Complex resistance of an end fed wire

[Thadde]

Hallo
I am interested to calculate the complex resistance of an end fed wire (impedance). The following is known:

-Length of wire

-Diameter of wire (mm)

-High above ground

-Working frequency

I know a calculation is very theoretical!! But I am interested in the formulas.
Is there anybody, who can answer my question?
Thanks in advance and best 73 de Thadde HB9DNB

 

[Wire Weasel]

One thing to consider is that Antenna Math is one thing, and Antenna Reality is another. You can do the math for a wire antenna.....but when you build and install the thing the actual results are different than what the math stated it would be.

Antenna Math is all theoretical performance based on laboratory conditions. Field performance contains innumerable variances.

Why do you want to know?

It may be easiest to build and install your wire based on known calculations, and then test actual performances with a meter. The MJF 259B and 269 Antenna Analyzers, and others, include impedance measurements, so the meter will directly tell you how your on-the-ground antenna is performing including Resonant Frequencies, impedance, SWR etc...


good luck

 

[W5LZ]

Thadde,
By accepted definition, a long wire antenna is one that is more than at least two wave lengths long at the design frequency. From that point everything is subject to availability.
To find the complex impedance of such an antenna (R +/- J), the easiest method is by measuring it with an instrument capable of telling you what those 'R' and 'J' are.
But that isn't what you asked, is it? So, how do you calculate those 'R' and 'J's? I'm sure that there are formulas that can do that. Unfortunately I can't tell you where to find them. Determining such formulas is done by taking measurements of existing antennas, tabulating the results, and then finding the equivalencies which would produce the same results (or nearly the same results).
That's would be a really huge amount of effort. And if someone else has already gone to that effort it makes sense to use their work instead of reproducing it! The best idea I can think of is to search the knowledge base of those who deal with this sort of thing, probably the 'IEEE', or less likely, the information published by the ARRL.
I wish I could help you, but I can't. Good luck!
- 'Doc

 

[Marconi]

Hallo
I am interested to calculate the complex resistance of an end fed wire (impedance). The following is known:

-Length of wire

-Diameter of wire (mm)

-High above ground

-Working frequency

I know a calculation is very theoretical!! But I am interested in the formulas.
Is there anybody, who can answer my question?
Thanks in advance and best 73 de Thadde HB9DNB

Thadde, I think you have seen some pretty good suggestions here so far, but I might add that such calculations have been around for many years, maybe even as far back as Maxwell and Ohm. It has been just recently that NEC took such algorithms and applied them to computers. Now we have fairly cheap devices that can get you close to seeing such with the hand held field devices as noted.

IMO, if you use one of these field type devices, you might find it very beneficial to use it right at the feed point for best results, but I'm not sure about the possible range and conditions you will experience with the starting match, so even that could be iffy if not in the range the device can measure and report accurately.