
XIEGU 
100 W Solid-State Linear Power Amplifier 
XPA125 
Instruction Manual 
Copyright © 2010~2017 Xiegu Communications 

Important reminder: 
Before operating the equipment please 
study this instruction manual carefully, and 
retain it for future reference. 
Safety considerations: 
Features: 
- 
RF power amplifier with inbuilt antenna 
tuner (ATU).
- 
Maximum RF output power of 
125 Watts. 
- 
Auto tuning function. 
- 
Wide frequency range of 0.5 – 50 MHz.
- 
Harmonic suppression of 39 dB 
- 
Maximum output power can be 
automatically regulated via the ALC 
control when used with an X108G or  
X5105 transceiver
Do not use equipment during an electrical 
    storm. 
Do not expose the unit to moisture. 
 Use this device responsibly and observe all  
 local laws and regulations. 
Caution! High RF voltage at antenna 
connector! 
Packing list: 
① XPA125.. .. .. .. .. .. .. .. .... .. .. ..1 
①
② Power supply cable ................ 1 
③ Date cable .............................. 1 
④ Communication cable ............. 1 
⑤ Service card ............................. 1 
② 
③ 
⑤
④ 

1  XPA125 Specifications 
1.1  Amplifier: 
Frequency range: 0.5 – 54 MHz 
Maximum operating ambient temperature: 55℃ 
Gain: 13dB ( 2dB) 
Supply voltage: 12 - 14.5 V DC  
Current draw @ maximum output: 
Standby:  260 mA 
Transmit: 30A 
1.2 ATU: 
Tuning frequency range: 1.8 – 30 MHz/50 – 54 MHz  
Maximum tuning range: 14 - 500Ω 
1.3 Product specifications: 
Dimensions:  260 x 150 x 100 mm (not including control knobs, feet, handles, etc.) 
Weight:2.66 
Kg(host only)
±
@Max
@Max

2 Equipment description 
2.1 Front panel layout: 
① Power key 
When XPA125 is turned on, press this button and hold for 2 seconds, 
XPA125 will shut down. 
When XPA125 is turned off, press this button and hold for 2 seconds, 
XPA125 will turn on. 
② ATU function key 
Via this button you can access the automatic antenna tuning function. 
③ BAND selection key 
Using this button you can select between manual band switching or 
automatic band switching. 
In manual band switching mode, the XPA125 will change bands in the 
following order: 
160m→80m→60m→40m→30m→20m→17m→15m→12m→10m→6m 
④ PA key 
Used to switch the power amplifier into or out of circuit. 

⑤ LCD 
All working status information is displayed here. The display is covered by an 
organic glass protective plate. 
2.2 Rear panel layout: 
○
6 DC IN Power supply socket: 
   The XPA125 requires a 12 - 14.5 V DC supply 
○
7 ANT Connector: 
The ANT socket is connected to the antenna, the connector model is SL16-K. 
○
8 FUSE Holder: 
Internal fuse holder. Fuse rating is DC 30A. 
○
9 Ground 
○
10 ACC socket: 
The data interface connections are as follows: 

○
11 TRX Socket: 
The TRX interface is connected to the transceiver output, the connector 
model is SL16-K. 
○
12 CIV interface: 
This interface is for XPA125 firmware updates and connection to a PC. 
○
13 Handle 
2.3 Display interface layout: 
⑴ Input SWR value: 
Displays the SWR value of the XPA125 input. 
⑵ Operating voltage: 
Displays the value of DC voltage supply to the XPA125. 
⑶ Operating current value: 
Displays the current being drawn by the XPA125. 
⑷ Output stage temperature: 
Displays the current temperature of the PA stage. 
⑸ Output SWR value: 
Displays the SWR value of the XPA125 output. 

⑹ Power amplifier status: 
Displays the overall status of the power amplifier as a whole. 
Indicates that bypass mode is selected, the power amplifier is switched out of 
circuit. 
Indicates that the power amplifier is operational. 
RX Indicates that the unit is in receive mode.  
TX Indicates that the unit is in the transmit mode. 
⑺ Input power value:  
    Displays the power input value to the XPA125 in Watts. 
⑻ Current working band status: 
Displays the current working band, and whether automatic or manual mode 
is selected. 
(9) Output power value: 
    Displays the output power being delivered by the XPA125 in Watts. 
 Automatic antenna tuner unit (ATU) status: 
Displays the status of the automatic antenna tuner. 
Indicates that the XPA125 is not connected to the automatic antenna tuner 
unit. 
Indicates that the XPA125 is connected to the automatic antenna tuner unit. 
When tuning is successful,【INUSE】will be displayed. 
If tuning fails,【Fail】will be displayed.
(10)

