K4SB wrote:
> Michael Tope wrote:
>
>>Steve,
>
> snipped....
>
>>to do for a fixed element length yagi. It could very well be that
>>a SteppIR can eek out an extra .5dB of forward gain when
>>you get rid of the bandwidth constraints.
>>73 de Mike, W4EF................................
>
>
> I would tend to agree more with Steve and Dave on this matter. There
> is simply no way in the world ( short of an advanced antenna range )
> to determine how an individual element in the SteppIR might be changed
> to get additional gain.
>
> As an example, the element length and spacing on my 5 element
> monobander on 20 * and its twin on 15 ) is so critical I had to use
> millimetres for the tips and element spacing. As it stands right now,
> the antenna models at 50 +/- j0, and shows 15.93 dbi of gain with 55.6
> db F/B. All this modelling was done with EZNEC. (DOS and Windows
> versions) I can vary the spacing of the 3rd director ( or length ) and
> that pattern goes to hell in a hand basket.
>
> Admittedly, 55.6 db F/B is excessive, but I have always gone with the
> theory that you
> shoot the "juice" in the desired direction at all costs.
Even at only 20 db front to back ratio, if all the energy from the rear
was redirected to the front instead, it would amount to less than .1 db
additional forward gain.
With only 10 db front to back that difference is less than .5 db of
forward gain difference if it all were redirected to the front.
Front to back ratio has almost no significance to forward gain after 10
or 15 db or so.
73
Gary K4FMX
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