cable brand and type for lab BNC cables 50 ohm? - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: June 09, 2021, 04:33:16 am
content: I am wondering since its been a while, whats good BNC cables for hookup for things like function generators, etc, with a focus on flexibility, durability and stability on a reduced frequency range. I would not mind getting the full performance at 4GHz but I mean for things like DDS systems, audio generators, and so forth, where there is good shielding, good flexibility, etc. I will say around 1GHz max but lower if necessary to get the other good attributes.I wanted to buy HP cables at first but I am thinking I should make my own. I have had a crap shoot when it comes to stuff I actually like, because I can look at specifications all day but I want something thats good in the lab, thats only going to come from someone that works alot.I know this thread is around kinda in some form in some places but it does not hurt to 'renew' this topic to discuss recent findings on durability and performance.My favorite thus far is old HP/Agilent BNC cables

author: DeepLink
author_rank: Regular Contributor
timestamp: June 09, 2021, 07:27:32 am
content: I had the same problem a while ago and asked the experts herehttps://www.eevblog.com/forum/testgear/quality-test-cable-rg58-alternative/msg3566595/?topicseen#msg3566595I wanted something better than RG58, as I starting to play with LNA and noise figure measurementsI decided to stay clear of solid inner conductor and foam dielectric, due to reliability on the test benchEnded up with "arnoflex 58 LSNH" from koax24.deSame dimensions as RG58, so I could use my stock of crimp connectors (quality H&S)Slightly lower loss, but useable to 3GhzMost important a lot better screen - minimum 30dB better than standard RG58Finally I got taper sleeves in Blue, so I could distinguish them from my normal RG58, which are Black or Red

author: HB9EVI
author_rank: Frequent Contributor
timestamp: June 09, 2021, 12:26:12 pm
content: if flexible and less loss than RG58 is a matter, I'd go for the H155; somehow, personally, everything thicker than a RG58 seems to me very unhandy in a lab environment

author: David Hess
author_rank: Super Contributor
timestamp: June 09, 2021, 07:18:13 pm
content: For RF, double shielded cables or better are needed for sensitivity measurements which will otherwise be corrupted by leakage through the cable shields. But I also like double braided shielded cables despite their extra stiffness because the connectors are more firmly attached making them more reliable.Another consideration is that cables with Teflon dielectric are much easier to solder without damage, which may be important in some applications and if you need to solder the center connector pin.So for low frequency non-RF applications, I like 0.1" diameter RG-316 for its extra flexibility and ease of soldering. Where low leakage through the cable shield is important, I prefer RG-223 (solid PE), RG-142 (solid Teflon), and especially RG-400 (stranded Teflon), for their ruggedness and low leakage despite their extra stiffness from having a double shield.

author: coppercone2
author_rank: Super Contributor
timestamp: June 09, 2021, 08:07:03 pm
content: do you have any preference on manufacturer? how about the outside coating?I am thinking maybe there is some reliability factors and maybe flexibility that come in from quality extrusion (i.e. better maintained dies and stuff). kind of hard to imagine but I would like to know if anyone noticed anything

author: David Hess
author_rank: Super Contributor
timestamp: June 09, 2021, 11:11:40 pm
content: I prefer to make my own cables, but I am sure someone else here can comment about who to buy completed cables from.

author: coppercone2
author_rank: Super Contributor
timestamp: June 10, 2021, 01:19:54 am
content: I mean, the cable manufacturer, like seller of the unterminated cable, not the terminated cables. I don't mean the connector splice job I mean how they put together the actual cable wire, braid, etc. It has some kind of specification but I am sure it depends on who made it

author: cdev
author_rank: Super Contributor
timestamp: June 10, 2021, 05:07:26 pm
content: If you use a lot of them it rapidly gets too insanely expensive (for me) buying them pre-made. Maybe if your employer has a policy of only using hugely pricey cables on their hugely expensive test equipment, but even if I have to remake them several times until I get it right I would rather do that, since I have a VNA now I resolved to always make my own cables. (and test them) Now I have no excuse for not doing so.Because you then have instant feedback what works you get better at making them yourself pretty rapidly.Pick a brand of the raw cable to buy and stick to it sounds like a good plan. Avoiding foam dielectric is easy, just watch what happens to the inner insulator when you solder to the outside braid. Foam basically liquefies and its volume reduces by 95%, so - guaranteed mismatch.Thanks for the tip about double shielded cable. I also need to get a bunch in a RG58 size 52 or 50 ohm cable for patch cables and stubs with low loss.

