23 AWG solid 0.023" bare copper conductor, gas-injected foam HDPE insulation, Duofoil + tinned copper braid shield (95% coverage), PVC jacket.

Newer coax constructions that have been designed specifically for digital transmissions offer performance advantages over the old analog designs. These new constructions employ several design parameters to provide the precision electrical characteristics required for high frequency transmissions over longer distances.

• Center Conductor - The center conductors are solid bare copper. Solid conductors provide better impedance stability and return loss (RL). RL expresses the amount of signal lost due to the signal reflecting back to the source. This reduces the signal reaching the receiver, thus increasing attenuation and decreasing effective transmission distance.
• Digital transmissions contain low frquency elements that travel down the center of the conductor and high frequency elements that travel on the outside of the conductor due to skin effect. For these reasons, uncoated pure copper conductors are used for optimum performance.
• Dielectric - The dielectric material (insulation) consists of foam high-density polyethylene. The special formulation Belden uses is more crush-resistant than standard foam polyethylenes and is less prone to conductor migration. Both crushing and conductor migration can cause a change in the cables impedance which, in turn, will cause an increase in RL. While the nominal velocity of propagation of a solid dielectric is 66%, gas injection technology provides extremely consistent foaming and high velocities of propagation (82 to 84%). The velocity is kept very constant to minimize timing problems. Foam dielectrics reduce the size of the coax compared to older solid dielectric designs.
• Shield - Precision analog cables utilize double braid shields which are not optimum for digital's high frequencies. Braid shields are ideal for frequencies under 10 MHz while foil shields work best above that frequency. Since digital transmissions contain both low and high frequencies, foil-braid designs are used.
• Testing - Lastly, to ensure that the cables are electrically sound, every reel must be 100% sweep tested for RL to at least the third harmonic of the fundamental frequency. For HD cables at an uncompressed data rate of 1.485 Gb/s, this gives an occupied bandwidth of 750 MHz and a third harmonic frequency of 2.25 GHz (3 x 750). For 3G (1080p/60) formats, the data rate is 3 Gb/s with an occupied bandwidth of 1.5 GHz. The third harmonic of that is 4.5 GHz. Belden sweep tests many of its HD cables to 4.5 GHz, with guaranteed minimum RL steps of 23 dB from 5 MHz to 1.6 GHz and 21 dB from 1.6 GHz to 4.5 GHz. More technical information on RL and other cable parameters can be found on Belden's website at www.belden.com.

Available colours include: Black, Green, Brown, Red, Orange, Yellow, Light Blue, Violet, Gray, White.

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Keywords: 1855, 1855A, 23AWG, 23 AWG, 1855, Multicore, Snake, Coax, Coaxial, SDI, HDSDI, HD-SDI, HD/SDI.