K2 Power Adjustment/Output Question

[MikeH-3]

I'm wondering if I have a problem with the transmitter in my K2. I
think other K2 owners will know if what I'm seeing suggests a problem.

In the process of comparing the power output reading on two different
wattmeters, I found the same odd behavior on both (so I think I'm
seeing K2 behavior, not wattmeter behavior). I was doing output
measurements at different power levels on the K2. So, for example, I
would start at a few milliwatts, transmit into the dummy load, record
the measurement, move up to say, a watt, and repeat the process. I
would continue up in power a watt at a time, recording the output on
the meter.

What I noticed is a failure to always get the same wattmeter reading at
a given K2 power level setting (as shown in the K2 display). For
example, at 0.7 watts (on the K2 display), the meter showed 1.0W. When
I moved the K2 power adjustment up to 1.0W (on the display), the meter
showed 0.8W. However, when I turned the K2 off, and repeated the
measurement at 1.0W, the meter then showed 1.0W again. I then turned
the K2 power adjustment down a bit (without transmitting), then turned
the adjustment back to 1.0W, and got only 0.8W on the meter again.
Tapping the key a few times at that power level did not bring the
reading back to 1.0W on the meter. Yet if I turned the K2 power knob up
(without transmitting), and then back down to 1.0W and transmitted, I
got 1.0W again. This sort of pattern was repeated throughout the
process. I could set the adjustment on the K2 for a certain power
level, get a reading, and then get a different reading after doing
something like turning the rig off or changing the power and
transmitting, or just moving the adjustment up and/or down, and then
going back to the original power level setting only to get a reading
that was off (always lower) by as much as 1W (say 3W rather than 4W). I
could always do something to get back to the original reading (like
powering down the rig, or changing the power level and tapping the key
a few times)  and  then remeasuring. Simply tapping the key a few times
does NOT bring the wattmeter reading back to the original reading
UNLESS I also change the power adjustment on the K2 (and then remeasure
at the original K2 setting).

So, does this variance of up to 1W while measuring output at a given
power setting on the K2 represent a problem with the rig? I experienced
this variance regardless of whether the rig was putting out 2W or 10W.

A couple of basic facts: the maximum power output for the rig is 12W
from bands 80M-20M; 10W on 17M-12M; and 8W on 10M. Whenever I transmit,
the output appears totally stable while keyed down. Signal reports have
all been good. Also, I do have the KAT2 installed (I get the same
behavior even if I turn the tuner off at the menu), and I don't think I
have power reading setting (via R1 adjustment) set as accurately as I
could. However, since I can replicate this issue with the tuner turned
off, I do not think that is a factor.

As always, I appreciate your thoughts.

Mike Hagey NR7F
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[Paul Saville-2]

> So, does this variance of up to 1W while measuring output at a given
> power setting on the K2 represent a problem with the rig? I experienced
> this variance regardless of whether the rig was putting out 2W or 10W.

http://www.elecraft.com/Apps/Power_Control_Mod.html

Mike,

It's a "feature" inherent to the K2 design, not a problem with your rig. The
mod at the above link describes how to reduce the power fluctuation to a
minimum. I ended up with 910 ohms for R98, if my memory serves me correctly.

73 de Paul ZL3IN

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