Johan,
A graph showing the gain and optimum number of elements for various Yagi
designs on boomlengths up to 1 Wavelength (typical for HF) is all shown in
my latest article, "Yagi/Uda Antennna Design, Part1: A Different Approach"
in the Winter edition of Communications Quarterly, page 49, figure 1. I
also published a similar graph in an earlier article on VHF/UHF Yagis ,
those greater than 1 wavelength, in "VHF/UHF World, Yagi facts and
fallacies", Ham Radio Magazine, May 1986, page 103.
73,
Joe, W1JR
>Its commonly know that gain versus boomlength is fixed
>You ought to read DL6WU and DJ9BV's paper on this.
>
>each doubling of boomlength gives you just over 2 db extra gain.
>
>It has been proved in europe with different experiments.. expecially on VHF
>UHF antennas where is is easier
>to perform such tests..
>
>I still laugh at the claims from certain manufactures..
>
>12 dbd free space gain for a 2 wave length antenne is a good design.
>10 dbd free space gain for a 1 wave length antenna is a good design
>8 dbd for a half wave
>6 dbd for a 1/4 wave (5m boom on 20m) is an excellent design
>
>so real 5.5 to 5.7DBD for a 20ft boom on 20m would be achievable
>
>All the rest is pure imagination of manufacturers..
>
>
>Johan
>ON4ANT
>
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