RF connectors smack down ...  AliExpress vs Amphenol - Page 1
Forum section: electronics / rf-microwave

author: BravoV
author_rank: Super Contributor
timestamp: May 14, 2018, 06:12:43 pm
content: N type male to male converter, just bought from AliExpress, 1st glance I didn't notice anything special, until I put both side by side with Amphenol, just look at the outer wall thickness.

author: technogeeky
author_rank: Frequent Contributor
timestamp: May 14, 2018, 06:16:42 pm
content: Would the outer wall thickness have a major effect on the RF signal? Or would there just be a mechanical advantage?

author: bd139
author_rank: Super Contributor
timestamp: May 14, 2018, 06:20:22 pm
content: That’s a great comparison. Cheap is cheap!I buy amphenol BNC, SMA and SO239’s regularly and they are waaaay better than any of the generic and rebranded shit. No snagging or anything when you use them and they last a lot longer. I’ve actually noticed that cheap BNCs knacker test gear as well.

author: BravoV
author_rank: Super Contributor
timestamp: May 14, 2018, 06:20:31 pm
content: Quote from: technogeeky on May 14, 2018, 06:16:42 pmI guess so, but not sure, lets hear from more experienced members.

author: BravoV
author_rank: Super Contributor
timestamp: May 14, 2018, 06:31:04 pm
content: Quote from: bd139 on May 14, 2018, 06:20:22 pmAgreed, some of my Amphenol BNCs treasure, bought few dozens of them NOS while ago, really good stuffs.

author: dmills
author_rank: Super Contributor
timestamp: May 14, 2018, 06:31:23 pm
content: Far more importantly compare the pin geometry.

author: BravoV
author_rank: Super Contributor
timestamp: May 14, 2018, 06:34:26 pm
content: Quote from: dmills on May 14, 2018, 06:31:23 pmYeah, I was wondering about that too.Also Amphenol pin doesn't need the bling of golden plated look.

author: Yansi
author_rank: Super Contributor
timestamp: May 14, 2018, 07:01:47 pm
content: Quote from: bd139 on May 14, 2018, 06:20:22 pmYeaaah. That is nice if yo big daddy pays them for you.$4 or more for a single PCB SMA termination won't happen, especially when I need tens of them for prototyping.

author: bd139
author_rank: Super Contributor
timestamp: May 14, 2018, 07:06:42 pm
content: $5 here. Worth it.

author: dmills
author_rank: Super Contributor
timestamp: May 14, 2018, 09:18:41 pm
content: One thing to be most careful of with N types is that the 50 ohm and 75 ohm versions are NOT compatible, you will damage the female if you mate a 50 ohm plug into a 75 ohm female, and I think the two connectors shown by the OP may be different impedances (Specifically I think the Ali one may be 75 ohm).Regards, Dan.

author: rhb
author_rank: Super Contributor
timestamp: May 14, 2018, 11:19:18 pm
content: What's the VNA say?

author: Monkeh
author_rank: Super Contributor
timestamp: May 14, 2018, 11:39:19 pm
content: Quote from: dmills on May 14, 2018, 09:18:41 pmI'm pretty sure they're both 50Ω from the pin diameter.

author: xaxaxa
author_rank: Regular Contributor
timestamp: May 15, 2018, 03:26:07 am
content: The TE connectivity sma connectors from mouser are not bad (in terms of mating repeatability and return loss), and more reasonably priced; for non-production use there are reasonable quality ones on taobao (not aliexpress); look for ones that specify gold plating and in the price range of 3cny to 4cny each. I have measured these and up to 3GHz the difference in return loss compared to genuine ones is typically less than 0.1dB (the return loss due to pcb impedance error still dominates). I have also tested the gold plating with acid (the aliexpress ones failed horribly, but the TE and taobao ones held up).

author: BravoV
author_rank: Super Contributor
timestamp: May 15, 2018, 04:35:07 am
content: Quote from: rhb on May 14, 2018, 11:19:18 pmDon't have VNA.

author: BravoV
author_rank: Super Contributor
timestamp: May 15, 2018, 04:36:11 am
content: Quote from: Monkeh on May 14, 2018, 11:39:19 pmYes, both are 50Ω, I'm aware of 75Ω type as it has much much smaller pin, looks like needle when compared to 50Ω one.

author: Wirehead
author_rank: Regular Contributor
timestamp: May 15, 2018, 05:57:54 am
content: Quote from: BravoV on May 14, 2018, 06:20:31 pmIt does not. RF in coaxial connectors flows on the outer skin of the central conductor and on the inner surface of the outside shield.The aliexpress connector could be just-as-good if you don't test it. This thread is pure FUD.

author: taydin
author_rank: Frequent Contributor
timestamp: May 15, 2018, 06:08:29 am
content: Even if the wall thickness doesn't contribute to the signal integrity, the durability of a thicker wall would certainly make a difference when you drop it. Those things are heavy enough that when dropped from a few meters to concrete, the thin walled connector could lose its round shape.I also suspect the Amphenol part is machined to tighter tolerances. If I had a $50,000 Keysight spectrum analyzer, I would DEFINITELY NOT insert a Chinese connector to itEven if the center pin is 0.03mm thicker than rated, it would widen the female inner connector and degrade it.

author: rfspezi
author_rank: Regular Contributor
timestamp: May 15, 2018, 06:39:33 am
content: Quote from: taydin on May 15, 2018, 06:08:29 amOh comeon... you don't really beleave that the inner part of your spectrum analyzers female connector gets permanently widened from a 0.03 mm thicker male pin, don't you?

author: hendorog
author_rank: Super Contributor
timestamp: May 15, 2018, 07:48:15 am
content: Quote from: rfspezi on May 15, 2018, 06:39:33 amThats surely an exaggeration, but it might not take much. You can imagine that if the blunt ended pin got very close to the end of the 'hole' then a tiny additional diameter would force the fingers outwards.

author: taydin
author_rank: Frequent Contributor
timestamp: May 15, 2018, 08:51:11 am
content: Quote from: rfspezi on May 15, 2018, 06:39:33 amIf I had that SA, I would certainly not try to find outBut in any case, with RF, contact quality makes a big difference. If you go to vendor's websites selling RF cables, you will find "precision" cables that are manufactured to much tighter tolerances, at a much higher price. Surely the buyers of those cables aren't the RF equivalent of "audiophools"

author: Wirehead
author_rank: Regular Contributor
timestamp: May 15, 2018, 09:50:12 am
content: That's why you have "connector" savers.. Sacrificial 1:1 adapters.As to dropping connectors: RF connectors are never made to be abused due to mechanical stress.I'm still waiting on objective performance data. Not much of a smack down here..

author: taydin
author_rank: Frequent Contributor
timestamp: May 15, 2018, 11:05:15 am
content: Quote from: Wirehead on May 15, 2018, 09:50:12 amOk, so you plug in an el cheapo 1:1 adapter into your 50K SA, which means, if that thing does not meet the tolerance requirements, it will have already damaged the SA's female connector. That kinda sacrificial 1:1 would ONLY make sense if it is a model that meets the precision specs, which means it would be a reputable brand 1:1Quote from: Wirehead on May 15, 2018, 09:50:12 amThat's only in theory. When you are working at a cell tower in the middle of nowhere, and people expect you to get the job done yesterday, you would want a connector that survives minor OOPS'es, and not drive back to headquarters to get a new connectorBut hey, you might be Mr Perfect who never OOPS'es, then this won't apply to you. But us mere mortals occasionally do screw up

author: taydin
author_rank: Frequent Contributor
timestamp: May 15, 2018, 11:16:40 am
content: Hopefully somebody with a VNA can compare this Chinese thing with a reputable brand adapter.I already know first hand that the impedance characteristics of Chinese RF terminators are all over the place throughout their rated frequency rance, so I have reason to suspect that the cheap Chinese adapter will have similar shortcomings, but it would be nice to see it in actual measurement.

author: StuUK
author_rank: Frequent Contributor
timestamp: May 15, 2018, 11:37:47 am
content: mmmm, this thread is starting to sound a lot like audiophoolery...

author: dmills
author_rank: Super Contributor
timestamp: May 15, 2018, 11:41:56 am
content: Quote from: taydin on May 15, 2018, 11:05:15 amYep, but a reputable brand 1:1 is still VERY MUCH cheaper then sending a VNA back to Keysight/R&S/Copper Mountain to have the connectors replaced, and even a non preciosn one will save the wear on the connector.Adding a hundred quid or so to the cost of a £50k instrument is hardly a big deal if it means you can avoid weeks of downtime while the thing is being repaired.Regards, Dan.

author: Mr. Scram
author_rank: Super Contributor
timestamp: May 15, 2018, 12:13:00 pm
content: Quote from: dmills on May 15, 2018, 11:41:56 amWho here has a "£50k instrument" on his desk?Where are the numbers, charts and other things that make this quantifiable? Right now it's just a bunch of people claiming things. Labs full of test gear and all we have to show for it are opinions?

author: bd139
author_rank: Super Contributor
timestamp: May 15, 2018, 01:03:21 pm
content: TBH the performance difference is probably negligible. Initially. Which is the problem.If you have shitty PL259’s you can watch your PA finals explode after a few tens of connection cycles which is evidence enough for the performance difference. Then your £80 of FETs works out more than an Amphenol or two.

author: capt bullshot
author_rank: Super Contributor
timestamp: May 15, 2018, 01:16:23 pm
content: Do you consider a PL259 a proper RF connector? Afaik they're even worse than a BNC.Otherwise, e.g with BNC connectors attached to RG174 one can see differences between these Radiall comression style gems and non-branded but not el cheapo crimping connectors on a Tek 1502.

author: xaxaxa
author_rank: Regular Contributor
timestamp: May 15, 2018, 01:27:02 pm
content: Return loss of an aliexpress sma connector, to 2.45GHz (I simply made a 50ohm termination by soldering two 100ohm resistors to the connector):Looks good right? problem is I can make the graph jump just by nudging the connector a bit, and it will probably become all rusty after a month of use (because of fake gold plating).

author: EVS
author_rank: Contributor
timestamp: May 15, 2018, 07:02:23 pm
content: Quote from: BravoV on May 14, 2018, 06:12:43 pmJust for comparison. Radiall (R161703000) vs Telegartner (J01008C0825)

author: taydin
author_rank: Frequent Contributor
timestamp: May 15, 2018, 08:13:13 pm
content: To keep it goingFrom top to bottom: Fairview, HP, Pasternack

author: G0HZU
author_rank: Super Contributor
timestamp: May 15, 2018, 10:36:14 pm
content: Quote from: Mr. Scram on May 15, 2018, 12:13:00 pmIf you mean >$50k when new I've got a few items that qualify.I have to be very careful when introducing 'anything' into my workroom that has an SMA connector on it. I try and only use the very best brands of SMA connector (and cable) to minimise the risk of damage to my VNA connectors/cables and the Ecal module that comes with it. The Ecal uses Agilent/Keysight's PSC series 3.5mm connector and these are extremely fragile. I think the Ecal module cost £13k here in the UK and it can be trashed with a moment's carelessness with a cheapo connector that has a tolerance issue or any kind of surface defect on the centre pin. So I inspect any new SMA connectors/cables under a microscope before allowing them into the workroom. Even a tiny burr could cause problems.You can see the Agilent PSC 3.5mm connector in the link below and how easy it is to damage it. I hate inspecting my Ecal kit for damage because it is quite stressful counting all the tiny petals within each PSC connector (4 connectors in total) to look for any defects.For this reason I usually only use some very expensive Gore cables to connect to the Ecal module. A good Gore cable can easily cost $1k USD. But these cables can easily be damaged by items under test and pass on the damage to the Ecal module. So I try and do all my testing via known Suhner or Johnson SMA connectors.Nearly all of my N type connectors/attenuators/cables are made by Suhner or Narda or HP. I have a few cheapo Amphenol ones but these only get used on cheaper test gear.https://www.microwaves101.com/encyclopedias/how-to-not-trash-a-calibration-kit

