HDMI: When Typical Installations Don’t Apply
Typical applications require tight tolerances in wire length due to inter- and intra-pair skew limitations.
There is no question that many have been gravitating to the ever-so-popular Cat 5 and 6 conversion products now flooding the market.
Many, however, still have the mindset that since it is a Cat 5 or a Cat 6, the installation can just follow a typical network-type installation. In some cases, that may be true, but in others, it is not.
A case in point: the 110-punchdown block, a very secure and reliable connection system used for years — it just does not cut it when it comes to HDMI.
There are two critical characteristics that affect the favorability of this connection technique. The first (and, no doubt, the most obvious) is length.
Typical applications require some tight tolerances in wire length due to inter- and intra-pair skew limitations. Since we work at achieving length differentials down to hundreds of thousandths of an inch, a typical installation would be near impossible.
The installer would also have to consider the increased frequency response and the higher resolutions commonplace today.
Sharp bends or turns of this transmission line have to be kept at a minimum, too. Punchdowns are typically 90 degrees to complete. This could hinder any high bandwidth connectivity.
So, why do we have so much success with an RJ45? Very simple; if you look at this connector, you will notice the connection to the wire is accomplished by press-fitting the copper into a predetermined connection leaf.
These "leafs" are the same in length, minimizing error.
Many, however, still have the mindset that since it is a Cat 5 or a Cat 6, the installation can just follow a typical network-type installation. In some cases, that may be true, but in others, it is not.
A case in point: the 110-punchdown block, a very secure and reliable connection system used for years — it just does not cut it when it comes to HDMI.
There are two critical characteristics that affect the favorability of this connection technique. The first (and, no doubt, the most obvious) is length.
Typical applications require some tight tolerances in wire length due to inter- and intra-pair skew limitations. Since we work at achieving length differentials down to hundreds of thousandths of an inch, a typical installation would be near impossible.
The installer would also have to consider the increased frequency response and the higher resolutions commonplace today.
Sharp bends or turns of this transmission line have to be kept at a minimum, too. Punchdowns are typically 90 degrees to complete. This could hinder any high bandwidth connectivity.
So, why do we have so much success with an RJ45? Very simple; if you look at this connector, you will notice the connection to the wire is accomplished by press-fitting the copper into a predetermined connection leaf.
These "leafs" are the same in length, minimizing error.
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About the Author

Jeff Boccaccio, President, DPL Labs
Jeff Boccaccio, president of DPL Labs, can be reached at either jeff@invisionstech.com or jeff@dplrating.org.
1 Comments (displayed in order by date/time)
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I’m sorry, but i’ve read through this a few times, and i must be missing something. I get that length is the problem when installing hdmi, but how does that translate to leafs in the rj45??
I don’t get this article at all…