MCL TN440-3 Instruction Manual

TN4400-3
Technical Note
Operation of MT4400 TWTA
August, 10, 2004
Mark Schmeichel 8/13/04
Engineering Date
Lars E. Agner 8/16/04
Sales Date

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TABLE OF CONTENTS
1.0 SAFETY SUMMARY ................................................................................................................ 4
1.1 Definitions of Warnings, Cautions, and Notes.................................................................4
1.2 General Safety Precautions...............................................................................................5
1.3 List Of Hazards.................................................................................................................6
2.0 SCOPE.........................................................................................................................................8
3.0 CONTROLS & INDICATORS.................................................................................................8
3.1 Discrete Status ..................................................................................................................8
3.2 Discrete Control................................................................................................................9
3.3 User Discrete Control & Status Interface .........................................................................9
3.4 Controls & Status via Communications Protocol.............................................................9
4.0 HPA OPERATION...................................................................................................................12
4.1 HPA Control Modes ....................................................................................................... 12
4.2 HPA Operating Modes.................................................................................................... 14
4.3 RF On/Off Control..........................................................................................................16
4.4 Faults & Alarms..............................................................................................................16
4.5 HPA Gain Control (Optional).........................................................................................18
4.6 Diagnostic Interface........................................................................................................19
4.7 Optional Linearizer.........................................................................................................27
4.8 Switchover Interface J8...................................................................................................27
4.9 Discrete Interface J5........................................................................................................28
4.10 Prevention of Excessive RF Input Power .......................................................................28
5.0 HPA INITIAL TURN ON........................................................................................................ 31
5.1 Initial Turn-On Check List..............................................................................................31
5.2 Operating Caution List....................................................................................................32
5.3 Power-Up Procedure – Remote Panel Usage.................................................................. 32
6.0 SHUT DOWN PROCEDURE ................................................................................................. 35

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LIST OF APPENDICES
APPENDIX A - 40A1546 CSP Protocol Specification
APPENDIX B - 40A1715 SABus Compatible Protocol Specification
APPENDIX C - 46A0204 CSP Command Set
APPENDIX D - 46A0203 SABus Command Set

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1.0 SAFETY SUMMARY
1.1 Definitions of Warnings, Cautions, and Notes
WARNING AND CAUTION statements have been strategically placed in the text to emphasize
certain steps or procedures for the protection of personnel (WARNING) or equipment
(CAUTION). A WARNING or CAUTION once provided will apply each time the related step
is repeated, regardless of the number of times the WARNING or CAUTION is repeated
throughout the text. Prior to starting any task, THE WARNINGS or CAUTIONS included in
the text for that task should be reviewed and understood.
An operating or maintenance procedure, practice, condition, statement,
etc., which if not strictly observed, could result in injury to or death of
personnel.
An operating or maintenance procedure, practice, condition, statement,
etc., which if not strictly observed, could result in damage to or
destruction of equipment, or loss of mission effectiveness.
NOTE
An essential operating or maintenance procedure, condition, or statement
which must be highlighted.
WARNING
CAUTION

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1.2 General Safety Precautions
The following are general safety precautions and instructions that personnel must understand
and apply during many phases of operation and maintenance to ensure personnel safety and
health and the protection of property. Portions of this information may be repeated in certain
chapters of this publication for emphasis.
KEEP AWAY FROM LIVE CIRCUITS
Operating personnel must at all times observe safety regulations. Do not replace components or
make adjustments inside the equipment with the voltage supply turned on. Under certain
conditions, dangerous potentials may exist when the power control is in the off position, due to
charges retained by capacitors. To avoid injuries, always remove power from, discharge, and
ground a circuit before touching it. Adhere to all lock out/tag out requirements.
DO NOT SERVICE OR ADJUST ALONE
Do not attempt internal service or adjustment unless another person capable of rendering aid
and resuscitation is present.
RESUSCITATION
Personnel working with or near dangerous voltage shall be trained in modern methods of
resuscitation.
COMPRESSED AIR
Use of compressed air for cleaning can create an environment of propelled foreign particles.
Air pressure shall be reduced to less than 30 psi and used with effective chip guarding and
personnel protective equipment.

