Cheap BNC adapers strike again - Page 1
Forum section: electronics / general

author: xrunner
author_rank: Super Contributor
timestamp: April 17, 2017, 10:43:24 pm
content: Testing a signal coming from an RF generator that was supposed to be -3 dB but was getting something like -10 to -30 dB depending on the frequency. When I tried a different right angle adapter (clearly a different design) the signal was correct. I started examining the right angle connector and it basically fell apart in my hands. Then I saw what the real issue was - the internal connection was never soldered at all!Watch out it's a jungle out there!

author: Shock
author_rank: Super Contributor
timestamp: April 18, 2017, 12:51:13 pm
content: The one thing I'm worried about now is mixing up the decent and cheap leads and connectors.A while back got a grab bag of freebie vintage banana plugs and large hooks etc. Recently went through a pile of these and buffed out the oxides with some cheap linen cloth. Came up really nice, the cheap 40 year old stuff looks way better than the cheap Chinese junk of today (plastic was hard plastic) but hey I have been guilty of some Chinese indulgences myself.Anyway I'd be running up new connectors and cables on the LCR meter and also the oscilloscope if you have a test circuit or can do comparative testing before using them for anything serious. I typically do that when making new cables to ensure I don't have a bad joint or contact somewhere.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 18, 2017, 05:05:39 pm
content: Quote from: xrunner on April 17, 2017, 10:43:24 pmyeah you watch out while a bunch of us enjoying it.ps: china product = cheap + fix it yourself = fixed = good.

author: edpalmer42
author_rank: Super Contributor
timestamp: April 18, 2017, 05:20:22 pm
content: Are you sure that it was supposed to be soldered? The serrated surface on the outer part of the male connector suggests that it might be just pressed into the female-female piece. I can't see the inner connector well enough to decide how it was intended to be assembled.Ed

author: xrunner
author_rank: Super Contributor
timestamp: April 18, 2017, 05:26:29 pm
content: Quote from: edpalmer42 on April 18, 2017, 05:20:22 pmYes.QuoteThat part is not soldered, it is supposed to be press-fitted (but the fitment sucks).QuoteThe inner partissupposed to be soldered - but was not.

author: james_s
author_rank: Super Contributor
timestamp: April 18, 2017, 06:13:17 pm
content: I've been burned a few times by cheap junk like this too, the problem is that some of it is really good and other stuff is trash, it's hard to know what you're getting until you have it. These days if I need RF cables and adapters I usually get them from somewhere like Digikey if I can't salvage what I need from scrapped equipment.

author: The Soulman
author_rank: Super Contributor
timestamp: April 18, 2017, 06:46:26 pm
content: Some time ago I was hooking up a monitor up to a camera system (everything composite video.).The cable run was about 60 meters and I didn't have a long cable at hand so used 10 and 20 meter cables with BNC female/female adapters toconnect them together.However no picture at the endAfter wasting time swapping the individual cables I finally found the culprit: a cheap brand new female/female adapter without a center contact installed...Don't cheap out when time=money is involved.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 20, 2017, 03:31:35 am
content: Yeah, there are at least three audiences on this forum.People getting paid to do electronics work (Engineers, technicians and the like). For people like that the cost in time of a few bad parts will dramatically outweigh the low cost.Knowledgeable people doing this after retirement or as a hobby or on the side for charities and the like. For this group time has little monetary value and good value can be had by buying cheap and either fixing or knowing how to live with the foibles.Newbies and others who don't know the difference between good stuff and junk. These people are the real tragedy. A bad part may sour them on the field forever, set them on a wrong knowledge path, reinforce wrong ideas or cost them time and money they don't have. And they may never know what went wrong.

author: xrunner
author_rank: Super Contributor
timestamp: April 20, 2017, 03:37:44 am
content: Really good summary (I'm in the second group)

author: JonM
author_rank: Unknown
timestamp: April 20, 2017, 03:42:27 am
content: I have an Amphenol BNC tee with no slots machined on the plug part. I saved it as a collector's item but I really should move it from my toolbox to my museum. A while back I tried to use it and had some frustration as I turned it way more than a BNC should need to be turned to connect.

