power in the basic screen (S. 3.4(e),(f)) show respective RF power presence. If the
reflected power exceeds the forward power, verify that you have not interchanged involuntarily the input and
output coaxial cables to the amplifier (S. 2-3(d),(e)).
N O T E
The power indication is optimized around the 600W level and normally it is
unreliable below 50W.
c) Entering Operate mode.
After a successful check in Stand-by mode, item (b), while you are in the basic screen, press the MENU button.
From the list select menu AMP MEASURE (Fig. 5-1). In the left-side of the screen select PA DC VOLTAGE and in
the right-side – PA DC CURRENT (use the ITEM1 or ITEM2 buttons to scroll the list if needed). Press twice the
rightmost EXIT button to return to the basic screen. The two selected parameters – PA DC VOLTAGE and PA DC
CURRENT - will be indicated in the basic screen as well – S. 3-4(b). In Stand-by mode they must be zero.
Now press the OPR/STB button to put manually the amplifier in Operate mode (S. 3-2 and Fig. 3-2). The OPER
or the AUTO OPER indicator must flash and the indicator RX/TX must remain in condition RX. Besides this, PA
DC VOLTAGE must become 48-52V while PA DC CURRENT must remain zero.
At entering the Operate mode the receiving of the transceiver should not suffer. If it worsens and together with this
the indicator RX changes into TX and any current appears on the drain (PA DC CURRENT) although the
transceiver is in the receive mode, check if they normalize at return to the Stand-by mode.
If the problem occurs only at transition into the Operate mode and disappears at return to Stand-by, check the
control cable connected to the KEY-IN input – S. 2-3(b) – it is possible that the conductor is shorted to the shield
(ground) or the connection to the transceiver is wrong, thus wrongly requesting transmit mode toward the amplifier
during transceiver reception.

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d) Check of the RX/TX switching and the amplifier idling current without RF power.
Put the transceiver in such a regime that at pressed PTT or TX button a transmit request is applied to the amplifier
but with no RF power on the transceiver output. For example, select SSB mode with microphone gain control
reduced to zero or CW mode with Morse key up to avoid any RF power while requesting transmit mode to the
amplifier by pressing the PTT or the TX button (do not use automatic CW keyer or VOX).
At pressing the PTT or the TX button without RF drive at the amplifier input, the green label “RX” on the basic
screen must become red “TX”. Note that the indicator reflects the TX request and not its performance. Besides
this, on indicator PA DC CURRENT must appear the final-stage idling current of around 1.0 – 1.4 A, but neither
forward, nor reflected power must appear at the output.
If at pressing the PTT or the TX button and without RF drive at the amplifier input any indication of RF power at the
output still appears, it might be due to self-oscillation or it may be externally induced by co-sited powerful
transmitters. If you suspect self oscillation, check-up the coaxial cables to the input and output of the amplifier, in
particular the contact of their shields to the coaxial connectors (S. 2-3(d),(e)). To check for externally induced RF
power (especially if the reflected power is higher than the forward power) connect the antenna to a dummy load
via an external RF wattmeter - it should read zero RF power.
e) Test transmission.
In the basic screen (Fig. 3-2) check whether the currently selected frequency band of the amplifier and the
transceiver frequency match the antenna band. If needed (when the CAT/AUX interface between the amplifier and
the transceiver is not connected), use BAND buttons (up and down) of the amplifier to switch to the desired
frequency band manually.
In order to continue with the test transmission, prepare the transceiver regime in the same way as it was done in
item (a) above: with continuous carrier mode and minimum power. Now in the Operate / RX mode choose a
frequency which is presently not occupied and press the actuator for transmit (PTT) briefly, while watching the
following indicators of the amplifier:
- RX mode must be changed to TX;
- the reflected power must be below 20W;
- the forward power must be between 20 and 150W with minimum drive power from the transceiver
(between 1 and 5W expected with the power control set at minimum);
- PA DC VOLTAGE must be within 48-52V;
- PA DC CURRENT must be between 1 and 8A (depending on the transceiver power with its power
control set at minimum).
