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The BNC Connector and How It Got That Way

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#3
The write up missed out on the best parts of the BNC connector. TNC is dimensionally the same, just threaded instead of a bayonet QD. Also the socket and inner diameter of the shield of the female BNC (and TNC) connector match up with the pin diameter and outer diameter of the inner shield of a Type N connector. So in a pinch, a male Type N connector can simply be pushed onto a female BNC or TNC connector for the respective impedance.
 

KE5MC

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#4
The write up missed out on the best parts of the BNC connector. TNC is dimensionally the same, just threaded instead of a bayonet QD. Also the socket and inner diameter of the shield of the female BNC (and TNC) connector match up with the pin diameter and outer diameter of the inner shield of a Type N connector. So in a pinch, a male Type N connector can simply be pushed onto a female BNC or TNC connector for the respective impedance.
As noted interesting article.

Mismatching always gets my attention. One drawing I found shows the BNC pin diameter at 1.35mm. Another for the N type was 1.60mm to 1.68mm without a nominal size. Difference is not significant but...

My last project was the cable design for large medical testing device. Biggest headache was troubleshooting equipment in the lab or line and someone had probed a connector contact that was not the fault, but it became a secondary intermittent symptom as the probing sprung the contacts.

Proceed with caution and use at your own risk...

Mike
 
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#5
Yes, I agree here. The 50 ohm N connector uses air dielectric around the pins, which allows for a larger diameter pin while keeping 50 ohm impedance compared to the BNC which uses a plastic dielectric and a slightly smaller pin diameter. They are compatible to the point of just barely making contact for test purposes but not for full insertion of a male N into a female BNC.

Another problem is different impedance connectors for type N where the 50 ohm has a much larger pin than the 75 ohm version. Plug a 50 ohm N male into a 75 ohm N female and you broke it. My last job had a guy that would always make the mistake of sticking a spectrum analyzer with a 50 ohm N male into 75 ohm N female jacks and destroying them. He would sometimes plug the wrong connector in destroying it and since he didn't get the expected reading he would go down the line of L-band dividers and break a bunch in a row.

Fortunately 50 ohm and 75 ohm BNC are mechanically compatible with the same size pin but the 75 ohm BNC is missing the plastic dielectric which raises the impedance.


As noted interesting article.

Mismatching always gets my attention. One drawing I found shows the BNC pin diameter at 1.35mm. Another for the N type was 1.60mm to 1.68mm without a nominal size. Difference is not significant but...

My last project was the cable design for large medical testing device. Biggest headache was troubleshooting equipment in the lab or line and someone had probed a connector contact that was not the fault, but it became a secondary intermittent symptom as the probing sprung the contacts.

Proceed with caution and use at your own risk...

Mike
 
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