[Elecraft] KX1 Low Power Output

[jim.r.johns@accenture.com]

I've been working on KX1 Serial Number 573 and everything has been going =
great up to the point where I'm supposed to measure the RF power output =
from the rig and verify that I'm getting between 3 and 4 watts output.=20
=20
With a solid 13.8 Volts to the rig, I'm seeing only 2.6 Watts on 20 =
Meters (14.100 MHz) and about 3.1 Watts output on 40 Meters (7.100 MHz). =
 This meets the .3 to .6 Watt recommended difference between 40 and 20 =
as described in the manual but 20 Meters doesn't meet the 3 to 4 watts =
spec.  With a Gel Cell (Voltage on transmit about 12.1 Volts to 12.2 =
Volts key down in tune mode) I'm getting close to 2.5 Watts on both 20 =
and 40 Meters.  Current draw from the battery (12.1 Volts) while key =
down was 450 mA on 40 Meters and 610 mA on 20 Meters.  Power was =
measured using a Coaxial Dynamics RF Termination Wattmeter (QRP) using =
the 5W full scale range, and verified on an Oak Hills Research QRP =
Wattmeter into a commercial 50 Ohm dummy load.
=20
I've checked the usual (toroid winding count, transformer windings, =
capacitors, resistors, drive potentiometer is full clockwise, etc.) and =
all the DC voltages (transmit mode) are within milivolts of the table =
values.  The receiver works great on both bands, and I can copy lots of =
signals using a 15 foot piece of wire on the floor.  I haven't installed =
the 30 Meter or ATU add-on modules yet.  I want to make sure the base =
rig is working correctly before I add another variable to the mix.
=20
I've noticed some other threads on this list that mention others with =
low power output.  Some were traced to windings on the toroids and =
transformers and some resorted to changing the base swamping resistor of =
the final amp.  I'm open to any suggestions or recommendations.
=20
The delta between 2.6 Watts and 3.00 Watts is insignificant.  I just =
want to make sure I haven't missed something.  I'm sure that Wayne =
intended the transmitter to output between 3 and 4 Watts, or the =
instruction manual would say to look for 2.5 to 3.5 Watts instead of 3 =
to 4 Watts :-)
=20
Ideas?  Suggestions?
=20
Thanks in advance.
=20
73
=20
Jim Johns KA0IQT
=20


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