[600MRG] Ground Conductivity -

[Frank Lotito]

I guess the following point can be made:  None of us are going to change the propagation between points "A" and "B".  However, regardless of how bad the immediate ground conductivity, we can minimize the local ground losses "at the antenna sites" by the extent of our radial system (assuming vertical antennas on both ends of the communications path.)    
..............
Correction to my original message - I used the term milliohms, it should have been millimhos.

73 Frank K3DZ / W2XHA

________________________________________
From: 600MRG <600mrg-bounces at w7ekb.com> on behalf of Brian Pease <bpease2 at myfairpoint.net>
Sent: Sunday, February 7, 2016 8:49 PM
To: 600mrg at w7ekb.com
Subject: Re: [600MRG] Ground Conductivity -

For a fair comparison, both the radials and the sea water would need to
extend all the way to the receiving station.  Normal radials just reduce
ground losses close to the antenna where the fields are strong, and
provide a low impedance reference for insulated verticals.  This
improves efficiency, but doesn't change propagation.

On 2/7/2016 8:31 PM, Frank Lotito wrote:
> " ground conductivity in the U.S. ranges between 0.5 and 30 millimhos (or millisiemens) per meter.  The conductivity of seawater is 5,000 millimhos per meter, resulting in the best propagation of AM signals."
> ......
> The above was copied from the FCC's recent publication on ground conductivity (https://www.fcc.gov/media/radio/m3-ground-conductivity-map)
> ................
> Obviously, the "gold standard" for ground conductivity is salt water.  I have a question - If one were to lay out 120 equally spaced radials, each a half wave long from the base of a vertical antenna, what would the estimated ground conductivity be compared to "seawater"?  For a more modest radial system, what does it take to achieve a conductivity of say 500 milliohms, which is almost 20 times better than the best ground conductivity in the US, but still one tenth that of seawater?
> ........
> 73 Frank K3DZ / WH2XHA
>
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