Ferrite Beads for RF Interference for Wah

[soupbone]

I've talked to a couple of folks on here about using ferrite beads for getting rid of radio frequencies from my older crybaby.A friend of mine that works at an electronics store here in town told me to "wrap" one of the wires going to the input jack about 3-4 times around the ferrite bead,and he said that should get rid of the RF signal.Does this sound like the correct way to use them?

[deadastronaut]

that's funny i just repaired a DVR for a neighbour,(replaced the scart socket)  and it had a large ferrite ring with a cable wrapped round it a couple of times...

must be something in it i guess...

[Derringer]

SELL ME YOUR MAGIC BEADS

[joegagan]

like i told you in the PM, reputable wah masters have the beads on the output. i gave you a way to look it up, try it.

a little frustrating when people hit you up for special PM advice and then don't bother with any reply at all . i don't even say it has to be  a thanks , could be a "F U ; for all i care. why do i give out advice in PMS?

then come on here after apparently not trying the advice and act like they are still starting from square one.

like my old friend tom may used to say  ' give em books, they eat the covers"

[soupbone]

like i told you in the PM, reputable wah masters have the beads on the output. i gave you a way to look it up, try it.

a little frustrating when people hit you up for special PM advice and then don't bother with any reply at all . i don't even say it has to be  a thanks , could be a "F U ; for all i care. why do i give out advice in PMS?

then come on here after apparently not trying the advice and act like they are still starting from square one.

like my old friend tom may used to say  ' give em books, they eat the covers"

I'm so sorry Joe!I thought i did reply to you?If i didn't I'm truly sorry!! I looked up the mu-metal like you told me,but i couldn't find any of it around here.I meant to say "output" not "input".I should have just p.m.'d you again,but i feel like i bug people sometimes because I'm OCD!!Bad!!

[Jdansti]

why do i give out advice in PMS?

They have medications for that... 

[joegagan]

sorry, went  off on ya there. i should have left allowance for a typo.
please accept my apology, you have always been good to me.

[John Lyons]

...have the beads on the output

Hmmm So this gives a little more clout to me having "solved" an oscillation issue by putting a cap to ground at the output
and nulling some pot scratch/oscillation? 

[joegagan]

john, damnit, like i told ya in a PM.....

[John Lyons]

Group hug! 

[joegagan]

( that john comment was humor, folks - we never PM, we only telepathic mind melt)

[PRR]

> "give em books, they eat the covers"

[joegagan]

nutritious AND delicious

[Jdansti]

Based on my personal experience, the small puncture marks surrounding the frayed corner indicate that a canine was very interested in physics.

[Seljer]

I rewired up my wah with shielded cable to and from the switch/jacks/circuitboard, it seems quieter than with regular cable

[soupbone]

sorry, went  off on ya there. i should have left allowance for a typo.
please accept my apology, you have always been good to me.

Apology accepted You've always been a big help to me.I just get real impulsive sometimes,and don't think things through.

[Jdansti]

sorry, went  off on ya there. i should have left allowance for a typo.
please accept my apology, you have always been good to me.

Apology accepted You've always been a big help to me.I just get real impulsive sometimes,and don't think things through.

The folks on this forum are overwhelmingly super decent people - absolute class acts. (Not being facetious, all of you guys are great!)

[amptramp]

Getting back to ferrite beads, there are several formulations that optimize the bead for various frequencies.

Some are used for VHF frequencies (like FM and television) and have low losses so the user will be able to make baluns (balanced to unbalanced transformers), impedance converters and the like.  They are low loss.  There are other materials optimized for lower frequencies but also low loss.

Some are optimized for filter work with resistive losses in the ferrite.  Low loss beads can sometimes make matters worse by playing whack-a-mole with circuit impedances - they may suppress interference at some frequency at the cost of increasing it somewhere else where you were not having a problem before.  Lossy beads convert the high frequencies to heat through the resistive ferrite they use.  The suppression is more broadband and they do not tend to cause impedance spikes at some unplanned frequency.  These are the ones you want.

[defaced]

Lossy beads convert the high frequencies to heat through the resistive ferrite they use.  The suppression is more broadband and they do not tend to cause impedance spikes at some unplanned frequency.  These are the ones you want.

Jumping in because this is an area I know squat about and doesn't come up often, but I wanna learn about it.  I did a very quick glance at Mouser and some data sheets and didn't find any verbiage about lossy vs lossless.  Following my nose from a datasheet to a manufacturer's site, there seemed to be some description toward inductive coils they made being lossless for the applicable frequency.  Going even further, they have a design guide that looks to have lots of plots of various materials but being absolutely ignorant here, is there an easy way to tell what materials are lossy, or are there just conventions that Materials XYZ are lossy and Materials ABC are lossless, or...?  I'm sure the info is in there, but I don't know what I'm looking at. 

Here's the design paper I mentioned:  
http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf

[amptramp]

There was information in the paper, but it is a little difficult to find.

Generally, the conductive ferrite material is most effective at low radio frequencies and tends to absorb energy because it acts like the secondary of a transformer connected to a low resistance with the wire going through the bead as the primary.  Another way to achieve the same effect is to add a resistor across the ferrite bead from one side to the other, which has the same effect with high-resistivity ferrite materials.  If the inductance and the current changes combine to make the voltage different at the input and output of the wire, the resistor damps it out whether the resistor is a discrete device or the resistance of the ferrite.

As for design documentation, welcome to the deep end.