author: coppercone2
author_rank: Super Contributor
timestamp: June 10, 2021, 07:53:31 pm
content: I am curious about the cable parameters as related to extruders, some people might maintain their extruder dies and wire tension equipment better then others, perhaps resulting in more mechanical stability, or better surface finish, so it might like bend better.. there is also foil surface finish quality to think about as it rubs on the braid, the quality of the braid weave (uniformity), how much it was handled, and so forth. more precise temperature control might make more settled dielectric too which has more stable electrical parameters over time, and there is feedstock quality.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 10, 2021, 09:50:41 pm
content: What about using RG 223 double braid, silver plated?Apparently this was the popular in the past for test leads.

author: coppercone2
author_rank: Super Contributor
timestamp: June 29, 2021, 01:56:24 am
content: I will try RG400 because it looks like the best one, maybe not 100% for flexibility but its irresistible otherwise

author: cdev
author_rank: Super Contributor
timestamp: June 30, 2021, 01:19:20 pm
content: LMR400 is very low loss, even above 4 GHz, but its so inflexible that it's a pain to do anything that needs to be moved with it. I have some N connectored patch cables made with LMR400 that feel like a policeman's truncheon for subduing difficult subjects. They are heavy and difficult to bend much at all.I keep s bit of it around but I try to use something thinner if I can. Certain kinds of applications really deserve it and nothing else, though.Far UHF anything really hates thin coax. Luckily I got my start using the thick cable so I noticed the difference when I tried to use RG-316 or RG-174 pretty fast.Lmr-200 is a good all around 50 ohm cable for almost everything. Much thinner than LMR-400 and also fairly flexible. And affordable.Quote from: coppercone2 on June 29, 2021, 01:56:24 amIt's a PITA to work with.

author: David Hess
author_rank: Super Contributor
timestamp: June 30, 2021, 02:36:45 pm
content: The problem with LMR cables besides melting is that the aluminum tape shield does not withstand the flexing required of a patch cable.

author: coppercone2
author_rank: Super Contributor
timestamp: June 30, 2021, 07:49:37 pm
content: the other problem is that its aluminum inside and not copperI thought RG400 might be ok since it was listed as 'stranded teflon' in the post, I figure it has better flexibility then solid teflon, but harder to mess up then foam

author: David Hess
author_rank: Super Contributor
timestamp: July 01, 2021, 02:32:31 am
content: Quote from: coppercone2 on June 30, 2021, 07:49:37 pmThe center conductor is stranded but the Teflon dielectric is solid. The big advantage of the Teflon dielectric, besides being non-contaminating, is that soldering will not melt it.RG-400 is pretty stiff and it does take some care to attach the center pin to the stranded center conductor. The solid center conductor version, RG-142, may actually be easier to use.

author: coppercone2
author_rank: Super Contributor
timestamp: July 01, 2021, 04:28:28 am
content: I have the pace resistance soldering tweezers which have so far made dealing with any kind of barrels much easierwell its not the end of the world because I only spent like $35, i think it will work for rack interconnects, I can free up the HP and other cables that I already have anyway before upgrading to something more flexible for benchtop use

author: coppercone2
author_rank: Super Contributor
timestamp: July 03, 2021, 09:18:20 pm
content: ok, whats a runner up cable. I got the rg400 and it reminds me of fighting some kind of alien but its not a loss because the back end is going to be improved (rack interconnects) and its going to free up alot of cables, great quality thoughI had a few test boxes and such that benefit from it heavily and need the shielding but I still need something for human handlingI cut a few lenghts and stripped some and my hands hurt to be honest, better then LM400 but I still need some spaghettiFor the dielectric, whats the softness range?Solid teflon + stranded is kinda OK but pretty hardIs there foam teflon?https://fluorogistx.com/products/teflon-ffr/

author: coppercone2
author_rank: Super Contributor
timestamp: July 04, 2021, 01:56:15 am
content: no kidding about that stranded wire being hard to solder on the center pin if you want to do it right, even with the tweezers its messy, as soon as you tin it it does not fit, so its better to melt a full bore of flux core solder in the tip with resistance tweezers, let it cool down, put the flux dipped wire inside while its being heated with the tweezers and then pull it out 1/2 way and add a dash of solder then recap it.. the barrel sometimes gets a little dirty but it seems to work okMaybe if you cut it extra long and twist it good it might work better, but doing it according to the instructions is hard

author: coppercone2
author_rank: Super Contributor
timestamp: July 05, 2021, 01:48:08 am
content: so the cables work well, and it does a good job on my setup, I think I will look in to the 0.1 inch cables now and make some more rg400 cables (made 6 , ran out of connectors, 5x3' 2x9'), probobly need alot moreBut I did notice the rg400 compatible plug is a little lose (amphenol), the cable has a bit of slack in the hole on the back of the connector. I thought to shove maybe some kind of shim in there.. is this a good idea? Maybe thin rubber ? Probably not a big deal but a little annoyingnot sure if I should try to shove something in there

author: David Hess
author_rank: Super Contributor
timestamp: July 05, 2021, 03:12:42 am
content: Quote from: coppercone2 on July 03, 2021, 09:18:20 pmI am not sure what you are doing but I never found it difficult. I use a razor blade for cutting the jacket and dielectric and both slide right off.Quote from: coppercone2 on July 04, 2021, 01:56:15 amThe only problem I had was that the stranded center conductor was usually slightly too thick to fit inside of the connector pins, so I had to remove some strands.

