Return-Path: Received: from rly-dc07.mx.aol.com (rly-dc07.mail.aol.com [172.19.136.36]) by air-dc02.mail.aol.com (v123.4) with ESMTP id MAILINDC023-b3249e71bd97d; Thu, 16 Apr 2009 07:52:09 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-dc07.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDC076-b3249e71bd97d; Thu, 16 Apr 2009 07:51:55 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1LuQ7g-0001aU-V5 for rs_out_1@blacksheep.org; Thu, 16 Apr 2009 12:51:16 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1LuQ7g-0001aL-9j for rsgb_lf_group@blacksheep.org; Thu, 16 Apr 2009 12:51:16 +0100 Received: from qmta02.westchester.pa.mail.comcast.net ([76.96.62.24]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1LuQ7e-0002u5-3w for rsgb_lf_group@blacksheep.org; Thu, 16 Apr 2009 12:51:16 +0100 Received: from OMTA05.westchester.pa.mail.comcast.net ([76.96.62.43]) by QMTA02.westchester.pa.mail.comcast.net with comcast id gAm21b0040vyq2s52BqmJp; Thu, 16 Apr 2009 11:50:46 +0000 Received: from DELL4 ([65.96.107.144]) by OMTA05.westchester.pa.mail.comcast.net with comcast id gBr61b01036xPMd3RBr6pU; Thu, 16 Apr 2009 11:51:07 +0000 Message-ID: <000c01c9be89$9ff54c60$6c01a8c0@DELL4> From: To: References: <38F4A9873A5B474DB6FB337B1B69ABA10D7B925641@HERMES8.ds.leeds.ac.uk> Date: Thu, 16 Apr 2009 07:51:05 -0400 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Karma: unknown: X-Spam-Score: 0.6 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,NO_REAL_NAME=0.55 Subject: LF: Re: Arcs and sparks - user beware too Content-Type: multipart/alternative; boundary="----=_NextPart_000_0009_01C9BE68.18BD86C0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.3 required=5.0 tests=HTML_MESSAGE,NO_COST, NO_REAL_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 X-AOL-IP: 193.82.116.20 ------=_NextPart_000_0009_01C9BE68.18BD86C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Electrically charged volcanic ash in a 'cloud' above the antenna? Have obser= ved some pretty impressive flashovers with thunderstorms passing overhead.=20 Charged ash particles descending on the antenna? Snow, rain and wind static=20= can make a pretty impressive showing...although not like the passing thunder= storm.=20 Jay ----- Original Message -----=20 From: Laurence BY3A-KL1X China=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Thursday, April 16, 2009 7:19 AM Subject: LF: Arcs and sparks - user beware too Chris - thanks =20 Yes it was very odd and one of those "what?" times in my professional and=20= ham career when you really want to check and recheck. =20 The cable was short circuited DC wise at the antennae end via the (working= ) Balun at the time it was unscrewed from the coax - I checked this afterwa= rds 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 s= itting on the "ground" for 80m. =20 Now - what that charge was is something that Ive been sleeping on. How ab= out 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 volcan= o and daily tremors were felt....Hmm perhaps not so outlandish after all...b= ut I did check again and again after the fact and no charge was present agai= n 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"=20= in pfs for 80m of RG213 aint that large and nothing like capable under norma= l circumstances to give such a wallop. Yes it could charge to many Kv I supp= ose 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=20= away (!) but what mechanism would cause the inner to get a gradient again th= e outer,,,,? =20 As I said before, apart for the Whiz Bangs in the deserts of whereever you= really 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 th= at its safe - even one that could normally not have a Pd across it, or is si= tting 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= similar story about working on 3-phase underground cables. You disconnect b= oth ends, then before you touch them you short each phase to earth. Rarely w= ill you have happened to disconnect at the zero-volts part of the cycle, so=20= apparently you get some satisfying bangs. >=20 > But that may not completely explain your recent experience. One would gu= ess that (a) you turned off the Tx before unplugging the aerial and (b) the=20= Tx has a DC path across the aerial socket (e.g a transfo secondary). So did=20= some other process charge up your cable? >=20 > Your experience might suggest that, for those who fiddle with their aeri= als frequently, it might be worth permanently fitting a resistor (100k, say)= across 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. Check= it out.=20 ------=_NextPart_000_0009_01C9BE68.18BD86C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Electrically charged volcanic ash in a 'cloud' above= the=20 antenna? Have observed some pretty impressive flashovers=20 with thunderstorms passing overhead.
 
