What is an HDMI Repeater

HDMI repeaters or HDMI boosters as they may also be called, are used to extend the distances over which HDMI data can be reliably transmitted using HDMI leads


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HDMI repeaters are one way in which reliable HDMI data (video, audio, etc) can be transmitted over longer distances whilst still preserving picture quality.

For a long time the rule of thumb has been that HDMI works up to a distance of around 50 feet or 15 metres, but in realty these cables are difficult to find and expensive to buy. Realistically the maximum distance that should be considered is about 25 feet or 7 to eight metres, and preferably less.

Also, it is found that picture integrity and reliability can fall if long cables are used, or even poor quality cables over shorter distances. Drop-outs, glitches and noise as well as delayed audio on some occasions can all result from poor transmission of the HDMI data. Also local noise and pick-up from mains wiring etc can cause an issue.

To improve the picture quality and ensure a reliable picture and generally ensure reliable operation of the HDMI link, a small unit called an HDMI repeater can be used.

These HDMI repeaters or HDMI boosters as they are also called provide a cheap and reliable solution to running HDMI over longer distances and also reducing the effects of interference, etc.

What is an HDMI repeater or booster

An HDMI repeater or booster can be considered within the general category of HDMI extenders. However it is different from most other forms of extender in that one is often placed about half way along the run, i.e. using two cables. It then boosts the signal, typically to overcome the losses that can occur over longer runs, so that the signal integrity is preserved and the picture quality maintained.

There are two main types of HDMI repeater that can be found:

  • Passive HDMI repeaters:   Passive HDMI repeaters are the simplest form of repeater. They typically consist of a transformer that increases the voltage on the line.

  • Active HDMI repeaters:   As the name implies, active HDMI repeaters utilise active electronic components within the repeater, restoring the HDMI signal and enabling it to be transmitted along the remaining cable length.


HDMI repeaters or boosters can provide a very useful function for many situations. However when considering buying and installing one, to is best to consider carefully what is needed and buy the best one for the given situation. Obviously one of the main considerations is whether to buy and install a passive or a more expensive active one that will probably provide better performance.

Ian Poole   Written by Ian Poole .
  Experienced electronics engineer and author.



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