Return-Path: Received: from rly-df12.mx.aol.com (rly-df12.mail.aol.com [172.19.156.25]) by air-df07.mail.aol.com (v123.4) with ESMTP id MAILINDF074-59349e714ae9b; Thu, 16 Apr 2009 07:21:33 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-df12.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDF122-59349e714ae9b; Thu, 16 Apr 2009 07:21:20 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1LuPdE-0001Pl-Rh for rs_out_1@blacksheep.org; Thu, 16 Apr 2009 12:19:48 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1LuPdE-0001Pc-7s for rsgb_lf_group@blacksheep.org; Thu, 16 Apr 2009 12:19:48 +0100 Received: from blu0-omc1-s7.blu0.hotmail.com ([65.55.116.18]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1LuPdB-000380-Gc for rsgb_lf_group@blacksheep.org; Thu, 16 Apr 2009 12:19:48 +0100 Received: from BLU146-W33 ([65.55.116.7]) by blu0-omc1-s7.blu0.hotmail.com with Microsoft SMTPSVC(6.0.3790.3959); Thu, 16 Apr 2009 04:19:38 -0700 Message-ID: X-Originating-IP: [221.198.51.73] From: Laurence BY3A-KL1X China To: Date: Thu, 16 Apr 2009 03:19:38 -0800 Importance: Normal In-Reply-To: <38F4A9873A5B474DB6FB337B1B69ABA10D7B925641@HERMES8.ds.leeds.ac.uk> References: <38F4A9873A5B474DB6FB337B1B69ABA10D7B925641@HERMES8.ds.leeds.ac.uk> MIME-Version: 1.0 X-OriginalArrivalTime: 16 Apr 2009 11:19:38.0446 (UTC) FILETIME=[3AE00EE0:01C9BE85] X-Spam-Score: 0.9 (/) X-Spam-Report: autolearn=disabled,HTML_10_20=0.945,HTML_MESSAGE=0.001 Content-Type: multipart/alternative; boundary="_662355c5-a039-4439-b6f6-07ef301a2e78_" Subject: LF: Arcs and sparks - user beware too X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.0 required=5.0 tests=FORGED_HOTMAIL_RCVD, HTML_MESSAGE,NO_COST 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-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --_662355c5-a039-4439-b6f6-07ef301a2e78_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Chris - thanks =20 Yes it was very odd and one of those "what?" times in my professional and ha= m career when you really want to check and recheck. =20 The cable was short circuited DC wise at the antennae end via the (working)=20= Balun at the time it was unscrewed from the coax - I checked this afterward= s in case it wasnt. I checked the TX/RX side too - nothing there. =20 So the time the coax had to charge was only the time from disconnection to "= touching" which was appx 5 mins. And remember the coax cable was defacto sit= ting on the "ground" for 80m. =20 Now - what that charge was is something that Ive been sleeping on. How abou= t a curved ball and seismic activity beneath where I was staying caused by r= ock movement and the piezo affect caused a field to be generated etc? - ok o= utlandish, but I was sitting at a base of an active and smouldering volcano=20= and daily tremors were felt....Hmm perhaps not so outlandish after all...but= I did check again and again after the fact and no charge was present again=20= until we shoved it all back up in the air again a few hours later. =20 However, logically (probably wrongly too given my luck) the amount of "c" in= pfs for 80m of RG213 aint that large and nothing like capable under normal=20= circumstances to give such a wallop. Yes it could charge to many Kv I suppos= e before it reached it breakdown Voltage - and it is a few, but wallop and (= White) flash and bang was audible and visible in daylight about 50 metres aw= ay (!) but what mechanism would cause the inner to get a gradient again the=20= outer,,,,? =20 As I said before, apart for the Whiz Bangs in the deserts of whereever you r= eally wouldnt think a cable could do that - but it did.=20 =20 I learnt a lesson - never, ever presume because a cable is open circuit that= its safe - even one that could normally not have a Pd across it, or is sitt= ing on the ground. =20 I seem to remember SIDE - Switch Off, Isolate, Dump and Earth. =20 Chaps - any more suggestions or solutions or was this an enigma? =20 73 Laurence=20 =20 > From: C.Trayner@leeds.ac.uk > To: rsgb_lf_group@blacksheep.org > Date: Thu, 16 Apr 2009 10:07:17 +0100 > Subject: LF: RE: Arcs and sparks - user beware >=20 > Dear Laurence, >=20 > Thanks for your post. > > (Its got a bit of MF in it honest)=20 > Whether it has or not, it could save one of our lives some day! >=20 > A friend who worked for the London Electricity Board years ago told me a s= imilar story about working on 3-phase underground cables. You disconnect bot= h ends, then before you touch them you short each phase to earth. Rarely wil= l you have happened to disconnect at the zero-volts part of the cycle, so ap= parently you get some satisfying bangs. >=20 > But that may not completely explain your recent experience. One would gues= s that (a) you turned off the Tx before unplugging the aerial and (b) the Tx= has a DC path across the aerial socket (e.g a transfo secondary). So did so= me other process charge up your cable? >=20 > Your experience might suggest that, for those who fiddle with their aerial= s frequently, it might be worth permanently fitting a resistor (100k, say) a= cross the two halves; or two, one from each pole to earth. >=20 >=20 > 73, > Chris G4OKW >=20 >=20 >=20 _________________________________________________________________ Rediscover Hotmail=AE: Get quick friend updates right in your inbox.=20 http://windowslive.com/RediscoverHotmail?ocid=3DTXT_TAGLM_WL_HM_Rediscover_U= pdates2_042009=3D --_662355c5-a039-4439-b6f6-07ef301a2e78_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Chris - thanks
 