author: coppercone2
author_rank: Super Contributor
timestamp: July 05, 2021, 04:30:17 am
content: yeah its very tight, when you set it you need to heat the connector in tweezers with thermal contact between the wire and connector for it to melt so the strands can slide in, very tricky, but if you 1/2 fill the barrel, melt it, slide a flux covered wire in there to wick up the solder while in the barrel, then slide it out half way and feed more solder and reinsert it, it works reliably, but you need to be quick with the foot pedal to keep the flux from being used up, a micro applicator needle helps to reflux the part taken out of the barrel after initial melt, then get solder ready so you can quickly heat and feed then release heat and cool.. would not want to try this with a iron.. after I melt solder in the barrel no matter how careful I am I can't get the strands to go in there unless the solder is molten, there must be a thin coating on the wall just enough to prevent it from going inThe stripping works fine with a cable strip tool, if you cut wires out it becomes easy, the hard part is the one you mentioned, you just need to carefully try it on a few pieces to get the correct blade depth, you can hear the blade of the stripper break through then yank it offI should have put heat shrink on there to thicken the wire up to the hole a little before I assembled all of them but I did not think of it for some reasonI can still put some electronics silicone in there with a syringe I supposeI hate trimming off strands to make wires fit, so jankyKinda think a indent crimper might work there too.. the barrel seems very thick but the fit is so good that crimping might work. have you ever tried a 4 indent crimp on a center pin meant to be soldered? it does not have a spec but I thought to do it and then do a tug test by hanging weights off a pin vise connected to the crimp, but I don't want to waste a connector.. I just bought ALOT so maybe I will try one since there will be connectors to spareIf anyone wants to think of settings to use on a 4 indent crimper with a linear adjustment for diameter on a Amphenol 31-202 then let me know, I 'restored' one of those tools a few months back but have yet to crimp anything with it, or at least tell me if its potentially destructive since the wall is too thick

author: coppercone2
author_rank: Super Contributor
timestamp: July 08, 2021, 06:04:48 am
content: made 12 cables by now, got ok at soldering the center pin on

author: David Hess
author_rank: Super Contributor
timestamp: July 08, 2021, 04:53:38 pm
content: Quote from: coppercone2 on July 05, 2021, 04:30:17 amI never liked having to trim strands off of the center connector either. When I use RG-400 with N-connectors, it has not been a problem.RG-142 which it otherwise identical but with a solid center conductor might be better for use with BNC connectors.

author: coppercone2
author_rank: Super Contributor
timestamp: July 08, 2021, 07:58:30 pm
content: do they have 0.1 inch teflon stranded double insulated cable?I don't see one on the master list

author: David Hess
author_rank: Super Contributor
timestamp: July 08, 2021, 11:15:59 pm
content: Quote from: coppercone2 on July 08, 2021, 07:58:30 pmApparently double shielded RG-316 with a slightly larger diameter does exist but it is exotic enough that I have never seen it. I expect that if you have to ask the price, then you cannot afford it.There is also LMR-100A which is foil and braid shielded solid polyethylene 0.1" cable. I do not particularly like foil shielded cables for patch cable applications where they will be repeatedly flexed but might make an exception in this case.

author: coppercone2
author_rank: Super Contributor
timestamp: July 08, 2021, 11:37:31 pm
content: https://www.shireeninc.com/osc/rg316ds-by-the-ft

author: coppercone2
author_rank: Super Contributor
timestamp: July 09, 2021, 05:12:24 am
content: 4 of the cables turned out to have short circuits, I thought I assembled them perfectly. what a bastardshould just have bought this shit, at this rate I will be not saving any moneywhen you make it hook it up to a function generator at high speed then wiggle the cable around looking at the scope to see if it fucks up

author: coppercone2
author_rank: Super Contributor
timestamp: July 10, 2021, 12:54:59 am
content: I think a strand of shield got under the dielectric tear because some cuts were not performed well. Teflon has a plastic bag effect (it kinds of like dough and deforms) I recommend an illuminating magnifier because if this happens then you won't see the reflection twirling it under a light easily

author: Hamelec
author_rank: Regular Contributor
timestamp: July 27, 2021, 07:58:03 am
content: a lot of data will be found here:https://www.kabelwissen.de/koaxialkabel/bildergalerie/for flexibility look into the datasheet "Min. bending radius"..

author: coppercone2
author_rank: Super Contributor
timestamp: July 27, 2021, 08:54:04 pm
content: that looks like a great website