Chinese Terminator

[Mr. Scram]

You better do, because Chinese poorly mechanicaly made connectors can ruin your equipment connectors.

I imagine they can, but do they do this enough to be a real problem?

[jjoonathan]

Yep, it's a real problem. Tight tolerances, tiny delicate structures, and relatively large forces (8 in-lb) are a recipe for connector destruction. Cheap ebay equipment frequently comes with horribly chowdered up input connectors.

A slightly-too-long male pin will split a slotted female pin. A slightly-too-wide or burred male pin will catch a "finger" of the female pin and push it back. A female pin with bad edges will scratch up a male pin. Twisting the connectors during mating will occasionally catch the female fingers on the male pin, bending one and scratching the other. It will always cause abrasion, which is quite visible at 50GHz. I see three of these (too long, bad edges, abrasion) frequently. Pin width seems to be better controlled; my guess is swiss lathe programmers/operators tend to know what they're doing. Everyone blames connector failure on twisting-during-mating, but I privately suspect that this accounts for only a small fraction of ruined connectors.

The male SMA connector for the subject of this thread was almost 10 mil out of spec lengthwise in the bad, potentially harmful direction, FWIW. Good connectors are typically 1-2mil in the good direction. We can speculate about what it would have done to the precision slotless connector on my VNA had I attached it, but we will never find out :-)


EDIT: see the precision 3.5mm female conector here in all its glory: https://www.microwaves101.com/encyclopedias/how-to-not-trash-a-calibration-kit

[mnementh]

Yep, it's a real problem. Tight tolerances, tiny delicate structures, and relatively large forces (8 in-lb) are a recipe for connector destruction. Cheap ebay equipment frequently comes with horribly chowdered up input connectors.

A slightly-too-long male pin will split a slotted female pin. A slightly-too-wide or burred male pin will catch a "finger" of the female pin and push it back. A female pin with bad edges will scratch up a male pin. Twisting the connectors during mating will occasionally catch the female fingers on the male pin, bending one and scratching the other. It will always cause abrasion, which is quite visible at 50GHz. I see three of these (too long, bad edges, abrasion) frequently. Pin width seems to be better controlled; my guess is swiss lathe programmers/operators tend to know what they're doing. Everyone blames connector failure on twisting-during-mating, but I privately suspect that this accounts for only a small fraction of ruined connectors.

The male SMA connector for the subject of this thread was almost 10 mil out of spec lengthwise in the bad, potentially harmful direction, FWIW. Good connectors are typically 1-2mil in the good direction. We can speculate about what it would have done to the precision slotless connector on my VNA had I attached it, but we will never find out :-)


EDIT: see the precision 3.5mm female conector here in all its glory: https://www.microwaves101.com/encyclopedias/how-to-not-trash-a-calibration-kit

Yeah, but SMA/RP-SMA are WAY overused in many applications where frequent connection/disconnection is part of normal service. Depending on the manufacturer, most are rated at only 200-500 mating cycles; I understand there are some all SS variants rated for more, but they are frightfully expensive.


mnem
*Relurk*

[Mr. Scram]

My mistake, I thought we were talking about BNC connectors too.