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I've put up a "random" length long wire antenna for HF in my yard at about 124ish feet about 15' off the ground. I got this length from an online resource. Here's my questions:

How does the anchor loop on each of the wire affect the length? Do I need to account for/add 6"ish of extra line to the measurement for each loop?

Because of the size of my property, power lines and tree I chose to run the wire from one end, bend at a 90 and end at the far corner. Basically this looks like an L or 1/2 of a square from above. Does the bend in the line negatively affect or negate the radiation of the signal? Would it be better to run a shorter line diagonal from point A -> C skipping the corner at point B?

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  • $\begingroup$ Hello and welcome to ham.stackexchange.com! $\endgroup$
    – rclocher3
    Commented Jan 6, 2021 at 0:26

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A random long wire is just that, random. While large loops at the end or bending the wire might change the resonant frequency, a random wire isn't (unless by chance) resonant anyway. So loops and bends just make a different random wire antenna which is neither better nor worse.

The shape of the antenna isn't going to affect efficiency directly. Think about conservation of energy: all your transmitter's generated power is either radiated or converted to heat in some form of loss. What kinds of loss are there?

  1. Losses in the resistance of the soil and other things near the antenna
  2. Losses in the tuner and the feedline
  3. Losses in the antenna wire's resistance

Of these three, the first two are by far the most significant. So worry about those things, if you're going to worry about efficiency.

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It's not clear to me from your question, so I'll mention here that best practice is to end your antenna with an insulator and attach the insulator via rope or whatever to your tree or building. And yes, the length of the antenna includes that loop of wire around the insulator.

antenna-insulator-rope [image credit: DX Engineering]

HOWEVER, it's not unusual for a testing setup (or perhaps a lazy setup) to simply loop the antenna wire around a tree or whatever, and you should include that extra length in your calculations as well... it's part of the antenna and will develop RF current and voltages (which is why you should really be using an insulator).

If needed, you can minimize the effective added length by attaching the tip of the wire back to the body of the wire where the loop is formed.

Happy building!

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    $\begingroup$ The effect of N inches of wire used to tie a knot, or looped around a tree, or whatever, is not the same as N inches of wire in a straight line. Were that the case, why bother stretching the wires out? Why not cram the whole antenna in a plastic jar and hoist that to the top of a pole? $\endgroup$
    – Phil Frost - W8II
    Commented Jan 5, 2021 at 23:02
  • $\begingroup$ hi phil! Love to hear your suggestion as to how it should be treated. $\endgroup$
    – webmarc
    Commented Jan 6, 2021 at 3:06
  • $\begingroup$ If the wire is uninsulated, measure to the point most distant from the center. If the wire is insulated and the loop at the end is small (as in your picture), then just ignore it. If the wire is insulated and not small (say, more than 1/10th wavelength), then you have to model the antenna or determine the impedance empirically. $\endgroup$
    – Phil Frost - W8II
    Commented Jan 6, 2021 at 18:23
  • $\begingroup$ I agree! I'm not sure how that's substantively different from my answer though. $\endgroup$
    – webmarc
    Commented Jan 7, 2021 at 17:16
  • $\begingroup$ Antennas are much more about the fields around the wire than they are the wire itself, but it's common for people new to electronics to have all kinds of misconceptions about some vague notion of "electricity" moving in wires, without any consideration of fields. By so plainly stating the length of the wire is what matters (ostensibly when adhering to a guideline like L=468/f) even if the geometry isn't a straight line you play right into these misconceptions, which will ultimately prevent an understanding of capacitors, inductors, or RF engineering. $\endgroup$
    – Phil Frost - W8II
    Commented Jan 7, 2021 at 17:29

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