Yes it was very odd and one of those "what?" times in my professional and ha= m career when you really want to check and recheck.
 
The cable was short circuited DC wise at the antennae end via the (work= ing) Balun  at the time it was unscrewed from the coax - I checked this= afterwards in case it wasnt. I checked the TX/RX side too - nothi= ng there.
 
So the time the coax had to charge was only the time from disconnection to "= touching" which was appx 5 mins. And remember the coax cable was defacto sit= ting on the "ground" for 80m.
 
Now  - what that charge was is something that Ive been sleeping on. How= about a curved ball and seismic activity beneath where I was staying caused= by rock movement and the piezo affect caused a field to be generated etc? -= ok outlandish, but I was sitting at a base of an active and smouldering vol= cano and daily tremors were felt....Hmm perhaps not so outlandish after all.= ..but I did check again and again after the fact and no charge was present a= gain until we shoved it all back up in the air again a few hours later.
 
However, logically (probably wrongly too given my luck) the amount of "= c" in pfs for 80m of RG213 aint that large and nothing like capable und= er normal circumstances to give such a wallop. Yes it could charge to many K= v I suppose before it reached it breakdown Voltage - and it is a few, but&nb= sp;wallop and (White) flash and bang was audible and visible in daylight abo= ut 50 metres away (!) but what mechanism would cause the inner to get a grad= ient again the outer,,,,?
 
As I said before, apart for the Whiz Bangs in the deserts of=20= whereever you really wouldnt think a cable could do that - but it did.
 
I learnt a lesson - never, ever presume because a cable is open circuit = ;that its safe - even one that could normally not have a Pd across it, or is= sitting on the ground.
 
I seem to remember SIDE - Switch Off, Isolate, Dump and Earth.
 
Chaps -  any more suggestions or solutions or was this an enigma?
 
73 Laurence
 
> From: C.Trayner@leeds.ac.uk
> To: rsgb_= lf_group@blacksheep.org
> Date: Thu, 16 Apr 2009 10:07:17 +0100
>= ; Subject: LF: RE: Arcs and sparks - user beware
>
> Dear Laure= nce,
>
> Thanks for your post.
> > (Its got a bit of M= F in it honest)
> Whether it has or not, it could save one of our liv= es some day!
>
> A friend who worked for the London Electricity= Board years ago told me a similar story about working on 3-phase undergroun= d cables. You disconnect both ends, then before you touch them you short eac= h phase to earth. Rarely will you have happened to disconnect at the zero-vo= lts part of the cycle, so apparently you get some satisfying bangs.
>=20=
> But that may not completely explain your recent experience. One wou= ld guess that (a) you turned off the Tx before unplugging the aerial and (b)= the Tx has a DC path across the aerial socket (e.g a transfo secondary). So= did some other process charge up your cable?
>
> Your experien= ce might suggest that, for those who fiddle with their aerials frequently, i= t might be worth permanently fitting a resistor (100k, say) across the two h= alves; or two, one from each pole to earth.
>
>
> 73,> Chris G4OKW
>
>
>

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