=  NOW 35 WPM  =  TEXT IS FROM FEBRUARY 2023 QST  PAGE 42 =

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/
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