Charged ash particles descending on the antenna? Sno= w,=20 rain and wind static can make a pretty impressive showing...although no= t=20 like the passing thunderstorm. 
 
Jay
----- Original Message -----
Laurence BY3A-KL1X China=20
Sent: Thursday, April 16, 2009 7:19= =20 AM
Subject: LF: Arcs and sparks - user= =20 beware too

Chris - thanks
 
Yes it was very odd and one of=20 those "what?" times in my professional and ham career when you really want= to=20 check and recheck.
 
The cable was short circuited DC wise= at=20 the antennae end via the (working) Balun  at the time it was unscrewe= d=20 from the coax - I checked this afterwards in case it wasnt. I checked the=20 TX/RX side too - nothing there.
 
So the time the coa= x=20 had to charge was only the time from disconnection to "touching" which was= =20 appx 5 mins. And remember the coax cable was defacto sitting on the "groun= d"=20 for 80m.
 
Now  - what that charge was is something that I= ve=20 been sleeping on. How about a curved ball and seismic activity beneath whe= re I=20 was staying caused by rock movement and the piezo affect caused a field to= be=20 generated etc? - ok outlandish, but I was sitting at a base of an active a= nd=20 smouldering volcano and daily tremors were felt....Hmm perhaps not so=20 outlandish after all...but I did check again and again after the fact and=20= no=20 charge was present again until we shoved it all back up in the air again a= few=20 hours later.
 
However, logically (probably wrongly too given m= y=20 luck) the amount of "c" in pfs for 80m of RG213 aint that large=20= and=20 nothing like capable under normal circumstances to give such a wallop. Yes= it=20 could charge to many Kv I suppose before it reached it breakdown Voltage -= and=20 it is a few, but wallop and (White) flash and bang was audible and=20 visible in daylight about 50 metres away (!) but what mechanism would caus= e=20 the inner to get a gradient again the outer,,,,?
 
As I sa= id=20 before, apart for the Whiz Bangs in the deserts of whereever you= =20 really wouldnt think a cable could do that - but it did.
 
I=20 learnt a lesson - never, ever presume because a cable is open=20 circuit that its safe - even one that could normally not have a Pd ac= ross=20 it, or is sitting on the ground.
 
I seem to remember SIDE - Sw= itch=20 Off, Isolate, Dump and Earth.
 
Chaps -  any more suggesti= ons=20 or solutions or was this an enigma?
 
73 Laurence=20
 
> From: C.Trayner@leeds.ac.uk
> To:=20 rsgb_lf_group@blacksheep.org
> Date: Thu, 16 Apr 2009 10:07:17=20 +0100
> Subject: LF: RE: Arcs and sparks - user beware
>
&= gt;=20 Dear Laurence,
>
> Thanks for your post.
> > (Its go= t a=20 bit of MF in it honest)
> Whether it has or not, it could save one=20= of=20 our lives some day!
>
> A friend who worked for the London=20 Electricity Board years ago told me a similar story about working on 3-pha= se=20 underground cables. You disconnect both ends, then before you touch them y= ou=20 short each phase to earth. Rarely will you have happened to disconnect at=20= the=20 zero-volts part of the cycle, so apparently you get some satisfying=20 bangs.
>
> But that may not completely explain your recent=20 experience. One would guess that (a) you turned off the Tx before unpluggi= ng=20 the aerial and (b) the Tx has a DC path across the aerial socket (e.g a=20 transfo secondary). So did some other process charge up your cable?
>= ;=20
> Your experience might suggest that, for those who fiddle with the= ir=20 aerials frequently, it might be worth permanently fitting a resistor (100k= ,=20 say) across the two halves; or two, one from each pole to earth.
>=20
>
> 73,
> Chris G4OKW
>
>
>
Rediscover Hotmail=AE: Get quick friend updates right in your inbox. Check it out.
<= /BODY> ------=_NextPart_000_0009_01C9BE68.18BD86C0--