Sunday 2 June 2013

How Long Can A HDMI Cable Be Before It Loses Quality?

A very common question I'm asked is how long can a HDMI cable be. Many people want to move their television to another part of the room, or they may want to run a signal to another TV in another room and are unsure about using a long cable.

A HDMI cable uses power from the sending device to power the cable. Most issues come from the loss of this power. I've experienced issues issues where a 20m cable has worked perfectly on one device but causes picture break up on another.

There is no simple answer to the question of length, it all depends on a number of factors including, the devices you are using, the quality of cable, level of shielding on the cable and other cables or electrical devices in the area that can cause interference.

Longer cable problems may manifest in a few ways, the most common would be picture break up, this is where the screen goes blank or flickers momentarily. Another common problem would be sparkles, this is where you get the odd white pixel appearing on the screen. A totally dead screen could also signal an issue with the cable length.

How To Avoid Issues With Cable Length.

If you are suffering issues when using a long HDMI cable; there are a few things that may help. The first thing you should try is a HDMI booster this a small electronic box with a socket on each side, it amplifies the voltage from the cable and repeats the signal, they are very effective are combating signal loss or picture drop out.

The image below shows a booster.


Another point to consider is buying a cable with ferrite suppressors, these are coils which are usually located a few inches from the end of the cable. They have a minimal effect on reducing interference but they have no effect on signal strength which is the cause of most signal drop out issues.

The image below shows a cable with ferrite suppressors.



It's also worth mentioning HDMI cables with built in repeaters. These are longer cables, usually 20m, 30m and 40m that have a booster box built in. They can be quite expensive and my own preference would always be to try a standard cable first and add a booster if needed.

The image below shows a HDMI cable with built in booster.




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