[TowerTalk] Vertical question

[Ignacy Misztal]

My feeling is that modeling with verticals is less than perfect or perhaps
the interpretation of results from modeling is imperfect.

In 160m contests we hear signals that are poor, OK and spectacular. In
cases I know, those OK have 30 radials and those spectacular have 100
radials. While the maximum angle radiation may be affected by < 1 db,
perhaps low angle radiation may be affected by 10db or more.

I had an inverted L with up 80 feet with 4 elevated and tuned radials. Then
a shunt fed a 100ft tower with 16 upgraded later to 36 radials.  Modeling
indicated little difference. When tested by RBN, the tower was 6 db better
with 16 radials and 8 db better with 36. Well worth the effort.

I used to have an inv L with a few 70 ft elevated radials used for both
160m and 80m. The performance was OK on 160m and pathetic on 80m. There are
papers showing that 4 1/8 wave radials on the ground are better than 4 1/4
wave radials.  Perhaps this applies to low elevated radials. Verticals with
short radials need a transformer, not a  balun.

Ignacy NO9E

On Mon, Mar 15, 2021 at 11:58 AM Patrick Greenlee <patrick_g at windstream.net>
wrote:

> What comes to mind is how true to reality is the model's results?  If
> the model is relatively true to reality then most of us would likely not
> bother with additional radials.
>
> You said, "It is working great."  Is that a reasonable motivation to add
> 4 more radials to maybe get 0.01 more dBi?  The term diminishing returns
> comes to mind.
>
> I would suggest leaving it alone and enjoy using it.
>
> Have fun.
> Patrick       NJ5G
> .
>
> ------ Original Message ------
> From: "Dave Sublette" <k4to.dave at gmail.com>
> To: "kj6y--- via TowerTalk" <towertalk at contesting.com>
> Sent: 3/15/2021 10:26:00 AM
> Subject: [TowerTalk] Vertical question
>
> >Good morning,
> >
> >I recently changed my elevated 160 meter quarter wave vertical with 8 full
> >sized radials to having only 1/8th wave length radials and only four of
> >them.  It is working great.  So I thought adding four more radials might
> >improve things.
> >
> >But before I went to all the trouble I decided to model it and see if
> there
> >was a difference in performance of the 8 radial version compared to the 4
> >radial system.
> >
> >I use a modelling program called Antenna Model.  The result of the
> >comparison is this:
> >
> >The 4 radial system showed a gain of 0.92 dBi with the main lobe at an
> >elevation of 20 degrees.
> >
> >The 8 radial system showed a gain of 0.93 dBi and an identical elevation
> >pattern.
> >
> >My question is:  Why is the gain figure so low?  A dipole exhibits 2.14
> dBi
> >gain. Why doesn't the vertical show gain?
> >
> >And lastly, I think these results tell me it isn't worth the effort to add
> >four more radials.
> >
> >Your thoughts?
> >
> >Thanks & 73,
> >
> >Dave, K4TO
> >_______________________________________________
> >
> >
> >
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