Barry,
I¡¯ve reviewed your slide show and must say I am impressed with your ambitiousness. That¡¯s a LOT of material to cover in a single presentation. I would think most ham clubs members would be hard pressed to absorb that much information in a single presentation. Perhaps breaking it up into a few parts would be more effective, but you know your audience. I have taught such material to amateur level students and found it a little daunting.
As far as content is concerned I don¡¯t have much to add to what Dr. Kirkby and others mentioned, but here¡¯s a thing or two.
Antenna resistance: You present antenna ¡°resistance¡± (along with reactance and phase) but don¡¯t specify ¡°Radiation Resistance¡±. Most people will think of wire resistivity, or resistance associated with loss when presented with this term. I think the natural ¡°radiation resistance¡± of an antenna is an important concept to distinguish. This being the resistive load presented to the RF source by the radiating field of energy the antenna creates. Generally speaking, the longer the antenna the higher the Radiation resistance. I describe it (mechanically) like casting a fishing pole. A very long pole exhibits quite a bit more resistance than a very short pole.
Another factor that is important to consider in this regard is that as reactance varies from resonance the net Z of the antenna rises, as does SWR. Hence, even a mismatched antenna will exhibit its lowest SWR at resonance. (There are minor deviations to this rule for reasons beyond the scope of amateur discourse. So I pray the experts don¡¯t beat me up on that :). ) But for things like multi-band verticals and short mobile antennas this becomes critical as Reactance to (low) Radiation Resistance ratios rapidly swing the antenna Z, resulting in high Q, low bandwidth antennas. You see this in some of your latter VNA Smith curves as tight snail shell curves. Whereas antenna with high resistive losses, like short mobile antenna with thin wire, swamp this out and present wider bandwidth. A seemingly "better" antenna... NOT even a little.
SWR "Losses", etc: The misapplication of this term make me nuts sometimes. If you¡¯ve read Walt¡¯s book you know his position on the Amateur obsession with SWR! With that in mind, I like to point out to my audience that the increase in loss due to SWR is simply because the reflected RF passes through the feedline multiple times from it's mismatched load multiple times with the SAME loss, which simply accumulates. Using a matching network at the system input can be misleading as it only accounts for a SINGLE point of mismatch in the system. For example: Matching a 50 ohm exciter to a 300 ohm line, feeding a 300 ohm folded dipole will match with great success. Matching that same exciter to a 300 ohm line feeding a 75 ohm dipole, not so much. The 300 to 75 mismatch WILL result in additional feed-line reflections and commensurate loss regardless of the tuner. Hence, it is important to stress the need to match the line to the load as best as possible. Many installations using mismatched antennas and feed line exist. The most popular being the OWL fed dipole. The belief that the OWL is so much less lossy than coax being a benefit is (IMHO) not warranted given the trade-offs. Not the least of which is (depending on line length) the extreme swings in voltage and current that can exist in such a system.
I¡¯ll forego my mantra on preferring resonant antenna and broadband transformer matching for radically long or short antennas. Best of luck with your presentation and kudos for your efforts. I hope I¡¯ve given you some useful things to consider conveying.
Mark
