End Fed antenna

  • endfed antenna
    endfed antenna

This end fed type of antenna was marketted in the UK and is a useful system for the portable set-up.

Being a half wave, no radials or counterpose wires are needed.

 

As the impedance will be high at the end of the wire, some form of matching unit is needed and a simple parallel tuned circuit housed in a plastic film container is fine (figure 1).

 

A hole in the container allows for tuning, by adjusting the ferrite core in the coil for maximum reading on a field strength meter nearby.

 

The inner of the coax goes to a tap about 1/4 of the way from the earthy end of the winding, to which the braid of the coax is soldered.

 

As a rough guide, a capacitor of 50pf across a winding of say 30 turns is a starting point for 40m. Some experimenting with turns and tapping point is necessary.

The coil former used was about 1/4 inches in diameter as found in old IF transformers.

The antenna wire (1/2 wave long) is soldered to the top of the coil as shown in figure 2.

The drawings illustrate the set up, I hope.

For portable use, throw the wire into a tree or whatever, using thin cord or rope onto the insulator (figure 1), tune for best filed strength reading and off you go!

 

Try it - it works!

 

Want to work two bands? Use a slightly bigger container with two tuned circuits which have some sort of terminal each, to which one of their respective wires can be connected.

Rough lengths of half wave wires:

80m - 132 feet, 40m - 66 feet, 20m - 33 feet.

Source: g3ycc