[TenTec] OT: Ground Radials at Tower Base

[Derwin Goliver]

Well now....
As far as radials go. I like to mount my verticals off the ground.
Becouse just a few 1/8 wave off the ground. Is better than many in the 
ground.
If I am not missaken. Some thing like 2 1/8 wave off the ground = something 
like100 in the ground.
I have a 5/8 wave 20 meter vertical with 3 off the ground (gound plane 
style) . Thas I made this antenna is smoken' .
I mounted it on the garage roof in  a tri pod. With 3 14 foot radials and a 
matching coil at the base.
Thing is this needs guys. Becouse of its 41 1/2 foot heighth .

Derwin


----- Original Message ----- 
From: "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>
To: <tentec at contesting.com>
Sent: Friday, August 15, 2008 10:40 PM
Subject: Re: [TenTec] OT: Ground Radials at Tower Base


> On Fri, 2008-08-15 at 19:46 -0400, Gary Hoffman wrote:
>> If you improve your grounding system, you will always be happy that you 
>> did.
>>
>> To say it will or will not reduce noise requires knowing a lot more about
>> the specific details of your setup.
>
> The grounding system for a vertical antenna is often deficient. That's
> easily seen when the antenna SWR is low, but there's no matching
> network. The perfectly grounded vertical should have a feed point about
> 35 ohms. If the number of radials and ground rods is small, they can
> contribute resistance to the feed point impedance raising it towards 50
> ohms for a better apparent match. But with the radiation resistance 35
> ohms and the ground resistance contributing half that much, the antenna
> efficiency is 2/3 what it ought to be for both radiation and reception.
> So improving the vertical antenna grounding (more radials, 50 is a
> start, 256 is considered enough in broadcast circles, and more rods)
> hurts the match but improves the antenna efficiency. That may actually
> increase the noise heard, but it will increase DX signals by the same
> amount so ought to be a wash. Unless a radial happens to contact a
> ground from a noisy power pole.
>>
>> If there are grounding issues (and maybe there are not) and you fix them, 
>> it
>> can certainly help.
>>
> The good noise reception on a vertical is why some 80 and 160 meter
> DXers use a loop or Beverage for reception (directivity, not efficiency
> is the goal) and the vertical only for transmission. Its hard to beat a
> vertical for low angle (and thus best DX) radiation and reception, but
> the propensity of a vertical to hear in all directions makes it hard
> without going to an array of verticals to hear the weakest of signals
> over the noise. Even atmospheric noise can be directional, so a
> directional receiving antenna can be a benefit.
>
> 73, Jerry, K0CQ
>
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