JUMA PA-100D User manual

JUMA PA100-D
Operation Manual
(Firmware Version 4.00a - 11 May 2020)
Adrian Ryan - 5B4AIY

Table Of Contents
FrontPanelControls.........................................................3
ControlDescription..........................................................3
PWR...............................................................3
UP/DOWN..........................................................3
DISPLAY/CONFIG...................................................4
OPER ..............................................................4
AUTO..............................................................5
BAND+.............................................................5
BAND!.............................................................6
UserConfigurationMode.....................................................6
AutoBandDetect.....................................................7
YAESUCAT ..................................................7
KX3..........................................................7
JUMA-TRX2 ..................................................7
F-Sense.......................................................7
FT-817/818....................................................7
Manual .......................................................7
SerialSpeed .........................................................7
SerialPortMode......................................................8
PollingIntervalTime..................................................8
LCDBacklighting.....................................................9
LCDContrast........................................................9
SWRTripLimit......................................................9
FanControl..........................................................9
Normal .......................................................9
Low..........................................................9
Medium.......................................................9
High..........................................................9
TemperatureUnitSelection.............................................9
FanCut-InTemperature...............................................10
BandUnits .........................................................10
GraphicLimitDisplay.................................................10
GraphicDisplayScale.................................................11
RFPowerMeterType.................................................11
Start-UpPage.......................................................12
PromptedSave ............................................................12
SystemConfiguration&Calibration ...........................................12
VoltageCalibration...................................................13
CurrentCalibration...................................................14
RFPowerCalibration(HighPower)......................................14
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RFPowerCalibration(LowPower)......................................15
BeepLength........................................................16
PowerSampleAveraging..............................................16
Over-Voltage........................................................17
Over-Voltage(Adjust) ................................................17
Under-Voltage.......................................................17
Under-Voltage(Adjust) ...............................................17
Pre-LimitVoltage(Adjust).............................................18
MaximumPower.....................................................18
FrequencyMeterCalibration ...........................................18
SplashScreenDisplay.................................................19
AnnexA.................................................................20
SerialTestSuite.....................................................20
TemperatureSensorCalibration.........................................24
AnnexB.................................................................28
JumaPA100DAlarmSystem...........................................28
HighSWR....................................................28
HighCurrent..................................................28
Over-Temperature..............................................28
Over-Voltage..................................................29
Under-Voltage.................................................29
Low-Voltage(FinalLimit).......................................29
AnnexC.................................................................32
PA-100D & Elecraft KX3 Interconnection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
ACC1toRS-232AccessoryCable.......................................33
ACC2toT/RAccessoryCable..........................................33
AnnexD.................................................................36
Juma PA-100D Remote Control & Status Monitoring. . . . . . . . . . . . . . . . . . . . . . . . 36
Examples...........................................................36
StatusReportMessageFormat..........................................36
AlarmMapping......................................................37
RemoteTimeout.....................................................38
PollingTimer .......................................................38
Cautions ...........................................................38
PA-100DQUICKREFERENCEGUIDE .......................................40
PA-100DCALIBRATIONSETTINGS.........................................41
PA-100DCONFIGURATIONSETTINGS......................................42
ii

