I need help understanding these different types of verticals.

What is the feedpoint Z of each of these?
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Feedpoint impedance is expressed in terms of R + jX. Both numbers are
functions of frequency or wavelength. For a simple wire vertical less than
3/8 waves, with sufficient ballpark accuracy -

R = Square( 24 * Height / Wavelength ) ohms,

X = - 550 / Tangent( Angle ) ohms, where -

Angle = 360 * Height / Wavelength ) degrees.

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I can't understand how a 5/8 can even work. It seems like it has to be
multiples of 1/4 wave for any antenna to work.
Why not a 7/8 wave antenna?
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Indeed, why not?

Any antenna WORKS quite satisfactorily REGARDLESS of how long it is. After
all it is only a length of wire. Why should it work better merely because
it is some special fraction of a wavelength?

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Why does a 5/8 wave antenna need a loading coil and a 1/4 wave antenna
doesn't?
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A 5/8ths antenna doesn't need a loading coil. It will work just as it is.
But a loading coil is useful to tune-out the reactance of the input
impedance and so provide a better match to a transmission line.

To assist in EXACT matching of a 1/4-wavelength antenna to a 50-ohm line a
loading coil plus capacitor is needed. But you can nearly always do without
either. With a 36-ohm line, if you can find one, there's a near-enough
perfect match. But then you have to match to 50-ohms at the transmitter end
so you get nowhere.

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Is there such a thing as a 1/2 wave whip ant. fed at the bottom?
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Yes. There is. Why not? It's quite a normal thing to do. The matching and
especially ground losses are exceptionally small.

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Are there other sizes of whip antennas?

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Yes, any size you like. As long as you can find room in your back yard. They
will ALL work quite efficiently. Unless, of course, they are extremely short
in terms of the free-space wavelength. Say less than 1/100th wavelengths.

Very short antennas result in losses in the matching or tuning arrangements
needed to match to the usual 50-ohm transmitter. Antennas are themselves
inherently very high efficiency devices.

For values of R + jX, and other information such as loading components,
download free programs from the following website. For clues, look under
each program name in the list for a brief one-line description of a
program's purpose.

Values of R + jX are usually of secondary importance. They are educational
in that they provide information about antenna behaviour. They are practical
only if it is the intention to design impedance matching networks or to
check the operating range of commercial tuners.

You could try program ENDFEED first. Just put the horizontal length of an
Inverted-L equal to zero and you are left with a vertical. But there are
several other programs dealing with verticals directly and which values of R
+ jX appear in the output data alongside values of L and C of the tuning
network.

Apart from the necessary nuts and bolts, you could dispense with half of the
ARRL Handbooks! All for free! ;o)

As for radiation patterns of verticals, from zero up to a height of about
0.6 wavelengths, for amateur practical purposes they are all the same.
Omni-directional. And in the vertical plane a couple of very broad adjacent
hemispheres with a vertical null.
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Reg, G4FGQ
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Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
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