Path: ...!2.eu.feeder.erje.net!3.eu.feeder.erje.net!feeder.erje.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Don Y Newsgroups: sci.electronics.design Subject: Re: Dressing RG6 Date: Tue, 14 May 2024 19:51:38 -0700 Organization: A noiseless patient Spider Lines: 64 Message-ID: References: <20240514b@crcomp.net> <66h74j1vfmbjvvl98jk1k017pimtinv2l5@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Wed, 15 May 2024 04:51:45 +0200 (CEST) Injection-Info: dont-email.me; posting-host="78f075c53cdcb0cf9fbdb6abd4df5c62"; logging-data="686820"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+fMc4q5LS21Hr3RFc+A2P6" User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Cancel-Lock: sha1:UyIHyId8EZcK6EscFwRYoaIQywk= Content-Language: en-US In-Reply-To: Bytes: 4193 On 5/14/2024 3:08 PM, Jeroen Belleman wrote: > I've been putting coax inside copper tubes or braids to measure > and/or reduce the transfer impedance (leakage). I did that to > measure small signals in a particle accelerator, which typically > has kicker magnets and RF cavities with kA currents and kV > voltages nearby. But you likely weren't ALSO relying on the tubing for it's mechanical characteristics? I see no real electrical issues -- a copper pipe is just a third (for RG6U) or fifth (for RG6'q') shield layer. But, its (desired!) inflexibility adds other complications to its deployment. - it inherently eliminates any "service loop" so the endpoints are fixed, spatially, wrt each other. So, positioning those points then becomes important along with its constraints on their disconnection! (imagine having two or more such connections between "end devices", potentially orthogonal to each other!) - it transfers any mechanical stresses encountered along its length to the supporting endpoints which likely weren't designed with that sort of "mechanical load" in mind (you're supposed to have a CABLE connected there, not some "cantilevered mass"). A passerby bumping it anywhere along its length poses a risk. - it makes on-site manufacture (by "semi-trained installers) more difficult -- e.g., fabricating the cable *inside* the tubing (few folks are proficient in handling EMT and *that* has much less constraints; how much does the inner cable "shrink" with each bend?) I assume your deployment was "one-off", done by someone skilled in the practice (or, at least able to evaluate the quality of their FINISHED work) and likely isolated from other "traffic"? You likely wouldn't expect some "jamoke" to be able to install it correctly? (dealing with the consumer market is a whole different set of challenges) It's also been suggested that "tubing" may not be rigid enough for my needs -- any impacts might deform it and leave lasting stresses on the connections. I will buy some type K (the thickest wall tubing commonly available, here) and see how much abuse it can take. I've been directed to explore plastic solutions as an alternative. And, technologies that would allow some of the critical dimensions to be avoided in their (on-site) manufacture. Sadly, ENT isn't (?) available in such small diameters... Maybe PVC?? Or, sell "assemblies" which means having to settle on a small number of configurations and expecting the market to adapt to them. :< > A colleague developed a special low transfer impedance coax > cable for this sort of application. It had two screens with > intermediate magnetic shielding. It was unpleasant to work > with, because part of the magnetic shielding was a steel > spiral foil tape that was razor sharp. But it worked really > well.