author: Mr. Scram
author_rank: Super Contributor
timestamp: May 15, 2018, 11:13:08 pm
content: Quote from: G0HZU on May 15, 2018, 10:36:14 pmWe're talking about replacement value, so it's the current cost of the device we're talking about. A device worth a fraction those 50k isn't a 50k machine. That's like saying what's in the toilet bowl is a top notch dinner.We were also taking about BNCs, but I haven't anyone actually show issues arising from cheap connectors. I'd love to know about any, as it would be information relevant to my setup and interests. I can understand people being careful with their treasured equipment and wanting to buy the best stuff to go with it, but there's a huge risk of audiophoolery type self deceit. The fact that measurable performance is apparently similar gives pause.

author: G0HZU
author_rank: Super Contributor
timestamp: May 15, 2018, 11:37:35 pm
content: QuoteOn decent high grade lab gear I think the manufacturer will still charge huge money for even a basic repair. One of my analysers probably cost >$60k new ten years ago but it still has a minimum repair cost of $15k USD today. This is a fixed initial repair price set by the manufacturer. Also, the $$$ repair could take weeks which I think was the point made by dmills? So suddenly it makes sense to protect those exotic RF connectors rated to many GHzQuoteThe connectors in the OP look like N connectors to me?QuoteIt's the risk of damage and accelerated wear and the difficulty of replacing the damaged connector. Also there is the reliability of the connection over time/temperature/movement and this can be critical if doing vector based measurements at a few GHz.Even some manufacturers advise (in the user manual) to use good quality 'connector saver' adaptors on the test ports of their precision analysers. This is to try and protect against long term wear but also to protect against damage and accelerated wear from cheap junk connectors that might get used by a sloppy operator.

author: hendorog
author_rank: Super Contributor
timestamp: May 15, 2018, 11:51:51 pm
content: One thing to consider is the replaceability of the connectors in the instrument.e.g. On the HP 8753A/B/C VNA's the N connectors on the front panel are reasonably easy to get, are not too expensive and are quite simple to replace. I have several spares for mine.OTOH, the 7mm connectors on the test sets are not replaceable to my knowledge (well not without replacing the attached bridge), but no-one is likely to be using them directly and so the adapter becomes a de-facto connector saver.Of course you may want to protect that adapter with a connector saver...

author: G0HZU
author_rank: Super Contributor
timestamp: May 16, 2018, 12:09:51 am
content: In my case I've got lots of high end RF gear here with N or 3.5mm connectors that are rated from about 10GHz to 20GHz because that is the frequency range of the test gear. I don't think it would be easy to find/fit cheap replacements so I have to be careful what I connect to them. I try and use connector saving adaptors (or DC blocks) as much as possible but it would still be unwise for me to then try and use unbranded/junk connectors to connect to the connector savers. It's a false economy for various reasons.

author: BravoV
author_rank: Super Contributor
timestamp: May 16, 2018, 04:47:42 am
content: Rosenberger LMR-400 clamp type connector vs Amphenol.

author: Yansi
author_rank: Super Contributor
timestamp: May 16, 2018, 07:42:14 am
content: Quote from: xaxaxa on May 15, 2018, 01:27:02 pmI am not sure how a connector's S parameters should be measured, but I'd say you likely measured the characteristics of the two resistors, not the connector in this case. You would need to calibrate the reference measurement plane to be right on the connector, so the termination (or second port) is out of the way.

