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the shorter the antenna is relative to a full 1/4 wavelength, especially @ the low end of the hf band, the lower the (single digit) radiation resistance. no surprise when you take into consideration that a full size 1/4 wl at 1.9 mhz. is almost 130 feet.

when you find the operating frequency (below 27.200 mhz.) where J = 0.00 let us know.

now if you are still determined to follow through with this then you'll need to start out with something that is shorter than a 1/4 wl. and i don't mean just a couple of inches. the whip at half of its physical length would be as good a place as any to begin, @ 54 inches. now you can use a...

from the link you posted: "The elements for the proposed Yagi were just under 75% of full size." there is absolutely no need for a capacitance hat on a full size 1/4 wl. antenna.

there's too much extraneous metal in the near field of the antenna creating capacitive coupling to the antenna itself. as the antenna is electrically shortened the swr will be lower on the uppermost frequencies and higher on the lower frequencies, indicating that the antenna is too short. that...

it's no rumor.

"The voltage distribution on the antenna does not contribute to radiation..." quoting an fcc field report for the field strength of a signal @ a frequency of 1640 kHz measured at 14,500 microVOLTS per meter (uV/m) at 62 meters. (203.41 feet) if we measure the RADIATED field strength of an...

with regard to all antenna modeling software, even with their shortcomings and the "work arounds" required to minimize their limitations, the validity of the output data is only as dependable as the accuracy of the user inputted data and information, the combination of all of the above...

https://duckduckgo.com/?q=j-pole+antenna+radiation+pattern&t=h_&iax=images&ia=images

"The current is 100% responsible for all radiation from an antenna. If the voltage contributed to radiation, the modeling programs would also show the voltage." this statement is patently absurd and makes a false assumption based on the limitation of an antenna modeling software program. in the...

https://duckduckgo.com/?q=10M15AA+crystal+filters+for+communications+equipment&t=h_&ia=web

the energy phenomenon known as resonance: electrical, mechanical, TransverseElectroMagnetic and acoustical. https://duckduckgo.com/?q=tesla+uses+the+principle+of+resonance+to+shake+a+building&t=h_&ia=web

if you're asking about determining the radiation resistance and loss resistance in the antenna system, those parameters are beyond the capabilities of your nanovna.

in a 50 ohm system maximum radiation efficiency occurs when antenna (load) radiation resistance = 50 ohms and total loss resistance in the load = 0 ohms. antenna radiation efficiency % = radiation resistance divided by radiation resistance + total loss resistance. in a 50 ohm system resonance...

Ladder Line to Eternity http://heartandhoof.com/radio/SWR_Meters_Make_You_Stupid.pdf

check out page 113 with regard to the current distribution in both 1/2 wl. & full wl. (dipole) antennas, figures 3.2-8(a), 3.2-8(b) and page 114; 3.2-9 & 3.2-10...

the vna is also providing information about resonance. the 24.4 nH figure is indicating that the antenna is inductively reactive yet close to resonance but a bit too long @ 27.200 mhz.. resonance is somewhere just below that frequency. 24.4 nH = .0244 uH. in the case of a loaded antenna this...

5 kW. will do that.

the input impedance at the bottom of an end fed 1/2 wl. antenna is high impedance. (max voltage, zero current) the impedance present at the opposite end of an end fed 1/4 wl. antenna is also a high impedance. (max voltage, zero current) i'm looking over the information in the link you posted above.

have you ever measured the input impedance of a center fed full wl. dipole?