[600MRG] Rain amplitude modulation
Laurence KL7 L
hellozerohellozero at hotmail.com
Fri Mar 16 16:47:13 EDT 2018
hi Ed - 474 wspr 2 rx is online in wasilla +24 between tx sessions
Laurence KL7L
On Mar 16, 2018, at 8:21 PM, Edward R Cole <kl7uw at acsalaska.net<mailto:kl7uw at acsalaska.net>> 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<mailto: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<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<mailto:600mrg-bounces at mailman.qth.net> <600mrg-bounces at mailman.qth.net<mailto:600mrg-bounces at mailman.qth.net>> on behalf of Ben Gelb <ben at gelbnet.com<mailto: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
______________________________________________________________
600MRG mailing list
Home: http://mailman.qth.net/mailman/listinfo/600mrg
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:600MRG at mailman.qth.net
This list hosted by: http://www.qsl.net<http://www.qsl.net/>
Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
600MRG mailing list
Home: http://mailman.qth.net/mailman/listinfo/600mrg
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:600MRG at mailman.qth.net
This list hosted by: http://www.qsl.net<http://www.qsl.net/>
Please help support this email list: http://www.qsl.net/donate.html
73, Ed - KL7UW
http://www.kl7uw.com
<http://www.kl7uw.com/>Dubus-NA Business mail:
dubususa at gmail.com<mailto:dubususa at gmail.com>
______________________________________________________________
600MRG mailing list
Home: http://mailman.qth.net/mailman/listinfo/600mrg
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:600MRG at mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/600mrg/attachments/20180316/48fa3137/attachment.html>
More information about the 600MRG
mailing list