Ferrite bead for composite/svideo input?

[Ben Jackson]

Can someone recommend a ferrite bead for composite video input purposes?
I can find beads that have ~75R impedence at 9MHz (which would be a 3dB
loss into the 75R termination) but I don't know if I should stay far,
far away from that corner with a bead.

I've looked at some consumer electronics and most seem to use a bead of
some kind but of course it's hard to know its properties without pulling
it out and applying a VNA.

 

[martin griffith]

Can someone recommend a ferrite bead for composite video input purposes?
I can find beads that have ~75R impedence at 9MHz (which would be a 3dB
loss into the 75R termination) but I don't know if I should stay far,
far away from that corner with a bead.

I've looked at some consumer electronics and most seem to use a bead of
some kind but of course it's hard to know its properties without pulling
it out and applying a VNA.

ISTR that LT spice has a whole pile of Wurth ferrites in the libraries


martin

 

[john jardine]

Can someone recommend a ferrite bead for composite video input purposes?
I can find beads that have ~75R impedence at 9MHz (which would be a 3dB
loss into the 75R termination) but I don't know if I should stay far,
far away from that corner with a bead.

I've looked at some consumer electronics and most seem to use a bead of
some kind but of course it's hard to know its properties without pulling
it out and applying a VNA.

I've seen no visible picture degradation using low pass filters in the
8-10MHz area.
Had a DVR video interference problem the other week. Turned out the DVR was
mixing down ~13Mhz noise peaks on the incoming composite signals. Crap DVR.
Sorted using external lowpass filters. So yes, filtering somehow at lowish
frequencies may be advisable.

 

[Winfield]

Can someone recommend a ferrite bead for composite video input
purposes? I can find beads that have ~75R impedence at 9MHz
(which would be a 3dB loss into the 75R termination) but I don't
know if I should stay far, far away from that corner with a bead.

I've looked at some consumer electronics and most seem to use a
bead of some kind but of course it's hard to know its properties
without pulling it out and applying a VNA.

Is this something we should emulate? I've not used lossy beads
in my video-processing designs, and I don't recall seeing them
used that way in professional video inputs. What's the story?
If a low-pass filter is required for some reason, let it be a
real properly-designed filter.