Scott Stephens wrote:
Since antennas have reactance and radiation resistance, are they always
critically damped, or will they ring-down?
No, they are not critically damped, NOR are they a simple resonator.


Is this implied by a swr plot? Can I take 3db points as antenna
bandwidth and assume a radiation-resistance loaded-Q from that?

No (this is a common error when folks first hear about the Chu limit and
read about Antenna Q. They mistakenly equate Antenna Q with "tuned
circuit Q" and then leap to the idea that center frequency/bandwidth =
Q.. nope.. Q, in both cases, is the stored energy divided by the energy
lost per cycle. But the mechanism is different...)



Does feed-point impedance change radiation resistance?
No. A folded dipole has a feedpoint impedance of about 300 ohms and a
dipole has a feedpoint impedance of about 72 ohms, but they have the
exact same radiation resistance.

Google for "radiation resistance" and "surrey" to find some pages by Dr.
Jefferies at UofSurrey..

http://personal.ee.surrey.ac.uk/Pers...es/radimp.html
http://personal.ee.surrey.ac.uk/Pers.../antennas.html

http://www.ece.rutgers.edu/~orfanidi/ewa/ is an online textbook which
you may find useful


Thanks