20m / 40m Trap Dipole Antenna
Welcome reader,
This article will give the the basic knowledge of how to construct a trap dipole for the 20m and 40m bands.
This design allows you to use two separate bands out of one dipole.
You will need to make some sort of 20m trap before you begin constructing the dipole.
*Here is the diagram with the measurements *
Any standard wire will do for the dipole. - I used copper flex-weave.
It is suggested that you use a 'dog bone' to support the traps.
If done correctly you should have a 1.5 : 1 SWR or below on 40m and 20m
If your SWR is too high, use this formule:
( (Freq of the lowest SWR for that band / Freq of wanted SWR) x section wire length) - section wire length
If you get a negative number then you need to shorten the antenna by that amount. If you get a positive number you need to increase your antenna length by that amount.
Top tip!
Try to not fold the dipole wire back on its self too much as it will affect the SWR. The wire does need to be cut almost to the exact length but it is acceptable to leave a bit folded to cable tie it into place.