If the above test goes normally, push briefly the transmit actuator (PTT) once again, this time watching the
transceiver SWR indicator (i.e. the input SWR of the amplifier) – it must be below 1.2:1.
f) Setting of drive level and typical regime.
After the successful passing of tests (a) to (e), in the same regime with continuous carrier and minimum power,
press the transmit actuator (PTT) for several seconds, observing the forward and reflected power at the output, as
well as the direct current consumed by the final stage – PA DC CURRENT. Increase the drive power gradually –
from minimum until the forward power at the amplifier output reaches 600W. Observe at the same time that none
of the indicators of the amplifier or the transceiver enters the colored alarm areas.
Reaching 600W forward power, check-up the following parameters (continuous carrier regime):
- the reflected power must not exceed 70W (for SWR 2:1) or better still to be below 25W (for SWR 1.5:1);
- PA DC CURRENT must be between 20 and 26A; it is normal that the current varies within these limits at
changing of the operating frequency and the antenna impedance;
- PA DC VOLTAGE must be within 48 – 52V;
- the SWR indication of the transceiver must be below 1.2:1.

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Enter menu MEASURE and check-up additionally:
- the drive power from the transceiver must be between 20 and 30W;
- PA BIAS must be between 2.5 and 2.9V (typically 2.8V);
- PA TEMPERATURE must be between the ambient and 80ºC (176ºF) depending on the power level and
the duration of transmission.
When possible, listen to the quality of the amplified signal using a monitoring receiver or ask some regular
correspondents for signal assessment and comparison with and without amplifier.
g) Elimination of electromagnetic compatibility (EMC) problems.
If you use an amplifier for the first time in your shack, you may need to make some improvements in its set up. It is
possible you might find tingling from metallic objects due to the stronger radiated RF field. It could affect the
operation of your station or systems outside it, if the latter are too sensitive – typical examples are the microphone,
the Morse keyer, the computer keyboard / mouse, as well as domestic radio / TV receivers, Hi-Fi, intercom or
telephone setups and others.
For instance, induction of RF currents into the microphone, Morse keyer or computer keyboard, may lead to rough
distortions in the peaks or self-oscillation in SSB mode, “sticking” or breaking off the dots or dashes from the
Morse keyer, or garbles on the computer screen, coming from the keyboard or mouse. For the elimination of
similar problems we recommend that you take the following general measures:
- minimize the radiation from the feed lines by reducing the common mode currents in them; improve the
balance of the antennas themselves and how they are fed;
- in case you use asymmetric antennas (GP and similar) install as many radials as practical (a more
developed counterpoise system);
- ground the coaxial cable shield additionally on at least one spot between the antenna and the shack or if
it is possible run the greater part of the feed line under ground;
- add current BALUN transformers in the coaxial feeders at the antenna itself, as well as at the feeder
entering the building (although this may seem unnecessary at GP);
- take away as far as possible (also by height) the radiating elements of the antennas from the premises
where the affected apparatus is located; in this sense, asymmetrical antennas without a feeder (type
Long Wire, simple Windom, and other similar) may cause more interference because their radiating
element begins immediately from the shack (it is the feeder itself);
- if the use of asymmetrical directly fed “wire” antennas is inevitable, use mainly half wave or half wave
multiple – they have a high input impedance, operate respectively with a small current in the feed point,
and in the grounding of the shack; thus you can reduce the strength of the disturbing RF fields in the
whole more than 10 times (at the same radiated power) compared to the case with quarter-wave and
multiple to quarter-wave antennas of this class – you should avoid them because they have a low input
impedance and operate with a large RF current in the grounding system and in the power supply network
respectively, i.e. they create stronger disturbances (RFI);
- improve the RF grounding system: use the shortest and widest possible metal strips for the connections
to ground and between the different gear in the shack; connect one or more counterpoises (sized for the
problematic band) to the feeder shield at the point, where it enters the building, and the same point - with
the possibly shortest and widest connections - to the grounding system: this is a very efficient measure,
in particular if the shack is located on a high floor above ground;
- to reduce the RF impedance of the grounding connections sheet metal strips instead of flexible braids
are preferred;
- thread ferrite beads with medium permeability (800-4000) over the power cord, the feeder and the signal
cables leading to the affected devices (TV etc); there are suitable “split” ferrites on the market for this
purpose with different sizes, shapes and parameters, inserted in locking plastic shells, which do not need
to be threaded through the connectors on the cable ends and are simply put and locked over it; besides

Page 16 of 33
the size, consider the frequency range in which the offered ferrites are effective – normally they are
optimized for suppression of interferences on HF (with larger permeability), with medium permeability for
HF-VHF or with low permeability - only the VHF range. The latter are ineffective for HF;
- whenever possible use shielded cables and ground their shields at both ends;
- screen (at least partly) the disturbed apparatus, for example, put under the keyboard, the mouse, the
desk microphone or the Morse keyer a large metal sheet, connected to the grounding system of the
shack;
- the addition of even quite simple low pass L/C or R/C filters directly to the disturbed inputs or outputs of
the apparatus is very effective, provided it is practically applicable.
