[Elecraft] K2: Stability of Output Power Level

[Michael J. Linden]

  I just completed construction of an Oak Hills Research WM-2 QRP
wattmeter. So, of course I wanted to compare its readings with that of
the K2.
 
  Here are some test results. Please let me know if what I'm seeing here
is normal or if you think Elecraft's "Optional K2 Power Control
Modification" may make any of this a little better. All of these tests
were performed at 7.145 MHz into the WM-2 wattmeter and then into a good
(50.3 Ohms resistive) OHR dummy load. For each test, I key the radio
several times using the Tune function (no KAT2 installed, yet).
 
#1
Set the K2's power control (request) for 4W and the output varied
between the following:
 
K2 Disp  WM-2
-------  ----
5.2      ~7
3.9      ~5
3.3      ~4
 
#2
Set the K2's power control (request) for 2W and the output varied
between the following:
 
K2 Disp  WM-2
-------  ----
1.5      ~2
2.4      ~3
 
#3
Set the K2's power control (request) for 0.5W and the output varied
between the following:
 
K2 Disp  WM-2
-------  ----
0.4      ~0.7
0.8      ~1.2
 
#4
Set the K2's power control (request) for 0.2W and the output varied
between the following:
 
K2 Disp  WM-2
-------  ----
0.2      ~0.4
0.3      ~0.5
 
#5
Set the K2's power control (request) for 0.1W and the output decreased
with each activation of the Tune function until there was no detectable
output:
 
K2 Disp  WM-2
-------  ----
0.1      ~0.2
0.1      ~0.1
0.2      ~0.05
0.2      no noticeable reading on 100mw scale
 
  I'm primarily concerned with cases 1 and 5. The variance in case 1 is
fairly broad and is among three values. Case number 5 concerns me
because the output level drops with each successive press of the Tune
button until no output can be detected by the WM-2 on its 100mw scale.
Clearly, I would not be able to reliably use my K2 when set for 100mw.
 
  Will this situation (with respect to output power sensing) get any
better after I install the KAT2? I haven't completed construction of the
KAT2, yet. Any input/explanations/ideas would be appreciated.
 
  Thanks! -Michael N9BDF, K2 #4137