Traps will not shorten your antenna appreciably. To shorten an antenna,
you use loading coils, which are just wires turned into a coil. Traps
consist of a coil and a capacitor in parallel with each other that stop
signal flow through them at a specific frequency.

So, if I understand what you want, is that you want the total antenna
length to be shorter than a normal half-wave dipole on 80M. The best
place to find the info you seek is in the ARRL Antenna Handbook. They
should be available at http://www.arrl.org/

You will first need to determine what length you want the antenna for
80M to be. Then, you will want to look in the chart in the book. You
will want to place the coils as far out from the center of the antenna
as practical. The further out the loading coils are from center, the
larger amount of inductance they need to be to a point where it is
impractical to build them. Usually putting them at the 50% point is
fairly easy but, if you are going to have a 40M trap in the antenna,
these would be right about where the loading coils would go, so, just
move the loading coils outward from center, just a few feet past the 40M
traps. You will most likely have to adjust the wire lengths from the
loading coils out to the ends of the antenna to find resonance.

Scott
N0EDV



Vinnie S. wrote:

I want to construct a 80-40-20 meter dipole, but want to trap the 80 meters to
shorten the length. Does anyone know where I can get good quality traps? I am a
beginner as far as antenna theory.

Vinnie S.