Return-Path: Received: (qmail 12480 invoked from network); 20 Jun 2001 09:52:02 -0000 Received: from unknown (HELO warrior-inbound.servers.plus.net) (212.159.14.227) by excalibur-qfe1-smtp-plusnet.harl.plus.net with SMTP; 20 Jun 2001 09:52:02 -0000 Received: (qmail 22751 invoked from network); 20 Jun 2001 09:51:51 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by warrior with SMTP; 20 Jun 2001 09:51:51 -0000 Content-Transfer-Encoding: 8bit Received: from majordom by post.thorcom.com with local (Exim 3.16 #2) id 15CeYb-00054X-00 for rsgb_lf_group-outgoing@blacksheep.org; Wed, 20 Jun 2001 10:45:53 +0100 Received: from bob.dera.gov.uk ([192.5.29.90]) by post.thorcom.com with esmtp (Exim 3.16 #2) id 15CeYZ-00054S-00 for rsgb_lf_group@blacksheep.org; Wed, 20 Jun 2001 10:45:52 +0100 X-Priority: 3 X-MSMail-Priority: Normal Received: by bob.dera.gov.uk; (8.8.8/1.3/10May95) id KAA22413; Wed, 20 Jun 2001 10:50:08 +0100 (BST) Received: (qmail 21433 invoked from network); 20 Jun 2001 10:38:14 -0000 Received: from gauntlet.mail.dera.gov.uk (172.16.9.10) by baton.dera.gov.uk with SMTP; 20 Jun 2001 10:38:14 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: by gauntlet.mail.dera.gov.uk; id KAA14224; Wed, 20 Jun 2001 10:29:18 GMT Received: from unknown(10.71.64.31) by gauntlet.mail.dera.gov.uk via smap (3.2) id xma014125; Wed, 20 Jun 01 10:28:42 GMT Received: from mailex.dera.gov.uk (unverified) by mailguard.dera.gov.uk (Content Technologies SMTPRS 4.1.5) with SMTP id for ; Wed, 20 Jun 2001 10:53:53 +0100 Received: (qmail 27044 invoked from network); 20 Jun 2001 09:34:53 +0100 Received: from softdnserror (HELO cchecker.dstl.gov.uk) (192.168.248.52) by mailex.dstl.gov.uk with SMTP; 20 Jun 2001 08:34:53 -0000 Received: from FRN-MAIL-R1.dstl.gov.uk (unverified) by cchecker.dstl.gov.uk (Content Technologies SMTPRS 4.1.2) with ESMTP id for ; Wed, 20 Jun 2001 09:35:14 +0100 Received: by frn-mail-r1.dstl.gov.uk with Internet Mail Service (5.5.2650.21) id ; Wed, 20 Jun 2001 10:43:57 +0100 Message-ID: <7D653C9C42F5D411A27C00508BF8803D55C4FA@pdw-mail-r1.dstl.gov.uk> From: "Talbot Andrew" To: rsgb_lf_group@blacksheep.org Subject: RE: LF: Re: Static effects Date: Wed, 20 Jun 2001 10:43:58 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2650.21) Content-Type: text/plain; charset=iso-8859-1; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: But much better still a bleed choke, making sure the inductance is high enough not to affect the matching. A good choke would be made from a ferrite core and as it is not carrying any power a smaller core can be used than would be the case for a matching transformer. Make sure there are enough turns to not saturate the ferrite with the highest RF voltage present. Saturation was almost certainly the case in an earlier posting where a choke 'got hot'. Use the formula Vrms = 4.44.F.N.A.B to calculate the Minimum turns needed on any given core, using a B of around 0.1 Tesla for a good safety margin. All non-gapped ferrites designed for SMPSU transformers will have more than enough inductance - up in the tens to hundreds of milli-henries - when wound with enough turns to satisfy this equation. Andy G4JNT > -----Original Message----- > From: Tom Boucher [mailto:tom@telemetry.demon.co.uk] > Sent: 2001-06-20 08:40 > To: rsgb_lf_group@blacksheep.org > Subject: Re: LF: Re: Static effects > > > > Dave G3YMC wrote: > > > >If you feed your antenna, as many do, via a matching > transformer (3C85 core) > >then the > >antenna and the line to the tx/rx will be automatically > grounded. Another > >advantage > >of this method of feeding antennas. > > Well I do Dave but I have rather an odd T/R relay arrangement based on > single pole on/off relays which I had available. This means > that when Tx > supply is switched off, the antenna is connected to neither > transmitter > nor receiver. > > I didn't fit a bleed resistor as Andy suggests because I figured it > would have to dissipate a fair bit of power unless it was a > high value, > however even a high value will be adequate to discharge any > build up of > static, I guess. > > 73, Tom > -- The Information contained in this E-Mail and any subsequent correspondence is private and is intended solely for the intended recipient(s). For those other than the recipient any disclosure, copying, distribution, or any action taken or omitted to be taken in reliance on such information is prohibited and may be unlawful.