JUMA PA-100D OPERATING MANUAL
5B4AIY Firmware Version: 4.00a
The PA-100D is a companion 100W all-band linear amplifier primarilyintended for the Juma
TRX-2 all-band 10W transceiver, but can also be used with almost any low-power
transceiver, such as the Elecraft KX3 Ultra-Portable HF Transceiver, the Elad FDM-DUO, or
the Yaesu FT-817/818.
This document describes the operation and setup of this equipment using firmware version
4.00a, software modifications and changes made by Adrian Ryan, 5B4AIY.
The revised firmware incorporates a number of changes to enhance the utility of this
amplifier:
1. User selectable temperature units of either Centigrade or Fahrenheit.
2. User selectable frequency/band units of either MHz or metres.
3. User selectable fan control option.
4. Enhanced alarm facility.
5. Enhanced serial test facility.
6. Improved resolution and accuracy of voltage, current and power displays.
7. Power Sample Averaging.
8. Improved temperature display, and added serial suite calibration feature.
9. Graphic meter scale selection.
10. Selectable graphical display of parameters.
11. Automatic band-switching compatibility with Elecraft KX3 transceiver.
12. Minor user interface modifications, including prompted exit from menus.
13. Safer Auto/Manual Band Change.
14. Auto-Increment added to the User Configuration and System Calibration menus.
15. User selectable start-up page.
16. Power display in either Watts or dBm.
17. Frequency meter display in MHz to a resolution of 1kHz.
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18. Both forward and reverse page stepping in Service and Configuration modes.
19. Power meter display active in both operate and standby modes without the necessity
to key the amplifier.
20. Improved low-power accuracyof output power meter down to 0.5W.
21. Improved frequency meter accuracy.
22. Brief press of PWR button in normal mode now decrements display page.
23. BAND+/BAND!buttons now auto-repeat.
24. Restored automatic page skipping in both the Calibration and Configuration menus
for inconsistent parameters.
25. Optimised the parameter incrementing/decrementing. The auto-repeat function now
chooses repeat speeds that are dependant upon the parameter being modified.
26. Re-designed the temperature measurement module.
27. Replaced original checksum calculation with more robust CRC.
28. Incorporated a remote control and status monitoring facility.
29. Added Yaesu 5-Byte Binary CAT protocol.
30. Automatic band request when changing band manually or switching to
AUTO/MANUAL.
31. Re-ordered the Auto Band Select to correspond with that in the Juma TRX-2.
32. Automatic setting of the Polling Interval Timer.
33. Set the default polling time interval to 2 seconds from 5 seconds.
34. Adjusted the filter switching points to coincide with the Juma TRX-2.
35. Added user adjustable Pre-Limit warning alarm.
36. Enhanced automatic band selection protection.
37. Added Manual Band Selection mode.
2

Front Panel Controls
Control Description
PWR
This button is used to power-up and power-down the amplifier, as well as several secondary
functions. To power up the amplifier, briefly press the button. The display will illuminate and
a sign-on message will be displayed:
JUMA-PA100 4.00a
OH2NLT OH7SV
After a short delay, the main screen will be displayed.
This button now has assigned to it the cancel alarms function, which takes priority. This is to
make the alarm system consistent with the Juma TRX-2, whose alarms are also cancelled
with its PWR button. In the event an alarm cannot be cancelled, press and hold this button for
an emergency shutdown. No user settings will be saved, the power latch signal will be
immediately dropped.
Press and hold the PWR button for the normal power down. In the previous firmware, a
counted down display would appear and the User Configuration settings were always saved to
the EEPROM. In this version, if no User Settings have been altered, then the amplifier will
simply shut down. However, if you have changed the AUTO/MANUAL setting, altered a
gain setting, or if in the manual band select mode you have changed bands, then you will be
prompted whether you wish to save these new settings.
To save the new settings, briefly press the BAND+ button. To power down without saving the
settings briefly press the PWR button.
In the Calibration and Service and User Configuration modes, a brief press of the button will
step back to the previous page. If the button is held, then the pages decrement automatically.
The power off function resumes when either the Service or the Configuration mode is
terminated.
A long beep will sound, and an increased page switch delay will occur whenever page zero is
selected.
In the normal mode, a brief press will step back to the previous measurement display page.
This allows for rapid switching between O/P power and SWR, or Voltage and Current, for
example.
UP/DOWN
These buttons are used to increment/decrement the various user settings, depending upon the
current operating mode. In the normal mode, these buttons alter the gain settings of the
amplifier, as shown by the G1 – G4 indicators on the display. G1 is the lowest gain, and the
gain can be increased in 2dB steps. In fact, the “gain” changes are simply an attenuator being
switched in and out of circuit, but it is convenient to think of this in terms of overall gain.
3

