[Elecraft] Re: Elecraft Digest, Vol 8, Issue 10

[Vic Rosenthal]

Mychael Morohovich wrote:

> The method I used was to first tune the antenna with my KAT100 for a 
> flat SWR, tune the counterpoise for max current at the rig, then tweak 
> both until the KAT100 reported a flat SWR for the antenna while the 
> Artificial Ground reported maximum current into the counterpoise. Using 
> the rf sensor, I measured the current of the antenna [and counterpoise 
> because I was curious] at a spot close to the back of the rig. I then 
> removed the counterpoise, retuned the antenna for a flat SWR, and 
> measured the current again for reasons of comparison.
> 
> This showed me the amount of current that was going into a properly 
> tuned antenna both with and without a tuned counterpoise in place.

Think of the antenna and everything connected to the ground terminal of the 
KAT100 -- including the counterpoise -- as an off-center fed antenna.  When you 
removed the counterpoise, you moved the feedpoint.  This changed the impedance 
seen by the KAT100 (which is why you had to retune it) as well as the current 
measured at the feedpoint.  If (for example) the current at this point 
decreased, how do you know it didn't increase somewhere else along the wire?

-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco