Author Topic: Difference between coax cable and shielded cable  (Read 875 times)

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Offline vk6zgo

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Re: Difference between coax cable and shielded cable
« Reply #25 on: October 19, 2019, 03:37:02 am »
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.

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:-




 

Offline soldar

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Re: Difference between coax cable and shielded cable
« Reply #26 on: October 19, 2019, 12:38:23 pm »
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..

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.
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Offline SL4P

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Re: Difference between coax cable and shielded cable
« Reply #27 on: October 20, 2019, 08:32:08 pm »
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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