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

Sat Mar 17 01:32:17 EDT 2018

I am a little skeptical the sprinklers will do much - both because I don't
think the water volume is that high relative to a rainstorm, and also
because it only covers the square footage within a ~30 ft radius of the
antenna (and even then, not 360 degrees around). I think a good cloudburst
is kinda like having radials that run through all my neighbor's yards.

But comic value alone makes it seem worth doing. Will keep y'all posted. :)

On Fri, Mar 16, 2018 at 9:14 PM, Merv Schweigert via 600MRG <
600mrg at mailman.qth.net> wrote:

> Be interesting to see what you get with the sprinklers running a while.
> Maybe when you need some
> "enhanced" signal you could run them ahead of time.
>
> Your signal is really decent with what you are using,  and I suspect a lot
> of operators will have the same
> type system and problems as more come on line from city lots etc.
>
> Have seen some use remote switchs and or remote motors to tune the antenna
> when conditions change.
> Sounds like a good idea.
> I do some switching of the antenna,  its about 400 ft away, so use the
> coax as the "carrier" and pull in different
> relays with +12 or -12 etc.
>
> Keep us informed Ben,  good experimenting.   73 Merv K9FD/KH6
>
> Glad folks found this interesting.
>
> I think Merv nailed it - my ground system is pretty terrible. Probably
> 10-12 short radials, and really only spread out over one quarter of the
> circle... I imagine a better radial field would reduce the variation a lot
> (and also just bring the baseline impedance down substantially - 200 ohms
> is pretty high!).
>
> There is ~5-6 ohms variation in X as well in the dataset from yesterday
> (not sure which direction as the AD8302 doesn't say, and I didn't do any
> manual tuning around to figure it out). I also don't trust this measurement
> very much because I haven't attempted any calibration of the phase detector
> (only magnitude has been measured/calibrated). On my TODO list but haven't
> got around to it yet.
>
> As Ike mentioned, I do see a 10-15% difference in input/output power to
> the transmitter depending on the conditions (TPO seems to drop when
> impedance drops, which is a bit counterintuitve.. maybe has to do w/ change
> in X? Not sure. Would sort of think it'd go the other way..). Been thinking
> about adding some relays on the matching transformer to be able to adjust.
>
> I remembered I have some inground sprinklers in the backyard I never turn
> on... hmmm sounds like next experiment...
>
> Have a good weekend all! :)
>
> 73,
> Ben
>
> On Fri, Mar 16, 2018 at 1:47 PM, Laurence KL7 L <
> hellozerohellozero at hotmail.com> wrote:
>
>> 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> 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).
>>
>> [image: []]
>>
>>
>> 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):
>> [image: []]
>>
>> 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 <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
>>
>> ______________________________________________________________
>> 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 <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
>>
>> 73, Ed - KL7UW
>>   http://www.kl7uw.com
>> Dubus-NA Business mail:
>>   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 <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
>>
>>
>> ______________________________________________________________
>> 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
>>
>
>
>
> ______________________________________________________________
> 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 <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
>
>
>
> ______________________________________________________________
> 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/20180316/70139de0/attachment.html>