Dipole length

[K8BBL]

I ask this as pure theory. Assume my required length for each leg of my dipole is 35 ft. If I cut a piece of wire exactly 35 ft and use 6 inches to tie it to the insulator and another 6 inches to make a strain relief at the balun end will it still have the effect of a 35 ft wire or is it now going to function as a wire of xxx ft?
I know about leaving a bit extra for trimming, I'm asking pure theory because I'm wondering how that portion of the wire that is tied in a knot or looped around an eye bolt, or doubled back on itself handles the signal.

 

[prcguy]

Doubling back the wire on itself to go around insulators, etc, cancels some of the length. Its not an exact 1:1 ratio but the overall length with wire doubled back will be similar to a single wire of the same overall length.

 

[jwt873]

The formula for calculating a dipole is theoretical.. In the real world there are other factors such as height above ground and the proximity to other conductors. (Power lines, house wiring, metal chimneys etc).

Best bet for cutting dipoles is to add a few feet to the overall length.. So if the formula says 35 feet, start with 40 feet of wire. Then cut back until you find resonance. This is better than finding out you're too short and having to add wire.

I've found that folding back six inches or so of wire doesn't make that much difference to the overall SWR.

 

[johnxb351]

Hi All . I want to build a uhf 477mhz ground plane antenna. would a full wave length work?.

 

[prcguy]

No, make it a half wavelength total or quarter wavelength each element.

Hi All . I want to build a uhf 477mhz ground plane antenna. would a full wave length work?.