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50 Ohm BNC vs 75 Ohm BNC

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According to Wikipedia, 75 Ohm BNC can be recognized from 50 Ohm BNC due to reduced or even absent dielectric material a8also according to some other websites I found).




But Wikipedia also mentions that this is by no means reliable.

Is there another reliable way to make 100% sure if it is 75 Ohm or 50 Ohm?


I suppose I could try and measure it somehow.


I have access to Oscilloscope and colour bar generator.

Any thoughts on how best to connect a test-setup to determine 50 Ohm or 75 Ohm?


Or another way of reliably recognizing one or the other.

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most 50 ohm is RG-58. Most 75 ohm is RG-59 or RG-6. physical specs can be googled. RG-58 & RG-6 should have one center conductor, RG-58 has many strands


The physical specs are considered to be more of a guideline than a contract in many asian countries. ebay BNC crimp on connectors don't crimp right on CCTV siamesed cable, which is apparently RG-58 1/2


you could make a TDR with a pulse generator and a scope. If you have to ask, don't bother, it would take way too long to explain


If you have a big spool of cable, connect the color bar generator to the monitor and the spool, with a T on the connection and a 75 ohm load on the far end of the cable. It it's 75 ohm cable, no reflection. It it's 50 ohm, you get a ghost image down and right of the real image




50 feet of cable is enough to see this effect

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Cool. I'll try the color bar generator, I got one of those.


I'll look more into Time-Domain Reflectometry, and when I learn more about it, I'll give that a go as well.

You pointed me in the right direction for that one.

Thank you for that.

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