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1.3 List Of Hazards
The operation of this amplifier may involve some of the following hazards; any of them could
result in serious harm to personnel if proper safety precautions are not taken.
HIGH VOLTAGE
Lethal Voltages up to 15,000 Volts are present in this amplifier when it
is operating. USE EXTREME CAUTION when inside the unit. Do not
insert objects through air intake screen on rear of drawer. When
testing, always ground the drawer chassis.
RF RADIATION
Exposure to RF radiation may cause serious bodily injury possibly
resulting in blindness and death. Cardiac pacemakers may be affected.
Always terminate both the RF input and RF output, even during tests,
which involve no RF drive, to avoid the RF hazard should the TWTA
oscillate.
BERYLLIUM OXIDE
The dust or fumes from Beryllium Oxide (BeO) ceramics used in
microwave tubes are highly toxic and can cause serious injury or death.
WARNING
WARNING
WARNING

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IMPLOSION HAZARD
Ceramic windows from microwave tubes can shatter on impact or crack
in use resulting in injury from Beryllium Oxide dust or fumes.
X-RAY RADIATION
High voltage tubes can produce dangerous, possibly fatal X-Rays.
HOT SURFACES
Surface temperature of tubes and other air cooled parts can reach
several hundred degrees centigrade.
RF OVERDRIVE
The unit may be damaged by drive levels as low as -17 dBm for the
MT4400 depending upon the settings of the system attenuator. Please
apply RF with caution. Always terminate RF input and output ports
properly when AC power is supplied to the TWTA.
RF OVERDRIVE – BLOCK UP CONVERTER OPTION
Never operate the MT4400 without the external semi-rigid cable that
connects to the tube input connector. Operating without this cable may
lead to a tube overdrive condition.
WARNING
WARNING
WARNING
CAUTION
CAUTION

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2.0 SCOPE
This document and its appendices will describe the controls, operator interfaces, and operating
procedures for a MT4400 HPA. This manual assumes a familiarity and working experience
with high power microwave RF amplifiers.
The MCL MT4400 is designed for long and reliable life under extreme environmental
conditions. All components utilized in this system are conservatively rated and selected for
high reliability and maximum use of existing designs. Mechanical and electrical safeguards are
utilized throughout the system to insure safety of operating personnel.
3.0 CONTROLS & INDICATORS
Complete operational control and status is available at the remote panel and/or computer
interface. There is a limited amount of controls locally; however, due to safety concerns these
controls will only be available when activated.
3.1 Discrete Status
On the MT4400 HPA there is a tri-color LED that provides the current mode/state of operation
of the HPA. These modes are the following:
STATE FAULT ALARM RED ON GREEN ON YELLOW ON
FALSE TRUE OR FALSE FALSE FALSE TRUE=100ms
FALSE=900ms
Filament Off
TRUE TRUE OR FALSE TRUE FALSE FALSE
FALSE TRUE OR FALSE FALSE FALSE TRUE=1S
FALSE=1S
Delay
TRUE TRUE OR FALSE TRUE FALSE FALSE
FALSE TRUE OR FALSE FALSE TRUE FALSEXmt
FALSE TRUE FALSE FALSE=100ms
TRUE=900ms
TRUE=100ms
FALSE=900ms
FALSE TRUE OR FALSE FALSE FALSE TRUEStby
TRUE TRUE OR FALSE TRUE FALSE FALSE
Xmt Selected FALSE TRUE OR FALSE FALSE TRUE=1S
TRUE=1S FALSE
* Alarms do not change LED states unless noted.
** Timings are approximate.
Table 1 – Current Mode/State of Operation for the HPA

