Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Phil Hobbs Newsgroups: sci.electronics.design Subject: Re: Dressing RG6 Date: Tue, 14 May 2024 23:49:45 -0000 (UTC) Organization: A noiseless patient Spider Lines: 78 Message-ID: References: <20240514b@crcomp.net> <66h74j1vfmbjvvl98jk1k017pimtinv2l5@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Wed, 15 May 2024 01:49:45 +0200 (CEST) Injection-Info: dont-email.me; posting-host="e35e65d3ec3cdb78d3dcb2e3cf71832b"; logging-data="495455"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/lv53/lrAdODOQhnOWo2Ts" User-Agent: NewsTap/5.5 (iPhone/iPod Touch) Cancel-Lock: sha1:vU+rROJpaeGQZsQGZwcr40BuK3k= sha1:btY9uxCVoI5VHASWJNpap7pCreY= Bytes: 3820 Jeroen Belleman wrote: > On 5/14/24 23:46, Phil Hobbs wrote: >> John Larkin wrote: >>> On Tue, 14 May 2024 19:22:12 -0000 (UTC), "Don" wrote: >>> >>>> Phil Hobbs wrote: >>>>> Phil Hobbs wrote: >>>>>> Don Y wrote: >>>>>>> I've several short (a few feet) lengths of RG6 that I >>>>>>> would like to "strongly coerce" into assuming a particular >>>>>>> dressing. >>>>>>> >>>>>>> Securing the cables to a stationary surface isn't practical >>>>>>> without significantly lengthening them and distorting >>>>>>> their "natural" routing. >>>>>>> >>>>>>> But, ISTM that I should be able to slip each cable into >>>>>>> a comparable diameter copper (?) pipe and then use traditional >>>>>>> tools to bend that pipe into the appropriate configuration. >>>>>>> I'd have to observe constraints like minimum bend radius >>>>>>> but are there other issues that I might "discover" down the >>>>>>> road? >>>>>>> >>>>>>> >>>>>> >>>>>> You’re planning to make a random- length shotgun balun. >>>>> >>>>> Bazooka balun. >>>> >>>> The parasitic capacitance created between coax and its metal armor can >>>> open a Pandora's box of potential problems. >>>> >>>> Danke, >>> >>> Capacitance between the coax outer and the copper pipe? Proper coax >>> shouldn't have any external field. >>> >>> >> >> If the whole system is really coaxial, that’s true. Leaky shields, ground >> loops, and so on, will modify that. >> >> Depending on the application, you may or may not care. >> >> Cheers >> >> Phil Hobbs >> > > 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. > > 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. > > Jeroen Belleman > Interesting, thanks. Is that better than real solid copper hardline or (my fave) RG402 semi-hardline? I’d like to read more about it, if you have a reference handy. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics