Topband: Impedance of inv l?

[donovanf at starpower.net]

Hi Jamie, 


I forgot to mention that nearby conductive objects, especially nearby 
towers can significantly affect the base impedance of a vertical. 


Nearby on 160 meters is about 200 feet... 


73 
Frank 
W3LPL 

----- Original Message -----

From: donovanf at starpower.net 
To: "Topband" <topband at contesting.com> 
Sent: Monday, November 19, 2018 1:31:27 AM 
Subject: Re: Topband: Impedance of inv l? 


Hi Jamie, 


I use my AA-54 frequently in exactly the manner you're using your 
AA-23, I've never had any reason to be suspicious of any of its 
readings. I'm lucky to have no AM broadcast stations within ten 
miles. 


Your AA-230 is telling you that at least half of your power is being 
lost to ground resistance and need to at least double the number of 
radials to significantly reduce your resistive losses. 


The 2000 feet of wire in your radial system likely would have produced 
much better results with twice as many radials of half the radial length 
you used. Quarter wavelength radials aren't cost effective until many 
more than 60 radials are used. 


www.w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html 


73 
Frank 
W3LPL 




----- Original Message ----- 

From: "Jamie WW3S" <ww3s at zoominternet.net> 
To: "Topband" <topband at contesting.com> 
Sent: Sunday, November 18, 2018 10:33:13 PM 
Subject: Re: Topband: Impedance of inv l? 

several have asked how I am measuring the impedance.....I'm using an AA-230, 
and am all the ALL PARAMS setting.....the 230 defaults to a series model, is 
that what I want, don’t see how to change it to parallel. I think the symbol 
for impedance is |Z|, correct? 

-----Original Message----- 
From: F Z_Bruce 
Sent: Sunday, November 18, 2018 3:20 PM 
To: wes_n7ws at triconet.org ; Topband 
Subject: Re: Topband: Impedance of inv l? 


The far end is high impedance voltage, and has minimum  horizontal 
current radiation.  The inverted L is a good trade off signal vs 
available height.  Not an expensive antenna to build.  

73 
Bruce-k1fz  
  
On Sun, 18 Nov 2018 12:31:38 -0700, Wes Stewart wrote: 

That also drives up the current in the horizontal wire with attendant 
increased 
horizontal radiation. 

I chose for a couple of reason to do the opposite; shorten the wire to make 
the 
feedpoint capacitive and use a shunt inductor to get a 50-ohm match.  
This 
really doesn't improve the 2:1 VSWR, that I consider acceptable, however. 

Wes  N7WS 

On 11/18/2018 8:55 AM, F Z_Bruce wrote: 
> That sounds about right. As you put a good ground system under it, that 
value will come down, and the efficiency will come up. 
> 
> Many add extra antenna wire that pushes the current up the wire, this 
also raises  the impedance, hopefully to near 50 ohms with the right 
length. 
> A capacitor (variable, then fixed) in series at the feed point can 
cancel the added inductance. 
> 
> 73 
> Bruce-k1fz 
> https://www.qsl.net/k1fz/beverage_antenna.html 
> 
>   
> On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: 
> 
> What should the Z be for a 1/4 wave inv l, with the radials attached to 
a radial plate? Mine seems to be 60 ohms or so.... 
> 
> Sent from my iPad 
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