Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-ma01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 97D3738000145 for ; Fri, 26 Apr 2013 20:04:58 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1UVs6N-0003sl-Ol for rs_out_1@blacksheep.org; Sat, 27 Apr 2013 00:30:51 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1UVs6N-0003sV-3k for rsgb_lf_group@blacksheep.org; Sat, 27 Apr 2013 00:30:51 +0100 Received: from mail-ob0-f178.google.com ([209.85.214.178]) by relay1.thorcom.net with esmtps (TLSv1:RC4-SHA:128) (Exim 4.77) (envelope-from ) id 1UVs6K-0006wN-Dy for rsgb_lf_group@blacksheep.org; Sat, 27 Apr 2013 00:30:50 +0100 Received: by mail-ob0-f178.google.com with SMTP id 16so4057951obc.9 for ; Fri, 26 Apr 2013 16:30:26 -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=ubu7heJ5jxlawxKrPFuYYfY+cccj+GeSQIbNvZg52NU=; b=ePR6vgCTKuCIwh4KXsl/JwpH0SSLa4pfPPpQjEsPs6IKvv9v9c7ckNFyXv5SNkovkk PJbetl+/RAmp3Z8h/3PnIhDfC542g8HYv2QAbicLk/ZqddmTwxfvMQfU97x2iUyXsZBk 5ybIOt7sYgBN7ckrfVRwt4RKOWgOxJH8uv3fg+D6/VKBLhNtDnlxJWLPmc9t52/GoCZS b+EZnkqOb9MxhBWyMWorR05KpAEftOwRr0QCmG2i5cwzpkrus6xRhMSENgagLZ57EkIy 3aCzY28SdbDR+TpCDZXjWp5gXFBA9dDkwtVEXc2g8n7bw/VpX/UGbKmgO79w314PM0W4 BGHw== MIME-Version: 1.0 X-Received: by 10.60.62.70 with SMTP id w6mr25495586oer.38.1367019026608; Fri, 26 Apr 2013 16:30:26 -0700 (PDT) Received: by 10.60.135.199 with HTTP; Fri, 26 Apr 2013 16:30:26 -0700 (PDT) In-Reply-To: References: <517ABCE1.8060802@iup.uni-heidelberg.de> Date: Fri, 26 Apr 2013 19:30:26 -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 Laurence, Good info, thanks! 73 Warren On Fri, Apr 26, 2013 at 7:09 PM, Laurence KL1 X < wrote: > 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 moment > 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 up > 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 shunt > my signal to ground? > > 73 Warren > > > > On Fri, Apr 26, 2013 at 1:44 PM, Stefan Schäfer < > 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 [...] 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 [209.85.214.178 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: fefa6d96b1284f767a869566d1bc7791 Subject: Re: LF: Was Fire in the wire Content-Type: multipart/alternative; boundary=089e01294f307b781d04db4bebca X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.1 required=5.0 tests=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-ma01.r1000.mx.aol.com ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d6009517b162a1b21 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --089e01294f307b781d04db4bebca Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hi Laurence, Good info, thanks! 73 Warren On Fri, Apr 26, 2013 at 7:09 PM, Laurence KL1 X < hellozerohellozero@hotmail.com> wrote: > 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 --089e01294f307b781d04db4bebca Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Hi Laurence,
=A0 =A0 =A0 Good info, thanks!=A0
73 Warren



On Fri, Apr 26, 2013 at 7:09 PM= , Laurence KL1 X <hellozerohellozero@hotmail.com> wrote:
Thanks Warren - interesting stuff !
=A0
Certain= ly the ground beneath the loop is probably a couple of Kv pd above the cond= uctor at my Kw level=A0-=A0I can create colorful violet coronas :-) - and t= he capacitive affects of raising the or lowering the horizontal section of = the loop just a few=A0feet=A0make a lot of change to the tuning -
=A0
Ive followed a suggestion to "relieve" earth losses/add a = little more tuning stability by=A0shoving a=A0Earth=A0mat under the loop he= re - at the moment it is untuned but=A0installing it did cause=A0an increas= e in loop current by a couple of percent=A0- I saw a paper tuning this eart= h=A0and it=A0is was said to improve the stability and increase the effectiv= e power in this NVIS set up at 137.
=A0
Im using the underslung pulley system on mine at the moment which ha= s survived one=A0Alaskan winter :-)=A0 Rough diagram attached - there are t= wo parallel conductors in this loop but a single black line is shown for cl= arity - adding a second conductor didnt change the efficiency much on 505kH= z where its nearly resonant, but helped=A0 on 137
=A0
http://kl7u= k.com/loopy.jpg
=A0
Cheers
Laurence KL 1X=A0 WE2 XPQ
Alaska=

=A0
Date: Fri, 26 Apr 2013 17:47:51 -0400From: wd2xgj@gmail.c= om
To: rsgb_= lf_group@blacksheep.org
Subject: Re: LF: Fire in the wire

Hi Stefan,

=A0 =A0 =A0 =A0There are thousa= nds 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= shunt my signal to ground?

73 Warren



O= n Fri, Apr 26, 2013 at 1:44 PM, Stefan Sch=E4fer <Stef= an.Schaefer@iup.uni-heidelberg.de> wrote:
Warren,

What is the voltage between the tree (GND) and loop? I thought that the vol= tages are rather small, i.e. below 100V, especially when a large loop is us= ed. 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 co= ax suspended from trees went open circuit (both center conductor and shield= ), some time later part of the wire actually came down. I had thought 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 a= ppeared that the insulation had melted for a considerable distance and ther= e were burn marks further up the cable. My hypothesis is that the outer ins= ulation was abraded away and the coax shield came into contact with the tre= e 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 insulation = or a better way of supporting the antenna than trees would be required!

--
73 Warren K2ORS
=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





--
73 Warren K2OR= S
=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



--
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
--089e01294f307b781d04db4bebca--