也不能這樣說
要正確説法（給普通人）
多長的電線 就需要配多粗的電線


http://www.monoprice.com/home/home.asp?pn=help&idx=12


HDMI® Cables - AWG Explained

A cursory examination of the Monoprice HDMI Cables pages will reveal that there are more choices than just Standard and High Speed. What is likely to jump out at you are the different AWG (American Wire Gauge) ratings of the different cables. There are 28 AWG High Speed HDMI Cables and 22 AWG Standard HDMI Cables. What does all this mean?

First, AWG (American Wire Gauge) is a measure of the thickness, or gauge, of a wire. The system is based on the number of times a wire could be wound around a spool of a given width, so a 30 AWG wire could be wound 30 times, while a 20 AWG wire could handle only 20 windings. Therefore a 20 AWG wire is thicker, with a larger diameter, than a 30 AWG wire.

Wire gauge directly relates to the amount of electrical current that can be carried on the wire. The larger diameter of wire, the more current it can carry. In terms of HDMI this means that a larger gauge wire (smaller AWG number) is capable of higher bandwidth than a smaller gauge (larger AWG number). Therefore, a 22 AWG wire is capable of higher bandwidth than a 28 AWG wire.

If you look closely at the HDMI Cables pages, you will see that there are cutoff points for High Speed HDMI Cables in each AWG grouping. Beyond the cutoff the cables of the same AWG are rated as Standard HDMI Cables. The longer cables are not made any differently, however. As the length of a wire increases, so does the overall resistance of the wire. Increased resistance means decreased current capacity and therefore decreased bandwidth in HDMI terms.

The cutoff points for High Speed HDMI Cables of each AWG rating are:

28 AWG = maximum 10 feet

26 AWG = maximum 12 feet

24 AWG = maximum 15 feet

22 AWG = maximum 25 feet

So a 12 foot 28 AWG HDMI Cable is not rated for the full 10.2 Gbps required for the High Speed designation. However, it doesn't just jump down to the minimum 2.25 Gbps required for Standard HDMI Cables. It may be capable of 9.5 Gbps, which is almost enough for the High Speed rating, but because it isn't 10.2 Gbps, it must therefore be classified as a Standard HDMI Cable. The longer the wire, the lower the bandwidth it will be able to handle. However, all of our HDMI Cables are capable of at least the 2.25 Gbps minimum required for Standard HDMI Cables.

從另外一個角度來看
如果 25ft + 25ft 然後中間可以加一個 Repeater 訊號會比較好 跟一條 普通 50ft 比較