Care and Feeding an Icom PW1
W6DE
Page 8
Copyright 2017, All rights reserved.
--Hemostats (6” and 8”) will be needed to pick up the screws that will fall into impossible to get to
places.
-- To get to some screws, a long blade 6” Phillips screwdriver will also be needed. Always use the largest
size Phillips screwdriver blade that will fit into the screw head slots.
Symptom: The Tuning Light changes from Steady On to Flashing when increasing the power level in
the PW1
The tuning light flashes when the tuner is trying to find a match. In the PW1 Instruction (operator’s)
manual on page 13 it says:
“The built-in antenna tuner automatically tunes the
antenna.
- SWR reading on meter-2 should be less than 1.2:1.
”
And later in the manual on page 14 it says:
“When the tuner cannot tune the antenna (SWR 1.5:1 or
greater), the tuning circuit is bypassed automatically after 20 sec.
.”
The first comment is telling you the amplifier wants less than a 1.2 SWR in order to operate.
The second comment is telling you that the tuner may not be able match an antenna if the starting point
is greater than 1.5 SWR.
I can attest that continued operation with the Tuning Light flashing can cause damage to the PW1 long
before the 20 seconds is up. If you continue operation long enough (not recommended) with the
blinking tuning light you will see the SWR meter vary up and down and eventually peg at full scale as the
tuner hunts for and fails to find a match. The PW1 tuner is really only intended for slight mismatches. I
now only operate with matched antennas (under 1.5:1 SWR). If your only antennas are so-called
multiple band, non-resonant, antennas, then my recommendation is to buy an external high
power/heavy duty antenna “tuner” that is advertised to handle 10:1 SWR.
Automatic antenna tuner failure: To prevent tuner run-away, you should only make the automatic tuner
adjustments at reduced power—100 watts or less. Use exciter power only or turn down the power on
the exciter. I have not had to repair a tuner, but accidentally using full a KW into a miss-matched
antenna caused my auto tune function to go wild as described above and take out a PA board. Arced
tuner capacitors in the tuner and failed tuners are also a result of allowing the tune function to be
performed at High Power with the PW1.
If you are trying to use a multiband antenna anyway, allow the tuner to find a match at low power and
then slowly increase the exciter’s power and watch the PW1 SWR meter. If the SWR starts creeping up
or the tuner starts to initiate another tune—tuner light blinks—immediately roll the power back and
start the process all over again. It may be that you can find a match at a lower PW1 power level that still
works without a tuner run-away.
.
