[TowerTalk] vertical antenna feedpoint

[Mpridesti]

I would think having a DC ground (short element and inductor) is better for lightening and lower noise?

Regards,

Mark, K1RX


> On Mar 16, 2025, at 9:55 PM, john at kk9a.com wrote:
> 
> I have been doing the opposite for decades.  I shorten the vertical slightly
> and use a hairpin coil to create a 50 ohm feedpoint.  Is one method better
> than the other?
> 
> John KK9A
> 
> 
> Jim Brown K9YC wrote:
> 
> <snip>
> 
> Once you've got a decent radial system, modeling software like NEC can 
> be used to design a simple way to match it to 50 or 75 ohm coax. The 
> concept is to increase the length of the antenna to move its resonance 
> down in frequency far enough that the resistive component of the 
> feedpoint impedance is 50 ohms, which makes it look inductive, which can 
> then be tuned out with a suitable capacitor. "Suitable" is this case 
> means of a type that has very low equivalent series resistance and a 
> sufficiently high voltage rating for the power you want to run. I simply 
> added enough length to the horizontal top of my 160M Tee to resonate it 
> down in the top portion of the AM broadcast band. I think I ended up 
> with capacitance in the range of 800-900 pF.
> 
> 73, Jim K9YC
> 
> 
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