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

[Merv Schweigert]

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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