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Maximum transmission distances for digital video cables

The serial digital interconnect standards are designed to operate where the signal loss at half the clock frequency does not exceed these approximate loss values:

SMPTE 259M (PAL, widescreen): Maximum length = 30dB loss at half the clock frequency
SMPTE 292M (HDTV): Maximum length = 20dB loss at half the clock frequency

This provides a method of defining the maximum calculated length of cable for satisfactory signal transmission. Interfaces such as connectors and patching may alter the overall "end-to-end" parameters as the cable is only one part of a signal path, and this also assumes installation of cables within their minimum bending radius limits and without crush effects of tie-wraps and other cable bindings that locally distort the construction profile. Having mentioned "the disclaimers", the values shown below are a reasonable guide to what might realistically be expected in a typical professional installation.

Data rate: 177Mb/s 270Mb/s 360Mb/s 1.5Gb/s 1.5Gb/s 3Gb/s 3Gb/s
Specification: ITU-R BT.601 SMPTE 259M SMPTE 259M SMPTE 292M Tests using Tektronix TG 700 generator and WFM 8300 waveform monitor SMPTE 424M Tests using Tektronix TG 700 generator and WFM 8300 waveform monitor
Application: Composite PAL Component 4:3 Component 16:9 1080i HDTV 1080i HDTV 1080p HDTV 1080p HDTV
Belden 179DT 137m 116m 104m 34m - 24m -
Canare L-2.5CFB 242m 199m 172m 54m - 36m -
Canford SDV-M - - - - - - -
Canford SDV 283m (255m) 255m (230m) 222m (200m) 66m 90m 50m 80m
Canford SDV-X - - - 70m 110m 50m 100m
Canford SDV-F & SDV-F-HD 319m (284m) 263m (237m) 227m (205m) 67m - - -
Belden 1505F 327m 253m 223m 66m 44m
Belden 1855A 290m 241m 207m 79m - 46m -
Belden 1855ENH - 261m - 87m - 52m -
Belden 1505A 415m 338m 296m 94m - 67m -
Canare L-5CFB 513m 420m 364m 112m - 76m -
Canford SDV-L 477m (430m*) 405m (365m*) 350m (315m*) 112m 140m 70m 130m
Belden 1694F - 326m - 87m - 58m -
Belden 1694A 521m 436m 378m 122m - 82m -
Canford SDV-HD 700m (630m*) 588m (530m*) 511m (460m*) 161m 240m 120m 230m
Belden 7731A 756m 622m 536m 168m - 110m -

Notes

  1. NOTE: It is extremely important NOT to compare maximum transmission distances quoted for Belden and Canford (Draka) similar types, as the two manufacturers have entirely different policies on how they quote these parameters, which means the figures are not expressed on a 'like for like' basis. Draka take a considerably more prudent and conservative view than Belden, hence Draka figures are always lower in this table, but not in a 'like for like' comparative test using the same equipment and the same test conditions. Canford does not share the views of several other cable distributors who may only quote the 'best case' figures for the cables they sell. It is recommended to 'de-rate' best case figures by at least 10%. To further add to the problems of comparison, typical installed systems using Canford (Draka) cables can give satisfactory performance 1.5 to 1.8 times the theoretical calculated values.
  2. Canford cable (manufactured by Draka) maximum transmission lengths are derived from worst case measurements undertaken using Tektronix TG700 and WFM7120, and Tektronix WFM8300. Measurements vary between the two test setups using the same cables, leading to the conclusion that transmission lengths are dependant on the hardware (equaliser) rather than the cable.
    Belden figures are based on typical test values provided by Belden.
  3. The bit error rate (BER) can vary dramatically as the calculated distances are approached. BER is dependant on the reciever design and the losses in the actual coaxial cable used.
    Distribution and routing equipment manufacturers should be contacted to verify the maximum recommended transmission distances of individual components.

The above information has been provided by Belden and Draka-Comteq (manufacturers of the Canford SDV series cables).

SDV™ is a registered trademark of Canford Audio PLC.

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