Both RG-6 and RG-6Q, or "quad" are deemed suitable for digital cable and satellite connections. Both have significantly higher capacity over longer distances than their smaller RG-59 cousin, using larger inner conductors and larger dielectrics. However, the differences between RG-6 and RG-6 quad are smaller than the differences between both of them and RG-59. Typically the two are only distinguishable by the markings on the jacket, unless insulation is physically cut away.
The key differentiator between the two cables lies with the inner shielding. RG-6 uses a single foil shield, covering 100 percent of the dielectric. This is surrounded by an aluminum braid. RG-6 quad uses two alternating layers of this foil and braid construction, making it virtually immune to external interference in normal installations.
Diameter and Thickness
RG-6 and RG-6Q share nearly the exact same outer dimensions and have similar flexibility. RG-6Q is slightly stiffer due to the increased amount of inner shielding, but does not present an installation challenge as a result.
EMI Interference and Signal Integrity
RG-6 quad is the preferred cable in any instance where moderate to high levels of electromagnetic interference may be a potential problem. RG-6 is completely acceptable in situations where the possibility of interference is negligible or non-existent. The carrying capacity over distance between the two cables, however, is virtually identical among the two cable types.