I see j-pole in this book but can't find reference to measuring real antenna impedance at end point of dipole.
I have been reading through this thread and am still trying to figure out what/where you are trying to measure?
WHAT do you mean by end point ? do you really mean
feed point ?
The feed point is the only place you need to be interested in the impedance and that is already a known + or - a few ohms for the 2 main styles of dipoles.
A standard 1/2 wave dipole is 75 Ohms and the folded dipole is 300 Ohms when they are at resonance at a given freq.
The 2 primary times that varies is ....
1) the dipole isnt cut to resonance at the required freq
2) the dipole is placed with other elements to form a yagi
The antenna analyser, like MFJ sells, is good for that final fine tuning of the dipole to bring it into resonance. or if its in a yagi the varying of the spacing of the reflector, driven element ( your main dipole) and the first few directors to bring the system into resonance.
Personally I have never used an antenna analyser in the 30+ years of building antennas. Like you, i have thought, for what it is, its too expensive haha
on the other hand a decent reflectometer for reading forward and reverse power is all you really need, and tune the system for max forward and minimum reflected power.
Ok granted, for what ever reason, you may actually want to know the real impedance at the feed point, and I guess, interesting from a learning and informative point of view. There's probably very few people in the real world that could quote you what the feedpoint impedance is of their antenna.
My commercial ones I use the datasheet that came with the antenna and hope the manufacturer could do a reasonably accurate measurement.
( Hey its in resonance and radiates well, so cant be too bad
)
my home built antennas I just test as above and tune for max forward/min ref. power
The effect of placing a dipole into a yagi system has the effect of reducing the impedance of the feedpoint. a plain dipole can drop to as low as 25 Ohms from that original 75 Ohms.
A 300 Ohm folded dipole in a yagi system can drop down to ~200 Ohms. Which is pretty handy as you can then use 50 Ohm coax and a 4 : 1 BALUN for a good match
just a few random thoughts
cheers
Dave