Last but not least, have in mind that the benefit of the above measures is two-fold. Firstly - they reduce the
interferences from your transmissions to the ambient environment and secondly - they reduce the background
noise floor for your reception. Practically, with no great efforts, implementing the above measures, you can reduce
the background noise floor with one or more S-units across the different bands. This will allow you not to miss
weaker stations, which will hear you because of your increased transmission power.
4. OPERATION WITH THE AMPLIFIER
4-1. Change of modes RX / TX and Operate / Stand-by; option AUTO OPERATE
a) In Stand-by mode, as well as with un-powered amplifier, receiving and transmitting with the
transceiver is implemented via RF by-pass between RF INPUT and RF OUTPUT of the amplifier. At
transmission in Stand-by, RF power of the transceiver is not amplified by the amplifier, the control
KEY-IN input does not influence over its operation, and the KEY-OUT output (S. 2-3(c)) follows the
state of the KEY-IN input unconditionally.
b) In Operate mode the final stage of the amplifier is powered and it is fully functioning; the receive-
transmit (RX / TX) direction is controlled by the KEY-IN input:
- at open KEY-IN (Operate/RX mode), the transceiver receives the signals from the antenna through the
same RF by-pass path between RF INPUT and RF OUTPUT through which receiving is done with
amplifier turned off or in Stand-by mode;
- at grounded KEY-IN (Operate/TX mode) the amplifier input relay connects the RF INPUT connector
(drive from the transceiver) toward the final stage input and the output relay feeds the amplified signal
from the final stage output to the antenna through the RF OUTPUT connector.
C A U T I O N
In order to provide time for the relays and the final stage in the amplifier to
switch safely from receive to transmit, the transceiver should provide a
dead time i.e. must “notify” the amplifier in due time grounding its control
KEY-IN input not later than 10ms before feeding drive power toward the
amplifier RF input. Otherwise, the “HOT SWITCHING ATTEMPT”
protection will trip.
In Operate mode the KEY-OUT output (S. 2-3(c)) follows the state of the KEY-IN input only after all conditions for
safe transmission have been satisfied and found OK by the amplifier control unit. The KEY-OUT output duly
disables transmission, if this is inadmissible or there is a potential risk for the amplifier or the transceiver.
The two modes - Operate and Stand-by - may alternatively be changed in three different, independent ways as
described below:
- manually (locally) – by successive pressing the OPR/STB button – Fig. 3-2;
- remote control – through the respective command “OPR” or “STB”, received through the serial RS232
Interface;
- automatic control – if the AUTO OPERATE option is activated – see next item and S. 5-4(b).

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N O T E
Access to the Operate mode can be banned in the menu AMP SERVICE,
the OPERATE ACCESS option (S. 5-2 and Fig. 5-2). The ban is universal.
c) AUTO OPERATE option - can be activated or deactivated by the operator in the USER
PREFERENCES menu – S. 5-4 and Fig. 5-4 - or through remote commands by the RS232 interface.
