Does the wire diameter of the reflector and the directors of a beam antenna affect the bandwidth or is it only the driven element diameter that has this effect?
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$\begingroup$ Check out the driven elements of the Woodpecker's antenna, extended from a large flat screen, which was made to cover all of HF: google.com/…: $\endgroup$– SDsolarOct 7, 2017 at 23:35
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$\begingroup$ Also, check out the crossed dipoles of the HAARP antenna system. 180 of them standing 180 feet above a mesh screen that is measured in acres. Designed to cover all HF, with transmitters and tuners for each set: google.com/…: $\endgroup$– SDsolarOct 7, 2017 at 23:38
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1 Answer
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This is a non-mathematical answer.
The only difference between the driven and non-driven elements is the connection of a feedline. Each of the elements resonance and position contribute to the characteristics of the antenna.
If the directors and reflectors are not of similar bandwidth to the driven element then they will not have a consistent phase and amplitude relationship with the driven element over the frequency range. The radiation pattern depends on the summation of the energy from each of the elements. The radiation pattern will change.
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$\begingroup$ In the two cases I mention in comments to the OP, the driven elements are all separate from huge mesh reflector screens. Both are designed for the wide-band purpose of covering all HF. $\endgroup$– SDsolarOct 7, 2017 at 23:39
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$\begingroup$ I agree that when there are more than one driven elements, the possibilities are increased. HAARP is a great case of a simple reflective surface and multiple, phase controlled, driven elements. I assumed from the question that we were considering conventional Yagi-like antennas, with one-or-more reflectors, one driven element, and zero-or-more director elements. $\endgroup$– cmmOct 8, 2017 at 16:13