Coaxial cable (Coax) comes in many types.
For satellite TV reception (Free to Air, Foxtel or VAST), we need only to concern ourselves with a few types.
By far the most common type of Coax used is the RG6Q. This is a 75-ohm (impedance) cable with 4 layers of shielding (2 foil and two braid). It provides excellent shielding to prevent interference entering the coax feed line. For the average house installation or for VAST, this cable provides the most economical cost effective solution to the type of cable you require.
RG6T (A tri-shield) and RG6D (a dual shield cable), were common a few years ago. These cable are fine, but the more layers of shielding the better the performance.
Before the advent of multi shielded coax, it was common to have single layer coax shield and sometimes a honeycomb dielectric. (The dielectric is the centre insulator that separates the copper centre conductor from the shielding). Some types of this coax were better than others. Some had a very loose shielding that allowed interference to break into the coax feed line, with digital transmission this will cause major problems. Unfortunately, some factory pre-made fly leads also have a very poor loose shielding and cause many problems. This type of coax and fly leads should be avoided to prevent digital problems.
At Satgear all our coaxial leads are hand made from premium RG6Q coax cable with compression joints at each end.