When the AUTO OPERATE option is deactivated, the two modes Operate and Stand-by can be changed
alternatively via the OPR/STB button or by commands OPR and STB by the RS232 interface. Besides this, at a
protection trip of the type SOFT FAULT, the amplifier returns to and remains in Stand-by mode, waiting for
external intervention. For restoring of the operation, the operator must press the OPR/STB button manually or to
feed remote command OPR by the RS232 interface.
When AUTO OPERATE is active (S. 5-4), the amplifier goes automatically to Operate mode immediately after
power on without waiting for an OPR command by the interface or pressing the STB/OPR button by the operator.
At a protection trip of the type SOFT FAULT, the amplifier will first go to Stand-by mode (same as at the
deactivated option), but afterwards it will return automatically to Operate mode after about 4 seconds without
need of the operator to press any button. Thus, the amplifier will automatically seek to "support” Operate mode
always when this is admissible.
Anyway, even at activated AUTO OPERATE option, the operator can return to and remain in the Stand-by mode
also manually – through the OPR/STB button or by STB command by the serial RS232 interface. This will
suppress temporarily the AUTO OPERATE function and the amplifier will go to and remain in the Stand-by mode.
The next pressing of the OPR/STB button or sending OPR command by the interface will turn the amplifier in the
Operate mode and will restore the normal operation of the AUTO OPERATE option (provided it had been active
before the command).
4-2. Band change, standard and expanded frequency coverage
When the amplifier is connected to a transceiver with the CAT/AUX interface or to a computer with the RS232
interface, the change of the frequency bands (i.e. change of the amplifier harmonic filters) occurs automatically,
following the operating frequency changes from the transceiver or from the computer.
N O T E
In the Stand-by mode the change of bands through the CAT/AUX interface
is deactivated temporarily; It is restored at returning to the Operate mode.
The RS232 band change commands operate continuously. If the amplifier gets a band change command during
transmission, the transmission is blocked temporarily while the command is being performed; the amplifier
operation is restored after the change of the low-pass filters for the new band.
When the amplifier is not connected to any interface, the band changes can be accomplished manually or again
automatically – through the built-in frequency counter in the amplifier.
Manual changes of the frequency bands can be done from the basic screen (Fig. 3-2) by the BAND buttons – up
and down. They can be done also in the Stand-by mode as well in the Operate mode, but only during reception.
Automatic change of a frequency band via the built-in frequency counter of the amplifier or with CAT/AUX is
performed only in the Operate mode. In the Stand-by mode the frequency changes are continuously followed (with
the frequency counter – only during transceiver transmissions) but are not performed physically by the low-pass
filters. The latest frequency change is performed at entering the Operate mode.
When you rely on an automatic change with the built-in frequency counter, it is a good practice (although not
compulsory), that selecting a new band the operator makes one quite short “preliminary” transmission (100ms is
enough) and leave a pause (also short) before the main transmission. During this pause the amplifier will change
the band according to the new frequency without RF power, after which the operator can continue his operation as
usual.
If the new frequency is within the range admissible for the amplifier but outside the currently selected band, the
amplifier control unit temporarily blocks transmission while the change of the harmonics filter for the respective
new band lasts, after which the transmission continues on the new frequency as usual.

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If the new frequency is out of the range admissible for the amplifier (S. 8-1(a)), the transmission request is denied
and the following fault message appears on the screen:
“FREQUENCY OUT OF RANGE”
The standard frequency bands within which all amplifier parameters are guaranteed are listed in S. 8-1(a)).
Extension or changes of the bands could be negotiated with the manufacturer.
4-3. Change of antennas and operation with an external antenna tuner
At a band change or moving frequency from one to the other end of the band it may be necessary that you change
the antenna and eventually retune the antenna tuner (unless your antenna is a multibander and / or is broadband
enough).
At antenna SWR over 1.5:1, it is preferable that you use an external tuner. Usually the procedure for retuning the
tuner requires a continuous carrier signal and small power. In such a case, go to the STBY mode of the amplifier
and feed the power necessary for tuning from the transceiver only. After you have retuned the antenna tuner on
the new operating frequency or with the new antenna, return to the Operate mode and adjust again the drive
power according to the operating mode used – S. 3-6(f)).
