Various visual mental simplifications of what is going on in inverted L's do
not map well with what a model will show if you vary one length, record the
results, vary it again, record, etc to create a mapping of what happens to
feed R, current max height, low angle field strength, etc, as a single
detail is varied.
To all those who are speculating, the answer is to model the situations.
Much of what occurs is not the least bit intuitive, some counter-intuitive.
Item (1) below is FALSE as a GENERAL statement because many up and out
combinations of 3/8 wave ALREADY have the current max somewhere in the
vertical, some in the BEST place. Further, the BEST spot for the current
max for say 15 degrees takeoff moves around, depending. It takes the math
of the model program to put that together.
These cases are easily apparent if a variety of 3/8 wave L situations are
modeled.
73, Guy.
On Sat, Sep 25, 2010 at 4:19 PM, Rik van Riel <riel@surriel.com> wrote:
> On 09/24/2010 07:15 AM, Edward Swynar wrote:
>
> > So allow me to run this by the group for comments& criiques, i.e., what
> if
> > I was to shorten each "L" from the existing 3/8-wave length, to something
> > approaching, say, "...one-quater-wave-plus-ten-feet"...? And what if I
> left
> > the tuning capacitor at the base of each "L"...?
> >
> > I believe that by doing so I'd accomplish two things:
> >
> > (1) The current node of each "L" would be more concentrated in the
> vertical
> > portion of the wire away from the horizontal, thus aiding& abetting the
> > pursuit of DX, and,
> >
> > (2) I could still benefit from resonating each "L" with base-mounted
> > variable capacitors (albeit with much SMALLER "C").
>
> Your idea makes perfect sense.
>
> One thing to keep in mind is that having the point of maximum
> current lower on the antenna could result in higher ground losses.
>
> This makes it a tradeoff between maximizing low takeoff angle
> radiation from the vertical partof the radiator and minimizing
> ground losses.
>
> --
> All rights reversed.
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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