Note that each of the 9 amateur bands has its own individual gain setting which can be saved
to the EEPROM. If you change a gain setting, a band, or the auto/manual setting, then when
you power the amplifier off you will be prompted whether you wish to save the new settings.
If either of the buttons is pressed and held, then the button will auto-repeat, and the repeat
speed depends upon the parameter being modified. This is particularly useful in the User
Configuration mode.
DISPLAY/CONFIG
This button has two functions. In the normal mode it allows the user to display a number of
internal parameters. From the normal display, a single push will show the current output
power. The next push will display the SWR, followed by the supply voltage, the amplifier
current, and finally the heat-sink temperature in either EC or EF.
If the frequency sense (F-SENSE) mode of automatic band detection is selected, then an
additional page can be displayed showing the input frequency in MHz to a resolution of 1kHz
and the current output power.
If the button is pressed and held, this will invoke the User Configuration mode, which is fully
covered in a later section. To exit from the User Configuration mode, briefly press the OPER
button, respond to the prompt, whereupon the normal display will return.
Whilst in the User Configuration mode, a brief press of the button will increment the page. If
the button is held, the pages increment automatically. A long beep will sound, and an
increased page switch delay will occur whenever page zero is selected.
If this button is pressed and held from the power off state, and then the amplifier is powered
up, it invokes the RS-232 loop-back test. If a computer running a terminal program is
connected to the RS-232 port, you can verify that the port is functioning correctly. Briefly
press the PWR button to exit.
OPER
This button has two primary functions. The first is used to place the amplifier in either the
standby mode or the operate mode. In previous versions of the firmware it was also used to
cancel alarms, this function has now been moved to the PWR button.
The second is to invoke the save settings menu from either the System Calibration or the User
Configuration functions.
With this firmware revision the amplifier will always power up in the standby mode as a
precaution, except when the System Setup is selected, when it will power up in the operate
state.
In the standby mode the signal path is straight through, with neither filters nor attenuation
present. A connected transceiver will be able to transmit and receive directly to the connected
antenna. The metering functions of the amplifier will operate to show the output power and
SWR, although at low power levels the accuracy is somewhat reduced.
4

Press this button to select the operate mode. In this mode the amplifier will be fully
functional.
If this button is pressed and held, and the power switch operated to turn the amplifier on, the
flash writer will be invoked. This is used with the Ingenia loader program to update the
firmware. For further details, please see the article on the Juma website which covers this
procedure.
AUTO
This button is used to select either the manual or automatic band selection, in conjunction
with the BAND+ and BAND!buttons.
The current selection is displayed on the lower line of the display. To use the manual mode,
press the button to select M on the lower line, and use the BAND+ or BAND!button to
select an amateur band from 160m – 10m.
You can also select the manual mode by simply pressing either the BAND+ or BAND!
buttons and selecting the desired band. This will select the appropriate low-pass output filter,
but exercise care, as inadvertent selection of the wrong filter could damage the amplifier. For
example, selecting the 80m band filter when transmitting on the 40m or higher band at high
power levels could seriously damage the filters.
In this version of the firmware a safety feature has been incorporated. Previouslythe
MANUAL mode was absolute – no changes could occur except via the BAND+ and BAND!
buttons. It was thus possible to inadvertently select an incorrect band. If an out-of-band
condition or an unknown band condition exists, then the default selection is 10m. In this new
version, if the currently selected Auto Band detect mode is active, then any band selection
occurring via this port will over-ride any manual selection that has been made.
To ensure this, if either the Yaesu, KX2/KX3 or Juma TRX-2 mode is active, then a
frequency request command will be automatically sent to the connected transceiver whenever
a BAND+ or BAND!button is pressed or if the mode is switched between MANUAL and
AUTO if polling is disabled.
If you wish to use absolute manual band selection, then select the Manual band select mode.
Be aware, however, that there is no protection in this mode! You are responsible to ensure
that the correct band is selected. You can seriously damage the filters or the output transistors
if an incorrect band is inadvertently selected. You have been warned! Onlyuse this mode as a
last resort.
It is preferable to use the AUTO band select mode, if possible. In this mode there are five
detection possibilities, selected via a setting in the User Configuration mode. Please refer to
this section for details concerning their use.
BAND+
There is a secondary function to this button. By pressing and holding this button in the power
off state, and then powering up the amplifier, the factory defaults can be reloaded. Previously
5

