EMI shielding techniques?
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Tourer
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From: Northern Virginia
EMI shielding techniques?
What solutions for EMI shielding have you used to reduce RFI for class D amps? Where do you place the shields? Do you use ferrite cores and where to place them? What type and how many do you use for AM and FM radio interference?
Grand HDF Member
Joined: Jan 2010
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From: Vancouver BC
You will want ferrite beads placed on all your wiring, a mix of #75 and 43. Place them as close to the amp as possible, 4-5 beads of each type per wire.
http://www.fair-rite.com/newfair/mob...sion_cores.htm
Other than completely enclosing the amp in a seamless metal cavity, you will have trouble completely shielding the amp from RFI leakage. The beads should drastically cut down a lot of both conducted and emitted interference.
http://www.fair-rite.com/newfair/mob...sion_cores.htm
Other than completely enclosing the amp in a seamless metal cavity, you will have trouble completely shielding the amp from RFI leakage. The beads should drastically cut down a lot of both conducted and emitted interference.
Thread Starter
|
Tourer
Joined: Jul 2008
Posts: 436
Likes: 5
From: Northern Virginia
You will want ferrite beads placed on all your wiring, a mix of #75 and 43. Place them as close to the amp as possible, 4-5 beads of each type per wire.
http://www.fair-rite.com/newfair/mob...sion_cores.htm
Other than completely enclosing the amp in a seamless metal cavity, you will have trouble completely shielding the amp from RFI leakage. The beads should drastically cut down a lot of both conducted and emitted interference.
http://www.fair-rite.com/newfair/mob...sion_cores.htm
Other than completely enclosing the amp in a seamless metal cavity, you will have trouble completely shielding the amp from RFI leakage. The beads should drastically cut down a lot of both conducted and emitted interference.
Grand HDF Member
Joined: Jan 2010
Posts: 3,518
Likes: 2,003
From: Vancouver BC
Because EMI/RFI is insipid, and every piece of equipment and installation is different, it requires overkill techniques to minimize or eliminate the problem. The problem "could" be from one or more wires that are radiating, but without knowing which one(s) you must go after all of them. Perhaps it's only your power lead, but maybe your speaker wires are radiating to a much lesser degree. Without proper test gear you'll never know. Every single lead except earth or chassis ground will require the ferrites. If possible get the beads oversized and loop a few turns of each wire through them. The EMI reduction will increase to the square of the number of turns on each bead. You do not want to place any beads on the antenna though, this will choke off any radio signal you're trying to receive. In reality, without lab grade test equipment it's a trial by error approach.
Thread Starter
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Tourer
Joined: Jul 2008
Posts: 436
Likes: 5
From: Northern Virginia
Because EMI/RFI is insipid, and every piece of equipment and installation is different, it requires overkill techniques to minimize or eliminate the problem. The problem "could" be from one or more wires that are radiating, but without knowing which one(s) you must go after all of them. Perhaps it's only your power lead, but maybe your speaker wires are radiating to a much lesser degree. Without proper test gear you'll never know. Every single lead except earth or chassis ground will require the ferrites. If possible get the beads oversized and loop a few turns of each wire through them. The EMI reduction will increase to the square of the number of turns on each bead. You do not want to place any beads on the antenna though, this will choke off any radio signal you're trying to receive. In reality, without lab grade test equipment it's a trial by error approach.
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