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[195.171.43.25]) by mx.google.com with ESMTP id jc15si1887670wic.62.2014.02.01.15.17.53 for ; Sat, 01 Feb 2014 15:17:53 -0800 (PST) Received-SPF: neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) client-ip=195.171.43.25; Authentication-Results: mx.google.com; spf=neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) smtp.mail=owner-rsgb_lf_group@blacksheep.org; dkim=pass header.i=@mx.aol.com Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1W9jLg-0003FD-HJ for rs_out_1@blacksheep.org; Sat, 01 Feb 2014 22:47:40 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1W9jLf-0003F4-PZ for rsgb_lf_group@blacksheep.org; Sat, 01 Feb 2014 22:47:39 +0000 Received: from omr-d04.mx.aol.com ([205.188.109.201]) by relay1.thorcom.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.77) (envelope-from ) id 1W9jLd-0003d5-7i for rsgb_lf_group@blacksheep.org; Sat, 01 Feb 2014 22:47:38 +0000 Received: from mtaout-mcc02.mx.aol.com (mtaout-mcc02.mx.aol.com [172.26.253.78]) by omr-d04.mx.aol.com (Outbound Mail Relay) with ESMTP id 3B0C270047BCD for ; Sat, 1 Feb 2014 17:47:34 -0500 (EST) Received: from Black (95-91-237-152-dynip.superkabel.de [95.91.237.152]) by mtaout-mcc02.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id 5964238000096 for ; Sat, 1 Feb 2014 17:47:33 -0500 (EST) Message-ID: <466E8C5E208D4BCC8A478137F6D9F9A3@Black> From: "Markus Vester" To: References: <20140201224005.Horde.aUYdHnziyDJS7VulPc-CAcA@posti.anvianet.fi> In-Reply-To: <20140201224005.Horde.aUYdHnziyDJS7VulPc-CAcA@posti.anvianet.fi> Date: Sat, 1 Feb 2014 23:47:30 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18197 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18463 x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1391294854; bh=jEcraFc8EnyRW+qx+lkuCOxpC+hYWh66L5OIFRyOeIw=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=Webj+AJuJ/chbslGd9wXNHtifO8FiFNOfE7j7XdnvC7dab95eDj+hzAkdNU6tKdP6 EvsInWgIjOVEaUCt4Ysl4U40K1fJoW23PRt/Y9KQ2KhxZx4oJPDWUCVsDWsnGu4wHv v3Q5udOx+D3u2eWPDhKoMcKkqlNCwMAUJ5GdkLWw= x-aol-sid: 3039ac1afd4e52ed79853e94 X-AOL-IP: 95.91.237.152 X-Spam-Score: -0.5 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: The apparent contradiction (why is higher impedance better?) is easy to understand if you look at surrounding trees as capacitively coupled shunt resistors. The loss contribution At the antenna can be deduced by transforming the series impedance -j X + R into a parallel shunt cunductance, whose real part will be G = R / (R^2 + X^2) Obviously G disappears when R is infinite (tree is transparent) or zero (tree is a metal pole), and reaches a broad maximum when R ~ X. [...] Content analysis details: (-0.5 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [205.188.109.201 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (markusvester[at]aol.com) -0.0 SPF_PASS SPF: sender matches SPF record -0.5 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: b16f5c37bc0c21b41453c2ac5e65973c Subject: Re: LF: Re: Ant current Content-Type: multipart/alternative; boundary="----=_NextPart_000_0046_01CF1FA7.F8682CD0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_20_30,HTML_MESSAGE, MISSING_OUTLOOK_NAME autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false This is a multi-part message in MIME format. ------=_NextPart_000_0046_01CF1FA7.F8682CD0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The apparent contradiction (why is higher impedance better?) is easy to = understand if you look at surrounding trees as capacitively coupled = shunt resistors. The loss contribution At the antenna can be deduced by = transforming the series impedance=20 -j X + R into a parallel shunt cunductance, whose real part will be G =3D R / (R^2 + X^2) Obviously G disappears when R is infinite (tree is transparent) or zero = (tree is a metal pole), and reaches a broad maximum when R ~ X. While the coupling capacitance X is determined by shape and size, the = resistance of the tree trunk and twigs varies with humidity and = temperature. During frost conditions, the sap is retracted and R becomes = much larger than X, thus G becomes very small. On the other hand, when = trees are wet, R is approaching X, and antenna losses G go up. For a = backyard amateur antenna, capacitive coupling to vegetation can easily = be the dominant loss mechanism, exceeding the series resistances of the = ground connection and the coil. Another effect is that partial shunting of displacement currents to = ground reduces effective height - with a given input current less is = getting out to the far field. A few years ago, I found by measurements = that my antenna efficiency almost doubled in a cold winter night: The = loss resistance went down by 30%, and the effective hight grew by 20%, = so each effect was contributing roughly 1.5 dB. =20 Best 73, Markus (DF6NM) =20 ----- Original Message -----=20 From: phl@netikka.fi=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Saturday, February 01, 2014 9:40 PM Subject: Re: LF: Re: Ant current Christian, LF "Ice is an insulator" If this is true it also means that all lossy trees in the surrounding =20 may have turned into nearly insulators. Unless there is ice or frost on my antenna and insulators I usually =20 have a lower Rtot (more antenna current) in the winter. This is in =20 line with your findings. It may well be lower environmental losses and =20 not the ground loss that are resonsible for this phenomenon here as my =20 antenna has lots of trees in the vincinity. BR Paul-Henrik, OH1LSQ Quoting Alan Melia : > Wet ground is lossy, ice is an insulator, antenna current is mainly =20 > determined by Rloss ?? If you measure the unloaded antenna with a =20 > bridge, you will measure values for C and Rtotal. Rtotal include =20 > Rrad and Rloss. Rrad is very smal for amateur size amtennas and =20 > doesnt change much. So the Ground loss must be reduced. > > Alan > G3NYK > ----- Original Message ----- From: "C. Groeger" > To: > Sent: Saturday, February 01, 2014 2:51 PM > Subject: LF: Ant current > > >> Hi all >> How can one explain that ant current rises when soil is frozen? >> >> Conductivity of water should be much higher than that of ice. >> >> So earth resistance would be higher and the current should drop =20 >> when soil is frozen... >> >> 73, df5qg >> >> >> Christian Groeger ------=_NextPart_000_0046_01CF1FA7.F8682CD0 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
The apparent contradiction (why is = higher impedance=20 better?) is easy to understand if you look at surrounding trees as = capacitively=20 coupled shunt resistors. The loss=20 contribution At the antenna can be deduced by transforming the = series=20 impedance
 -j X + R
into a parallel shunt cunductance, = whose real part=20 will be
 G =3D R / (R^2 + = X^2)
Obviously G disappears when R is = infinite (tree is=20 transparent) or zero (tree is a metal pole), and reaches a broad = maximum=20 when R ~ X.
 