this was assigned to the OPER button, but also assigned to this button at power up is the flash
writer. As it can be a little disconcerting to see this prompt, the default reload function has
been moved.
Release the BAND+ button and the display will prompt you for a selection, either press the
BAND+ to reload the default settings, or the PWR button to abort and continue.
BAND!
In addition to its use in selecting bands, there is a secondaryfunction to this button. By
pressing and holding this button in the power off state, and then powering up the amplifier,
the KX3 message timeout value will be changed from its default of 200mS to 5 Seconds. A
message will be displayed to this effect.
This allows you to test that the PA-100D is responding to KX3 messages by connecting it to a
PC via the serial port and using a terminal program to send the necessary ASCII data packets
to the amplifier. See Annex C for further details.
In this version of the firmware, the normal band select function of these buttons now auto-
repeat if they are held.
User Configuration Mode
This mode is used to setup the various options and settings for proper operation of this
amplifier. To select this mode, press and hold the DISPLAY/CONFIG button until you hear a
long beep, and the message:
User
Configuration
is displayed. Release the button, and the last displayed menu page will be selected. The
various settings are changed with the UP/DOWN buttons.
To move from one menu item to the next, briefly press the DISPLAY/CONFIG button. To
rapidly scroll to a menu item, press and hold the button, and after a short delay, the page will
be incremented. Release the button to stop the scrolling and edit the value/parameter in the
normal way with the UP/DOWN buttons.
To decrement the page, briefly press the PWR button. If the button is pressed and held, the
page will decrement automatically.
A long beep will sound, and an increased page switch delay will occur whenever page zero is
selected.
To exit, briefly press the OPER button. Respond to the prompt, and you will return to the
normal operating mode.
6

Auto Band Detect
Default: F-Sense
This governs the operation of the AUTO feature. There are six selections:
a. YAESU CAT This mode uses the Yaesu 5-Byte Binary command protocol, and can
be used with the Yaesu FT-817 and FT-818 transceiver if they are equipped with the
CT-62 level translator interface. Since these transceivers do not automatically update
the amplifier whenever a band change occurs, when selecting this mode the polling
interval timer will be automatically set to 2 seconds. It can be increased or disabled if
necessary.
b. KX3 This mode is used with the Elecraft KX3 Ultra-Portable HF Transceiver, or in
fact any transceiver that uses the ASCII command protocol. It uses a serial data link
between the ACC1 socket of the KX3 and the RS-232 socket of the PA-100D. As
with the Yaesu FT-817/818, polling is automatically enabled and set to 2 seconds
whenever this mode is selected. See Annex C for further details.
c. JUMA-TRX2 This mode should be selected when the amplifier is connected to the
Juma TRX2 transceiver. It relies on the presence of a serial data link between the
amplifier and the transceiver. The transceiver’s RS-232 port mode should be set to
JUMA TRX2, and the port speeds must be the same. The default of 9600 Baud is
satisfactory. Note that polling is not required for this mode, and is automatically
disabled as the Juma TRX-2 sends a change of band message whenever either a band
is changed or the transmit mode is selected if using my firmware. However, polling
can still be enabled if required.
d. F-Sense With this mode selected, the incoming RF signal from the transceiver is
measured in frequency, and the result used to select the correct low-pass filters. No
connections other than the RF cable and the PTT line are required. To use this mode,
select the TUNE mode on the connected transceiver and inject between 100mW – 10
watts. The amplifier will detect the signal and select the appropriate filter
automatically.
e. FT-817/818 This setting will allow automatic band detection when connected to a
Yaesu FT-817 or similar transceiver with the appropriate accessorycable. This
transceiver outputs a stepped DC voltage which can be detected by the amplifier and
used to automatically select the correct band. The rear accessory BAND socket should
be used.
f. Manual This setting allows completely manual band selection without any band
detection protection. Only use this setting as a last resort. You can seriously damage
the output filters as well as the PA transistors if you inadvertently select the wrong
band!
Serial Speed
Default: 9600 Baud
Limits : 1200 – 115200 Baud
7

