Jeff Liebermann wrote:

Huh? I can tune across the frequency range of a Yagi-Uda antenna,
measure the VSWR, and most certainly see a resonance dip at the design
center frequency. I can also attach a grid dip meter to the feed,
through a coupling loop, and see the resonance. Take away the

That's not resonance, it's matched at that frequency.

reflector and directors, and we're left with an ordinary dipole, which
is most certainly a resonant antenna. If the driven element is not
resonant, what is producing the dip in VSWR at the design frequency?

The match. It's normally not a resonant element when in the middle of a
Yagi-Uda array, although it's _near_ resonance when the rest of the
elements are removed.

It is possible to have a resonance at the match frequency, but unusual.
Run a couple yagis through Eznec and check the driven element impedence.
For instance, the NBS yagi that comes with Eznec. At 50.125 it's
11.7+j5.9, not very resonant. I have a 222 yagi that has a DE longer
than the reflector, also unusual, but it works fine.

tom
K0TAR