author: Shock
author_rank: Super Contributor
timestamp: April 20, 2017, 05:54:52 am
content: Quote from: CatalinaWOW on April 20, 2017, 03:31:35 amThat is what annoys me, when I buy cheap I know that unless research is done it could be throwaway junk. But this is even slipping through to western consumer level gear as well. Had an expensive audio cable and the insulation broke down crumbly within 2 years, guess where it was made.It's not like there has been and absence of cheap low quality before with Radio Shack, Tandy and Dick Smith etc. But with the internet the race to the bottom is at an all time low, you have someone selling a connector for 10 cents and another guy selling that same connector trying to scam you for $10 and they both are defective.

author: apelly
author_rank: Unknown
timestamp: April 20, 2017, 08:41:37 am
content: My primary gripe is with the usual suspects selling cheap ass junk for premium prices. I'm looking at you digikey.If I want quality I get hauled over the coals.If I'm OK with low-end junk, I get hauled over the coals.I might as well get my junk straight from China, pay bugger all, and get functional stuff 95% of the time.

author: mcinque
author_rank: Unknown
timestamp: April 20, 2017, 11:20:43 am
content: Quote from: Shock on April 20, 2017, 05:54:52 amExactly.I'm very surprised to hear things like "I bought a cheap item; I'm angry because its quality is ridiculous". What can we expect from a cheap object?Of course, if you spend a lot you can't be sure you're buying a quality item (anyone can overprice), butyou can bet it will be a terrible quality itemif you pay too little for it.

author: xrunner
author_rank: Super Contributor
timestamp: April 20, 2017, 11:39:51 am
content: I haven't had any issues with N or UHF or F or SMA connectors. It seems it's just the BNC, and it's not just the internals. I've posted on this too - there are issues cropping up where the male BNC won't fit properly into the female of another one, or the female on a piece of gear. I've tried to figure out what the issue is, but I am still not sure what they are doing wrong. It has something to do with an internal dimension, but I have no way to measure whatever it is that's out of tolerance.Put three or four BNCs side by side if you have purchased some in the last year from different suppliers and see if you don't see different machining patterns, especially the locking notch cutouts. I see clear differences in the way the parts are made, telling me that the original specification is not being followed for some reason. Time for more pics I guess.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 20, 2017, 01:46:24 pm
content: Quote from: xrunner on April 20, 2017, 11:39:51 amJust a difference in machining method doesn't make a part out of spec or bad. There are different ways to skin a cat. An example would be the locking lugs. Some are made from a solid billet. Others have the lugs brazed on. Done right, either works fine. The key is whether critical dimensions are in tolerance.In some cases I actually prefer out of spec parts. I have top quality BNCs from the best manufacturers. They fit extremely tight, and are difficult to mate and un-mate. I have some cheapies that require no effort to use. They work fine at for the relatively low frequency stuff that dominates what I do.

author: xrunner
author_rank: Super Contributor
timestamp: April 20, 2017, 02:25:58 pm
content: Quote from: CatalinaWOW on April 20, 2017, 01:46:24 pmWell that's what I mean. Look at these male BNC. The middle one is pretty old - probably 35 years old. The ones on either side are new. Look carefully at the way the guide slots are cut. You can clearly see they are not the same as they used to be per the older BNC, or should be according to the standard you would get from a company like Amphenol. The one on the right is just a horrible example.I do not know why they are cutting them differently, but it's causing issues.

author: james_s
author_rank: Super Contributor
timestamp: April 20, 2017, 06:49:42 pm
content: It looks to me like in the cheap newer one they used a single endmill and did the cut in one operation. To enlarge the end of the slot as in the older connectors would have required a slightly more complex machining operation and when you're trying to crank out a bazillion parts for as low a price as possible, adding even half a second to each operation adds up quickly. It sucks but that's why things are the way they are, decades of people shopping by price driving manufactures to produce to a price.