Maximum transmission distances for digital video cables
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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 |
| Specification: |
ITU-R BT.601 |
SMPTE 259M |
SMPTE 259M |
SMPTE 292M |
| Application: |
Composite PAL |
Component 4:3 |
Component 16:9 |
HDTV |
| Belden 179DT |
137m |
116m |
104m |
34m |
| Canare L-2.5CFB |
- |
195m |
- |
55m |
| Canford SDV |
283m (255m*) |
255m (230m*) |
222m (200m*) |
66m (60m*) |
| Canford SDV-X |
- |
- |
- |
70m (63m*) |
| Canford SDV-F & SDV-F-HD |
319m (284m*) |
263m (237m*) |
227m (205m*) |
67m (61m*) |
| Belden 1505F |
327m |
261m |
223m |
69m |
| Belden 1855A |
290m |
241m |
207m |
79m |
| Belden 1505A |
415m |
338m |
296m |
94m |
| Canare L-5CFB |
- |
370m |
- |
100m |
| Canford SDV-L |
477m (430m*) |
405m (365m*) |
350m (315m*) |
112m (100m*) |
| Belden 1694A |
521m |
436m |
378m |
122m |
| Canford SDV-HD |
700m (630m*) |
588m (530m*) |
511m (460m*) |
161m (145m*) |
| Belden 7731A |
756m |
622m |
536m |
168m |
Notes
- * When comparing distances, it should be noted that Draka, who manufacture Canford's HD and SDI video cables, always quote maximum transmission distances that are de-rated by 10% to allow headroom. These "headroom de-rated" figures are shown in brackets and are marked with an asterisc. Some other cable distributors and manufacturers also quote maximum transmission distances and do not give a "headroom de-rated" figure, care should be taken when comparing figures. Canford recommends that users always allow some headroom in planning cabling installations, as many factors can affect system performance, not just the cable itself.
- To make life harder for the system designer, some manufacturers quote theroetical calculated values, others quote "test" results (particularly in advertising and marketing literature) but without always being specific about the test - making comparisons even harder! As you might imagine, these "test" figures are always higher than the theoretical values.
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.