Topband: Inverted-L with coil on the top of the vertical section

[Adrian Fabry]

Thank you Rick. 
I can see an increase in the horizontal radiation but it seems there is
still enough vertical radiation.

Without load
https://cloud.orange.ro/share/93be10d491e0c6b632fe49b9804e78e3?d=&c=&r=#1

With 75uH load
https://cloud.orange.ro/share/e035179a07e18f4832fe49b9804e78e3?d=&c=&r=#1

(Vertical=red, horizontal=blue)

I don't know what other TX antenna will be suitable for my condx:
House top @29 ft, a pillar @19ft and a pole @8ft, see bellow.
https://cloud.orange.ro/share/36474948adb7a57132fe49b9804e78e3?d=&c=&r=#1

 I don't expect much, I just hope this INV-L will perform better than my FD3
(OCF dipole 20m long Z=1-j2600 on 160m)

TNX & 73 Ady YO2NAA

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Richard
Karlquist
Sent: Wednesday, February 11, 2015 1:38 AM
To: topband at contesting.com
Subject: Re: Topband: Inverted-L with coil on the top of the vertical
section

On 2015-02-10 14:09, Adrian Fabry wrote:

> The simulation (with MMANA software) indicate 3.5 +j0 Ohm impedance. 
> This is
> very low so I think most of the power will be lost in the ground.
> 
> In order to raise the impedance, I would insert a coil (about 75 uH) on 
> the
> top of the vertical section and restore the resonance with 48.7 pF 
> series
> capacitor on the feed point.
> 
> This will raise the impedance to 34 ohm.
> 

You have to be careful with loading inverted L antennas.  What is 
happening
here is that the horizontal top wire is now doing most of the radiating.
You basically have a very low dipole.  There will be a lot of ground 
loss
due to the height.  I think you would be disappointed if you built this.

Rick N6RK
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