Long firewire cable run

finn_mccool

finn_mccool

Active member
I'll be using HDV Rack with my HD100 and was wondering if anybody's using long firewire cable runs with it. Has anyone used 50, 75, or 100-ft. lengths with success (or not)?

Thanks,

Keith
 
Hi Keith. The longest FW cable I have seen for sale is 10m, so I expect that you will not get good results with such long cable runs. There is a fibre optics converter that can be used to extend the distance. This should be a good solution for what you are doing, but it is a bit pricy. Link is below.

Richard Hunter

http://firewirestuff.com/opticisfw.html

Edit. Just found a much cheaper solution using repeaters. Link below.

http://www.gefen.com/kvm/product.jsp?prod_id=1329
 
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Actually, Stephen is correct. 15' is the absolute maximum run before you begin to realize signal degradation. While SD seems to hold up better longer, the damage for both SD and HD starts after about 12 feet. With an HD-type signal, the degradation is apparent sooner like at 12-15 feet while an SD signal is already deteriorating at 12 feet but you don't see it as quickly, maybe up to 20 feet or so because it's a less complex signal.
 
The issue isn't SD vs. HD -- it's the Firewire speed that the HD100 tries to use in each mode. In DV mode, the HD100 sends 25 Mbps of data at the 100 Mbps "S100" rate of Firewire. In HDV mode, the HD100 only sends 19.4 Mbps of MPEG 2 data, but insists on using the 400 Mbps "S400" Firewire speed. There is no way to make the HD100 use the "S100" speed in HDV mode.

This is a problem because the long Firewire cables (such as Datavideo's) are only rated for the "S200" speed. So the HD100 in DV mode will work great, but in HDV mode you won't be able to initialize a Firewire bus over the cable at all.

Possible solutions including buying a Firewire-over-fiber repeater pair. (Don't buy a Firewire-over-CAT5 repeater pair, because these only work at S100.) Another option that we have used is the $20 15-foot-cable (with built-in repeater) that pccables.com sells: http://www.pccables.com/cgi-bin/orders6.cgi?action=Showitem&id=ID1433447&partno=70922 . You can get away with at least five of these in a row before needing a powered hub.
 
Very good information, thanks. KeithW: do you find the cables pulling out of each other with this setup? It looks like it might be somewhat flimsy, to have three or four of these daisy-chained.

Keith (also W, for Ward)
 
Hi Finn,

The specification for IEEE 1394 limits the cable length to 4.5 Meters (approx 15 feet). At that length your data is safe. Beyond that length there may be signal loss. It's not that you can't use a longer cable and have success but it is recommended to use a repeater beyond 4.5 meters.
 
Thanks, Stephen. Maybe those folks on the other thread are experiencing some signal loss, but don't see it, or it doesn't bother them.

Keith
 
Keith, that other thread wasn't in an HD100 forum, and the original question was about "DV Rack," so I don't think those people were talking about any HDV camera at all, much less the HD100. As I said, the HD100 in DV mode (that is, the "S100" Firewire speed) works fine over long-distance cables. But in HDV mode (which uses the "S400" Firewire speed), it doesn't, at least not over Datavideo's 66-foot cables. If you can find long-distance Firewire cables rated for "S400" operation, it may work fine.

The chaining of repeaters has worked acceptably for us, with liberal use of gaff tape, but it's true that you run the risk of people tripping over the cables. You also want to gaff the Firewire cable to your tripod arm so there's no flexing the HD100's Firewire connector when you pan the camera.
 
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