quality male-male BNC cablse? - Page 1
Forum section: electronics / general

author: SArepairman
author_rank: Frequent Contributor
timestamp: October 17, 2013, 01:50:10 am
content: I would like to get some quality BNC cable. The cables that I bought on the cheap are very stiff.I see pamona brand bnc cables and HP brand BNC cables on ebay, are these any good?Can you get BNC cables that are nimble like silicone test leads (or at least similar?).I would like to know before I spend 20-40$.

author: edavid
author_rank: Super Contributor
timestamp: October 17, 2013, 03:14:39 am
content: Pomona cables with molded ends are the standard. They have a confusing number of kinds made in slightly different ways, but they are all OK. The gray HP cables are fine too. If you are patient you should be able to get them used for $3-5 each (or even less at a hamfest). Be careful not to buy 75ohm though (unless that's what you want).I have not had a problem with used cables except for one batch that must have been owned by a smoker. They had to air out for a few months before I could use them.There is no silicone coax, but you can look for cables made with thinRG179RG174 coax instead of RG58.

author: c4757p
author_rank: Super Contributor
timestamp: October 17, 2013, 03:20:27 am
content: RG179 is 75 ohm.I made my own withthis RG316 cableandthese BNC plugs. Very nice, flexible and sturdy and well insulated.

author: Bryan
author_rank: Frequent Contributor
timestamp: October 18, 2013, 09:57:58 am
content: Amphenol also does a good cable with molded ends. Usually cheaper than Pomona

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: October 18, 2013, 10:15:43 am
content: Hi,I make my own.RG58 comes either with a 20 awg solid conductor in the center and this is marked RG58/U.What you are looking for is RG58 A/U or C/U this has a stranded center conductor and is more flexible.I use crimp connectors on the ends. I also cable boots like 3-1478996-6 from TE Connectivity.A tool like this one:http://www.ebay.ca/itm/Rotary-Coax-Coaxial-Cable-RG58-Stripper-Cutter-Tool-v-h9-/221297393137?pt=US_Tools_Crimpers_Strippers&hash=item33865a3df1#ht_4609wt_1399Makes it really easy to prepare the cable.Buying the cables is cheaper than making them if you only need a few. Making them allows me to make custom lengths.Jay_Diddy_B

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: October 18, 2013, 02:41:22 pm
content: These are my favorite BNC cables:http://www.digikey.ca/product-search/en?WT.z_header=search_go&lang=en&site=ca&keywords=J6436-ND&x=-1691&y=-51&formaction=on. They made of very flexible coax - Belden 8218 that is more like test lead cables - does not make any loops on my table. I do use rigid SMA-SMA with RG402 cables when I need low loss which is pain to handle.

author: rastro
author_rank: Frequent Contributor
timestamp: October 18, 2013, 04:58:15 pm
content: Quote from: c4757p on October 17, 2013, 03:20:27 amAfter receiving some poor quality RG316/BNC cables on ebay going the same route.

author: codeboy2k
author_rank: Super Contributor
timestamp: October 19, 2013, 09:47:12 am
content: That combination from the Hong Kong ebay seller comes to US $4.00/meter for a completed cable (which you make yourself, of course), and free shipping, no taxes.The Belden cable linked to from Digikey comes to approx. USD $12.75 per meter, plus shipping and taxes (approx. because I see Digikey in Canadian dollars)So making your own is definitely cheaper. However, coming from China I can't really trust it. Does the cable really meet the spec? Even the connectors can be bad, too (choice of materials, inferior construction, pin diameter out of tolerance, plating, etc)So you don't really know what you have until you test the cables you make. Are you able to test one of your homemade cables to get an impedance profile? You really don't want to introduce signal distortions, and although it should be 50 ohms everywhere and flat up to 3 GHz, it would be nice to know the limits of your cable/connector combination.I need some cables too, and I would love to have 3 for the price of 1, instead of 1 for the price of 3, if those 3 are just as good as the 1.To test a cable's bandwidth you will need a network analyzer, or a spectrum analyzer with a tracking generator. To get the impedance profile (impedance vs. distance) you will need a modern TDR that can do this. Sadly, I have none of these here in my home lab, but maybe you have access at your school lab. It would be nice to see how those cables made from HK parts actually perform.Cheers!

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: October 19, 2013, 05:41:05 pm
content: RGB-174 is small diameter (about 1/8") inch and very flexible, but....The core is copper-clad steel. When the cable is flexed a lot, the steel core can punch through the soft dielectric and short to the shield! Believe me, this is next to impossible to troubleshoot since moving the cable will clear the short.

author: Fraser
author_rank: Super Contributor
timestamp: October 19, 2013, 06:47:36 pm
content: I was lucky enough to find a load of Multi-contact cables with the fully insulated BNC plugs at a good price.The 50 Ohm cable is very flexible and high quality. Fluke equipment use these MC manufactured cables as well as their Pomona seriesUninsulated versions are also available.I attach the MC catalogue. They are not cheap but they are good and long lived.The leads that I have are the XLSS type found on page 18 and are available in PVC or Silicone insulation. The Silicone ones are the extra flexible type like quality test leads found on multimeters.I bought some clones from China and though similar in looks, the quality and cable flexibilty was not as good.I also use MC brand oscilloscope safety probes. These are the same as the ones FLUKE provides with scopemeters.