author: Yansi
author_rank: Super Contributor
timestamp: May 16, 2018, 07:46:05 am
content: Quote from: G0HZU on May 15, 2018, 10:36:14 pmThat is what these are for, if you want to minimize wear on test gear connectors. Also seen them in the N type connector variant, used on some VNAs.

author: Yansi
author_rank: Super Contributor
timestamp: May 16, 2018, 07:49:34 am
content: https://www.microwaves101.com/encyclopedias/how-to-not-trash-a-calibration-kitThis is also "all opinion". I get the fact of destroying the expensive kits and get the procedures of correctly attaching SMA connectors, however I would like to see a proof, what impact the slightly bent finger of the connector "cunt" will have on the cal kit's performance, if you will be able to measure any.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 16, 2018, 08:04:37 am
content: Quote from: Yansi on May 16, 2018, 07:49:34 amWhile not true proof, I remember some Agilent/Keysigth cal engineers in one of Dave's videos talking about people using poor connector systems and thinking their device was in spec, but was in fact out of spec because the poor connector was ruining the measurement.Regarding the "one slightly bent finger": Considering you need a torque wrench to get them to spec, I can't imagine it's hard to see how a bent finger would cause issues. It is hard to get true 'evidence' since nobody want's to ruin their $10k cal kit, or the ports on their >>$100k VNA.

author: BravoV
author_rank: Super Contributor
timestamp: May 16, 2018, 08:08:36 am
content: Regarding sacrificial N connector to preserve the one at the instruments, I used the right angle instead of straight, as its less stressful for the cables on my bench.What you people used most ? Straight or right angle ?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 16, 2018, 08:10:11 am
content: Quote from: BravoV on May 16, 2018, 08:08:36 amI tend to use N-to-SMA sacrificial connectors as all my test cables at home use SMA. I usually get straight ones and then use cables with angled connections instead.

author: Yansi
author_rank: Super Contributor
timestamp: May 16, 2018, 08:14:02 am
content: Quote from: TheUnnamedNewbie on May 16, 2018, 08:04:37 amThe question is by what amount it will be out of spec. By 0.1dB at a 5GHz? Or by what?I have never seen a proof of the torque wrench effect on an actual measurement either. Do you know about any resources?Please note I never stated that you should use cheap connectors. I would just like to see some real figures that would describe the problem scientifically.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 16, 2018, 08:25:23 am
content: Quote from: Yansi on May 16, 2018, 08:14:02 amI can try and do some tests with torque wrenches next time I'm working on a VNA.The difference is also mainly in the \$S_{11}\$ and not the \$S_{21}\$.Quick google I found this, but this talks about cables and not connectors:https://www.tek.com/blog/improving-vna-measurement-accuracy-quality-cables-and-adaptersThis paper I found does not show the true impact of cheap connectors, but does illustrate the impact of imperfections:Yeou-Song Lee and T. Roberts, "Accuracy study on the newly introduced Anritsu W1-connector calibration and verification kit," Conference, 2003. Fall 2003. 62nd ARFTG Microwave Measurements, 2003, pp. 109-118.Ofcourse, it does show that this is mostly an issue at MM-wave frequencies

author: Yansi
author_rank: Super Contributor
timestamp: May 16, 2018, 08:33:23 am
content: mm frequencies, like 30GHz+ ?Having such a VNA is out of scope of many of us.S11 makes sense, as the geometric imperfections have impact mainly on the impedance.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 16, 2018, 08:38:08 am
content: Quote from: Yansi on May 16, 2018, 08:33:23 amI never claimed that was well within everyday hobby territory, but I was not aware that this debate here was limited to hobby applications.

author: Yansi
author_rank: Super Contributor
timestamp: May 16, 2018, 08:46:01 am
content: I do not understand you point. If you have a 30+ GHz VNA, you will not likely care about connectors from china, or will you?I thought the discussion was about using the chinese conenctors at applications well bellow that and to find where the limits are. I.e. to find connector torquing and chinese SMA has that much of an effect in that kind of application.Using chinese SMA at K-band and such is out of the question.

