There are lengths that tune easier, depending on the feed point and feed
line length. A center fed wire tune easiest when near a half wave long.
An end fed wire tunes easiest when about a quarter wave long. A short
center fed wire tunes a little easier when the sum of the feed line
length plus one half the flat top is about a quarter wave, or 3/4 wave.
These "magic" lengths came from the 1930s before internet and many say
the optimum magic length with a modern tuner is the antenna should be
the length that fits between the supports with feed line that reaches
from the middle to the tuner in the shack.
Log the tuner dials when you get it dialed in and expect RF in the TV
and audio equipment in the house and noise from them in the ham receiver.
73, Jerry, K0CQ
On 11/7/2010 3:56 PM, John B. Egger wrote:
> A friend (a Tech+) with an Icom 718 and a manual MFJ tuner will have to
> use an indoor antenna due to restrictions. I'm trying to help her get on
> 40 meter HF. I was going to try simply a wire with a ground
> counterpoise, but I'm not sure what length to use. I think there are
> some principles about best lengths, and those to avoid, but don't
> remember what they are. Any help, or links elsewhere? Googling "amateur
> radio indoor antenna" gave some ideas, but nothing about this question
> of lengths.
>
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