[TowerTalk] Vertical and radials

[Steve Jones]

Bob,
The map legend says those numbers are in "millimhos per meter".  I couldn't
see one greater than 30 in the US.  It says seawater is assumed to be 5,000
millimhos per meter, quite a difference!
73,
Steve
N6SJ


-----Original Message-----
From: TowerTalk <towertalk-bounces at contesting.com> On Behalf Of Robert
Harmon
Sent: Saturday, January 22, 2022 9:22 AM
To: towertalk <towertalk at contesting.com>
Subject: Re: [TowerTalk] Vertical and radials

I love your perfect QTH description.   A hill of salt water, sloping gently
in all directions.   hihihi

I am having trouble finding ground conductivity fro my area in the north San
Francisco Bay Area.  Napa county.
Looks like my area shows a number 8.  Where is he chart to find out what
this means in conductivity ?
Wish I could find a map that I could drill down closer to my QTH.  I know it
is pretty good right now, we have had lots of rain the last few weeks.

Bob
K6UJ



> On Jan 22, 2022, at 3:58 AM, John Langdon <jlangdon1 at austin.rr.com> wrote:
> 
> The other thing that K5IU was clear about is that the ground under the 
> antenna is the dominant factor in performance regardless of the 
> radials you use.
> 
> 
> 
> If you have really low conductivity soil under the antenna, even if 
> you mount a vertical on a 1/4 wavelength radius copper disc, 
> essentially an infinite number of buried radials, you are going to get
poor performance.
> Elevated radials will be as good or better in that situation, and are 
> less work, but a high dipole, over poor soil, will be equal or better.
> 
> 
> 
> If you have really high conductivity soil, a modest number of buried 
> radials or a set of 4 1/8 wavelength elevated radials tuned with an 
> inductor will probably give you good performance.
> 
> 
> 
> If you are over salt water, a single resonant radial will work very well.
> 
> 
> 
> BTW the ground conductivity maps most of us have access to, like 
> https://commons.wikimedia.org/wiki/File:United_States_Effective_Ground
> _Condu ctivity_Map.png , are from data averaged over a large area  and 
> any given location within an area on the map may vary widely from the 
> average. The perfect QTH is a hill of salt water, sloping gently in 
> all directions.
> 
> 
> 
> 73 John N5CQ
> 
> 
> 
> 
> 
> 
> 
> 
> 
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> 
> 
> 
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