what is the characteristic of a coaxial cable that makes it unbalanced?

The characteristic that makes a coaxial cable “unbalanced” is that its two conductors have unequal impedance to ground along their length: the central conductor is isolated from ground, while the outer conductor (the shield) has a low-impedance path to ground and can be directly connected to chassis or earth.

Quick Scoop

In transmission-line terms, a line is called unbalanced when its conductors do not “see” ground in the same way. In coax:

• The inner conductor is surrounded by dielectric and shield, so its impedance to ground is high.
• The outer conductor is a conductive tube or braid that often sits at or near ground potential and can carry both the differential return current (inside surface) and unwanted common‑mode current (outside surface).

This asymmetry of impedance to ground is what defines coax as an unbalanced line, not just the fact that it is physically coaxial.

Mini Breakdown

1. What “unbalanced” really means

• In an unbalanced line , the two conductors have unequal impedance to ground , so one conductor tends to be “ground‑referenced” and the other “signal‑carrying.”

• In a balanced line (like a twisted pair), both conductors have (approximately) the same impedance to ground , so neither is inherently “the ground side.”

Put simply: in coax, one conductor is effectively ground , the other is the live conductor.

2. How that applies to coax

• The coax shield can be bonded directly to chassis or earth, giving it a low‑impedance path to ground all along the cable.

• The center conductor is isolated from ground by dielectric and only connects to circuitry at its ends.

• This difference in grounding and return paths makes the line unbalanced by the standard definition.

3. Common‑mode vs differential currents

• The inside of the shield carries the differential return current, equal and opposite to the inner conductor, which ideally cancels external fields.

• The outside of the shield can support common‑mode currents with respect to ground, which is a behavior available only to that conductor, not to the center wire.

• Having only one conductor that can host these common‑mode currents (the shield) is another way engineers describe coax as unbalanced.

Tiny story-style example

Imagine a two‑wire ladder line: both wires are suspended in air, same size, same spacing to nearby objects, and neither is tied to ground; they “share the burden” of any interference and ground coupling equally, so the line is balanced.

Now picture coax: the outer tube is bolted to the metal case of your radio, which is bolted to the station ground; the inner conductor floats inside. Noise or RF on the station ground couples primarily to the shield, not to the center conductor in the same way, because their impedances to ground are completely different. That’s the unbalanced nature in action.

TL;DR

The key characteristic that makes a coaxial cable unbalanced is its asymmetrical impedance to ground : the shield has a low‑impedance, ground‑referenced path, while the center conductor does not, so the two conductors are not equivalent with respect to ground.

Information gathered from public forums or data available on the internet and portrayed here.