| Electronics > Beginners |
| Difference between coax cable and shielded cable |
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| vk6zgo:
--- Quote from: tkamiya link=topic=214566.msg2741556#msg2741556 date=1571250522 8) ---I wonder if anyone with VNA would be willing to characterize a good quality shielded 1 conductor cable....? Then compare it against say RG174. Unfortunately, this is well outside of my capability. --- End quote --- A VNA is nice, but you can find out a lot about cables using "old school" methods. http://users.tpg.com.au/users/ldbutler/TransLines.pdf You can determine the cable impedance Zo, using formula [3] on page (2), with test setup as per figure [8] on page (4) Lloyd goes on to describe other methods, which can determine Zo, & velocity factor of an unknown cable. Alan, w2aew looks at pulse testing of cables in this video:- & revisits the theme in these two videos:- |
| soldar:
--- Quote from: vk6zgo on October 17, 2019, 12:49:28 am ---Single conductor shielded cable used to be common, but maybe, not so much now. That "single" conductor is not concentric with the shield, as in coaxial cable, & the cable's impedance is not well specified.. --- End quote --- Well, it is loosely concentric but with very loose tolerance. I remember, decades ago, when I was more into radio and was always messing with microphones that I could only get single conductor shielded cable which was a problem because I needed a second conductor for the PTT pushbutton. You could buy twin shielded cables for stereo audio but not two wires with a single shield. Whenever I found that cable I would buy it. That kind of shielded cable is fine for audio and relatively low frequencies but no good for RF. In fact, one of the oscilloscope cables I have is plain, very thin, shielded cable and it works fine at low frequencies. |
| SL4P:
Remember there are braided and foil wrapped coax cables, along with solid and stranded centre conductors. Choosing the right connectors is important for this as well as impedance. |
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