I see.... that's very true.
OK, then what's the difference between single center conductor shielded cable and a coax?
Who even makes such a thing yet does not market it as coax?
You could have one-conductor cable made up with foil screen and/or braid just like a multiconductor cable, but this would only have the effect of cheapening the insulation (e.g., using crummy old PVC instead of low loss PE or PTFE) and worsening the shield resistance or effectiveness, and probably giving poorer impedance (but that's already understood given the lossy PVC insulation).
Related note, I've heard of ferrite-loaded hookup wire, which gives reasonable attenuation (filtering -- absorption) at high frequencies. It's a distributed ferrite bead. Really oddball, mil spec I think. No electric-field shielding (as you get from a foil or braid shield), nor magnetic shielding beyond the surface layer.
Tim
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..
In many cases, if twin conductor shielded cable is available, people will use it, instead, either ignoring one conductor, or paralleling the two.
Alternatively, they may use thin coax, just because it is widely available & durable, without actually needing the special characteristics coaxial cable brings.
The connectors commonly used with,"single ended" audio are not the most rugged, either..
An example:-
When I worked at the TV Studio, we had some "standalone" TV projectors, which we used to make available, free of charge, along with a VCR, to various community groups, as part of our commitment to being "good corporate citizens".
These needed one BNC to BNC video cable, & two RCA to RCA audio cables.
The former was easily found, but the latter was not normally used in the Studio, where audio was normally
balanced, not "single ended".
We, perforce, had to "make them up".
The store had twin audio cable, & some "Consumer grade" RCAs, so we would do so.
One problem was that the "twin" cable was quite a bit more bulky than the cable the RCAs were intended for, & after one or two outings, the latter would fail, & need to be replaced.
They also needed to be specially stored, so they wouldn't be lost, something which happened regularly, so we would need to make new ones, all for no profit to the company!
Eventually, we'd "had enough", so we fitted BNC to RCA adaptors to the VCR & projector.
Now we only needed to provide three BNC to BNC coax cables.