Why is an un-powered CAT6 cable able to extend the length a video signal can be transmitted compared to a HDMI cable?

Is the limitation on high speed data transmission cables such as HDMI mainly due to attenuation of high frequencies rather than the impedance of the cable?

  • \$\begingroup\$ Wouldn't the attenuation be a result of cable's impedance among other things? \$\endgroup\$
    – AndrejaKo
    Mar 8, 2012 at 13:19
  • \$\begingroup\$ I've not seen CAT6 used for video, only for Ethernet... \$\endgroup\$
    – pjc50
    Mar 8, 2012 at 13:55
  • \$\begingroup\$ I debated if this is off-topic or not, but I will go ahead and answer and see if others think it is off-topic. \$\endgroup\$
    – Kellenjb
    Mar 8, 2012 at 14:19

1 Answer 1


It actually doesn't extend the length of the video signal. The HDMI spec does not include any max distances, rather it only specifies a minimum signal quality at the end of the cable. Typically it is possible to meet spec in cables up to about 50 feet, but cable manufactures have made longer.

The longest I have ever seen advertised for passive hdmi over cat6 is 100 feet. These typically come with a warning that basically say that if you add any other connections you are likely to burn up the output amp on one of your devices. The reason this warning is there is because at 100 feet the cable no longer is meeting spec. The spec allows for some head room, while these passive extenders try to push everything to the limit, even if they don't meet spec. You also become limited at that range in other ways such as being limited to 1080p with no support for higher resolutions, which is not an issue for most people.

Now there are HDMI over Cat6 converts that might look to be passive, but they will actually pull power off of the hdmi cable (there is a 5v pin with max of 50mA) in order to add an active amp to get longer distances.

  • \$\begingroup\$ Does 100' stand for 100 feet? \$\endgroup\$
    – sipsorcery
    Mar 8, 2012 at 19:58
  • 1
    \$\begingroup\$ Yes. ' stands for feet and " stands for inches. \$\endgroup\$
    – Kellenjb
    Mar 8, 2012 at 20:37

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