[600MRG] [DETECTED AS SPAM] Re: Rain amplitude modulation
Merv Schweigert
k9fd at flex.com
Sat Mar 17 00:14:32 EDT 2018
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
> <mailto: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
> <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 <tel:%28907%29%20488-0483>
>>> (907) 371-7120 <tel:%28907%29%20371-7120>
>>> 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
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>>
>> 73, Ed - KL7UW
>> http://www.kl7uw.com
>> <http://www.kl7uw.com/>Dubus-NA Business mail:
>> dubususa at gmail.com <mailto:dubususa at gmail.com>
>>
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