author: c4757p
author_rank: Super Contributor
timestamp: October 19, 2013, 06:58:19 pm
content: Quote from: codeboy2k on October 19, 2013, 09:47:12 amI may talk to a professor and see what I can do. I haven't really needed to - for most of my applications, if I can't measure their performance at a level, I don't really need them to perform at that level anyway. But I am curious now.Quote from: Jon Chandler on October 19, 2013, 05:41:05 pmMy RG-316 is just as thin and flexible, and has a stranded core. I still wouldn't want to sit there bending it back and forth for an hour, but I have no doubt it can stand up to normal use.I will say, as unquantitative as it is, that it all feels excellent. The plugs sit perfectly on a BNC jack the same way as the expensive ones on name-brand Agilent equipment, the cable is nice and solid, transmits high rise-time signals with aplomb, and receives little to no outside interference when transmitting a very low signal. Keep in mind, this is all coming from someone who previously had to deal with some spectacularly poor cables.

author: rastro
author_rank: Frequent Contributor
timestamp: October 19, 2013, 08:57:39 pm
content: Quote from: codeboy2k on October 19, 2013, 09:47:12 amI wonder if you could use J.W. avalanche generator mentioned on some other threads to do a rough sanity check of the cable performance against a known good cable?

author: c4757p
author_rank: Super Contributor
timestamp: October 19, 2013, 09:00:40 pm
content: Nope. In theory you could measure the rise time of the cable, in practice you won't have an oscilloscope with enough bandwidth for that. I don't, and I've got a 400 MHz one. The signal isn't clean enough to check for reflections, and if the frequency response isn't perfectly Gaussian it doesn't tell you anything about frequencies under the maximum.Now, if you have all the equipment (high bandwidth oscope, good feedthrough termination at least) to do the test anyway, itmayhelp you find the horrific, cheap-ass eBay rejects that I had before.Thosecable turds would not be able to transmit the JW pulse - I know that from experience. Significant distortion and ringing, basically they make the cable ill and it vomits into the oscilloscope... They also pick up higher-frequency noise if a transmitter is nearby, and mains noise too if your signal is low enough. All of this you can check for pretty easily. But you can't really discern a good cable from an excellent cable that way.

author: rastro
author_rank: Frequent Contributor
timestamp: October 19, 2013, 10:53:10 pm
content: You're right the o-scope bw is a key bottle neck.I see in a previous post that you are building your own RG316/BMC cables. I take it you had pretty good luck from the ebay components at least?I just just received 10 BNC's and 5M of RG316 from ebay. It's from a different vendor but I'm pretty sure that some of these vendors are the same source with different alias'. I finally got the correct crimp tool (for the outside shield). Making up a couple is on my 2do list this week.

author: c4757p
author_rank: Super Contributor
timestamp: October 19, 2013, 11:22:13 pm
content: I had good luck with those particular eBay parts. They seem to be of excellent quality. Of course, if I can get hold of a network analyzer at school, that'll tell how good theytrulyare, but I haven't seen anything that would lead me to believe they are poor.I have, however, bought some other RF/signal/coax-related stuff from eBay that was of stunningly poor quality. The BNC jacks I bought most recently are the worst I have ever seen (cheapest too, though - I got precisely what I paid for). And have you ever seen a T-adapter with an internal intermittent open? I have... two out of four, actually...I will admit to having crimped them with a Vise-Grip... though very, very carefully, I suspect I did the best one could do without the right tool.

author: rastro
author_rank: Frequent Contributor
timestamp: October 20, 2013, 01:25:04 am
content: I had the same problem on tee connectors where 2 of 3 where defective. On two the press fitted barrels came loose from the housing. Also one started intermittently shorting. After looking inside the one's with the loose barrels I noticed very fine metal shavings (using a 10X stereo microscope). I assume this was from poor or sloppy machining process. l did get my money returned from the ebay vendor. I also came across a number of poor SMA and BNC cables that where intermittent - however I did not identify a problem in time to file an action through ebay/paypal. Now I'm wondering if those cables that seem to work don't have more subtle problems!That said I'm still going to build my own with ebay components. I'm running under the assumption if they error in the process (even with good components) they can't reuse the parts. So the marginal/intermittent completed cable assembly's get passed off to the unwary. So if I do my own cables I can attest to the process and workmanship.

author: Unknown
author_rank: Unknown
timestamp: October 20, 2013, 08:48:31 pm
content: How about getting quality connectors and cables from a reputable distributor? Are the poor quality connectors and cables not enough proof of the quality of these no-name RF components? Is it the process that's the problem or the parts? Do you really want to invest a bunch of time and money in making cables and find out that you used crappy, unreliable parts?I guess you can make your cables without the right tools from cheap connectors, but don't expect to equal either the reliability or the quality of the "quality male-male BNC cables" from manufactures like Pomona that this topic was about. Unless you need a lot of cables the cost of a good crimping tool alone may offset any savings.

author: c4757p
author_rank: Super Contributor
timestamp: October 20, 2013, 09:01:13 pm
content: I took a chance with them because I was impressed by the overall quality of that seller's entire store. It's all RF stuff, well specified, well organized - it's not like they're selling off a bin of questionable coax Ethernet terminations as RF-grade equipment. Then I got them and saw that as far as I could tell, they were as good as I had hoped. Obviously you could do better, but I suspect most of us don't really need to.

author: metalphreak
author_rank: Frequent Contributor
timestamp: October 21, 2013, 02:40:11 pm
content: FYI: "lm4871n" and "connekt" appear to be the same seller. Ordered some things from both users, got the shipping notifications one right after the other, and received the same generic "thanks for buying blah blah" messageWill see how good the quality is when they arrive. Grabbed a few BNC T/F adapters, and some RG316 BNC cables of varying lengths.