[TowerTalk] Measuring RF ground characteristics

[Artek Manuals]

Jim

That is basically N6LF's and my approach so far as well.

As I said I was hoping for a more direct measurement approach that 
didn't involve an actual antenna.

I basically live on a large (prehistoric) sandbar approximately 65 feet 
above MSL. ( A mountain ridge by Florida standards) A tidal river is 
~1/4 mile away

Dave
NR1DX

On 2/13/2021 3:22 PM, Lux, Jim wrote:
> On 2/13/21 10:57 AM, Richard (Rick) Karlquist wrote:
>> Just a heads up:
>>
>> Gerry Burke, of LLL/NEC fame had some discouraging news
>> about their ground measurements.� He told me that in
>> some cases there was no configuration of NEC parameters that would
>> correlate with some real life ground measurements.
>
>
> Alan Christman's PhD dissertation talks about this too:
> https://etd.ohiolink.edu/apexprod/rws_etd/send_file/send?accession=ohiou1172605318&disposition=inline 
>
>
>
> Burke, G. J., "Recent advances to NEC: Applications and Validation", 
> UCRL-100651, 3 March 1989
>
>
>>
>> The other disclaimer is that NEC only models a uniform ground.
>> I know my ground is far from that.� After 1 to 5 feet of pure
>> clay, I hit "cemented hardpan" waterproof clay.� About 40 feet
>> down I hit sand, according to the well diggers.� No way to
>> model that with NEC. 
>
> This is very much so. What I do is model with NEC and use several 
> different ground properties, varying both sigma and epsilonr, and see 
> how much difference it makes.
>
> I did some analysis for the� OVRO - Long Wavelength Array, which is a 
> field of hundreds of fan dipoles.� They had some buried probes that 
> measured actual RF properties, and data for about half a year (long 
> enough to see rain storms, snowmelt, etc.).� What we were interested 
> in is whether the "ground screen" under the dipoles made a big or 
> little difference.
>
>
>
>
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-- 
Dave Manuals at ArtekManuals.com www.ArtekManuals.com


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