Does V8 - HDV need a flux capacitor?

farss wrote on 5/15/2008, 3:14 AM
This thread over at DVInfo talks about firewire problems with the JVC HD110 camera and how they can be solved / reduced by fitting ferrite beads to the firewire cable. Sound pretty whacky to me. Being digital signals it'd take a heck of a lot of RFI before a "1" got turned into a "0" but who am I to know for sure. If there is any truth in this it would explain some of the flaky problems that some seem to suffer from and others don't.
I've got a number of clamp on ferrite beads lying around. They're not overly expensive so for those having ongoing issues I guess it's worth a try.

Bob.

Comments

Coursedesign wrote on 5/15/2008, 3:44 AM
Being digital signals it'd take a heck of a lot of RFI before a "1" got turned into a "0".

The beads stop extraneous high frequency signals from the digital circuitry in either the camera or the PC (more likely the PC here) that can quite easily create false transitions.

It's not exactly that it makes a 0 look like a 1 per se, it's that it makes the receiver think that there was a transition when there wasn't.
farss wrote on 5/15/2008, 4:17 AM
Um, so if the receiver sees a false transition that doesn't cause an incorrect bit then nothing goes wrong?
Typically though those beads are used to stop the fast transitions travelling along cables from causing the cable to radiate RFI although they'd likely work the other way around as well.

Which is all kind of academic really, the real question is could RFI cause a data error in the communication along a firewire cable. Without knowing the protocol and how much error checking and correction is done it's hard to know for certain. But if it was a general problem then I'd assume it'd show up in data transfers between any firewire devices and that doesn't seem to be the case.

On top of that 1394 seems to be speced for significant lengths, I've seen cables that are 5M long.

Of course the answer might just be that this a problem unique to just this JVC camera due to some oddity in PCB layout etc.

Bob.
apit34356 wrote on 5/15/2008, 5:12 AM
it would suggest that the cable shielding connection at the camera or the camera is leaking a of rf from its pcb. ---- if it is camera specific problem as it sounds.
Coursedesign wrote on 5/15/2008, 10:17 AM
There are many different input circuits, with a different sensitivity to jitter and extraneous noise in the signal.

Lots of hard work has gone into minimizing this problem, but there is always some bean counter who figures out a way "to save money."