Radio Interference ?

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Radio Interference ?

Postby travsbluz » 15 Apr 2009, 18:00

Hello, I use both Single coil guitars and Humbucker guitars. With humbuckers the radio interference isn't noticable. But when I switch to my strat etc. it is real bad. (mainly with fuzz/distortion circuits)

I'm looking into properly sheilding my single coil guitars, but I was wondering if there is something to tame the radio down in your pedal builds, or do you just try to ignore it?

I really would like a couple of my fuzz style builds if I could just get rid of the radio interference.

Thanks for your time,
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Re: Radio Interference ?

Postby RnFR » 15 Apr 2009, 18:49

the basic radio interference protection configuration that i've seen is a small, say 220pF, cap to ground at the beginning of your circuit. this should take care of any RF interference you might have. if this doesn't work, i'm not sure. anyone else have anything to add?
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Re: Radio Interference ?

Postby Scruffie » 15 Apr 2009, 18:59

Can only add the way i shielded my strat from this site http://www.guitarnuts.com/wiring/shielding/shield3.php which worked a treat for hum and im sure alot of noise protection (my fuzz factory occasionaly gets mild noise/radio interference, seems greatly reduced if at all with the strat thats been shielded)

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Re: Radio Interference ?

Postby rrhoads33 » 15 Apr 2009, 21:00

To block RF and other noise, Gus Smalley suggests a 10k resistor in series with the input and incorporating a power supply bypass cap.
http://www.runoffgroove.com/sili-face.html

Just to be sure: Your distortions are in a metal enclosure, which is connected to ground (via the jacks). I had already the pleasure to listen to Radio Moscow, when I tried out my distortion+ clone without enclosure. Some Wah and Volume pedals can be not adequate shielded.

If the hum of the singlecoils doesn't annoy you so much, you don't need to shield them. Too much shielded area in a Strat affects like a capacitor towards ground, which means that some high frequencies get lost. It's often described, that shielded guitars lost their "liveliness".

Edit: Ahh, just read, that you've already shielded your guitar; Maybe this post will someday help someone else...
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Re: Radio Interference ?

Postby Scruffie » 15 Apr 2009, 21:07

Hmm i'm not sure that always applies, probably have to do it on a guitar to guitar basis. My strat is actually too bright for me even after shielding it and i've got a 0.47 Cap so Average Warmth But that's just my strat. And alot of the shielding process is also good wiring process with removing all the ground loops n' Such But maybe it's just my preference.

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Re: Radio Interference ?

Postby rrhoads33 » 15 Apr 2009, 21:16

Hmm, yours is too bright? The sound of singlecoils is brighter than that of humbuckers of course. What Potentiometers are used? 250k? With a lower value you'll get a less bright sound.
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Re: Radio Interference ?

Postby Scruffie » 15 Apr 2009, 21:33

Yea 250k CTS Pots, it is a rather bright guitar though, i built it to be pretty bright (just needs that edge taken off), Ebony Board, Maple Neck & American Ash Body, I'm not bothered by it, it's just the single coils im using at the moment which are too lower output which shall soon be bareknuckle Singles, I was just saying that shielding some guitars is ok for brightness and had to be done on a guitar for guitar basis.
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Re: Radio Interference ?

Postby earthtonesaudio » 15 Apr 2009, 21:43

Hearing radio stations requires gain and rectification. Half-wave rectifying the signal can occur with a BJT base-emitter junction, so that bit is hard to eliminate, but you can reduce gain at radio frequencies pretty easily. Just a cap to ground can actually tune in certain frequencies and make it worse. Better to use a R-C lowpass filter or negative feedback at radio frequencies. Shielding the guitar will probably help too.
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Re: Radio Interference ?

Postby RnFR » 15 Apr 2009, 23:05

earthtonesaudio wrote:Hearing radio stations requires gain and rectification. Half-wave rectifying the signal can occur with a BJT base-emitter junction, so that bit is hard to eliminate, but you can reduce gain at radio frequencies pretty easily. Just a cap to ground can actually tune in certain frequencies and make it worse. Better to use a R-C lowpass filter or negative feedback at radio frequencies. Shielding the guitar will probably help too.

ok, so say a 10K series resistor, and a 220pF cap at the beginning of the circuit, along with the large(>10uF) cap from 9v to gr that gus recomends. or some sort of neg feedback through a small cap to filter highs. give that a shot.
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Re: Radio Interference ?

Postby Fuzzer » 16 Apr 2009, 14:19

Add a Cap (0.1 non electrolytic) in parallel to the >10 [uF]. :thumbsup
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Re: Radio Interference ?

Postby travsbluz » 16 Apr 2009, 14:38

Thanks for all the replies. I will try these out today when I get the chance.


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