4-4. Cooling and fans operation; modes with increased heat loading
During operation in modes with increased heat loading (continuous carrier, RTTY, SSTV, some digital modes, and
others), the amplifier itself will monitor its temperature regime, automatically increasing or decreasing fans velocity
depending on the loading and ambient conditions (temperature, humidity, atmospheric pressure etc.).
4-5. Monitoring the amplifier operating regime
Because of the availability of a continuously operating protection system in the amplifier (S. 4-6), the operator is
not required to monitor its regime regularly. However, whenever he wishes, he can digitally measure the 11 most
important parameters connected with the amplifier operating regime. Besides this, the operator can select two of
them arbitrarily for indication also in the basic screen (Fig. 3-2, S. 5-1).
4-6. Automatic protection system
The control unit (S. 7-3(b)) keeps track with most amplifier analogue and logic signals in all modes. Monitored are,
for example, the control signal receive / transmit, the output relay contact status and switching times, the RF drive
frequency and drive power (the input power), the DC current and the DC voltage on the drains of the final
transistors, the bias voltage of their gates and the temperature of their heat sink, the temperature of the main
components in the power supply unit, the forward and reflected power at the RF output, and others. Besides this,
monitored and assessed are some derivative parameters, such as the power gain, the SWR, the heat power
dissipated by the final transistors dynamically etc.
If anything abnormal has been found out in an arbitrary moment, the amplifier will assess the risk of the situation
and can use three levels of protection according to the problem nature and seriousness, as described in items (a)
to (c) below. Every event is accompanied by a warning text on the screen (Fig. 4-1), which is blinking to attract the
operator’s attention. Besides this, a sound signal is produced, whose volume, can be reduced by the operator if he
so wishes – menu “USER PREFERENCES” – Fig. 5-4.

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Fig. 4-1 – Appearance of an alarm message
a) The first protection level is the WARNING type. Only a warning message appears on the screen
accompanied by a sound signal, but without any physical reaction from the amplifier – Fig. 4-1. This
occurs when some of the values monitored by the control unit approach too close the threshold of
tripping the respective protection. The transmission is not interrupted, but a message appears – for
example “Drive Power too High”, “Drain Current too High”, or another.
You can continue to transmit in these conditions, but you also have to take some measures, for example, to
reduce a little the drive power from the transceiver, because the respective protection trip will be too close. The
warnings for the first level remain on the screen for at least three seconds so that they can be read through and
they disappear by themselves after the reason has dropped off.
b) The second protection level is the SOFT FAULT type – it trips at crossing the threshold of some
protection, as long as it had not been fatal (then the third level trips – see item (c) below).
At the second level (SOFT FAULT) the amplifier itself does not turn off fully but only returns into Stand-by mode
for four seconds or permanently - depending on whether the “AUTO OPERATE” option had been activated. Return
into Stand-by mode is accompanied with the respective message on the screen, for example “Excessive Reflected
Power”, “Excessive Drain Current”, and others, as well as with a sound signal (unless its volume had not been
decreased to zero – S. 5-4).
Unlike those for a WARNING, the SOFT FAULT messages remain on the screen and persist until the operator
presses any button (including the two unused in the basic screen) - thus it is understood that he has read the
message - or until the AUTO-OPERATE function returns automatically the OPERATE mode if the option is active
– S. 5-4.
SOFT FAULTs presume performing fast and simple correcting actions by the operator, such as, for example,
reducing the drive power, improving of load SWR through retuning of the antenna tuner, selection of another
antenna, another frequency etc.
c) The third and most serious protection level is the HARD FAULT type, which turns off the amplifier
automatically to avoid possible further damages.
At tripping the third level of protection, the amplifier turns off its main power supply automatically, stores all data
about the fault in its nonvolatile memory, the front panel screen blanks and a specific sound signal is emitted
(namely a series of Morse letters F, which continues until the control unit still has residual energy).