[Elecraft] K2: Tune For Low SWR or Max Power?

[Don Wilhelm]

  Jon,

You will have to fix something, but I am not sure what.
The KPA100 will throttle back power if the SWR exceeds 2.0 (as indicated 
by its wattmeter).  So that is the reason you have to fix it.
Two questions arise.  First (and most likely), what kind of tuner?  Is 
it a T-match tuner?  If so, be aware that you may be setting the tuner 
to a setting where the tuner is creating the loss - a T-match tuner can 
have multiple positions which give a low SWR, but they are not all 
optimal.  You could also be exceeding the range of the tuner on 80 meters.

Secondly, is the wattmeter in your KPA100 properly balanced (nulled) and 
calibrated for forward power and SWR?  Since your external meter and the 
KPA100 indicate about the same, I don't think this is likely the 
problem, but since it is a possibility, I mention it.

Merry Christmas for all who celebrate it, for those who do not - Happy 
Holidays - and a very Happy New Year for all those on the Elecraft 
reflector.

73,
Don W3FPR

On 12/25/2010 5:12 AM, Jon Perelstein wrote:
> I'm running a K2 (with KPA100) with an MFJ941E Versatuner.
>
> My antenna is a multi-band Windom that will load up on 80, but is less than a
> half-wave on 80.  On most bands, lowest SWR per the tuner coincides with the
> highest output power showing on the K2 (usually 20 or 21 watts).  However, when
> in TUNE mode in the CW portion of 80, the lowest SWR per the tuner shows a
> reduced power output per the K2 (about 16 or 17 watts).  In that portion of 80,
> I get the maximum power output showing at about a 2.5:1 SWR per the K2.  The
> readings on the tuner's forward and reflected power meters are consistent with
> what the K2 is showing, with a noticeable dip in forward power when I get
> minimum SWR.
>
> Receive signal strength is also consistent with what the K2 is showing.  By ear,
> received signal strength is lower at the minimum SWR point than at about a 2.5:1
> SWR setting.  Similarly, the K2's S-Meter shows that the received signals are
> about 1 S-Unit lower at lowest SWR than they are when I tune for that 2.5:1 SWR
> setting.
>
> I understand that this antenna is not "optimal" for the lower stretches of 80,
> but given that it's all I can put up at the moment, am I better off tuning for
> the best output power or for the lowest SWR?  If I tune for the best output, how
> much should I back off on the output power to adjust for the fact that I'm
> getting more reflected power coming back into the rig?
>
> Thanks
>
> Jon
> KB1QBZ
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