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3.2 Discrete Control
3.2.1 AC Breaker
The AC Breaker is used to protect internal components and to turn prime power on and off.
When the Breaker is off, all HPA control and power circuits are de-energized. Turning the
Breaker on energizes all circuits. The HPA will recover to last “On State.”
3.3 User Discrete Control & Status Interface
Discrete Control & Status Interface is supplied to allow various earth station equipment (such
as exciters) to be wired into the HPA. Refer to TN4400-2 – Technical Note, Installation Guide
for MT4400 paragraph “Discrete Interface Connections,” for a detailed signal description. The
Discrete Control & Status Interface contains the following signals:
• WG Pressure Fault Input
• External Interlock Fault Input
• External RF Inhibit Input
• Sum Fault Indicator Output
• Sum Alarm Indicator Output
3.4 Controls & Status via Communications Protocol
The indicators and controls described in this section are provided on the HPA Remote or
Computer Terminal. Further description of these functions follows in later sections of this
document. Refer to 46A0203 and 46A0204 for a full listing of Control & Status.
3.4.1 Filament Off Command
When this command is sent from any state except Transmit, the Filament Power Supply will be
turned off.
3.4.2 Delay State
Indicates the HPA is going through a filament warm up cycle and is not yet in Standby.
3.4.3 Standby Command
There are two functions for this item. First, if sent while the HPA is in the Filament Off state
filament delay will be initiated. Second, if sent while the HPA is in the Transmit state the HPA
will switch to the Standby state.

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3.4.4 Transmit Command
While no faults are present, if this command is sent the HPA will cycle into the HV On state. If
sent while the HPA is in Delay, the HPA will go into the Xmit Selected State. Upon
completion of filament delay, the HPA will go into Transmit.
3.4.5 Band/Sub-Band Command/Indication-Optional
For HPAs which have Band or Sub-bands, this command is used to place the HPA in the
appropriate Band and Sub-band. The HPA can also report the current Band/Sub-Band, along
with a Band Label and the Start and Stop Frequencies for all the Bands and Sub-Bands. The
“Set-Band” command must be sent after the HPA is placed in Standby with RF Off. There are
no restrictions on the report Band/Sub-band command.
3.4.6 Summary Alarm Flag
The Summary Alarm Flag is set to true when the HPA has an alarm state that can lead to a fault
condition if it is not corrected.
3.4.7 Reset Command & Summary Fault Flag
When this command is sent, the fault reset will be initiated. When the Summary Fault Flag is
set to true, the HPA has a fault and the high voltage is turned off.
3.4.8 RF On Command/Flag
When this command is sent, the SSA RF switch will be put into the ON state if no other
interface is causing a RF Off state. When the RF Inhibit Flag is set to false, the SSA RF switch
is enabled.
3.4.9 RF Off Command/Flag
When this command is sent, the HPA will disable the SSA RF switch. When the RF Inhibit
Flag is set to true, the SSA RF switch is disabled.
3.4.10 RF High Flag
This Flag along with the summary alarm flag will be set to true when the detected forward
power exceeds the user specified level.
3.4.11 RF Low Flag
This Flag along with the summary alarm flag will be set to true when the detected forward
power is lower than the user specified level.

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3.4.12 Computer Mode
When this mode is activated, the HPA will allow the device on the computer interface to
control the HPA operating configuration. This mode is set through the Diagnostic Port.
3.4.13 Remote Mode
When this mode is activated, the HPA will allow the device (remote panel) on the remote
interface to control the HPA operating configuration. This mode is set through the Diagnostic
Port.
3.4.14 Auto Switching Command/Flag
When this command is sent, both HPAs in the 1:1 switchover will be put into the Auto
Switching Mode. When the Auto Switching Flag is set to true, the HPA is in the Auto
Switching Mode.
3.4.15 Manual Switching Mode/Command
When this command is sent, both HPAs in the 1:1 switchover will be put into the manual
switching mode. When the Auto Switching Flag is set to false, the amplifier is in manual
switching mode.
3.4.16 Antenna Command/Flag
When this command is sent, this HPA will be put into the antenna port of the RF switch. When
the Flag is set to true, the amplifier is switched to the antenna port of the RF switch.
3.4.17 Load Command/Flag
When this command is sent, this HPA will be put into the dummy load port of the RF switch.
When the flag is set to true, the amplifier is switched to the dummy load port of the RF switch.
3.4.18 RF Low Switching Flag
This Flag will be true when RF Low alarm switching for the Auto Switching mode has been
enabled through the Interface Port.
3.4.19 Hold Power Command/Flag
When this command is sent, the HPA RF output power will be automatically regulated by the
Auto Power function. When the Flag is true, this indicates the RF output power is being
automatically regulated by the Auto Power function.
3.4.20 Auto Power Command
This command is used to regulate the HPA output power within a certain specified window.
This command can also be used to change the HPA output power level.

