Coax type best suited for longish RF cables assemblies for N-type or SMA?? - Page 1
Forum section: electronics / rf-microwave

author: dazz1
author_rank: Frequent Contributor
timestamp: April 22, 2018, 08:31:48 am
content: HiI am going to buy a Spec An and I am now looking at cable assemblies.I have decided to standardize on SMA connectors. The obvious exceptions are the SA inputs and the antenna (N-type).It looks like short cable assemblies (<=1m), pre-made from Element14 is the best path.I do not want to buy el-cheapo stuff from ebay because I don't think buying cable sets of dubious quality makes good sense.I need a longer cable or two (5-10m) for pre-compliance testing.The price of longer cable assemblies is high enough to justify buying the tools, cable and connectors for DIY.I want to make up 3 types of cables sets with crimp connectors:SMA to SMA <=5mSMA to N <=5mN to N <=10mIf I buy the tools and parts to make up longish cables, I might as well make the shorter ones as well.My test equipment will not be heavily used.My question is, what coax types are best suited for this type of application??It seems that the hi spec cables (LMR400) are also stiff while the flexible types (RG223) are lossy.In saying that, RG223 looks like a promising candidate. It looks like I can get both N and SMA connectors to fit.Dazz

author: bob225
author_rank: Frequent Contributor
timestamp: April 22, 2018, 08:55:05 am
content: Its swings and roundabouts MIL spec RG58 (M17/28-RG58) is lower loss, slightly lower pf, RG223 has the higher temp rangeThen you can get RG58 double shielded (depending on manufacturer)N-type over a longer run I would use Westflex W103 (depending on freq requirements)iKN.

author: dazz1
author_rank: Frequent Contributor
timestamp: April 22, 2018, 09:14:29 am
content: Quote from: bob225 on April 22, 2018, 08:55:05 amI don't need high temp stuff so RG58 would be OK.Unfortunately Westflex is not available in my part of the world.RG58 double shield is.Dazz

author: garboui
author_rank: Regular Contributor
timestamp: April 22, 2018, 11:17:06 am
content: These guys are a good value. On custom, lead times can be a bit for certain configurations and quantities. I have used these guys for one of's and also for production volumes and they are a good value either way. THe2 connectors are mostly Chinese equivalents (unless you specify) but are not the same junk you would expect from aliexpress.http://www.rfconnector.com/

author: dazz1
author_rank: Frequent Contributor
timestamp: April 22, 2018, 11:21:13 am
content: HiI have found LMR400 UF (stranded conductor) and RG400.Both look better than RG58.Dazz

author: bob225
author_rank: Frequent Contributor
timestamp: April 22, 2018, 11:51:41 am
content: RG58 - LMR200LMR 400 it is then, or maybe Belden 9913 but you need to pay attention to plug fitment

author: ahbushnell
author_rank: Frequent Contributor
timestamp: April 22, 2018, 03:56:13 pm
content: Quote from: dazz1 on April 22, 2018, 08:31:48 amWhat is a Spec An? What frequencies and power do you plan to use?

author: CopperCone
author_rank: Super Contributor
timestamp: April 22, 2018, 05:16:11 pm
content: if you got the money nice VNA cables that are flexible and phase stable.

author: dazz1
author_rank: Frequent Contributor
timestamp: April 22, 2018, 07:48:14 pm
content: Quote from: ahbushnell on April 22, 2018, 03:56:13 pmLocal slang for spectrum analyser.

author: dazz1
author_rank: Frequent Contributor
timestamp: April 22, 2018, 07:53:23 pm
content: Quote from: CopperCone on April 22, 2018, 05:16:11 pmWaaaaaayyyyyy beyond my $$$ limit and frequency range.

author: dazz1
author_rank: Frequent Contributor
timestamp: April 22, 2018, 08:06:38 pm
content: Quote from: bob225 on April 22, 2018, 11:51:41 amFor the benefit of other readers, LMR has a single inner conductor. LMR200 UF is multi-strand and therefore more flexible.RG400 (multi-strand inner) seems to be commonly used on aircraft.

author: tautech
author_rank: Super Contributor
timestamp: April 22, 2018, 08:07:42 pm
content: If you're still looking at the Siglent Dazz they do some cables as 'one offs' and I'm thinking their 700mm N-SMA cable could suit your needs for directional work close to the SA.https://www.siglentamerica.com/accessory/n-sma-6l/The one's I have use a different coax than the one pictured however they're all characterized to 6GHz.'Not' un-affordable at $49 USD.

author: dazz1
author_rank: Frequent Contributor
timestamp: April 23, 2018, 12:48:21 am
content: Quote from: tautech on April 22, 2018, 08:07:42 pmShort test cables are plentiful and reasonably priced. It is cheaper to buy an assembly than the component parts.It's the long ones that cost enough to justify buying the tools, cable and connectors to DIY.My plan is to buy all the relatively cheap accessories before buying the expensive Siglent SA. I can't do anything meaningful without the accessories so no point in having expensive equipment on the bench doing nothing.RG400 from reputable suppliers is expensive but still within reach. I am going to go down this path because at least I will know the test cable isn't the weakest link. There is nothing to be gained by going cheap on test cables.

author: David Hess
author_rank: Super Contributor
timestamp: April 23, 2018, 04:03:59 pm
content: Quote from: dazz1 on April 22, 2018, 11:21:13 amQuote from: dazz1 on April 22, 2018, 08:06:38 pmQuote from: dazz1 on April 23, 2018, 12:48:21 amAfter some experiences with contaminated and damaged cables, I switched to using RG400 for exposed antenna feeds and for patch cables and I really like it. RG142 is the solid center conductor version of RG400 and might be less expensive.I also like Teflon cables for direct attachment because soldering does not melt the dielectric unlike polyethylene but there I am more likely to use the RG174 equivalent RG316. For some reason I have an entire spool of the even smaller Teflon RG178 but it is inconveniently small.