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[195.171.43.25]) by mx.google.com with ESMTP id fh3si1958908wib.84.2014.02.01.16.32.52 for ; Sat, 01 Feb 2014 16:32:53 -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 (test mode) header.i=@comcast.net Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1W9kaV-0003SZ-Rw for rs_out_1@blacksheep.org; Sun, 02 Feb 2014 00:07:03 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1W9kaV-0003SQ-4R for rsgb_lf_group@blacksheep.org; Sun, 02 Feb 2014 00:07:03 +0000 Received: from qmta04.emeryville.ca.mail.comcast.net ([76.96.30.40]) by relay1.thorcom.net with esmtp (Exim 4.77) (envelope-from ) id 1W9kaS-0003p1-C1 for rsgb_lf_group@blacksheep.org; Sun, 02 Feb 2014 00:07:02 +0000 Received: from omta13.emeryville.ca.mail.comcast.net ([76.96.30.52]) by qmta04.emeryville.ca.mail.comcast.net with comcast id MBvD1n00117UAYkA4C6ynF; Sun, 02 Feb 2014 00:06:58 +0000 Received: from Owner ([166.137.183.18]) by omta13.emeryville.ca.mail.comcast.net with comcast id MC6d1n0050QDnGu8ZC6jYd; Sun, 02 Feb 2014 00:06:53 +0000 From: "hvanesce" To: References: <20140201224005.Horde.aUYdHnziyDJS7VulPc-CAcA@posti.anvianet.fi> <466E8C5E208D4BCC8A478137F6D9F9A3@Black> In-Reply-To: <466E8C5E208D4BCC8A478137F6D9F9A3@Black> Date: Sat, 1 Feb 2014 17:06:36 -0700 Message-ID: <0b3801cf1faa$ad486d20$07d94760$@comcast.net> MIME-Version: 1.0 X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQE8qAqLQUotHpTfHlV3Ck2UFz67SAImumk5AgdD6hMBY2+nEpuZeb5w Content-Language: en-us DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net; s=q20121106; t=1391299618; bh=meipXbxV4Lz2QgmcbtjX81NFnmBNi9fISJSGSMrHoUA=; h=Received:Received:From:To:Subject:Date:Message-ID:MIME-Version: Content-Type; b=ndmKgwQAvVVQ5hp+nml+ubDOM4MdlSP/kPvln6TPml8JGEiTlM5rJ/cRtFLU+GS81 5RwUvRDBN9v1v2a9Xae2YmyDUgTSqw9zWjAtuCkpuumCUgk6vZLuNgVHg01Xj/RSFJ vsCRpCIoPHPW8kwv2zuvfgNxtvOoO8HYFZZVWkXTmZjmFSPO3763Co+RXW0FoELWQ6 iqRGkASlA4RPTE9Ygy5wYIIqb0RJqXumFTQNcmw1edxZkb7Ms9vp5kHrpGi4R24oEa 6b7Mz8CxB+4WZk4QskL+NDheik7Wu2sqJibfX/xTItjXTqv76pJt3QhH0RGOacUM6+ 0am9uvhxzkAWA== 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. 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Content preview: Markus, Well said. 73, Jim AA5BW [...] 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 [76.96.30.40 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (hvanesce[at]comcast.net) -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: f4625b23d277cf453c74a2300a95877d Subject: RE: LF: Re: Ant current Content-Type: multipart/alternative; boundary="----=_NextPart_000_0B39_01CF1F70.00EACDA0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_40_50,HTML_MESSAGE 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 multipart message in MIME format. ------=_NextPart_000_0B39_01CF1F70.00EACDA0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Markus, =20 Well said.=20 =20 73, Jim AA5BW =20 =20 From: owner-rsgb_lf_group@blacksheep.org = [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Markus Vester Sent: Saturday, February 1, 2014 3:47 PM To: rsgb_lf_group@blacksheep.org Subject: Re: LF: Re: Ant current =20 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. =20 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. =20 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 =20 Best 73, Markus (DF6NM) =20 =20 =20 =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 =20 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_0B39_01CF1F70.00EACDA0 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

Markus,

 

Well said.

 

73,  Jim AA5BW

 

 

From:= = owner-rsgb_lf_group@blacksheep.org = [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Markus = Vester
Sent: Saturday, February 1, 2014 3:47 PM
To: = rsgb_lf_group@blacksheep.org
Subject: Re: LF: Re: Ant = current

 

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 =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.   

 

Best = 73,

Markus = (DF6NM)

 

 

 

 

----- = Original Message -----

From:<= /b> phl@netikka.fi =

Sent:<= /b> = 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 
may have turned into nearly = insulators.


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


BR

Paul-Henrik, = OH1LSQ



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

> Wet ground is lossy, ice is an insulator, antenna = current is mainly 
> determined by Rloss ?? If you measure = the unloaded  antenna with a 
> bridge, you will = measure values for C and Rtotal. Rtotal include 
> Rrad and = Rloss. Rrad is very smal for amateur size amtennas and 
> = doesnt change much. So the Ground loss must be reduced.
>
> = Alan
> G3NYK
> ----- Original Message ----- From: "C. = Groeger" <aot.aot@gmx.de>
> To: <rsgb_lf_group@blacksheep.org= >
> 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 
>> when soil = is frozen...
>>
>> 73, = df5qg
>>
>>
>> Christian = Groeger



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