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3.4.21 Event Log
The Event Log can be obtained via the Computer, Remote, or Diagnostic Ports. The event log
is stored in Non-Volatile memory on the HPA and will contain operational state changes,
alarms, and faults, which have occurred in the HPA. The event log will contain the event name
with a date and time stamp for when the event occurred. Events that can be stored in the log are
listed in the following table. If one of the user adjustable trip levels is exceeded causing an
event entry, the level that was exceeded will also be stored in the log and presented on the
fourth line of the display.
The time resolution of the log will be to the nearest second (±1 second). The event log is able
to store 200 events. If the log size exceeds the available memory size the oldest events will
scroll out of the log. The log is purged only through a diagnostic interface command. The
event log can be downloaded through the diagnostic interface.
3.4.22 Communications Set Up
Communications are verified and set-up via the Diagnostic Port. Please use the Diagnostic
Program that came with the HPA. To set up or view the parameters look under the Settings
Tab.
4.0 HPA OPERATION
4.1 HPA Control Modes
The MT4400 will be designed to provide continuous status to multiple interfaces all at the same
time; however, only one of these interfaces may control the operational states of the HPA at any
one time (these control modes are mutually exclusive). These interfaces are the Remote
Interface and Computer Interface.
4.1.1 Local Control
While the HPA is in the Local mode, the operator will be able to operate the MT4400. This
mode can only be used for troubleshooting.
4.1.2 Remote Control
4.1.2.1 Control Priority
While the HPA is in the Remote mode, the operator at the Remote panel or device on the
remote interface will be allowed to control the HPA. While in the Remote mode, the Computer
Interface cannot change the operating state of the HPA, but they can still get status. From the
Remote panel the operator can pass control to or take control away Locally or from the
Computer Interface.

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4.1.3 Communications Configuration
The Protocol, Communications address, and bps rate for the Remote Interface of the HPA can
be configured through the remote panel (see the “Communications Set-Up” paragraph of this
document), or the Diagnostic Interface (see the “Diagnostic Interface Settings” paragraph of this
document). The default values and adjustment range for each is shown in the table below.
Configuration of the Remote Interface is independent of the Computer Interface.
Table 2 – Remote Control Communications Configuration
PARAMETER DEFAULT ADJUSTMENT RANGE
REM PROTOCOL CSP CSP (46A0204 & 40A1546) or
*SABUS (46A0203 & 40A1715)
REM ADDRESS
(Hexadecimal) 01 01 through 7F (CSP) 31 through 7E (SA7670)
REM BAUD RATE 9600 1200, 2400, 3600, 4800, 9600, 14400, 19200, or
28800
*Not Available on all Models-Contact MCL for Details
4.1.3.1 Protocol & Command Set
The Protocol specifications and command sets for both CSP & SAbus are attached to this
document as appendices.
4.1.4 Computer Control
4.1.4.1 Control Priority
While the HPA is in the Computer mode, the operator at the Computer device will be allowed
to control the HPA. While in the Computer mode, the Remote Interface cannot change the
operating state of the HPA, but it can still get status. From the Computer Interface, the operator
can pass control to or take control away from the Remote Interface.
4.1.4.2 Communications Configuration
The Protocol, Communications address, and bps rate of the HPA can be configured through the
Remote panel (see the “Communications Set-Up” paragraph of this document), or the
Diagnostic Interface (see the “Diagnostic Interface-Settings” paragraph of this document). The
default values and adjustment range for each is shown in the table below. Configuration of the
Computer interface is independent of the Remote Interface. The hardware interface
configuration also requires a cable connection change internal to the HPA (see TN4400-2
Technical Note, Installation Guide for the MT4400 TWTA).

