Unfortunately - opinions on the internet is like butt holes, everybody has one and occasionally they stink.
read this;
http://www.mitcables.com/pdf/RG-6.pdf
Are there differences?
Is there really a difference between one RG-6 and another? Why should I buy
a cable for $0.60/ft when I can get one for $0.09/ft.Should I buy quad-shielded
cable instead of dual or single-shielded? I’ve heard terms like VP, bandwidth, and capacitance used when describing coax cables.
What do these terms mean?
Do the materials used to construct the cable really effect the
performance,and are they worth the extra cost?
The differences– All cables are not created equal.
The better the materials,construction techniques and technology—the better the performance.
Understanding this is extremely critical,since you can’t easily upgrade your cable once it’s in the wall.
Make sure you get it right the first time, install a cable that provides the best performance.
Wiring with the correct product will ensure all of the performance possible and will not limit future system upgrades.
This is especially true, once you consider the extreme bandwidth
demands of modern High-Definition and Digital TV signals.
There are just a few determining factors when it comes to coaxial cable design. But if the proper specifications are not followed, the performance of the cable will suffer.
Here is some background technology information on
those determining factors and how they effect performance:
conductors- Copper is the best choice due to its high conductivity, affordability and workability. The purer the better, with the standard at, at least 99.99%pure.
In less expensive cables, copper-clad steel is often used.
Steel cables are undesirable due to the increased resistance/impedance created by thesteel conductor.
Silver is often used,in some more expensive “upgrade”
cables (due to its very low resistance/impedance at higher frequencies),but the cost can be prohibitive.
For high performance,high bandwidth systems, a
great alternative to solid silver is silver-clad copper which provides excellent performance at a fraction of the price of pure silver.
Shielding -
The shielding is what protects the signal from outside
interference such as EMI and RFI, while also providing a return for
the negative signal back to the source.
So, shield materials can have a large effect on performance.
dual-shield vs. quad-shield —
It’s really not the number of shields, but how well they cover that really matters.
Coverage, and resistance is everything when we consider shielding.
The rule is at least 95% coverage copper braid (for low frequency protection) and at least 20° to 30° overlap on the foil shield (for high-frequency protection).
Shielding is not cumulative
Two braided shields that are 60% and 40% coverage will not give you 100% coverage.
The combination can actually only end up to be about 80%, leaving 20% uncovered.
Also,more is not necessarily better.
Anything more than 100% shielding can be overkill, just creating more capacitance, which reduces the bandwidth of the cable, and in turn system performance.
Quite often, quad-shielded cables will tend to increase capacitance to such high levels,they will actually reduce the systems overall performance.
So,in most cases, a well designed dual shielded
cable will work best. This is why most manufacturers top level cables are dual-shielded.
Dielectric material-
The primary dielectric is the insulating material that separates the center conductor from the shield, the more air in the dielectric material , the lower the capacitance , and the higher the velocity of propagation (VP).
Foamed or gas-injected dielectrics are more costly to manufacture, but are necessary for low capacitance and high velocity of propagation .
VP - is the speed that the signal travels through the wire and its value is expressed as a percentage of the speed of light.
Low capacitance and high velocity of propagation
are key for wide bandwidth high-quality video transmission.