SDI Cable Maximum Length: Distances by Rate and Cable
There is no single maximum length for an SDI cable. The distance depends on two things: the SDI speed you run and the coax you run it on. A low-loss RG6 cable that carries HD-SDI for 150 m may carry 12G-SDI for less than 100 m. A thin patch cable may stop at 45 m.
Here is the short answer. For single-link 4K60 (12G-SDI), plan for about 45 m on mini RG59 and up to about 98 m on a low-loss RG6 cable such as Belden 4794R. For HD-SDI, good RG6 stays within its chart figure at 100 m. For 3G, check your receiver’s loss budget first. Always keep a margin, because the figures below count cable only.
SDI cable length by speed and cable type
Each SDI generation runs at a higher bit rate. Higher rates lose more signal in the cable, so the same cable reaches less far. The SMPTE standards set the speeds, as AMD’s standards list shows: SD-SDI at 270 Mb/s (ST 259), HD-SDI at 1.485 Gb/s (ST 292), 3G-SDI at 2.97 Gb/s (ST 424), 6G-SDI at 5.94 Gb/s (ST 2081) and 12G-SDI at 11.88 Gb/s (ST 2082).
The table shows cable-only distances in metres. RG6 values come from the Belden transmission distance chart. Mini RG59 values come from Belram and its 1505F page.
| SDI rate | Belden 1694A (RG6) | Belden 4794R (low-loss RG6) | Belden 4855R (mini RG59) | Belden 1505F (flexible RG59) |
|---|---|---|---|---|
| HD-SDI (1.5G) | 113 m | 151 m | 67 m | 68 m |
| 3G-SDI | 78 m (155 m) | 105 m (209 m) | 47 m (94 m) | 46 m (91 m) |
| 6G-SDI | 105 m | 144 m | 66 m | 60 m |
| 12G-SDI | Not rated | 98 m | 45 m | Not listed |
Two 3G numbers appear because Belden uses two loss budgets. The lower figure assumes a receiver that copes with 20 dB of loss at half the clock frequency. The figure in brackets assumes 40 dB. Check which one your gear is built for.
Why there is no fixed limit
The SMPTE standards do not print a maximum length. They describe how much signal loss a receiver must tolerate. Belden turns that loss budget into metres using each cable’s attenuation, as it explains in its video cable performance article.
This is why gear makers often quote shorter distances than the cable chart. Barco, for example, lists 50 m of Belden 1694A for 12G-SDI. Belden’s own chart shows no 12G distance for 1694A. The cable may work for short 12G runs, but you have little reach headroom.
The practical rule: find your gear’s own cable guidance first. Use the cable chart second.
What shortens your real run
The chart counts cable only. Connectors, bulkheads and patch panels all add loss and are not in the numbers. Real runs usually have at least two connectors, and often more.
Check these four things before you buy cable:
- Connectors. SMPTE ST 424 calls for 75-ohm BNC connectors. A 50-ohm BNC may mate, but it reflects signal at SDI frequencies. Barco also warns that standard BNCs are not made for 12G and cut usable length. Use connectors rated for 12 GHz on 12G links. The Gigatronix 12G BNC bulkhead jack is one such part.
- Patch points. Every bulkhead or panel eats into your margin. Fewer is better.
- Bends. Tight bends damage the cable’s impedance. Belden’s 4694R, for example, has a minimum bend radius of 2.75 in (69.9 mm).
- No gradual warning. SDI fails at a cliff edge, not slowly. The picture is fine, then it drops out. So do not run at the limit. WireFlow advises taking the datasheet figure and then derating for connectors and patch points.
A worked example: 60 m to a 4K60 switcher
Say you need 12G-SDI from a camera position to a switcher 60 m away, with one bulkhead on the wall.
- Belden 1694A: not rated for 12G. Barco’s 50 m is already short of 60 m. Skip it.
- Mini RG59 (4855R): 45 m. Too short.
- Low-loss RG6 (4794R): 98 m on the chart. The 60 m run uses about 60% of that. That leaves room for the bulkhead and connectors.
As a rule of thumb, we suggest staying below roughly 70% of the chart figure when a run has patch points. That is our planning habit, not a standard. For this example, 70% of 98 m is about 69 m, so 60 m fits.
If your run were 90 m, the same cable would leave almost no margin. Use an extender instead.
Choosing cable for the job
Thin cables are easy to handle, but they reach less far. Match the cable to the way you work:
- Camera rigs and short patches (under 10 m). Use flexible, thin cable. Reach is rarely the issue. The Belden 4855R 12G SDI cable handles 12G up to about 45 m, and the Belden 1505F is a more flexible 6G option up to about 60 m.
- Fixed installs and long runs. Use thicker low-loss RG6. It is stiffer, but it reaches further.
- Moving cameras. Choose flex over reach. Keep the run short.
Browse our full range of coax cables for 12G, 6G, flexible and coiled BNC patch cables. If you need a length that is not listed, the 4855R and 1505F listings say custom lengths are available on request.
When coax is not enough
If the run is longer than your cable allows, do not buy a thicker cable first. Look at three other options.
Equalising or reclocking gear. Some receivers and distribution amplifiers rebuild a weak signal. Reach depends on the chip and the rate. One Texas Instruments equaliser lists 75 m at 12G, 120 m at 6G, 200 m at 3G and 300 m at HD on Belden 1694A. That is more than the cable chart. Other devices reach less, so read the datasheet of the gear you plan to buy.
A repeater placed mid-run gives you two shorter legs. The Atomos Connect Repeat SDI is listed for taking 3G, HD and SD-SDI sources beyond 200 m on coax.
Fibre. Fibre is the better answer for long, high-rate runs. A fibre extender converts SDI to light and back. Muxlab’s 12G kit, for one, lists up to 10 km on single-mode fibre at all rates, against 40 m at 12G on coax. Fibre also ignores electrical interference. The AVMATRIX FE1121-12G fibre extender takes 12G, 6G and 3G-SDI.
Wireless. For moving cameras, a cable may not be the right tool at all. See our guide to wireless video transmission systems.
If you are still deciding between SDI and HDMI for a long run, our guide to choosing HDMI cables for video rigs covers where HDMI runs out of reach.
Key Takeaways
- No standard sets one SDI length. Distance depends on the SDI rate and the cable.
- For 12G-SDI, expect about 45 m on mini RG59 and about 98 m on Belden 4794R, cable only. Belden does not rate 1694A for 12G.
- Chart figures exclude connectors, bulkheads and patch panels. Keep a margin, because SDI fails suddenly.
- Use 75-ohm BNC connectors rated for your SDI speed.
- Past your cable’s reach, use an equaliser, a repeater or a fibre extender instead of guessing.
Tell us your SDI rate, run length and number of patch points. Our team will help you pick the right cable or extender. Contact MediaGear and we will check your setup before you buy.
