Topband: Optimal radial wire type and gauge?

[Charlie Cunningham]

Well, I suspect that one can't get a complete picture of the correlation
between base driving point impedance and radiated field intensity unless we
could measure at a multiplicity of elevation angles. Has anyone looked into
changes in the elevation pattern as the ground systems are modified? Much
easier said than done!!

Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of DAVID
CUTHBERT
Sent: Sunday, December 16, 2012 8:06 PM
To: Tom W8JI
Cc: topband at contesting.com; Rick Kiessig
Subject: Re: Topband: Optimal radial wire type and gauge?

Tom,
I think you are extrapolating one case with a particular radial length to
all vertical antenna ground systems.

The N6LF radial papers detail his NEC-4 simulations and measurements of
vertical antennas and radial systems. If I read his papers correctly base
impedance does track field strength measurements.

http://www.antennasbyn6lf.com/

Dave WX7G


On Sat, Dec 15, 2012 at 5:10 PM, Tom W8JI <w8ji at w8ji.com> wrote:

> There is no magic about 120 radials, and long before 120 radials are 
> reached the increase in field strength pretty much stops.
>
> At my house around 30 radials or so, about 1/4 wave long, go flat on 
> efficiency increase on 160 meters.
>
> I could have a million radials and it would be insignificantly 
> different than 30 radials when they are 1/4 wave long here.
>
> I found this by measuring field strength, and I also found feed resistance
> change did NOT necessarily track the field strength changes.     Good luck
> on using base impedance to determine effiency changes! In a 40 meter 
> test, for example, one ground system provided 35-40 ohms of feed 
> resistance and another different system that provided almost 60 ohms 
> of feedpoint resistance had equal field strength.
>
> I think N6RK and others have measured the same.
>
> 73 Tom
>
> ----- Original Message ----- From: "DAVID CUTHBERT" < 
> telegrapher9 at gmail.com>
> To: "Rick Kiessig" <kiessig at gmail.com>
> Cc: <topband at contesting.com>
> Sent: Saturday, December 15, 2012 10:49 AM
> Subject: Re: Topband: Optimal radial wire type and gauge?
>
>
>  Read the N6LF radial papers and you will see that 1/8 wavelength 
> radials
>> are about as good as one can do. I use #14 stranded copper THHN wire 
>> because it is easy to work with.
>>
>> But how good can we get? For a 30' base loaded vertical I have 90 
>> radials having an average length of 18 ft. The ground loss is 5 ohms, 
>> which is less than the loading coil loss. If I were to install 120 
>> quarter wavelength radials I would gain 2 dB.
>>
>>
>>     Dave WX7G
>> ______________________________**_________________
>> Topband reflector - topband at contesting.com
>>
>>
>
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