aunwin wrote:

Why must only series circuits be considered for radiators?.

Just thinking out loud. I'm not sure I'm correct but the following seems
to make a little sense.

In a series resonant circuit the net reactance is zero. As the frequency
is changed slightly from resonance the reactance increases slowly from
zero. This is algebraic addition of plus and minus terms.

In a parallel circuit the net reactance is the product of the two terms
divided by the sum [and has a high net value]. As the frequency is
changed slightly from resonance the net reactance does not change from
'zero' it changes from a high value to a lower value.

My conclusion is that a series circuit more closely matches actual
antenna performance as the antenna impedance varies from resonance.

DD

SNIPPED