SMA connectors

The price range is fantastic. We buy a really nice edge-launch SMA from Shining Star for $1.88, probably a few per cent of what Pasternack would charge.

These guys are great,

probably imports.

Den tirsdag den 21. april 2015 kl. 22.03.29 UTC+2 skrev John Larkin:

unless it explicitly says "made in the USA" I'd guess all of them

you can get a bag of 50 standard edge launch SMAs for ~$10 on ebay

but some of them are crap, like the plastic meting when soldered which shouldn't happen if it was really Teflon like it is supposed to be

-Lasse

Which are those? I have uses for connectors without teflon. Teflon is disastrous when it gets irradiated.

Jeroen Belleman

I don't know, just some random noname bought on the interweb because they were too cheap not to try

is it even possible to make a "real" SMA without teflon?

-Lasse

If you think those are pricey, try precision 2.4 mm connectors.

Cheers

Phil Hobbs

On a sunny day (Tue, 21 Apr 2015 10:44:12 -0700) it happened Paul Colby wrote in :

I dunno, but I got a lot of SMA stuff free chipping from China. If you can wait the 2 week or more it is sjeeper than local postage without the parts.

Or APC7s. Luckily, flea markets have lots of APC7s.

I bought a pair of SMA->2.4 mm adapters, $68 each NOS, to go on the front of my HP 70820A. They're going to stay there permanently, with a pair of SMA connector savers to protect them!

Cheers

Phil Hobbs

I did that same thing for my SD-32 50 GHz (single channel) sampling head. I guess, theoretically, we are compromising the bandwidths or something.

This is what I did. $1.98 or $59? 1.98 or $59?? Hum, I guess $1.98. Then I went to HT and bought what I needed for $3. In two weeks I'll have spares :)

Something is truely broken.

You might think about making your own with machinable ceramic - Macor - as the insulator

It's wonderful stuff for that kind of work. The dielectric constant is higher than Teflon/PTFE at about 5.67, so you'd have to fudge the inner dimensions.

That must be about the least practical and most expensive suggestion I've had to date. I can't afford the time and expense of designing my own rad-hard SMA. Designing a well-matched connector is a lot of work! I need it to be well-matched. No fudging allowed. I'm dealing with signals having ball-park 70ps rise times and they must stay clean!

I bought a length of PEEK insulated UT-141 some time ago and intended to use dielectricless SMAs, which use the coax central conductor as the centre pin of the connector. This works fine for standard UT-141, which has a Cu or Ag plated steel centre conductor with the right diameter, but alas, not for the PEEK-insulated stuff, which uses thinner and very soft copper. Bummer.

There *are* several SMA-compatible rad-hard connectors on the market. Alas, other criteria prevent me from using them. For example, Radiall has SMA-3.5 or SMA-2.9 connectors with polyetherimide insulator and Huber and Suhner have similar connectors using kapton. Alas, neither seem to have compatible halogen-free cables. They *do* have halogen- free cables, but none that fit the halogen-free connectors. Bummer!

Times-Microwave sells mineral-insulated cable assemblies, but there the required phase matching specs can't be upheld. Sigh!

I've given up. I ended up buying cables which still have bits of teflon in the connectors. If I don't touch them after irradiation, they may hold for long enough.

Jeroen Belleman

It's perfectly practicable. Practical and expensive depends on your situati on and budget. At Cambridge Instruments we wanted vacuum feed-throughs for sub-nanosecond beam-blanking pulses. The project got canned before we'd act ually got our hands on them, but - as far as I know - we'd sourced our part s from a local sub-contractor by then.

It's not rocket science.

So what does happen to Teflon/PTFE after serious irradiation?

says some swelling and embrittlement.

situation and budget. At Cambridge Instruments we wanted vacuum feed-throughs for sub-nanosecond beam-blanking pulses. The project got canned before we'd actually got our hands on them, but - as far as I know - we'd sourced our parts from a local sub-contractor by then.

Designing a connector may not be rocket science, but it takes time and money. I have deadlines and budget envelopes to respect, like anyone else. I buy my connectors from Huber+Suhner or Radiall, and my vacuum feedthroughs from Times Microwave.

As for the problems caused by halogenated materials under irradiation: Embrittlement is an issue, yes, but the main problem is corrosion of contact surfaces and subsequent poor contacts. I suppose the irradiation liberates F_2 or HF. Copper turns green. Even gold-plated surfaces turn whitish.

Jeroen Belleman

The messy bit is getting the centre connectors to wipe and engage. For the rest you've got the diameter of the inner conductor - which is pretty much fixed by inner connector design you end up copying - the dielectric constan t of the material you use as an insulator, and the outer diameter that give s you the correct characteristic impedance. You've got to get a smooth tran sition from the cable into the connector, but that's something else you can copy.

Deadlines and budget envelopes have to bow to getting components that work and keep on working. The British formulation of this principle was "we are never given the time to do it right, so we always have to find the time to do it again".

Development is an exploration of the unknown, and rigid deadlines and tight budgets are generated by people who don't understand this as well as they should.

Managements school apparently tell managers that if they don't lean on thei r development staff, they'll never finish the job. What they don't seem to tell them is that if they lean too hard, the job may stay 95% complete for rather longer than anybody likes.

I was on a project where we desperately wanted to get to a particular indus try get-together, and ended up skipping design reviews "to save time". What this gave us was bug-infested hardware that took a long time to debug. If we'd started off trying for the six-month later version of the event, we mi ght have made it, but instead missed that too.

Stick the corroded bits in an electron-microscope set up for X-ray fluoresc ence analysis. That will give you an elemental analysis of the corroded sur face - or at least the surface you can see, though the electrons don't go a s far in as visible light photons do, and the X-rays they kick out can't ge t through many heavy atoms either.

I don't think so.

I like these K (2.92 mm) connectors that avoid Teflon yet mate with SMA:

They are a bit pricy, but are reusable. They are solder-less. Really nice.