Randomly picking radio signals

[DeusM]

Hey guys! I just finished my BMP and I noticed something. I have a radio nearby from a Church and the noise gets into the pedal, but I was testing it before and I heard nothing. I opened it and checked everything but I'm not sure what could it be. My usb interface makes some noises at high volume, I think it can be but I'm not sure. Maybe the radio doesn't sound all day. My amp also grabs that signal and I'm sure I heard it during the day before (I tested it around 7 P.M.). Anyway, I want o know if maybe something is not working. This is my first pedal so it has a lot of issues and I wish to know what could be causing that signal to get into the circuit. Everytime there was a connection missing or a short the pedal stopped working, so I don't know about this. I pressed the pots and it somehow stopped (not sure if the pedal still worked during those brief moments) but Now I opened and isolated the pots and the radio signal never stops. Also, when I moved the pots it seems to stopped but all the sound stopped also (sometimes). Anyway, here is a video of me testing the pedal when there was no church radio coming in.

Also: -No radio noise when By pass
- When guitar is conected raido noise increses A LOT
- I moved the 9v power suply and noise seems to reduce A LOT (maybe thats the problem)

[Transmogrifox]

If there is strong radio signal around it will get in, and the BMP will rectify it and make it audible.

If you unplug your guitar is there still radio noise?
If you turn your guitar volume all the way down is there radio noise?
If you unplug your guitar and ground the tip to the ring on the cable is there still noise?
Those are all things that can be done to find out if the radio signal is getting into the input.

Now, is there radio noise if you use a battery instead of 9v supply?

Some things you can do to make your circuit more immune to RF noise:
Put a 100 ohm resistor to the input of the pedal followed by 100 pF cap from pedal input to ground.

Put a 47nF capacitor from 9V input to ground right at the input connector. If you can find a common mode choke, add that to the output of your 9V power supply, or get a different 9V supply.

Put a 470 ohm resistor between the output and the tip of your output jack.  This prevents the cable in the output from acting like an efficient antenna.

There are more things you can do to the BMP circuit to band-limit it, but if you can keep the stuff from getting in through the input, output and power jacks then you won't have a problem.

I'm guessing the pots are more of a side-effect than a cause.  Changing gain and tone on the circuit will have an effect on how the circuit responds to radio interference.  The pots are grounded to the enclosure and shielded by screwing them to the metal enclosure.

[DeusM]

Yes. I did something similar from what you are describing and its very quiet. After writing the post I noticed that when I moved the power supply around the radio signal from the church (it's a church) sometimes almost disappeared so my guess is that the first time I tried the pedal the supply was in a position that no signal when in. Also, moving the pedal around reduced the noise, so I guess that was the problem all the time.

If you unplug your guitar is there still radio noise? Some

If you turn your guitar volume all the way down is there radio noise? Nope, well, maybe a little

If you unplug your guitar and ground the tip to the ring on the cable is there still noise? It's a little late to try now.

I'm still very curious about those tip you said. The signal from Jesus is still very strong here since even my amp gets that signal. Even on clean Chanel and without the guitar plugged in, so I guess is a problem of this area and not the pedal. You can see in the video how silent it is even when the gain was at 10 most of the time and volume at 8. It started to clip at 9.

"Put a 100 ohm resistor to the input of the pedal followed by 100 pF cap from pedal input to ground" Is that a ban filter?

"Put a 470 ohm resistor between the output and the tip of your output jack.  This prevents the cable in the output from acting like an efficient antenna." It has to be the tip of the ouput? Or the conection in the circuit. I used shielded wire in the output and grounded it. Shlould it be enough?

[anotherjim]

The signal from Jesus is still very strong here since even my amp gets that signal.

Surely, it's only a matter of time before that quote makes it into someone's signature line?

Interference coming in from the output is counterintuitive but possible, although I've mainly seen it with op-amps and chip amps. Resistance suggested in the circuit output ought to be good enough.
Screened wire is good, but it can inject noise into the signal path via ground loop if you ground both ends of the screen. Normally, wires will connect input, output and circuit grounds so the screens should only connect to ground at one end, which, in the short distances in a pedal build, can be either end of each screened connection.

[PRR]

I assume this is an AM station.

AM reception in audio can be very level specific. Consider a simple BJT input. If the AM signal is a few mV the carrier will not demodulate to audio. If it is many mV it *will* demodulate and you do the duet with Jesus (or news or baseball...). Sometimes slight change in cord routing or small capacitor at input will cause just enough reduction of carrier to go from big Jesus to no Jesus (news, sports, etc).

Metal box with all jacks and pots well-screwed is a first line of defense. Your box is fine but I wonder about the radio changing when you touch the pots... may be a poor connection.

[pinkjimiphoton]

speaking of ground loops, check all your ground connections, particularly anything with small caps going to ground.

also, try a different outlet. if its the same one with a lot of digital hash being dumped to the power grid, all kindsa weird stuff can happen.

the beginning of one of my old songs, "loose in da head" my boy mike bloomer was doing a guest track. and just as we began the song, we picked up jesus radio... "and he wants to work thru your life to minister to others"... for this song <nsfw> it was particularly funny so i left it in... the first line after that female voice is
"well, she loose in da head..... and she sux in bed...." it was a moment of serendipitous perfection if ever one was captured on tape.

https://drive.google.com/open?id=0BzMJxNNgY3_yZDhhcFctdzVna2M

[DeusM]

speaking of ground loops, check all your ground connections, particularly anything with small caps going to ground.

also, try a different outlet. if its the same one with a lot of digital hash being dumped to the power grid, all kindsa weird stuff can happen.

the beginning of one of my old songs, "loose in da head" my boy mike bloomer was doing a guest track. and just as we began the song, we picked up jesus radio... "and he wants to work thru your life to minister to others"... for this song <nsfw> it was particularly funny so i left it in... the first line after that female voice is
"well, she loose in da head..... and she sux in bed...." it was a moment of serendipitous perfection if ever one was captured on tape.

https://drive.google.com/open?id=0BzMJxNNgY3_yZDhhcFctdzVna2M

It definitly gives the intro a nice touch  totaly a moment of serendipitous perfection

[pinkjimiphoton]

on the original version without the fade <about 8 minutes long lol> i forget what it said at the end, but it was even funnier. i just cut it down cuz i figured the intro was good enough lol