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PARAMETER DEFAULT ADJUSTMENT RANGE
COMP PROTOCOL CSP CSP (46A0204 & 40A1546) or
*SABUS (46A0203 & 40A1715)
COMP ADDRESS
(Hexadecimal) 01 01 through 7F (CSP) 31 through 7E (SA7670)
COMP BAUD RATE 9600 1200, 2400, 3600, 4800, 9600, 14400, 19200,
or 28800
COMP HARDWARE RS485 RS485 or RS232
*Not Available on all Models-Contact MCL for Details
4.1.4.3 Protocol & Command Set
The Protocol specifications and command sets for both CSP and SAbus are attached to this
document as appendices.
4.2 HPA Operating Modes
The following paragraphs describe the operating states of the HPA. The reported status for
these states is shown in the table below.
STATUS FROM BFC
STATE FILAMENT
OFF DELAY STBY XMT SELD XMT SUM FAULT
DC power on, no operator action has
been taken. ON OFF OFF OFF OFF OFF
DC power on, no operator action has
been taken, with a fault. ON OFF OFF OFF OFF ON
During filament delay, without
transmit power fail recovery. OFF ON OFF OFF OFF OFF
During filament delay, with transmit
power fail recovery. OFF ON OFF ON OFF OFF
During filament delay, with a fault. OFF ON OFF OFF OFF ON
Standby OFF OFF ON OFF OFF OFF
After filament delay, with a fault. OFF OFF OFF OFF OFF ON
Transmit OFF OFF OFF OFF ON OFF
Notes: 1. Sum Fault state disables Standby, Transmit, or Transmit Selected.
2. Alarms can occur in any of the above states.
3. Standby and Transmit are mutually exclusive.
Table 3 – Computer Control Communications Configuration
Table 4 – HPA Operating Modes

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4.2.1 Filament Off
This state occurs after a Filament Off command (Remote or Computer) has been issued. In this
state the TWTA logic will be activated along with any power supplies or cooling required to
keep the logic powered on. During this state the HVPS and Filament PS circuits will be shut
down. The HPA cannot be in Transmit when this state is initialized.
4.2.2 Filament Delay
This state occurs after the HPA is turned on or a Standby command (Remote or Computer) has
been issued when the HPA is in the Filament Off State. During this state all TWTA circuitry
will be activated except the high voltage power supply. At the end of this delay the TWTA will
be in the Standby mode.
4.2.3 Standby
This state occurs after the filament warm-up delay has ended or after a Standby command
(Local, Remote, or Computer) has been issued while the TWTA was in Transmit. During this
state all TWTA circuitry will be activated except the high voltage power supply. The Transmit
and Standby modes are mutually exclusive states.
4.2.4 Transmit
This state occurs after a Transmit command (Local, Remote, or Computer) has been issued
when the TWTA was in the Standby mode. During this state all TWTA circuitry will be
activated including the high voltage power supply. The Transmit and Standby modes are
mutually exclusive states.
4.2.5 Transmit Selected
There are three ways Transmit Selected can be activated. First, when the HPA was in the
Transmit mode then the HPA has a power failure, and then the HPA power returns. After the
power failure, Transmit selected will be activated during filament delay if no faults are present
during delay. Second, while the HPA is in the Delay or Filament Off mode if the operator were
to press the Transmit button, Transmit Selected mode would be activated and at the end of
filament warm-up delay the HPA will go into Transmit. Third, during a tube fault counter
cycle, Transmit selected is a warning to the operator that the TWTA will automatically go into
Transmit soon. If the Standby function is selected, the Transmit Selected mode will be
canceled. Transmit Selected will be indicated in two ways on the Remote panel during the
proportional delay. First an indication will appear on the front panel vacuum fluorescent
display (VFD), and second, the Transmit LED located on the Transmit button will flash.

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4.3 RF On/Off Control
The RF On and RF Off modes are mutually exclusive.
4.3.1 RF Off State
While the HPA is in the RF Off mode, the SSA module RF switch will be in the RF Off state.
Any of the following sources may cause an RF Off state and override all other RF On controls.
Each source will be latched and must be returned to the RF On state to clear the RF Off state.
• Remote Interface
• Computer Interface
• Switchover Interface
• User Interface
• Tube Overdrive Fault
4.3.2 RF On State
While the HPA is in the RF On mode, the SSA module RF switch will be in the RF On state.
All of the above control sources must be in the RF On state to allow the HPA to enter RF On.
After the HPA goes into RF On the RF Low Alarm will be delayed for two seconds.
4.4 Faults & Alarms
There are two types of warning status signals produced by the MT4400. An alarm WILL NOT
affect the operating state of the HPA. A fault will shut down the high voltage power supply of
the HPA.
4.4.1 Summary Alarm
Alarms WILL NOT affect the operating state of the HPA. All alarms are self clearing and do
not require a Fault Reset, except RF Switch Failed alarm, which will latch until the Reset
button is pressed. All alarms that will be combined to generate the Summary Alarm are listed
in the table below. While any alarm condition is present:
• the Summary Alarm LED located on the local panel will illuminate,
• a Summary Alarm will be indicated on the User Interface (J5), and
• the display will present the name of the alarm on the screen (press Accept button
to clear).
ALARMS
Summary Tube Temperature P.S. Temperature Filament Foldback
HPA Overdrive* Tube Overdrive* RF Reflected RF Low
RF High
* Function available with optional SSA.

