Author Topic: homemade SMA cable pin recession  (Read 1106 times)

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Offline electrolustTopic starter

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homemade SMA cable pin recession
« on: July 25, 2021, 12:35:42 am »
I'm making my own SMA patch cables. The connectors are solder on. It's very hard to get the pin depth correct. The standard is 10 mils. Am I correct in thinking that this isn't actually super critical, as long as the pin is recessed and not processed? If the pin is processed, the pin base may interfere with the female socket. If the pin is overly recessed (say 15-20 mils) then physically you just have that much less contact in the socket. Maybe you can't get up to 18Ghz because of the extra dielectric "gap" but for lower frequencies 1-2 GHz I mean this should be fine? All the chinacom commercially made cables I have are waaaay worse than my hand-made ones and they perform fine.

Even if I can get one connector correct, I then have to keep cutting and re-doing the other end until I get that side correct. And those connectors are damn pricey.
 

Offline jjoonathan

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Re: homemade SMA cable pin recession
« Reply #1 on: July 25, 2021, 02:40:16 am »
Yep, that's correct. At 2GHz you can get away with just about as much pin recession as you want, as long as you don't have protrusion. You're also correct to note that the low-end cables are quite shocking in this regard. You'll find protrusion, you'll find recession so severe that the tip of the pin is barely visible, you'll find intermittent shorts from big solder blobs at the center-conductor/pin interface that aren't mechanically secured or otherwise prevented from contacting the outer shell, you'll find outer conductor mesh so scant that wifi packets will get into a terminated cable like it was an antenna, you'll find center pins that erupt into a full coat of green copper oxide even though the coupling nut still looks shiny and golden -- it's really the wild west out there in the world of cheap cables.
 

Offline Brumby

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Re: homemade SMA cable pin recession
« Reply #2 on: July 25, 2021, 05:53:27 am »
So .... you may think such cables would be like a well mannered horse until you hop on and find out (the hard way) that it's a wild bucking bronco.


Never happened to me  ::)
 

Offline Joel_Dunsmore

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Re: homemade SMA cable pin recession
« Reply #3 on: July 30, 2021, 02:13:53 am »
Horse is a not my go to simile; "Cables are like dogs, either they are bad, they've been bad, or they're going to be bad; and if they're good, they only stay good with great care"
 

Offline electrolustTopic starter

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Re: homemade SMA cable pin recession
« Reply #4 on: September 30, 2021, 09:11:46 pm »
After making a bunch of these, I finally figured out I can gauge the cables before the final crimp (which sets the pin and dielectric depth). The crimp process does upset the depth but I found a pre-crimp range and technique that works and I can now reliably make test-quality cables.
 


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