Quality test cable - RG58 alternative - Page 1
Forum section: electronics / testgear

author: DeepLink
author_rank: Regular Contributor
timestamp: May 10, 2021, 01:07:55 pm
content: Looking for a replacement for my normal RG58 bench test cables, but with better data (insertion loss, screening, i.e.)Mainly used with BNC or N type connector and up to 3GHz, between signal generator, power meter, spectrum analyzer and DUT'sWould like to keep roughly the same diameter, flexibilityWhat cable would be a good alternative?

author: ocw
author_rank: Regular Contributor
timestamp: May 10, 2021, 02:00:36 pm
content: I recommend an upgrade to RG142.

author: tautech
author_rank: Super Contributor
timestamp: May 10, 2021, 02:07:58 pm
content: Have you looked at Siglents's offerings ?Scroll down to Optional Accessories here:https://www.siglenteu.com/spectrum-analyzers/ssa3000x-plus/Their very nice 18 GHz cables are 2 or 300 Euros but the 6 GHz series are a more reasonable at ~50 or a little more.All come with characterization sheets and most are made by Rosenberger.Early 6 GHz knurled nut ones weren't but the later Hex nut ones and certainly the 18 GHz ones are definitely Rosenberger.

author: tkamiya
author_rank: Super Contributor
timestamp: May 10, 2021, 05:19:11 pm
content: I'd go with TimesMicrowave branded cables. From your description, I'd go with LMR-195. Be sure to get quality connectors!

author: David Hess
author_rank: Super Contributor
timestamp: May 11, 2021, 03:34:09 am
content: At a minimum, RG223 which is double shielded RG58 will provide a considerable improvement in leakage and the double shielding allows the connectors to hang on better.I really like RG400 which is RG58 sized, Teflon insulated, stranded, and double shielded for patch cables. RG142 is the solid version.

author: DeepLink
author_rank: Regular Contributor
timestamp: May 11, 2021, 01:55:29 pm
content: Thank you for the reply'sI go for LMR-195 (from Koax24.de)Better specs than RG142 and cheaperAnother plus - same connectors as for RG58 (which I have from H+S)

author: David Hess
author_rank: Super Contributor
timestamp: May 11, 2021, 05:38:19 pm
content: I would not even consider LMR-195 for test cable unless it would only get little mechanical use which is the kind of applications they recommend for it. Foamed polyethylene is lower loss and flexible but tends to creep allowing the center conductor to shift, especially if it is solid rather than stranded. It is also more difficult to solder and subject to contamination but that does not matter in a test environment. Foil shields tend to crimp when flexed.

author: xmo
author_rank: Regular Contributor
timestamp: May 11, 2021, 06:14:41 pm
content: A few comments:RG142 is excellent but has a solid center conductor. which can be an issue for cables that are constantly flexed.RG400 is basically the same as RG142 but has a stranded center conductorBoth RG142 and RG400 are Teflon and somewhat stiff (they don't like to bend)Huber + Suhner make an RG142 compatible cable that seems a little more flexible and has a black jacket.I like Belden 9222 for making test cables. It is supple and being tri-ax, has two shields. Also, the yellow color says: "I am a test cable" The loss is the same as RG58For more critical applications, consider Huber + Suhner Sucoflex and Sucotest

author: vutt
author_rank: Contributor
timestamp: May 11, 2021, 06:20:39 pm
content: What about RG316 for your 50 ohm bench needs.Shiny and flexible..

author: David Hess
author_rank: Super Contributor
timestamp: May 11, 2021, 06:27:11 pm
content: Quote from: xmo on May 11, 2021, 06:14:41 pmThey are definitely stiffer than RG58. I do not have any RG223 to compare them to. Even so I like the Teflon because it is much easier to solder to and I like the double braid shielding because it makes for a much stronger connection at the connector.When I make patch cables for my workbench, I make them in lengths of whole number nanoseconds.I used to use RG8X (stranded center conductor, foamed PE, and single braid shield) which is much more flexible than even RG58 despite its larger diameter, but I had too many reliability problems with it and the leakage through the single shield eventually became unacceptable.

author: David Hess
author_rank: Super Contributor
timestamp: May 11, 2021, 06:33:59 pm
content: Quote from: vutt on May 11, 2021, 06:20:39 pmI have a couple spools of it. RG316 is great except of course that it leaks much more due to its single braided shield, so it is not suitable for sensitive RF applications. I use RG316 for BNC patch cables where I need the extra flexibly, and for SMB patch cables. You can sometimes find RG179 which is the 75 ohm version for cheap in surplus video equipment.If you like RG316, then try the even smaller RG178, although it is actually difficult to work with because of its diminutive size. I am going to use RG178 to make shielded Kelvin clips today for my DE-5000, but only because I have a spool of it and it is easier to solder than RG174 which tends to melt.

author: nctnico
author_rank: Super Contributor
timestamp: May 11, 2021, 08:06:01 pm
content: Quote from: vutt on May 11, 2021, 06:20:39 pmI agree with that. I just threw all the RG58 cables out. Way too thick and stiff for general purpose bench use. RG316 and RG58 are pretty lossy at 3GHz anyway so for high frequency stuff I have a couple of huber+suhner cables. For anything else mostly RG316

author: ocw
author_rank: Regular Contributor
timestamp: May 11, 2021, 09:13:29 pm
content: While I still have some Belden 9222 cables in use, its attenuation on the higher frequencies makes me want to hide them. It is still good for the lower frequencies.Quality RG142 (like H&S) is flexible and has the same minimum bend radius as RG400. You just do not want to repeatedly come any where close to that figure (5 cm).For new test cables I have lately been using SF142. It has a lower minimum bend radius (2.54cm) and everything else is better than that in the other mentioned cables. See:https://www.timesmicrowave.com/DataSheets/Categories/StripFlex.pdfBut, it can be harder to find and higher priced. It has its own unusual color to stand out.

author: YetAnotherTechie
author_rank: Regular Contributor
timestamp: May 11, 2021, 11:14:52 pm
content: wow, both rg316 and SF142 have steel braids, and still they cost >8€ per meter?!

author: ocw
author_rank: Regular Contributor
timestamp: May 11, 2021, 11:26:48 pm
content: QuoteYou left out that the RF conductive metal for SF142 is the silver plating. It is not the cable to use for DC where the steel center will matter.

author: tautech
author_rank: Super Contributor
timestamp: May 11, 2021, 11:43:26 pm
content: Dropping this old chart found useful over the years.