Return-Path: Received: (qmail 7155 invoked from network); 24 Jan 2001 13:36:40 -0000 Received: from unknown (HELO warrior-inbound.servers.plus.net) (212.159.14.227) by excalibur.plus.net with SMTP; 24 Jan 2001 13:36:40 -0000 Received: (qmail 17591 invoked from network); 24 Jan 2001 13:30:55 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by warrior with SMTP; 24 Jan 2001 13:30:55 -0000 Content-Transfer-Encoding: 8bit Received: from majordom by post.thorcom.com with local (Exim 3.16 #1) id 14LPte-000794-00 for rsgb_lf_group-outgoing@blacksheep.org; Wed, 24 Jan 2001 13:23:34 +0000 Received: from bob.dera.gov.uk ([192.5.29.90]) by post.thorcom.com with esmtp (Exim 3.16 #1) id 14LPtd-00078z-00 for rsgb_lf_group@blacksheep.org; Wed, 24 Jan 2001 13:23:33 +0000 X-Priority: 3 X-MSMail-Priority: Normal Received: by bob.dera.gov.uk; (8.8.8/1.3/10May95) id NAA21688; Wed, 24 Jan 2001 13:24:49 GMT Received: (qmail 1815 invoked from network); 24 Jan 2001 14:16:56 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from gauntlet.mail.dera.gov.uk (172.16.9.10) by baton.dera.gov.uk with SMTP; 24 Jan 2001 14:16:56 -0000 Received: by gauntlet.mail.dera.gov.uk; id OAA24133; Wed, 24 Jan 2001 14:08:15 GMT Received: from unknown(10.71.64.31) by gauntlet.mail.dera.gov.uk via smap (3.2) id xma024074; Wed, 24 Jan 01 14:07:46 GMT Received: from FRN-MAIL-3.dera.gov.uk (unverified) by mailguard.dera.gov.uk (Content Technologies SMTPRS 4.1.5) with ESMTP id for ; Wed, 24 Jan 2001 13:26:12 +0000 Received: by frn-mail-3.dera.gov.uk with Internet Mail Service (5.5.2650.21) id ; Wed, 24 Jan 2001 13:22:38 -0000 Message-ID: <65AECDF1F89AD411900400508BFC869F0D7553@pdw-mail-1.dera.gov.uk> From: "Talbot Andrew" To: rsgb_lf_group@blacksheep.org Subject: RE: LF: Testing LF losses in materials Date: Wed, 24 Jan 2001 13:22:55 -0000 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: That sounds more like a mismatch issue than dielectric loss. Standard PVC tape has a dielectric constant (Er) about the same as the polyethylene insulator in the cable. So as your joint must have increased the diameter of the inner conductor, its Zo will have reduced and given you a small section of mismatched line at 50cm (cable) wavelength. However, as the foamed is part air the resultant lower Er would partly compensate for the increased conductor diameter. Mind you, PVC is a lot more lossy than polyethylene so still some element of real loss in this. Andy G4JNT > I used to use plastic sticky tape (any colour) to insulate > between inner > and outer of RG-213 coax cable where I'd joined it (typical > amateur using > odd lengths!) . Then I found I was losing 1-2 dB at each > joint at 70 cms so > abandoned it and used foamed polyethylene instead which is > fine. Don't > know if there are different types of plastic tape with > different RF properties. > > Walter G3JKV. > > > > > -- 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.