This sets the communications speed for the RS-232 port and can be set from 1,200 Baud –
115,200 Baud. The other parameters are fixed at 8 data bits, 1 stop bit, no parity.
Serial Port Mode
Default: Off
Limits : Off – Remote – Test
The Remote mode allows the amplifier to be controlled and monitored remotely. (See
Annex D).
The Test mode allows the user to perform various low-level tests, as well as obtain a dump of
the current internal configuration and calibration values.
Note: Both the Remote and Test Modes are only active if the Auto Band Detect is set to
either F-Sense or FT-817. If Auto-Band Detect is set to Yaesu CAT, KX3, or Juma
TRX-2 modes, then this page is skipped.
Polling Interval Time
Default: 2 Seconds
Limits : 0 – 10 Seconds
The polling interval timer is used for automatic band detection as well as remote control and
monitoring.
If either the Yaesu CAT or the Elecraft KX3 mode is used, then this setting determines
whether the transceiver will be polled for band information, and at what interval. The default
setting is 2 seconds, but if this is set to zero, then polling is disabled.
If you are using the TRX-2, then any band changes are normally conveyed automatically via
the serial port. Setting the rate to 0 will disable polling.
The latest firmware for the Juma TRX-2 now includes the feature wherebyevery time the
transceiver switches into the transmit mode or a band change is made, it automatically
updates the PA-100D, and thus polling is unnecessary.
If you are using the PA-100D with the Elecraft KX3 transceiver, then depending upon the
settings for this transceiver polling may be required. Please see Annex C for full details. The
default rate of 2 seconds is normally quite sufficient.
If the serial port is used for remote control and status monitoring, then enabling the polling
interval timer will allow the amplifier to automatically transmit status messages at the
selected interval. (See Annex D for full details.)
In this version of the firmware this feature has been modified. In all previous versions the
polling interval was capable of being set in increments of 100mS from 0 to 30 seconds.
Extensive testing revealed a number of potential shortcomings, and in this version the polling
rate is set in increments of 1 second from 0 to 10 seconds. As before, setting the rate to zero
disables polling.
8

Note: This page is only applicable if the Auto-Band Detect mode is set to Yaesu CAT,
KX2/KX3, Juma TRX-2 modes, or the REMOTE serial port mode is selected. In all
other modes this page is skipped.
LCD Backlighting
Default: 300
Limits : 50 – 1100
Set the level you wish for the display illumination using the UP/DOWN buttons.
LCD Contrast
Default: 2000
Limits : 0 – 3500
Adjust with the UP/DOWN buttons for a suitable display.
SWR Trip Limit
Default: 3.0
Limits : 1.0 – 10.0
Adjust with the UP/DOWN buttons over a range from 1.0 – 10.0, a default setting of 3.0 is
recommended.
Note: An SWR alarm is only generated with the amplifier in the OPERATE mode.
Fan Control
Default: Normal
Some users prefer the cooling fan to operate all the time irrespective of the heat sink
temperature. Use the UP/DOWN buttons to select one of the following modes.
Normal: In this mode the fan operation is entirely determined by the heat-sink
temperature.
Low: In this mode, the fan will run continuously at the low speed, but will switch to
the medium or high speed in response to the heat-sink temperature.
Medium: The fan will run at medium speed, but will switch to high speed in response to
heat-sink temperature.
High: The cooling fan will operate at high speed all the time.
Temperature Unit Selection
Default: Celsius
Using the UP/DOWN buttons select either the Celsius or Fahrenheit scale.
Note: If the scale units are changed, then the following menu settings for the alarm and fan
cut-in temperatures will be automatically preset at their respective default values in the
new scale.
9

Over-Temperature Limit
Default: 70EC/158EF
Limits : 50EC – 100EC or 120EF – 212EF
Using the UP/DOWN buttons, select a suitable limit.
Fan Cut-In Temperature
Default: 40EC/104EF
Limits : 0EC – 80EC or 32EF – 170EF
Using the UP/DOWN buttons, select a suitable temperature for the cooling fan to start.
When the heat-sink temperature reaches the cut-in point, the fan will start at low speed,
assuming the normal mode of operation has been selected in the previous menu.
When the heat-sink temperature has risen to 5EC/10EF higher than the preset cut-in
temperature, the fan speed will increase to the medium setting. If the temperature rises by
10EC/20EF above the cut-in temperature, the fan will run at its maximum speed.
Although the range of cut-in temperatures is from 0EC – 80EC, or 32EF – 160EF, the actual
maximum cut-in temperature will be determined by the Over-Temperature Limit setting. The
maximum permissible cut-in temperature will always be 20EC/40EF lower than the Over-
Temperature Limit setting, or 80EC/160EF.
Although a zero temperature setting may seem somewhat odd, its purpose is to allow you to
quickly verify that the fan operates in response to temperature. As an example, assume room
temperature is 25EC, if you reduce the cut-in temperature to 25EC you should hear the fan start
at low speed. Reduce the setting to 20EC, and the fan should run at medium speed. Reduce it
to 15EC, and the fan should run at its maximum speed. Reset the temperature to the desired
setting when done.
Note: The fan drop-out temperature is 2EC/4EF lower than the cut-in temperature. This
hysteresis prevents “fan twitch” whereby the fan blades would otherwise “twitch”
when the cut-in temperature is close to room temperature.
Band Units
Default: MHz
Using the UP/DOWN buttons select either MHz, or metres.
Graphic Limit Display
Default: Off
Using the UP/DOWN button select Off or On. If this feature is turned off, then the graphic
meter on the top left of the display acts as in the original firmware, and simply displays RF
output power. In fact, whereas in the previous firmware the actual display was the forward
voltage from the SWR bridge, this version now displays true power.
The full-scale of the meter is adjustable in the Calibration section to display from 40W to
160W in 1W increments.
10