author: BravoV
author_rank: Super Contributor
timestamp: May 16, 2018, 09:17:18 am
content: Quote from: TheUnnamedNewbie on May 16, 2018, 08:10:11 amMy gripe is, whenever the sacrificial connector is installed, at my SA I could not install the front cover as I don't use it often, as it protrudes out even the right angle one. Also I don't like to increase the attach & detach cycles at my SA's N connector.

author: rfspezi
author_rank: Regular Contributor
timestamp: May 16, 2018, 09:25:16 am
content: Quote from: Yansi on May 16, 2018, 08:46:01 amThat's exactly what i thought too.The real art is not to buy expencive precision adapters (that's easy and every smart ass can do that and come with frightening arguments) but to find the best compromise between affordable price and performance.From the N type connector in the opening post it's somehow clear that we are not targeting at the 30+ Ghz range.

author: BravoV
author_rank: Super Contributor
timestamp: May 16, 2018, 03:12:58 pm
content: Quote from: rfspezi on May 16, 2018, 09:25:16 amHow does a N type connector for 30+ GHz looks like ? Or specific differences say compared to the one at the 1st post ?Or I asked the wrong question ? Like at 30+ GHz, N type is not suitable anymore ?

author: dmills
author_rank: Super Contributor
timestamp: May 16, 2018, 03:37:08 pm
content: N type tops out at about 18GHz, the geometry is too physically large to work higher up there because multiple propagation modes become possible once the dielectric thickness becomes a significant part of a wavelength.There is a reason the 3.5mm, and later 2.92mm and smaller connectors are used at high microwave.Regards, Dan.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 16, 2018, 03:52:14 pm
content: Two points: I never said "only applies at mmwave frequencies" , but that it becomes a major issue at those frequencies. But that does not mean that it cannot be an issue to consider at lower frequencies.And second: from the replies to the op, I thought this had become a more general "is there a difference/what is the difference", instead of just covering the N connector.But whatever, as usual I try to share some information about the topic and people get annoyed that it is not the exact type they were looking for, I'll just stop commenting.

author: G0HZU
author_rank: Super Contributor
timestamp: May 16, 2018, 10:46:11 pm
content: Quote from: Yansi on May 16, 2018, 07:46:05 amThose look like SMA RP (reverse polarity) connectors? The gender of the centre pin is swapped on one end of them.

author: dazz1
author_rank: Frequent Contributor
timestamp: July 19, 2018, 07:29:18 am
content: HiI have got to the end of this thread and all I have read is fluff and puff. I am not interested in +30GHz gear or reading how much companies can charge for so little.My old professor used to say if it isn't measured, it isn't true.Show us the data.Dazz

author: rhb
author_rank: Super Contributor
timestamp: July 19, 2018, 03:28:39 pm
content: FWIW I made the mistake of buying a bunch of Chinese adaptors on eBay. I've already discovered two defective ones. As in no signal defective. And others which are intermittently -30dB notch filters when swept from 100 KHz to 2.9 GHz. I bought 10 BNC M-M jumpers which are useless for anything but 50 MHz notch filters because the manufacturer twisted the braid and soldered it to the connector shell. The truly sad part was these were no-solder screw on connectors.I'll test the adaptors and keep any that are actually usable, but I'll never buy Chinese connectors or cables again.

author: xaxaxa
author_rank: Regular Contributor
timestamp: July 19, 2018, 04:43:38 pm
content: From my experience taobao/aliexpress > ebay; on taobao the descriptions are generally correct and I have yet to receive anything defective. You can find decent quality RF connectors if you pick the right price range and read item descriptions carefully. All the connectors I've measured so far show <-30dB return loss to 2.5GHz. Ebay however is just full of garbage quality stuff so I don't bother with it anymore except for local items.