3. Operating instructions 
3.1 Wiring connection method 
3.1.1 Method for connecting XPA125 with X108G 
The XPA125 can be directly connected to an X108G, which can then control 
the band switching and ALC functions of the amplifier. 
- 
The ACC data cable supplied with the XPA125 is connected between 
the ACC ports of the two units.  Both connectors are the same so 
either end of the cable can be connected to either socket. 
- 
Use suitable RF coaxial cable to connect the X108G ANT port to the 
XPA125
 TRX port. 
- 
XPA125 ANT port should be connected to the antenna.
3.1.2 Method for connecting XPA125 with X5105  
Use the dedicated connection cable CN-115 to connect the X5105 ACC port with 
the XPA125 ACC port. Please note the need to distinguish between the different 
plugs of the connection cable CN-115. 
3.1.3 Method for connecting XPA125 with X1M  
As the X1M does not have a dedicated ACC interface and PTT signal output, it 
can’t be directly connected to the XPA125. A CN-17 converter is required to 
connect an X1M to the XPA125. 

3.1.4 Connection method between XPA125 and other QRP radio 
If you want to start the XPA125 power amplifier and put it into the transmit 
mode, you need to set the PTT port to a low level [level≤0.1V]. 
If the PTT output signal of the transceiver is at high level, the high level 
needs to be converted into a low level, and then input to the XPA125 
[ACC-PTT] port. 
Pin 2 of the XPA125 ACC port is the PTT input port 
In order to achieve automatic band switching, the corresponding band voltage   
is needed. XPA125 band control voltage information is as follows. 
3.2 Procedure: 
3.2.1 Using the power amplifier unit [PA unit] (ATU unit is set to BYPS) 
- 
Press the PA key, so that the state of the amplifier is 
[INUSE].
- 
If your connected transceiver is an X108G or X5105, please set 
the output power to 5 W. 
- 
If you are using any other QRP transceiver, please set the output 
power to 1 W. 
- 
Set your transceiver to CW mode, press the 
CW key
to 
transmit, 
and the XPA125 amplifier will be activated
. 
- 
The output power of the XPA125 can be adjusted by adjusting 
the output power of 
the connected transceiver. 

Warning: 
1. Do not allow the maximum output power of the amplifier to exceed 120 W. 
2. Using the XPA125 at high power levels for extended periods can lead to 
overheating and potential damage to the PA stage.  
3.2.2 Band switching 
- 
You can switch between the two modes of 
[AUTO- MANUAL]
via this key. 
- 
If you want to connect the XPA125 to an X108G or X5105, 
please set XPA125 to 
[AUTO] 
mode.
- 
If you want to connect the XPA125 to other devices, 
please set XPA125 to 
[MANUAL] 
mode and manually 
switch to
 the desired frequency band. 
Manual switching of frequency bands follows this order:  
160m→80m→60m→40m→30m→20m→17m→15m→12m→10m→6m 
3.2.3 Using the automatic antenna tuner unit [ATU] (PA unit is set to BYPS  
state). 
- 
Press the 
[ATU] 
button so that the current state of the amplifier
is [INUSE]. 
- 
Set the transceiver mode to CW & set the output power to 5 W.
- 
Press the CW key to transmit, and the 
XPA125 PA 
amplifier 
stage will be activated. The XPA125 ATU unit will start, the 
screen will display [TUNE]. 
- 
If tuning is successful, the screen will display 
[INUSE]. 
- 
If tuning fails, the screen will display 
[Fail]. 
If you need to re-tune, you can press the [ATU] button for two seconds to 
force the XPA125 ATU unit to start re-tuning. 
After successful tuning, switch the transceiver to the desired state for use. 

