"a 1/2 wave segment is resonant no matter where you feed it." That allows for a
large single coil to 'tune' one arm of an antenna and for the other to be
adjustable.

Simulation predicts the impedance will change when it is not feed at the center,
it appears to go up as the feed point is moved.

I will play with the segmentation and see what happens.

Thanks - Dan

Frank wrote:
"dansawyeror" wrote in message
...

All,

I have been experimenting with various loaded antennas to use in my
relatively limited space. For this I assumed the two arms of a dipole must
be identical to support resonance, this assumption has not been supported
by modeling.

Actual model runs show that if the two arms of a dipole are close then
there is sufficient interaction that they will combine to form a single
resonance. The model below shows a simple example of this. The loads and
length of the arms are not equal, however nec predicts a single resonance
at about 3.5 MHz. Changes of 10 to 20 percent around resonance seem to
create one resonance.

Is there an explanation for this?

Thanks - Dan kb0qil


No matter what Dan, you should see only one resonance at the overall length
of a half wave. Not that resonance has any bearing on antenna efficiency.

Also; your NEC model has uneven segmentation, which does produce significant
errors. Interesting to note that your antenna is also resonant at 7 MHz.

73,

Frank