"Roy Lewallen" wrote in message
...


Jerry Martes wrote:
"Buck" wrote in message
...
I have a wire dipole and an inverted Vee each cut to resonance on a
desired frequency. I would like to add a reflector and/or a director
(one at the time) to make each one a beam. Will adding the reflector
and/or director change the resonant frequency, or just the impedance?

Thanks
Buck
n4pgw

--
73 for now
Buck
N4PGW

Hi Buck

Isnt Resonance defined as the frequency where the Impedance has *no*
reactance? Wouldnt that imply that the resonant frequency of the
antenna will always change if its impedance changes?
Can you *ever* change one without changing the other?

You're correct about the definition of resonance.

Buck's statement would have made more sense if it the last words were
"just the resistance", and that's likely what he meant.

Sure, you can change the impedance without changing the resonant
frequency -- a transformer will do that, for example. At resonance, the
resistance will simply be a different value.

But to answer Buck's question, adding another element will almost
certainly change both the resistance and reactance at the feedpoint, and
therefore the resonant frequency.

Roy Lewallen, W7EL

Hi Roy

I'm not qualified to enter into a theory discussion with you. But, I'd
expect the introduction of a nearly half wave long comductor into the near
vicinity of an antenna that has a purely resistive Terminal Impedance
(Resonant) will change the Terminal Impedance of the new antenna which is
the combination of the two.
I would have considered that transformer doesnt actually change the
antenna's Terminal Impedance (Resonance) the transformer converts the
antenna's impedance *at a new location*.
So, I'd expect the antenna's "resonance" to be defined by its "impedance".

I've considered that any R+/-jX can be Transformed to an impedance thats
purely resistive. But, with antennas, thats a matching situation, while
the antenna's terminal impedance remains reactive.

Jerry