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4.4.2 Summary Fault
All faults that are listed in the table below will cause a Summary Fault. Notice the Second HPA
Switchover fault is not included in this list. While a Summary Fault condition is present, the following
will be true until a fault reset occurs.
• The tri-color LED on the MT4400 will be red.
• A Summary Fault will be indicated on the Discrete Interface (J5).
• A Switchover Fault will be indicated on the Switchover Interface (J8).
• The high voltage power supply will be forced off.
• Auto Power will be forced off.
• Standby and Transmit are disabled.
FAULTS
Summary Chassis Interlock User Interlock P.S. Temperature
Tube Temperature Filament Under Current HV Under Volt HV Over Volt
Helix Run Current Helix Surge Current RF Reflected Tube Overdrive
Up Converter RF High*
* Linear TWTs Only
4.4.3 Fault Reset
The Reset button is used to reset latched faults, and to clear the RF Switch Failed alarm. Once the Reset
button is pressed the following will occur.
• All fault statuses will be cleared.
• The HPA will be forced into the Standby state.
4.4.4 Tube Fault Counter Operation
If the MT4400 is to be left in an unattended earth station, or during a degassing operation, or if the tube
is nearing the end of its life, the Fault Counter may be turned on to allow the HPA to automatically reset
the tube faults and return to Transmit. When the tube fault counter is enabled, it will count tube
electrode faults. If any fault other than those listed in this paragraph, were to occur at any time in the
Fault Counter sequence, the fault counter timer would be disabled and the timer reset. After a tube fault
is counted and displayed it will be reset; then after the power supply has been off for 5.0 seconds the
HPA will be commanded back into Transmit. After the fault is reset and before the HPA is put into
Transmit, the HPA will be in the Transmit Selected mode for about 3 seconds. The fault counter delay
time is 5.0 seconds, which allows the power supply and tube time to cool down. Each time a fault is
counted a fault event, reset event, and transmit event will be placed into the event log.
• High Voltage Under Volt Fault
• High Voltage Over Volt Fault
• Helix Surge Current Fault
• Helix Run Current Fault
The number of faults counted and the window of time during which they are counted are both adjustable
by the operator (see the “Adjustment Menu Screen” paragraph of this document). The window size must
be greater than five times the number of faults counted in seconds.
)faultsofnumber(5]ondssecin[SizeWindow ×=

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4.5 HPA Gain Control (Optional)
There are a couple of ways to control the HPAs output power; they are detailed in the following
paragraphs.
4.5.1 Manual Attenuation Adjustment
On the Computer and Remote Interfaces this can be accomplished in two ways. First, a Set
Attenuator command has been provided which directly sets the level of HPA input attenuation.
Second, Increase Attenuation and Decrease Attenuation commands have been provided. These
commands adjust the attenuator from the current setting by the specified amount.
Since the attenuator is in the input side of the HPA, there is not a direct correlation between
input attenuation and output power in dBm or dBW. The difference is due to the gain
compression of the HPA. For example, a 3.0 dB change of the input attenuator will not
necessarily produce a 3.0 dB change at the HPA output.
4.5.2 Auto Power Function (Not available on some Multi-Band HPA—Please Consult MCL)
Auto Power function will regulate the RF output power within a window around the Auto
Power set level. There are several conditions that can prevent turn on of Auto Power or can
turn it off when it is on.
4.5.2.1 Initializing Auto Power (Not available on some Multi-Band HPA—Please Consult MCL)
On the Computer and Remote Interfaces an Auto Power command has been provided which
turns on Auto Power and sets the regulation level.
4.5.2.2 Conditions that will Prevent Turn On of Auto Power (Not available on some Multi-Band
HPAs—Please Consult MCL)
The HPA will refuse to perform an Auto Power command if any of the following conditions are
present.
• If the TWTA is not in Transmit.
• If the Forward power sample is 0000W.
• If the Computer or Remote Interface were to set the Auto Power level to 0006W
or less.
• If RF is Off.

