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
- 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.
- 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.
- 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.