For design of short coil-loaded centre-fed dipoles begin with a short loaded
1/4-wave vertical and, in-effect, connect a pair of them back to back.

Download programs VERTLOAD or LOADCOIL or ADDALOAD. For even shorter loaded
dipoles download MIDLOAD. All these programs will tell you how may turns are
needed on a former of given length and diameter at whatever position along
the wire you chose to locate it.

In most cases the length of the coil is taken into account in the overall
length.

When using the design of short-verticals to design short-dipoles the ground
loss estimates can be assumed zero.

Some of these programs include assistance with bottom-end tuner design
which, of course, is of no use when a pair is connected back to back. It
should be remembered the feedpoint resistance of a short resonant dipole
will be considerably less than the desirable 50 ohms and a poor match to a
coax feedline will exist. But the mismatch may not be excessive.

The main disadvantage is single-band working whereas an unloaded short
dipole can usually be effective on several bands by using a 450-ohm or
600-ohm feedline and a good tuner. But you will need a tuner with whatever
length of dipole, loaded or unloaded, you end up with.

As for myself, when using short antennas, I prefer not to use heavy-weight
loading coils in antenna wires but concentrate on keeping home-brew tuner
losses to a minimum.

Programs can be downloaded in a few seconds and run immediately.

As were Bolton & Watt's condensing steam engines - Made in Birmingham.
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Regards from Reg, G4FGQ
For Free Radio Design Software
go to http://www.g4fgq.com
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