Dealing with Cellular RF noise, or determining if it is the culprit.

[BebopBlues23]

This post will be long, my apologies, but I want to be as detailed as I possibly can be in explaining both what I'm experiencing and what I've tried/tested so that any obvious answers or responses are covered and I can hopefully get into the root of the problem. If you read or respond I thank you for your patience and time. Secondly, this is copy pasted in multiple communities just to hopefully get the most amount of information possible.


I recently moved into a new apartment and set up my recording studio/office and am experiencing a massive road block of noise. I have finally narrowed it down to being some kind of cell tower RF noise being picked up in my equipment and had a few questions regarding if A.) I'm correct in my diagnosis, B.) general information on the phenomenon, and C.) if there is any way to mitigate or eliminate it.


Signal chain is:


(Furman SS-6B Pro) Peavy EXP V-Type guitar with brand new pickups, wiring, and grounding -> a brand new Livewire 10ft guitar cable -> brand new out of the box Orange Super Crush 100 Amp Head -> the amp's balanced XLR DI Out into -> a brand new 6ft Mogami Gold Balanced XLR cable -> a used Mackie ProFX 10v3 or a new Focuseite Solo 3rd Gen-> a recently new battery powered HP Laptop that only has the bare recording programs needed to mix/master and is not plugged into wall power.


Other things I've done when testing are: turning off every circuit in my main panel except the one to the room I'm currently in; including unplugging every single device not currently in use in the entire unit, and completely shutting off my Wi-Fi and turning all wi-fi/Bluetooth devices off when testing to ensure the noise is not caused by my router, phone, other electronics in the unit, furnace, etc. I also took out any and all bulbs. The noise issue does persist in every room in the unit, and all outlets have been tested and are grounded properly. I also purchased a battery powered amp to see if I got the noise even when not plugged into a wall outlet, and I did. This led me to believe it has to be some kind of EMF or RFI. After having someone from the power company come out and look into it and some further research on my own we discovered it was most likely a cellular data transfer noise, a suspicion I think I've confirmed with the video listed below.


This video below is one I found on YT demonstrating what a cell tower sounds like on an RF meter. It sounds IDENTICAL to the noise I'm experiencing in my set up, so I'm pretty confident it's not a grounding/ground loop problem as is a cell tower somewhere.


https://youtu.be/bLnueLgxOHg?si=H8e2vgrvzqNEQb8F


So if I'm correct in thinking it is cellular RF interference, is there any way at all (other than moving or faraday solutions) that I could mitigate or eliminate the noise?


A couple other questions just for research sake.

Another thing I noticed is my mixer and audio interface do not make/pickup the noise at all until the amp is plugged into it. My studio monitors also do not have the noise problem at all.


I have a separate Orange Crush 35RT combo amp that makes the noise even when nothing is plugged into it at all. I have no guitar plugged into that amp, or cable plugged into that amp and yet the noise is still there.


So would that mean the amp itself is picking up the noise somehow, or is it possible that even though the outlet is grounded properly the noise is still somehow being introduced into my power/outlets?


Is there a way I could test if the noise is coming from the outlets specifically?


I also noticed when I have my guitar plugged in, the noise is present even with the volume knob fully at 0. If the guitars volume is at 0 shouldn't that mean that the pickups aren't sending any audio into the amp?


If so, does that mean the more likely culprit is the guitar cable itself even though it's brand new?


I also tried plugging in a noise gate pedal in between the guitar and the amp (powered by a Strymon Zuma 9), and then into the effects loop; in both spots even with the noise gate all the way up the noise is still present. Any reason that it would prevail even with a noise gate?


Again thank you for taking the time to read all this, and any help potentially provided, I've been tearing my hair out for months unable to record anything and moving or faraday treatment are currently not an option unless there are faraday options that are cost effective and don't require lining the entire room with EMF paint or foil.

[g1]

If so, does that mean the more likely culprit is the guitar cable itself even though it's brand new?

I won't comment on how likely odds, but you absolutely must verify each piece that you are assuming is good just because it is new. Try other cables, try the cable somewhere else.

[The Dude]

......I have a separate Orange Crush 35RT combo amp that makes the noise even when nothing is plugged into it at all. I have no guitar plugged into that amp, or cable plugged into that amp and yet the noise is still there......

This would indicate the amp is picking up the noise, although it wouldn't necessarily eliminate the guitar as there could be multiple sources. I can't find a schematic for the amp, but I wonder if there is any RFI filtering in the power supply of the amp. The Focusrite has an instrument level input. If you plug your guitar directly into it, do you have noise?

