Topband: Impedance of inv l?

Jamie WW3S ww3s at
Sun Nov 18 11:48:14 EST 2018

well, I THOUGHT I had a good ground.....16 radials I think, 1/4 I thought I'd see around 30-35 ohms impedance.....not sure what to think now.....I was going to get either a balun and unun at the feed point, was going be someone else's statement that there inv l was around 22 ohms, glad I measured mine before I ordered one.... 

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

From: "F Z_Bruce" <k1fz at> 
To: ww3s at, "Topband" <topband at> 
Sent: Sunday, November 18, 2018 10:55:47 AM 
Subject: Re: Topband: Impedance of inv l? 

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. 


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.... 

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