While the coupling capacitance = X is determined=20 by shape and size, the resistance of the tree trunk and twigs=20 varies with humidity and temperature. During frost conditions, the = sap is=20 retracted and R becomes much larger than X, thus G becomes = very small.=20 On the other hand, when trees are wet, R is approaching X, and = antenna=20 losses G go up. For a backyard amateur antenna, capacitive coupling = to=20 vegetation can easily be the dominant loss mechanism, exceeding the = series=20 resistances of the ground connection and the coil.
 
Another effect is that partial = shunting of=20 displacement currents to ground reduces effective height - with a given = input=20 current less is getting out to the far field. A few years ago, I = found by=20 measurements that my antenna efficiency almost doubled in a = cold=20 winter night: The loss resistance went down by 30%, and the effective = hight grew=20 by 20%, so each effect was contributing roughly 1.5=20 dB.   
 
Best 73,
Markus (DF6NM)
 
 
 
 
----- Original Message -----=20
From: phl@netikka.fi =
Sent: Saturday, February 01, 2014 9:40 PM
Subject: Re: LF: Re: Ant current

Christian, LF

"Ice is an insulator"

If this = is true=20 it also means that all lossy trees in the surrounding 
may have = turned=20 into nearly insulators.


Unless there is ice or frost on my = antenna=20 and insulators I usually 
have a lower Rtot (more antenna = current) in=20 the winter. This is in 
line with your findings. It may well be = lower=20 environmental losses and 
not the ground loss that are = resonsible for=20 this phenomenon here as my 
antenna has lots of trees in the=20 vincinity.


BR

Paul-Henrik, = OH1LSQ



Quoting Alan=20 Melia <alan.melia@btinternet.com&g= t;:

>=20 Wet ground is lossy, ice is an insulator, antenna current is = mainly =20
> determined by Rloss ?? If you measure the unloaded  = antenna with=20 a 
> bridge, you will measure values for C and Rtotal. = Rtotal=20 include 
> Rrad and Rloss. Rrad is very smal for amateur = size=20 amtennas and 
> doesnt change much. So the Ground loss must = be=20 reduced.
>
> Alan
> G3NYK
> ----- Original = Message -----=20 From: "C. Groeger" <aot.aot@gmx.de>
> To: <rsgb_lf_group@blacksheep.org= >
>=20 Sent: Saturday, February 01, 2014 2:51 PM
> Subject: LF: Ant=20 current
>
>
>> Hi all
>> How can one = explain that=20 ant current rises when soil is frozen?
>>
>> = Conductivity of=20 water should be much higher than that of ice.
>>
>> So = earth=20 resistance would be higher and the current should drop  =
>> when=20 soil is frozen...
>>
>> 73,=20 df5qg
>>
>>
>> Christian=20 Groeger




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