If the feature is turned on, then the graphic meter will display the measured parameter in
relation to the current trip limits. In other words, when displaying current, the full-scale of the
graphic meter is the 24A hardware trip limit, and the display shows the instantaneous value of
the current in relation to this limit.
Note: Whilst the graphic meter displays the instantaneous current, the digital meter is a peak
reading long hold time meter. The hold time is fixed at approximately 1,000mS. This
allows for a reasonably stable meter display when using either SSB or CW.
When displaying temperature, the lower scale limit is either 0EC or 32EF depending upon the
current scale selection, and the full-scale is the current over-temperature limit.
When displaying SWR, the lower limit is a SWR of 1:1, and the full-scale is the current SWR
trip limit.
When displaying voltage, the display is effectively a suppressed-zero voltmeter with the
minimum reading being the undervoltage trip setting, and the full-scale being the over-voltage
trip setting.
The power meter display shows the instantaneous output power as a fraction of the preset full-
scale value. It is recommended to set this feature on when using the dBm scale for the output
power.
Graphic Display Scale
Default: Original
Select one of three different types of scale displays for the analog bar graph. The selections are
Original, Large, or Small scale markers.
RF Power Meter Type
Default: Watts
This page allows you to configure the RF power meter to display in either Watts or dBm. The
latter units are often used for professional applications, as it facilitates gain, loss and
attenuation measurements.
POWER
WATTS POWER dBm
1 +30.0
2 +33.0
3 +34.8
4 +36.0
5 +37.0
10 +40.0
20 +43.0
30 +44.8
11

40 +46.0
50 +47.0
100 +50.0
Remember that this is a logarithmic display of output power. It is strongly recommended that
the graphic display is turned on when using the dBm power scale, and the maximum value set
to 100W to alert you to the current output power in relation to the maximum permitted power.
Start-Up Page
Default: O/P Power
This option allows you to choose which measurement system page is displayed on start-up.
The options are: O/P Power – SWR – Voltage – Current – Temperature.
Prompted Save
To exit from the User Configuration Menu, briefly press the OPER button to invoke the
prompt screen. To save your current settings, briefly press the BAND+ button. To exit without
saving your settings and restore your previous configuration, briefly press the PWR button.
System Configuration & Calibration
To enter the calibration mode, from the power off state press and hold the PWR button until
the message:
Calibration
Mode v4.00a
is displayed.
To calibrate the amplifier, connect a suitable transceiver to provide a drive signal, and ensure
that the amplifier is connected to a dummy load. In this mode, the Frequency Sense mode of
band detection is selected. It is recommended that you use a frequency in the 20m band as this
is at the centre of the amplifier’s frequencyrange.
Prior to using the System Configuration & Calibration mode, select either the AUTO or
MANUAL band select mode, and save this configuration.
If the AUTO band select mode is selected, then the output filter will be selected depending
upon the frequency measured in the frequency sense logic. If the MANUAL band select mode
is selected, then the 10m filter is automatically selected.
To key the amplifier into transmit if you are not using a TRX-2, make a suitable connection to
the T/R socket. If using a 3.5mm patch lead, the amplifier can be keyed into transmit by
simply grounding the tip.
In the Calibration Mode, the amplifier will power-up in the operate state. If the AUTO band
detect mode has been selected, and the input power is too low, then the default 10m band will
remain in effect. The mode and band will be displayed on both the ammeter and power meter
12