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4.5.2.3 Conditions that will Suspend Auto Power (Not available on some Multi-Band HPAs—Please
Consult MCL)
When the HPA is in Auto Power, it will stop all Auto Power attenuator action while the HPA is
in the RF Off state. The HPA will remain in the Auto Power state, but no attenuator action will
be taken while in the RF Off state. The Auto Power attenuator action will resume once the
HPA is placed back into RF On.
4.5.2.4 Conditions that will Turn Off Auto Power (Not available on some Multi-Band HPAs—Please
Consult MCL)
The HPA will terminate the Auto Power function if it is active when any of the following
conditions occur.
• If the set Auto Power level exceeds the top Forward Power calibration point.
• If the TWTA drops out of Transmit.
• If a Disable Auto Power command is received while the TWTA is in the
Computer or Remote mode.
• If the Forward power sample is 0000W.
• If the Computer or Remote Interface was to set the Auto Power level to 0000W.
• If the RF attenuator is manually adjusted.
4.5.3 Hold Power (Not available on some Multi-Band HPAs—Please Consult MCL)
The MT4400 remote panel contains a Hold Power control and indicator, which will be used to
control the Auto Power Function. The operator will set the RF output power using the Gain
Adjust. Once he has obtained the desired power level, Hold Power Command is sent. The
Hold Power Flag will be true, and the Auto Power function will regulate the RF output power
to the level currently set. If the operator were to send the Hold Power Command again, the
Auto Power regulation function will turn off.
4.6 Band/Sub-Band Selection (Optional)
The MT4400 is available for single or multiple band application. With the multi-band or sub-
band optimized HPA, there is a necessity for the user to set the HPA to the band of interest.
The MT4400 also has optional sub-band Linearizer tuning available on some models.
Typically a Linearizer is adjusted for the best broadband performance, The MT4400 can be
optimized within a band for possible further improvement. Please contact MCL for details on
sub-band tuning.

TECHNICAL NOTE – OPERATION OF MT4400 TWTA 08/10/2004
TN4400-3 MCL, INC. 20 of 36
4.7 Diagnostic Interface
A RS232 diagnostic interface (J4) is provided on the MT4400. This interface is designed to
connect to a PC through a MS3116-10-6S connector. Through this interface the operator is
able to calibrate analog channels, set or adjust system parameters, download the complete event
log, download analog channel calibration tables, or upload analog channel calibration tables.
TN4400-6 – Technical Note, Troubleshooting & Customer Service Guide for MT4400, will
describe calibration procedures; upload analog channel calibration tables, and data logging
function of the 45A0158 or 45A0189(Multi-Band HPAs) Diagnostic Test program.
The following procedures assume that a PC is connected to the HPA diagnostic interface that
has the 45A0158 Diagnostic Test Program loaded onto it. These procedures give an outline for
viewing, downloading, and uploading data to the HPA. The diagnostic interface program has
information built into the Help menu to give the operator additional assistance. The Windows
cut and paste functions are enabled on all program tabs except “Calibrate.”
4.7.1 Downloading Status
1. On the Diagnostic Interface program click on the “Status” tab (see the following figure).
2. Click on the “Now” button to refresh the status or check the “Update every” box to
automatically update status.
3. To save the data to disc, once the status is done downloading, click on the “File” menu,
select “Save” on that menu, then on the Save menu select “Status.” The diagnostic
program will automatically produce a file name, which includes the HPA serial number,
“status,” and today’s date.
4. The “add to database” box when checked will automatically save the downloads to an
Access 97 or better compatible database. Downloads are stored by HPA ID, Serial
Number and download time. The database can therefore handle multiple HPAs. Access
2000 can be used for advanced charting and reporting of this data. The file is stored in
the application directory under filename hpa-log.mdb.