Belden Essential Cable Facts: High Frequencies

The loss of signal is an important parameter measuring signal strength.

Attenuation (the loss of signal) is an important parameter measuring signal strength. Less attenuation provides a stronger signal which results in a better performing, more robust network.

 

Investing in a top-notch audio visual system and saving on cabling is a classic example of being penny-wise and pound-foolish. But even when you take your cabling seriously, it is not that easy to pick the right cable. Inferior grade cables can often show a comparable AWG in their basic specification but record very different electrical results!

What cable components are critical?

When it comes to high frequencies, the key component is:

  • The conductor: the core of the cable that transfers energy or signals from point to point.


The cross section of a cable conductor plays a crucial role in the cable design. This cross section is represented as an AWG measurement (American Wire Gauge). What makes it tricky is that there is a wide tolerance between the different AWG sizes. Inferior grade cables can often show a comparable AWG in their basic specification but report very different electrical results.

 

For example:

file

Cable Design 1              

AWG 26
Cross section: 0.126 mm2
Attenuation 28.66 dB over 100 MT

file

Cable Design 2               

AWG26
Cross section: 0.140 mm2
Attenuation 26.71 dB over 100 MT

The higher the size of the cross section, the higher the copper amount. Within the same AWG-size there is a possibility for lower attenuation (signal loss) and higher resistance.

What is the threat of high frequencies?

  • The frequency being applied to a cable has a direct impact on the strength of the signal and the decrease in its magnitude as it travels from point to point.
  • At high frequencies the rate of electron absorption by the conductor increases, resulting in a loss in transmission of the signal strength ('attenuation').

What is the effect of high frequencies on sub-standard cable?

  • Cables unable to withstand high frequencies due to insufficient amounts of conductor material can result in sound and visual distortion and system incompetence.
  • High frequencies can have a detrimental impact on the performance of audio, video and Tannoy speaker systems, as less signal makes it to the display from the source.