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Message from discussion What is the use of ferrite core?
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Bertho Boman  
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 More options Aug 18 2000, 9:52 pm
Newsgroups: rec.photo.digital
From: Bertho Boman <bo...@vinland.com>
Date: Sat, 19 Aug 2000 01:52:13 GMT
Local: Fri, Aug 18 2000 9:52 pm
Subject: Re: What is the use of ferrite core?
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Yes, really.
A shield is used to prevent radiated signals from getting in and out.

A ferrite choke (or other types of chokes) is  preventing the wires
attached to the electronics from acting as antennas.  Again, both
ways. It prevents conducted signals from coming in and conducted
signals going out.

Some products are only tested for spurious radiation leaving the
equipment and the manufacturer might not test for immunity to external
signals but the ferrite will help for that also.  (I do this type of
stuff for a living)
Bertho Boman
======================================

On Fri, 18 Aug 2000 , dhay...@jersey.net (Dave Haynie) wrote:
>On Fri, 18 Aug 2000 03:29:42 GMT, Bertho Boman <bo...@vinland.com>
>wrote:

>>It works both ways.  It is also used to prevent external interference
>>from getting into the electronics inside the camera.

>Not really -- you use a shield for that. It's also extrememly rare
>when a product is unduely influenced by external RF (a bit more likely
>is conducted interference, such as via ground loops). And for a
>digicam, if this was really a means to shield the device in the
>comfort of your home, you're be completely doomed out in the real
>world, where RF emissions are often 100's of times greater (I was
>working at a carnival once where 25ft unshielded cable I used for
>remote camera trigger was picking up about a volt and a half, just
>clean out of the air).

>Typically, if a product ships with a clamp-on or slip-in ferrite ring,
>it's an indication that the product failed in FCC (or CE in Europe)
>testing on radiated RF emissions. You try to avoid having these
>external if you can, but they're much easier to add last-minute that
>way.

>Dave Haynie  |  frog pond media  |  dhay...@jersey.net
>     "Whomever dies with the most cameras wins"


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