>> "I own one FT-9000d, one IC-7800, and one K3/factory assembled. The only
>> one where I can get "over shoot" or a full-power brief spike of RF is the
>> K3. The rig is set for, say, 40 watts output and on its first key down,
>> voice or CW, it jumps to 100 watts for a very brief moment and strangely
>> does not repeat this spike as that one key-down session continues, but
>> repeats again after a longer stand-by period. This is a common and very
>> well known problem with the K3, but not often discussed due to the
>> powerful love people have for their K3 radios."
That's not right. It's an occurrence only when the menu-driven TX Gain is
not calibrated at the 5W/50W set points. The easiest remedy is to use the
K3 software utility. In the utility, select the tab under "Calibrate," then
select "Calibrate TX Gain." The wizard will then take you through gain
calibration which sets ALC on a band-by-band basis. If after calibration a
spike is seen or detected by an amplifier, then there's a more pervasive
problem with your K3. With TX Gain set correctly, the envelope should look
like the one displayed on pages 11 and 12 of DL9NC's paper:
http://www.ov-n15.de/joomla/images/zoom/DL9NC/pz_32.pdf
I use a Tektronix TM test set with SC504 scope while transmitting CW. A
spare output from a microHAM CW Keyer triggers the scope such that the
leading and falling edges are accurately displayed and precisely triggered
from the keyer. This allows for the keyed RF waveform to remain stable
without having to chase it by changing either CW speed or the scope's time
base.
As a test, I just set power to 40W on 20m and looked at the keyed envelope,
allowing for various settling times in between transmissions up to 30
seconds. At no point does a power spike occur. In fact, the envelope never
reaches a maximum, then some minimum point as is usually the case after ALC
stabilization with other transceivers.
Referring back to the DL9NC paper, power spikes from transceivers other than
the K3 show a period of about 1 ms or so. That's under the sampling period
required by commonly available sampling wattmeters.
Paul, W9AC
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