Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mk06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 81D7D380000A9; Fri, 26 Apr 2013 20:36:27 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1UVt6S-0004GE-AS for rs_out_1@blacksheep.org; Sat, 27 Apr 2013 01:35:00 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1UVt6R-0004G5-I5 for rsgb_lf_group@blacksheep.org; Sat, 27 Apr 2013 01:34:59 +0100 Received: from mail-ob0-f172.google.com ([209.85.214.172]) by relay1.thorcom.net with esmtps (TLSv1:RC4-SHA:128) (Exim 4.77) (envelope-from ) id 1UVt6O-00077o-ND for rsgb_lf_group@blacksheep.org; Sat, 27 Apr 2013 01:34:58 +0100 Received: by mail-ob0-f172.google.com with SMTP id v19so4075252obq.31 for ; Fri, 26 Apr 2013 17:34:34 -0700 (PDT) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:x-received:in-reply-to:references:date:message-id :subject:from:to:content-type; bh=ES3w3d9cVNBIUz8hwSoAgv51aEjlnFTWHX4yoxK59Zw=; b=xt5b4GbfwqJZ2MhT8lPCJrr6npfVexllxx90LMiPai9d2dHA7EqtUaAE8u8zpr0PQb reJ+hUO2C1pI9MdZbI6EGkT8oPM778ACVrb9/FerLD3yYj2i7yNDc/Shm3w0kdrMiK6Z lkRf6GrvGGKoJa+RgPEO69H/lu2fnqj4Os3G2J+2+fNQ9yHeq8esy+UE0F72zHWjrMhV VUgZnj/Tp6GrwPXO7yVMF8KSZWxkLG/acS2m2Cv8xSrhXO9HKSOpX5RCTWPLeTsiqLki QCVWHf5UGxNdCALYkh21nvfAA1fHaJzwGQgKiYJ0yX+Rhv59rY03hmX27fZxqQHUmcKh YvOQ== MIME-Version: 1.0 X-Received: by 10.60.155.209 with SMTP id vy17mr1381343oeb.83.1367022874714; Fri, 26 Apr 2013 17:34:34 -0700 (PDT) Received: by 10.60.135.199 with HTTP; Fri, 26 Apr 2013 17:34:34 -0700 (PDT) In-Reply-To: <3D784CBB778342CABB2AB4CCDC45ACC5@Black> References: <517ABCE1.8060802@iup.uni-heidelberg.de> <3D784CBB778342CABB2AB4CCDC45ACC5@Black> Date: Fri, 26 Apr 2013 20:34:34 -0400 Message-ID: From: Warren Ziegler To: rsgb_lf_group X-Spam-Score: -0.7 (/) 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: Hi Markus, Interesting ideas but putting capacitors in series increases the ESR and is difficult to implement especially when the upper part of the loop is over 20 meters high! 73 Warren [...] Content analysis details: (-0.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [209.85.214.172 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (wd2xgj[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 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: d4b11820086e28e9e085cef3e7768d06 Subject: Re: LF: Re: Was Fire in the wire Content-Type: multipart/alternative; boundary=047d7bd74c3ad8e59704db4cd07c 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_FONTCOLOR_UNSAFE,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 x-aol-global-disposition: G X-AOL-SCOLL-AUTHENTICATION: mtain-mk06.r1000.mx.aol.com ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d618a517b1d8b3f0f X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --047d7bd74c3ad8e59704db4cd07c Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hi Markus, Interesting ideas but putting capacitors in series increases the ESR and is difficult to implement especially when the upper part of the loop is over 20 meters high! 73 Warren On Fri, Apr 26, 2013 at 7:41 PM, Markus Vester wrote= : > ** > Warren, Laurence, > > the earth losses beneath the loop could either be inductive or capacitive= . > In reality probably both, but which effect dominates depends on voltages, > surroundings (branches etc), and also ground conductivity (higher > conductivity increases eddy currents but lowers capacitive losses). Ideal= ly > you would have maximum voltage at the capacitor terminals and zero in the > middle of the loop. One way to generally reduce voltages for a given > inductance would be to split the resonance C into several larger pF > capacitors