3.2.4 Combined use of power amplifier + automatic antenna tuner 
- 
Press the [PA] button so the current state of the PA unit displays
[INUSE]. 
- 
Press the [ATU] button so the current state of the ATU 
unit displays 
[INUSE]. 
- 
Set the transceiver mode to CW, the output power to 5 W, and 
press the CW key.
- 
If the current SWR value is more than 3.0, the ATU unit will start 
tuning automatically. At this time 
the PA unit will be disabled. 
- 
If the current SWR value is less than 3.0, the ATU unit will start 
tuning automatically, and the PA unit will be activated.
- 
If the current SWR value is more than 3.0, and automatic tuning 
fails
, the XPA125 will automatically switch to bypass mode 
and display this information on the screen.
3.2.5 Flexible configuration of PA unit and ATU unit 
The ATU unit and PA unit of XPA125 can be used independently of each other.  
You can therefore use the XPA125 as either an automatic antenna tuner or a 
separate power amplifier. You can also bypass both units, and your transceiver 
will then be connected directly to the antenna. 
3.2.6 Protection and warning  
The XPA125 incorporates a variety of intelligent protection functions to ensure 
as far as possible the safety of the equipment in daily use. When the XPA125 
enters an abnormal state, it will immediately enter protection mode and switch 
to bypass mode. 
 3.2.7 Remove protection and warning 
Release the PTT button. Protection will be disabled and the XPA125 will return 
to the receiving state. 
Warning messages are as follows: 
SWRI too high!  (Input value of 
SWR is high) 
Idd too high! (Operating 
current is too high) 
PIN too high! (High input 
power) 
Vdd too high!  (Input voltage is 
too high) 
SWRO too high! (Output value of 
SWR is high) 
Wrong band!  (Filter error) 
PO too high!  (High output 
power) 
Temp too high! (Operating 
temperature is too high) 

When high SWR, high current, high voltage, over temperature and other 
error states are detected, the XPA125’s internal sensors will trigger the 
protection function beyond a certain threshold. The threshold of each 
sensor is as follows: 
- 
High SWR:≥3.0 
- 
High current:≥30A 
- 
High voltage:≥15V DC 
- 
Over temperature:≥100℃ 
Warning
When the XPA125 current dra w  is too high (more than 30A), o r  a 
short circuit occurs, the fuse on the rear panel may blow.  The unit will 
then no longer turn on. Please check the status of the fuse if this occurs. 

Fault 
description 
Possible reasons 
Solution 
Unable to turn on 
your XPA125 
Power cord is not connected  Connect power cable correctly 
The fuse on the back of the machine
has blown 
Replace fuse(30A) 
Power cable connection is bad  Replace or repair power cord 
Power supply connection reversed  Return to distributor 
Other circumstances  Return to distributor 
No reception 
Antenna is not connected  Properly connect the antenna 
Antenna failure  Replace or repair antenna coax 
No communication 
Please confirm the propagation 
characteristics of the current band 
Other circumstances  Return to distributor 
No trasmission 
Antenna is not connected  Connect antenna 
Inadequate power supply current  Replace the power supply 
SWR is too high, protection has 
been triggered 
Start ATU/replace antenna/coax 
Incorrect working mode 
Select the correct working
mode 
Power amplifier unit not enabled  Set the PA unit to INUSE  
Other circumstances  Return to distributor 
Antenna tuning
function does not
work 
Antenna tuning function is not 
enabled 
Set the ATU unit to INUSE 
Screen has no 
display 
Power cord is not connected  Connect power cable correctly 
The fuse on the back of the machine
has been blown off 
Replace fuse(30A) 
Other circumstances  Return to distributor 
Smoke comes 
from equipment 
Replace smoke – Only joking, 
return to distributor 
4. General troubleshooting 
The following are general troubleshooting suggestions. If they do not resolve 
the problem the unit will need to be returned to your distributor. Please do 
not disassemble the unit as this will invalidate the warranty. 

After-sales service policy 
1. Warranty: 
This product has a one-year warranty effective from the date of purchase. 
This warranty covers only manufacturing- and parts defects. It does not 
cover damage caused by lightning, excess voltage on the power supply, 
accidental damage or purposeful damage or misuse. 
If the product needs warranty repair within two weeks of receiving the 
product, XieGu will pay for the shipping both ways. After two weeks XieGu 
will pay only for return shipping. 
If the product is not covered under warranty, the customer pays for shipping 
both ways plus the cost of the repair. 
2. Warranty limitations: 
Any of the following will void the warranty applicable to the product and its 
accessories: 
A. Modification-, removal-, or maintenance of the internal circuitry, 
without permission and authorization; 
B. Unauthorized change of product’s embedded software;  
C. Immersion in liquid or signs of external damage;  
D. Warranty period expired;  
E. Product’s serial number is missing, torn or blurred so we cannot determine if 

the radio is under warranty; 
F. Product was not bought from XieGu or authorized distributor of XieGu. 
*None of the following conditions, are covered by the warranty:  
A. Damage caused by improper use by the user;  
B. Damage caused by an accident;  
C. Damage due to incorrect testing, maintenance, debugging, or other changes;  
D. Damage is not caused by the material or the quality of production; 
E. Damage to the shell or other external components due to improper use. 
Contact us:  service@cqxiegu.com
制造商:深圳协谷通信技术有限公司
地址:东莞市塘厦镇蛟乙塘宝石路12号B栋4楼
电话:+86 0769-86346464