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Your UnUn probably has a counterpoise lug on it, and if it doesn't you can simply attach a wire using a stainless steel hose clamp the the PL-259 and place it at a right angle to the coax and the feedpoint of the antenna. You can then experiment with the length since it sounds like your UnUn...

Nice! I think a doublet is the way to go for much of HF, that and a tuner is all you need. As far as non-resonant antenna efficiency, the 5/8λ antenna is non-resonant, and because of it's length, and not the fact that it is non-resonant, when operated vertically, it creates a pattern that has...

A couple of comments for the OP; If you are running balanced transmission line, you will need a BalUn at the antenna end, for one reason, you are feeding an unbalanced antenna, but also, I'm guessing your feed point is ground level, and your transmission line is going to enter the antenna system...

I've built all three of these antennas, and found the impedances to be similar to what this article describes: https://0x9900.com/ground-plane-antenna/ If you model a 90 degree ground-plane antenna using the same lengths as a 135 degree ground-plane, with only two counterpoises, you will see...

Keep in mind that radials/counterpoises, mounted 90 degrees to the radiator, gives you an impedance of 37 Ohms, so even at resonance, the lowest possible VSWR is 1.5:1 However, you can raise the impedance by offsetting the feedpoint, make your radiator longer, and your radials shorter, and you...

Interesting idea for a dipole, but then if it were just a dipole, you'd call it a dipole with a hairpin match, as for using a slot style antenna as your hairpin, I don't think that would work, at least not without doubling the length of the RF current path so that the "slot" doesn't radiate, but...

Your feed-point being at or less than a 1/4 wavelength off the ground (for 40M), will lower your antenna's input impedance. The way to raise input impedance in any capacitive antenna, is to increase the angle between the elements, and with an Inverted-V, that may mean making it a horizontal...

The simple answer is because your input impedance on those 3 bands is closer to 2450Ω But you discovered why SWR only tells you what ratio you are reflecting, and not what the actual impedance is; for that, buy a NanoVNA and use the Smith Chart function to determine impedance and resonance. If...

I'd prefer a plastic coated wire, because magnetic wire is just enamel coated copper wire, so as long as you scrape the enamel off your connection point, then fine. But you said you wanted a lot of radials, so even though you can shorten the radials to under a 1/4 wavelength of your lowest band...

@Riverman With 1 radial your radiation pattern is favoring that direction. Also, without choking your feed-point, your coax shield is acting like another radial/counterpoise. Last point, since your angle between your radiator and your counterpoise(s) is less than 135 degrees, your feed-point...

Buy coated aluminum garden wire; it's cheap and won't deteriorate as fast as copper. Here's a link to coated steel wire, but I've purchased it in aluminum from home centers and my local hardware store, in the past...

First of all, a vertical dipole is highly impractical unless you can keep the feedline at a right angle to the radiators for at least 1/2 a wave length. Secondly, the impedance of a dipole that close to the ground on 11M, will likely be less than 50 Ohms. Thirdly, I don't understand how your...

Great, I saw your images. Yes, I noticed that the far-field plots had <1dB difference; I don't think those scenarios are going to be detectable outside of laboratory conditions & instruments. About your graphs though, the modeling software I've used, EZ-NEC & MMANA-GAL, don't consider source...

The OP's write up is informative (even though I can't see his images), but seems to be missing a crucial piece of information that is missed by subsequent commenters. The OP says he "tunes for field strength"; O.K., that would be like making a 1/2λ vertical antenna a little longer, say to 5/8λ...

Now that I did the arithmetic, I see you are correct, 70cm is very close to 3/4λ, so yes, a 1/4λ antenna for 2M antenna will have a 50 Ohm feed-point, and so will the 70cm band since 3/4λ is also fed at a current loop.

First of all, how are you getting a 1/4λ ground-plane antenna to give you the proper input impedance on both 2M & 70cm? Unless you are using a 70cm trap, this is not possible as your input impedance at 70cm, for a g-p antenna, designed for 2M, would probably be over 400 Ohms, not 50 Ohms...

Unless you're going to use band traps, you will immediately run into a problem when you use the antenna on 80M, while on 160M your center-fed dipole is at a current loop, on 80M, each leg is now a 1/2 wavelength, and you are feeding each element at a high impedance point, eg., a voltage loop. So...

I said what the A99 antena really is; so to quote myself: "...to be clear, the Antron 99 is just a half wave antenna, with no less gain than a half wave dipole, and there is no way to get a radiator of one length to impersonate a radiator of another length." ...and I like it too.

I would imagine your transformer is actually an UnUn, if you're feeding an off-center-fed antenna. So you've said you can get to 45 feet in height, but what are your dimensions of the area you can have the antenna occupy?

Yes, a ground plane antenna has a low feed-point impedance because it is fed at a current loop, and that's because the antenna is a 1/4 wave length, or some odd multiple of 1/4 wave length. A J-pole is an end-fed 1/2 wave length antenna, making its input impedance and its radiation resistance...