in series, distributed around the circumference. This is often > done with MRI loop antennas ("surface coils") to minimize resistive > coupling to the patient's skin. > > Best 73, > Markus > > ----- Original Message ----- > *From:* Laurence KL1 X > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Saturday, April 27, 2013 1:09 AM > *Subject:* LF: Was Fire in the wire > > Thanks Warren - interesting stuff ! > > Certainly the ground beneath the loop is probably a couple of Kv pd above > the conductor at my Kw level - I can create colorful violet coronas :-) - > and the capacitive affects of raising the or lowering the horizontal > section of the loop just a few feet make a lot of change to the tuning - > > Ive followed a suggestion to "relieve" earth losses/add a little more > tuning stability by shoving a Earth mat under the loop here - at the mome= nt > it is untuned but installing it did cause an increase in loop current by = a > couple of percent - I saw a paper tuning this earth and it is was said to > improve the stability and increase the effective power in this NVIS set u= p > at 137. > > Im using the underslung pulley system on mine at the moment which has > survived one Alaskan winter :-) Rough diagram attached - there are two > parallel conductors in this loop but a single black line is shown for > clarity - adding a second conductor didnt change the efficiency much on > 505kHz where its nearly resonant, but helped on 137 > > http://kl7uk.com/loopy.jpg > > Cheers > Laurence KL 1X WE2 XPQ > Alaska > > > ------------------------------ > Date: Fri, 26 Apr 2013 17:47:51 -0400 > From: wd2xgj@gmail.com > To: rsgb_lf_group@blacksheep.org > Subject: Re: LF: Fire in the wire > > Hi Stefan, > > There are thousands or perhaps tens of thousands of volts from the > loop to ground. > If I grounded the loop with and there was a large potential difference, > wouldn't that cause a large current to flow to ground and effectively shu= nt > my signal to ground? > > 73 Warren > > > > On Fri, Apr 26, 2013 at 1:44 PM, Stefan Sch=E4fer < > Stefan.Schaefer@iup.uni-heidelberg.de> wrote: > > Warren, > > What is the voltage between the tree (GND) and loop? I thought that the > voltages are rather small, i.e. below 100V, especially when a large loop = is > used. Isn't it possible to ground the loop? > > 73, Stefan > > Am 26.04.2013 19:21, schrieb Warren Ziegler: > > > Just a quick report on a failure mode for LF TX antennas. > Last Fall my original TX loop made up of approximately 500 feet of RG-11 > coax suspended from trees went open circuit (both center conductor and > shield), some time later part of the wire actually came down. I had thoug= ht > that abrasion from contact with the trees had eventually worn through it. > > What I found was a little more interesting. Looking at the downed end, it > appeared that the insulation had melted for a considerable distance and > there were burn marks further up the cable. My hypothesis is that the out= er > insulation was abraded away and the coax shield came into contact with th= e > tree limb causing the burning/melting. > Will try to get some pictures this weekend and put them up on my website. > > Long term if one wants to operate at the kW level either better insulatio= n > or a better way of supporting the antenna than trees would be required! > > -- > 73 Warren K2ORS > WD2XGJ > WD2XSH/23 > WE2XEB/2 > WE2XGR/1 > > > > > > -- > 73 Warren K2ORS > WD2XGJ > WD2XSH/23 > WE2XEB/2 > WE2XGR/1 > > > --=20 73 Warren K2ORS WD2XGJ WD2XSH/23 WE2XEB/2 WE2XGR/1 --047d7bd74c3ad8e59704db4cd07c Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Hi Markus,

