TheF 0 Posted February 20, 2018 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). https://en.wikipedia.org/wiki/BNC_connector https://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/BNC_50_75_Ohm.jpg/220px-BNC_50_75_Ohm.jpg 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. Share this post Link to post Share on other sites
tube tech 1 Posted February 28, 2018 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 Share this post Link to post Share on other sites
TheF 0 Posted March 8, 2018 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. Share this post Link to post Share on other sites