[mozz]

If you are in the US, file a complaint with the FCC. You could always do the old trick of walking around with a old style portable AM radio to pinpoint the noise. They usually have a directional antenna wound inside.

[Helmholtz]

It seems the RF noise is picked up/conducted by the amp's mains/power cable.
Tube amps rarely have adequate RF filtering at the mains input.
Maybe inquire about separate mains RFI filter units.

Not sure an AM radio will respond to GHz frequencies even if modulated.

[BebopBlues23]

I won't comment on how likely odds, but you absolutely must verify each piece that you are assuming is good just because it is new. Try other cables, try the cable somewhere else.

I have taken the equipment over to a friends house and verified that I do not pick up the noise unless I'm at home, so I do know the equipment is all functioning correctly; aside from something in the chain picking up something that is only present at home.

[The Dude]

Sure the equipment is functioning correctly, but that doesn't mean it was designed with enough RFI filtering for your particular needs. In case there's a misunderstanding, I wasn't saying your amp is broken. I was saying that it might not be designed to reject your high levels of RFI interference.

[BebopBlues23]

If you are in the US, file a complaint with the FCC. You could always do the old trick of walking around with a old style portable AM radio to pinpoint the noise. They usually have a directional antenna wound inside.

Sounds like a good thing to look into! I was considering getting an RF meter alongside an AM radio. With this method would I just have to dial in until I find a channel that is making/picking up the same noise experienced in my amp?

[BebopBlues23]

Sure the equipment is functioning correctly, but that doesn't mean it was designed with enough RFI filtering for your particular needs. In case there's a misunderstanding, I wasn't saying your amp is broken. I was saying that it might not be designed to reject your high levels of RFI interference.

No worries! That's a good point, I might see if I can reach out to the manufacturers and see if they have that kind of information listed somewhere.

[Mick Bailey]

A high level of RFI can be very difficult to eliminate with equipment that's not designed specifically with this in mind. Marshall invested in their own test lab so that they can develop amps that can operate noise-free in all kinds of environments. I had a situation a few years back to try to eliminate noise from an amp that was generated from mobile phones immediately prior to receiving a call. In a full pub or bar the noise was overwhelming.

What that highlighted was just how problematic it is to identify where the noise emanates from and I was surprised to find among other things that the speaker leads transmitted noise and radiated this inside the cabinet. This despite me fully screening the electronics. The mains cable also did the same.

Here's what I did;
Fitted a mains cable that had an earthed, braided screen.
Installed a Common-mode, filtered IEC socket.
Fully lined the electronics enclosure with aluminium screening foil (grounded to mains earth).
Separated signal from mains ground and elevated the signal ground with a 25A bridge rectifier etc.
Used a common-mode suppressor on the speaker leads.
Re - routed the exit point for the speaker leads.
Screened the speaker leads Internally.
Made up a screening can to fit the back of the guitar input sockets.

I also tried sheet steel for screening as an experiment, but no change.

All of this made only a slight difference, but didn't solve the problem and the amp was still not good enough to use. The main problem for me was in not being able to specifically pinpoint where the noise was getting into the amp. I think fairly sensitive equipment is needed that I don't have, both to sniff where the noise is getting in, but also it would be good in your own situation to positively identify the source. You could have a mixture of noise sources and some may be coming from your immediate neighbours.

[BebopBlues23]

This would indicate the amp is picking up the noise, although it wouldn't necessarily eliminate the guitar as there could be multiple sources. I can't find a schematic for the amp, but I wonder if there is any RFI filtering in the power supply of the amp. The Focusrite has an instrument level input. If you plug your guitar directly into it, do you have noise?

Just confirmed this morning that yes, I do have the noise even when plugging the guitar directly into the Focusrite. Weirdly the noise is worse when plugging my guitar directly into the Focusrite compared to plugging into my Mackie. I'm going to personally open up the guitar and see if the technician who installed the new pickups and wiring configuration properly grounded and shielded everything.

I will say that when I plug my guitar directly into the Mackie the noise is greatly reduced compared to when plugged into the amp, so at this point it seems like I'm trying to determine if it's just the guitar/pickups and the amp is just amplifying the noise coming in from the instrument OR if both the guitar and amp are picking the noise making it even worse.

At the very least since none of my speakers or the mixer itself seems to be affected, I know it has to be something earlier in the chain.

Also if anyone knows of a good RF meter that has the capability to also hear what the meter is picking up, or send it to headphones/a speaker let me know. I've found plenty of meters but I need a way to also still hear the noise so I can walk towards it and potentially find the culprit. The noise is directional, so I can tell what direction it's coming for, but no matter which way I face while attempting to play it still overpowers the guitars sound.