My least understood subject is impedance as applied to antenna design. Normally, given auto tuners in most modern transceivers, why bother with learning the fundamentals? The button is pressed and electromechanics matched the wireless set with antenna load; easy as one, two, three? Then something happened to my inner engineer; I wanted to see the Great Oz, I wanted to know the great Oz, then understand why he could pull this lever and produce that effect.
Joel Hallas, W1ZR, in Basic Antennas, Understanding Practical Antenna Design, shared several nuggets on the topic of antenna impedance. For example, I did not grasp the concept, as conductor diameter increases then the length of the resonant dipole decreases; as conductor diameter increases a corresponding change in impedance with frequency decreases, according to the author (2012).
Additionally, Hallas answered one nagging question, why can I position my transceiver in the shack practically any distance from the antenna? His answer is another nugget of gold that is if one matched the impedance of the antenna with that of the transmission line then your transceiver acts as if at the center of the antenna (2012).
Please refer to Table 4-1 and Figure 4-3 on page 4-3 as Hallas further explained load diameter including resistance and capacitive reactance. Furthermore, in the paragraph Impedance of a Dipole near Earth, Hallas revealed the nugget of nuggets, that is reflections from the ground couple with the dipole. He stated that the impedance of a dipole differs at various heights because of the magnitude and phase of the reflective wave (2012).
Admittedly, a wow moment for me, because I never put together reflective wave, height above ground, and ground characteristics as influencing antenna efficiency. His explanation satisfied why my off center fed Buddipole failed to load when positioned over a patio brick ground. Literally, I was likely transmitting most of the energy directly back into the antenna, as a reflective, out-of-phase wave.
I need to keep in mind as one living in a regulated community with significant constraints that sometimes my problems are not related to the antenna itself. Instead, it is antenna environment confounding both physics and mathematics, not antenna design. I'd recommend logic charting your potential antenna system before installation followed by reverse engineering problems after the fact.
73 from the shackadelic near the beach.