Antenna Design: 20 meter 4-element Colinear

After looking at articles in the ARRL Antenna Book and on L.B. Cebick’s web site, I thought a 4-element colinear wire antenna might be useful for my station. I currently use only wire antennas which work fine on 40 and 80 meters, but on the higher Bands, I need some gain. My main goal is to be able to improve my ability to reach Stations in the Northwestern US and Canada. Since this is a bi-directional antenna, it will also help with my DX contacts.

This is a classic antenna design that has been used by many people. I am not claiming to be doing anything unique here. I am just keeping some notes to track my attempts to make this antenna work at my QTH. There is an excellent description of HF Colinear antennas in the ARRL Antenna Book.

Here is the basic design of the antenna

The picture of the antenna above is a little hard to see. It consists of 4 half-wave elements in a line, with two quarter-wave stubs between the pairs of elements. Each stub is a piece of ladder line, with the end shorted. This provides the necessary phase shifting to align the half-wave sections to provide gain. The antenna is fed at the center and the feedpoint impedence is near 450 ohms.

In case anyone is interested in experimenting with the EZNEC model, here is the listing of the wires for this antenna.

Note – this is just one trial set of element lengths. It may not be ideal for any particular location, and may not even be the actual dimensions I use in the final antenna. But if you have EZNEC, you can take it from here and see what works for you.