There is another mechanism in the MCU that helps do that, but it is not
always effective - that is the CAL CUR setting.
It must be set to 3.50 Amps for a K2 with a KPA100, and often the K2
will show HiCurr when the wattmeter diodes fail.
The problem I see with that is many users continue to operate in spite
of that warning. The situation gets worse if the user turns the power
knob to maximum. I recommend that the power knob be set to no more than
10 watts for the base K2 and no more than 100 watts with the KPA100.
Your signal will be cleaner on the bands and the power control will be
smoother.
If you "do the math", you will find only a miniscule difference between
100 watts and 120 watts at the receiving end. So why stress your
equipment by squeezing that last ounce of power out if it. I know,
historically hams have tried to get all they can out of a device, and
may not think of the stresses involved in that process.
There is another thing to watch to keep your Elecraft K2 or K3 or KX3
transceiver running with less stress, and that is to keep the power
supply voltage up. There is less stress on the components when using a
14.4 volt power source than when running at 12 volts. Your signal IMD
will be better with the increased voltage as well. The reason is that
the K2, K3, and KX3 attempt to maintain the requested power - for any
given power level, if the voltage is increased, the current will be
reduced. It is typically current that kills solid state devices in any
proper design.
73,
Don W3FPR
On 4/18/2013 8:42 AM, Greg Troxel wrote:
Don Wilhelm <[email protected]> writes:
What normally happens with a static surge on the antennas is that the
wattmeter diodes fail, and that causes the K2 to not sense the power
output - the MCU in the base K2, thinking there is no power output,
cranks up the drive to maximum possible, and that stresses the PA in
the base K2.
Maybe this is too complicated, but perhaps the MCU could check for there
being a reasonable partial derivative from drive to perceived output,
and if not decline to increase drive, so that the secondary finals
damage could be avoided?
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