calibration pages. The amplifier can only be keyed into the transmit mode if either of these
pages are selected.
To avoid an accidental over-drive, the input attenuator is set to the minimum gain, which is
approximately 10dB. A 5W input signal will drive the amplifier to about 40W – 50W output.
The calibration menu pages can be selected by briefly pressing the DISPLAY/CONFIG button.
To rapidly scroll through the pages, press and hold the DISPLAY/CONFIG button until the
desired page is displayed. Release the button, and adjust the value/parameter with the
UP/DOWN buttons in the usual way.
To return to a previous page, briefly press the PWR button. To rapidly scroll in the reverse
direction, press and hold the PWR button.
In either mode, a long beep and an additional page delay will occur whenever page zero is
selected.
Voltage Calibration
Default: 5250
Limits : 4750 – 5750
The measurement system of the amplifier has been modified to obtain increased resolution and
precision.
The voltage measurement section is the most precise, as its sample voltage is obtained directly
from a precision potential divider formed by R27/R28 on the control board, and this voltage is
directly sampled by the A-D convertor.
Measure the input voltage at the amplifier’s power connector with a precision 4-digit digital
multimeter, and using the UP/DOWN buttons alter the calibration factor so that the displayed
voltage matches as closely as possible the measured value.
Briefly pressing either button will cause a single increment or decrement of the existing value,
if you press and hold the button, a continuous increment or decrement will occur.
It should be possible to arrive at a display that matches within ±1 digit in the least significant
figure – if the measured value was 13.84V, then you should be able to adjust the display to
read between 13.83 – 13.85.
Note that as with all digital sampling systems there is an inherent quantisation uncertainty of
±1 in the last digit.
The display is a direct sample of the A-D convertor’s output, no averaging takes place, and
thus you will see significant jitter at some calibration settings. When the display is used with
the amplifier in its normal mode, the voltage displayed is the result of a 50-sample running
average, and is thus much less prone to jitter. The non-averaged value allows you to adjust the
calibration for both the most accurate and the most stable display.
13

