[600MRG] [DETECTED AS SPAM] Re: [DETECTED AS SPAM] Re: Rain amplitude modulation

[Merv Schweigert]

I live where the salt in the ground is very high.  the soil is sandy and 
volcanic,  the sand
blows in from sand dunes on the shore about 2 miles distance to the east 
of me.
I have 120 - 350 ft radials, and 120- 60 ft radials, a former AM 
broadcast location,  I see
almost no change in 6 inchs of rain or bone dry summer.
Thats why my question.   I can understand if one had only a few short 
radials in place
that the change would be large,  but with a large ground screen it would 
seem there would
not be the same change.

The set up that was here was a two tower array on 830KHZ,  phased to 
null CA.  there was
no change that had to be adjusted for between rainy season and summer,  
station was here
since 1981 until I tore it down about 8 years ago.
I am a little over a mile from the ocean,  elevation 600 ft.  it can 
rain 6 inchs and in 15 mins
you can drive on the ground,  so porous as it comes.

Interesting to hear of so many having problems with R changes. Wonder if 
others with a good
ground system see such change??  Eric NO3M or Frank W3LPL ??

Thanks  73 Merv  K9FD/KH6

>
> Hi Merv, et al:
>
>     I worked in broadcasting for (eesh...I hate to even think how 
> long...HI).... up here in the world's worst ground conditions.   The 
> change in conductivity between summer and winter was tremendous....a 
> full time job just keeping a two-tower array in line.   In general, 
> it's the amount of salt in the ground (not necessarily sodium 
> chloride) that determines just how much the conductivity changes.  
> When it's dry, the conductivity is zilch; when it's wet the salt goes 
> into solution and becomes electrolytic.   If there aren't many salts 
> in the ground, then the conductivity stays lousy all year. :)
>
>
> ---
> Eric P. Nichols, KL7AJ
> AlasKit Educational and Scientific Resources
> 3763 Lyle Avenue
> North Pole, AK 99705
> (907) 488-0483
> (907) 371-7120
> http://alaskit.co
>
>
>
> On Fri, 16 Mar 2018 07:16:28 -1000, Merv Schweigert via 600MRG 
> <600mrg at mailman.qth.net> wrote:
>
>     Any reflection perhaps on the quality of the ground system in use
>     for so much
>     change in R at the antenna with ground moisture?
>
>     Merv K9FD
>>     Tnx Ben. That was quite revealing. I did not know it could have
>>     that much of an effect.
>>     Neil, w0yse
>>     Sent from Neil's iPad....
>>     ------------------------------------------------------------------------
>>     *From:* 600mrg-bounces at mailman.qth.net
>>     <600mrg-bounces at mailman.qth.net> on behalf of Ben Gelb
>>     <ben at gelbnet.com>
>>     *Sent:* Friday, March 16, 2018 7:58:33 AM
>>     *To:* Posting 600m 600mrg
>>     *Subject:* [600MRG] Rain amplitude modulation
>>     We've been getting some rain in the SF Bay Area finally, which
>>     has presented a fun opportunity to observe fluctuations in ground
>>     losses during rain events. Below are some plots from last night
>>     of the R component of my antenna impedance (captured while
>>     WSPRing) as well as some precipitation data from a local weather
>>     station.
>>     I retuned the antenna a few weeks back to present right around 50
>>     ohms to the TX. Last night it ranged from about 35 ohms to 48
>>     ohms (or really 140 to 192 ohms before the transformer). Rr is
>>     estimated at about 0.2 ohms, so that variation is really all
>>     variation in ground loss (and I guess a pretty large
>>     corresponding change in antenna efficiency).
>>     Maybe a really clever WSPR listener could estimate the rate of
>>     rainfall at my QTH based on changes in signal strength... hi.
>>     Hopefully the plot images come through... or everyone is going to
>>     wonder what I'm talking about!
>>     My measured feedpoint resistance (stepped down from loading coil
>>     by 4:1 ratio).
>>
>>     Rainfall data from the Weather Underground station in my
>>     neighborhood (wraps at 12 midnight, so you have to use your
>>     imagination to fix the line, but there's a big step from the
>>     downpour around midnight):
>>
>>     73,
>>     Ben N1VF
>>
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