[600MRG] And now for something lighter!

[kl7aj at acsalaska.net]

There are enough old geezers on this list who will appreciate this story. :)

73,

Eric

 

---
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 12:20:47 -0800, Edward R Cole  wrote:
 
I found that I had to add two turns on my loading coil in winter as frozen soil had lower conductivity. I attached leads to the two tap locations so I t only required moving my short antenna leader to the proper tap wire that uses a 1/4-20 brass stud. I use about three foot of RG-213 center conductor as leader (shield un connected either end). My antenna is back in the air and only awaiting retuning from 495 to 473 KHz.

73, Ed - KL7uW

At 09:33 AM 3/16/2018, kl7aj at acsalaska.net wrote:
 
By the way, don't ignore the REACTIVE component of the impedance! Ground conductivity is a COMPLEX number, containing both a resistive AND a capacitive (dielectric constant) component, the latter of which can affect reactance significantly. The reason for this is the REFLECTED signal (ground image) signal has a virtual depth dependent on the dielectric constant. A change in this has the same effect as changing your antenna height....which, of course, reflects in BOTH reactance and feedpoint resistance. EVERYTHING interacts with everything else. This is why RF is so much fun. :)
---
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 15:54:23 +0000, Neil Klagge wrote:
 

	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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73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
dubususa at gmail.com
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