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Monitor Extension with RF chokes?


Dec 27, 1999
I bought a monitor extension lead but there is an issue:
(i) the extension doesn't have those little
barrel-shaped thingies on each end (I think they're called RF chokes and
suppress radio interference) and I've noticed interference on the screen.

Is there any where where you can buy 3m+ (5m pref) extension cables for a monitor with these RF chokes on ?


Diamond Member
Aug 10, 2000
Do you mean something like this?

If you're getting interference, the best way to go is with BNC cables if your monitor has these inputs.


Senior member
Nov 10, 2000
Odds are your problem is NOT RF interference. The ferrite cores are not put on cables to prevent external interference, they are they so that the cable itself does not act as an antenna and send RF to other electronic equipment. Your computer is a source of RF noise, the ferrite cores reduce the noise from your computer not the other way around.

Extension Cables and switchboxes are notorious for causing ghosting or streaking on the screen. This is almost always due to an impedance mismatch at the cable connection to the extension cable or switchbox rather than the cable itself.

I would recommend you avoid extension cables and switch boxes for video. If you really want to use extension cables, it's best to go the BNC route. Find a cable that has a d-sub on one-end (to connect to the video card) and BNC connectors on the other. Use BNC barrel connectors to attach the extension cables together. These can be found in almost any retail electronics shop. The quality of the cable also can cause some amount of video degrading. Use high quality 75 Ohm coaxial cables.

It will always be better to try and find a longer single-piece cable, however I do not know where to find such a beast (anyone??). Remember it is the point of connection that is creating the problem. More connections means more impedance mismatches.

Good luck