=  NOW 40 WPM  =  

GREATER THAN 3 1.  OPERATING I WAS ABLE TO TEST THE XPA125B WITH MY
XIEGU G90, XIEGU X5105, AND ELECRAFT KX3, AND A QRP LABS QCX MINI 20
METER TRANSCEIVER.  I USED THE OPTIONAL CE 19 INTERFACE WITH THE
XIEGU RADIOS, AND IT WORKED WELL BY PROVIDING KEYING AND AUTOMATIC
BAND CHANGING FOR THE XPA125B.  THE XPA125B CONTROL INTERFACE IS A
MINIDIN6 CONNECTOR, SO I BUILT INTERFACE CABLES FOR THE KX3 AND THE
QCX MINI USING A MINI DIN6P CABLE.  THE KX3 KEYS THE XPA125B
DIRECTLY.  AS T ALWAYS SHOWS 1 1, AS IT IS LOOKING INTO THE INPUT OF
THE ON LINE AMPLIFIER.  FINALLY, THE GAIN DROPS AS YOU INCREASE
DRIVE.  THIS INDICATES THAT THE AMPLIFIER IS GOING INTO COMPRESSION
AT THE HIGHER POWER LEVELS.  THIS IMPLIES THAT YOU ARE DEGRADING IMD
AS YOU NEAR THE AMPLIFIERS RATED OUTPUT.  MY KX3 HAS A BUILT IN TWO
TONE GENERATOR, SO I LOOKED AT THE BAREFOOT KX3, AND THEN THE KX3
DRIVING THE XPA125B TO 94 W ON 20 METERS EXTERNAL POWER SUPPLY SET
TO 13R8 V.  AS YOU CAN SEE IN FIGURES 2 AND 3, THERE IS SIGNIFICANT
DEGRADATION OF IMD PERFORMANCE WHEN THE AMPLIFIER IS USED.  THE
XPA125B AUTOMATIC ANTENNA TUNER THE XPA125B INTERNAL ATU PROVIDES
MANUAL USER INITIATED TUNING.  TUNING IS INITIATED WHEN THE ATU/
TUNE BUTTON IS PRESSED FOR SEVERAL SECONDS, AND 5 W OF RF CARRIER IS
APPLIED.  THE ATU CAN BE USED WHETHER THE AMPLIFIER IS ON LINE OR
NOT.  IF YOUR QRP TRANSCEIVER DOESNT INCLUDE AN ATU, THE XPA125B
WILL TAKE CARE OF THIS FOR YOU.  HOWEVER, AS MENTIONED EARLIER, THE
XPA125B SWR METERS DO NOT WORK UNLESS THE AMPLIFIER IS ON LINE AND
KEYED.  THE AUTOMATIC TUNER WILL TUNE, BUT YOU HAVE NO INDICATION OF
THE FINAL SWR UNLESS YOUR QRP TRANSCEIVER HAS AN SWR METER.  TUNER
MATCHING AND LOSS MEASUREMENTS RESISTIVE MATCHING RANGE AND LOSS
TESTING WAS PERFORMED WITH THE PRECISION SETUP DESCRIBED IN THE
PRODUCT REVIEW COLUMN IN THE AUGUST 2012 ISSUE OF QST SEE WWW. ARRL.
ORG/ QST IN DEPTH FOR DETAILS.  TUNING POWER WAS SET AT 5 W, PER
XIEGU RECOMMENDATIONS.  ALL MEASURED LOSSES ARE SUBJECT TO THE 3
ACCURACY OF MY NIST TRACEABLE TEST EQUIPMENT.  THE XPA125B TUNING
RANGE IS SPECIFIED AT 14 500 RESISTIVE, THOUGH LAB NOTES XIEGU
XPA125B 1R8 50 MHZ 100 W AMPLIFIER THE XIEGU XPA125B AMPLIFIER
PRESENTED QUITE THE CHALLENGE FOR THE ARRL LAB TO TEST.  WE HAD
ORIGINALLY OBTAINED A SLIGHTLY OLDER VERSION OF THIS AMPLIFIER.  IT
WORKED WELL ENOUGH, EXCEPT FOR THE PROBLEM THAT THE RF POWER OUTPUT
WAS LOW ON THE UPPER BANDS.  THIS MIGHT NOT HAVE BEEN A PROBLEM IN
AND OF ITSELF, BUT WHEN WE PUSHED IT HARD TO GET CLOSER TO THE RATED
POWER, THE TRANSMIT IMD PERFORMANCE WAS NOT GOOD AT ALL.  WE THEN
FOUND THAT XIEGU HAD A NEW AND IMPROVED VERSION OF THE AMPLIFIER, SO
THE EDITORS DECIDED TO REVIEW THE NEW UNIT.  WHEN WE RECEIVED THE
NEW VERSION, WE SAW THE SAME PROBLEM WITH POWER OUTPUT ON THE 10 AND
6 METER BANDS.  WORSE, THIS UNIT DID NOT MEET THE FCC LIMITS FOR
SPURIOUS EMISSIONS ON 6 METERS.  WE HAD PURCHASED THE AMPLIFIER
THROUGH HRO, SO WE CONTACTED THEM.  HRO IMMEDIATELY AGREED TO
EXCHANGE THE AMPLIFIER FOR US.  THE REPLACEMENT ARRIVED PROMPTLY.
=  END OF 40 WPM TEXT  =  QST DE W1AW  <