[Elecraft] Question about K2 power meter

[Don Wilhelm]

Jeff,

Is this into an antenna or into a dummy load?  If it is into an antenna, 
'strange things can happen' in the basic K2 configuration when the 
antenna is not 50 ohms pure resistive.

Work into a dummy load first to resolve the situation (or answer your 
questions).  The LED bargraph should be fairly accurate (but it only 
goes up to 10 watts).

If your external wattmeter does not give a good indication at a 5 to 10 
watt level, you may find success in measuring the RF voltage across the 
dummy load with the RF probe, then calculating the power output from the 
voltage (P=V^2/R if your probe reads RF volts RMS - the one provided 
with the K2 does read RMS voltage).  A high range external wattmeter can 
be really far off when indicating lower powers - 20% of the full range 
value is a common spec for wattmeter accuracy, and on a 200 watt scale, 
that is 40 watts potential error!

Yes, stick with the basic K2 until you can answer the question of how 
much power is actually being developed.  Once you determine that, you 
can chase the cause of the problem if one exists.  Don't jump to 
conclusions before knowing the answer to this part of the question.

73,
Don W3FPR

Jeff Kinzli N6GQ wrote:
> Don and others,
> 
> A few weeks back, a user posted about an issue with low power output
> with his K2. Don said:
> 
>> If you do not have either the KAT2, the KPA100, or the KAT100 
>> installed, the
>> K2 does not display the actual power output on the LCD (the requested 
>> power
>> is displayed briefly when the power control is changed). What is the
>> indication on the LED bargraph during transmit?
> 
> I'm going through an issue with my K2 where it *appears* to be putting
> out too much power. With the KPA100 installed, the output sometimes
> jumps up to 150+W.
> 
> I removed the KPA100 from the picture and have been seeing if I can
> reproduce higher than normal output with just the base K2. So far, the
> behavior is that if I enter TUNE mode, the indicated power on the
> display of the K2 will rise to 16-17W. My watt meter isn't accurate
> enough to tell me what it's *really* putting out though, although with
> the KPA100 it is accurate enough to see the 150W+ peaks.
> 
> So I was trying to think if it's really putting out 16+W, or if the
> power meter is really telling me it's TRYING to put it out (because my
> external wattmeter looks like actually less, but again not accurate).
> 
> I also thought maybe it's an ALC issue, because if I rotate the power
> knob back then back up to max, the indicated power on the K2 will go
> to about 15W, but the next time I do TUNE again, it again goes back up
> to 16+W.
> 
> Any thoughts on this? Should I keep chasing ALC issues? I've already
> gone through the base K2 RF board resoldering T1-T4, reheating
> anything that looks suspect, etc. to no avail.
> 
> I also sent something to this effect to Gary at Support, I'm just hoping
> someone might have any ideas that I could chase down.
> 
> Thanks,
> 
> Jeff
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