=A0 =A0 =A0Interesting= ideas but putting capacitors in series increases the ESR and is difficult = to implement especially when the upper part of the loop is over 20 meters h= igh!

73 Warren

<= div class=3D"gmail_extra">

On Fri, Apr 26= , 2013 at 7:41 PM, Markus Vester <markusvester@aol.com> w= rote:
Warren, Laurence,
=A0
the earth losses beneath the loop could either be= =20 inductive or capacitive. In reality probably both, but=A0which effect=20 dominates depends on voltages, surroundings (branches etc), and also ground= =20 conductivity (higher conductivity increases=A0eddy currents but lowers=20 capacitive losses). Ideally you would have maximum voltage at the capacitor= =20 terminals and zero=A0in the middle of the loop. One way to generally reduce= =20 voltages for a given inductance would be to split the resonance C into seve= ral=20 larger pF capacitors in series, distributed around the circumference.=20 This=A0is often done=A0with MRI loop antennas ("surface coils") t= o=20 minimize=A0resistive coupling to the patient's skin.
=A0
Best 73,
Markus
=A0

Thanks Warren - interesting stuff !
=A0
Certainly th= e=20 ground beneath the loop is probably a couple of Kv pd above the conductor a= t my=20 Kw level=A0-=A0I can create colorful violet coronas :-) - and the=20 capacitive affects of raising the or lowering the horizontal section of the= loop=20 just a few=A0feet=A0make a lot of change to the tuning -
=A0
Ive=20 followed a suggestion to "relieve" earth losses/add a little more= tuning=20 stability by=A0shoving a=A0Earth=A0mat under the loop here - at the=20 moment it is untuned but=A0installing it did cause=A0an increase in loop=20 current by a couple of percent=A0- I saw a paper tuning this earth=A0and=20 it=A0is was said to improve the stability and increase the effective power = in=20 this NVIS set up at 137.
=A0
Im using the underslung pulley system on= =20 mine at the moment which has survived one=A0Alaskan winter :-)=A0 Rough=20 diagram attached - there are two parallel conductors in this loop but a sin= gle=20 black line is shown for clarity - adding a second conductor didnt change th= e=20 efficiency much on 505kHz where its nearly resonant, but helped=A0 on=20 137
=A0
http= ://kl7uk.com/loopy.jpg
=A0
Cheers
Laurence=20 KL 1X=A0 WE2 XPQ
Alaska

=A0
Date: Fri, 26 Apr 2013 17:47:51 -0400
From: wd2xgj@gmail.com
To:=20 rsgb_lf_g= roup@blacksheep.org
Subject: Re: LF: Fire in the wire

Hi Stefan,

=A0 =A0 =A0 =A0There are thousands or perhaps tens of thousands=20 of volts from the loop to ground.
If I grounded the loop with and there was a large potential difference= ,=20 wouldn't that cause a large current to flow to ground and effectively s= hunt my=20 signal to ground?

73 Warren



On Fri, Apr 26, 2013 at 1:44 PM, Stefan Sch=E4fer &l= t;Stefan.Schaefer@iup.uni-heidelberg.de> wrote:
Warren,

What is the voltage between the tree (GND)=20 and loop? I thought that the voltages are rather small, i.e. below 100V,= =20 especially when a large loop is used. Isn't it possible to ground the= =20 loop?

73, Stefan

Am 26.04.2013 19:21,=20 schrieb Warren Ziegler:


Just a quick report on a fail= ure mode for LF TX=20 antennas.
Last Fall my original TX loop made up of approximately 500= feet=20 of RG-11 coax suspended from trees went open circuit (both center condu= ctor=20 and shield), some time later part of the wire actually came down. I had= =20 thought that abrasion from contact with the trees had eventually worn= =20 through it.

What I found was a little more interesting. Looking = at=20 the downed end, it appeared that the insulation had melted for a=20 considerable distance and there were burn marks further up the cable. M= y=20 hypothesis is that the outer insulation was abraded away and the coax s= hield=20 came into contact with the tree limb causing the burning/melting.
Wi= ll=20 try to get some pictures this weekend and put them up on my=20 website.

Long term if one wants to operate at the kW level eithe= r=20 better insulation or a better way of supporting the antenna than trees = would=20 be required!

-- <= br>73 Warren K2ORS
=A0 =A0 =A0 =A0=20 =A0 =A0 =A0 =A0 WD2XGJ
=A0 =A0 =A0 =A0 =A0=20 =A0 =A0 =A0 WD2XSH/23
=A0 =A0 =A0 =A0 =A0 =A0=20 =A0 =A0 WE2XEB/2
=A0 =A0 =A0 =A0 =A0 =A0 =A0=20 =A0 WE2XGR/1

<= font color=3D"#888888">



--
73 Warren=20 K2ORS
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XGJ=20
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XSH/23
=A0=20 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XEB/2
=A0 =A0=20 =A0 =A0 =A0 =A0 =A0 =A0 WE2XGR/1

=A0=20



--
73 Warren K2= ORS
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XGJ
=A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 WD2XSH/23
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XEB/2
=A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 WE2XGR/1

=A0 --047d7bd74c3ad8e59704db4cd07c--