Current Calibration
Default: 2520
Limits : 1500 – 4000
The current sense is obtained from a precision 0.005Ωcurrent shunt resistor, R7, in series with
the main power bus. The voltage developed across this shunt is processed by IC1, a MAX4373
high-side current sense amplifier/convertor and the scaled voltage is measured by the A-D
convertor. The nominal scale factor is 100mV/A.
The most accurate method of calibrating the ammeter is to use a clip-on DC ammeter and a
precision digital multimeter. Alternatively, if you have access to a precision high-current shunt
you can connected this in series with your supply and measure the shunt voltage. If neither of
these means is available but either your power supply has an accurate digital ammeter, or your
digital multimeter has a suitable amps range, then this can be used as the reference.
Inject a suitable drive signal to obtain a CW output power of about 30W – 80W, wait for the
current reading to stabilise, then using the UP/DOWN buttons adjust the calibration factor to
obtain a match as closely as possible the reference measured value.
This measurement is less accurate than the voltmeter for a number of reasons. First, although
the current shunt is principally the current shunt resistor, in addition there is the contact
resistance of the four solder pads.
The varying construction techniques as well as differing types of solder will all add a varying
contact resistance which will affect the calibration. Equally, at high currents the current shunt
resistor tends to heat up as it dissipates a certain amount of power, adding a further uncertainty
to the measurement. Thus, although the resolution of the ammeter is 0.1A, the accuracywill
probably not be better than ±0.2A at the nominal maximum output power of the amplifier.
Note: The ammeter display in the operating mode is a peak reading long hold meter. In the
calibration mode the meter displays the instantaneous current.
RF Power Calibration (High Power)
Default: 1149
Limits : 750 – 1500
The RF output power is measured from the DC output voltage obtained from a dual directional
coupler on the main board. This measurement is probably the least accurate.
Because power is proportional to the square of the voltage, any errors or differences in either
components or construction will be magnified when the A-D output is squared to perform the
power calculation.
Further, the reference voltage of the A-D convertor is obtained from the +5V logic supply, and
the accuracy and stability of the voltage regulator’s internal precision band-gap reference will
also affect the accuracy.
Equally, the output voltage of the diodes is only reasonably linear at fairly high powers, as the
output power is reduced the accuracywill degrade.
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In order to calibrate this measurement, either you will need access to a fairly accurate RF
power meter, or you can use an accurate directional coupler and an oscilloscope. In my case I
had access to both methods, and was thus able to confirm the relative accuracyof both
methods.
Note: Most SWR meters having a power scale are notoriously inaccurate as power meters.
The power meter method is by far the easiest. Inject a suitable RF drive signal to provide an
output of 50W – 100W CW, wait for the output power reading to stabilise, and using the
UP/DOWN buttons adjust the calibration factor to obtain the closest possible agreement
between the display and the measurement reference.
To use the direction coupler/oscilloscope method, connect the output of the amplifier to the
directional coupler with as short a piece of co-ax as possible, and connect the output of the
directional coupler to a high-power 50Ωdummy load. Connect the oscilloscope to the
directional coupler’s coupled port and terminate the input to the oscilloscope with a 50Ωfeed-
through termination.
If it is a digitising oscilloscope, set it up to measure the RMS voltage at the input. With a
!30dB coupler, at 100W the coupled port will provide a 100mW signal into the feed-through
termination. This will give a 6.3V p-p signal into the oscilloscope. Measure the amplitude of
the signal, and calculate the coupled power level. Taking into account the coupler loss, adjust
the calibration for the best match.
If you do not have access to either of these pieces of test equipment, then the default
calibration value will be accurate enough for most purposes – this is the least accurate of the
measurements, and is really intended as an indication of output power rather than a precision
measurement.
RF Power Calibration (Low Power)
Default: 120
Limits : 0 – 250
With this version of the firmware the low power accuracy of the power meter has been
significantly improved.
Inject a frequency in the 20m band, and at about 4W – 5W power level. Using the UP/DOWN
buttons adjust the offset to achieve the most accurate match.
Then, remove the drive signal, briefly press the PWR button to re-select the previous page, and
inject the drive signal and, if necessary, re-adjust the calibration. By switching between the
high and low power pages and adjusting the calibration factors, it should be possible to
achieve a reasonably accurate display at both high and low powers.
Note: It is necessary that the driving source’s output power is known fairly accurately in
order for this compensation factor to be accurate.
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Because there are two calibration factors, the overall adjustment tends to be somewhat
divergent. If you find that you are arriving at a setting that is near or at the limit of the
adjustment factors, then reset the high power calibration factor to around 1150, and the low
power calibration factor to about 120, and start again.
Use a drive power setting that gives an output power in the high power setting of around 50W
– 60W. You may have to sacrifice some accuracy at the high power setting in order that the
low power reading corresponds with the power meter or the power reading on the drive
transceiver.
Nevertheless, provided the reference power meter is reasonably accurate (within ±10%) and
the output power of the driving transceiver is also accuratelyknown, then it should be possible
to arrive at a set of calibration factors that allow close agreement at the low power end of the
range as well as reasonable agreement (within ±10%) at the high power end.
Bear in mind that of all the parameters, accurateRF power measurement is the most difficult.
Whereas voltage, current, and temperature can all be measured to an accuracy of better than
1%, RF power is usually a derived measurement from an indirect source, and thus is subject to
numerous errors and uncertainties. The best that can usually be achieved with the fairly simple
techniques that are common for amateur equipment is about ±10%.
Note: The minimum displayable power is approximately 400mW/+26dBm.
Beep Length
Default: 50mS
Limits : 0 – 100
Using the UP/DOWN buttons, adjust for the desired time.
Note: A time of 0 will disable the beeper, no audio annunciator tones will then be generated.
However, certain major function changes, such as selecting the User Configuration
menu or invoking the fast page switch feature will always be acknowledged with a
beep.
Power Sample Averaging
Default: 1 (Off)
Limits : 1 – 16
This feature was added at the request of an amateur who was using the amplifier as the driver
stage of a high-power linear.
When operating CW there were occasions when there would be a transient high SWR alarm
caused by the finite time it took for the transmit/receive relays to operate. The overall
measurements are performed veryquickly, and thus there is the possibility of registering a
transient whilst the relays are changing state.
This feature can also be used when using separate transmit and receive antennas where the
relay operating time might also provoke a transient alarm.
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