Improve RFI

I am out of town for a week so I won’t be able to do any more investigations or to see if my new location for the relay is still working.  Will report when I get back.

  I have a follow up question about the mu Metal.  Someone up thread said that it is not to be used around the antenna of relay unit.  My initial thought when it was suggested was that by wrapping it around the antenna it would filter RFI but allow the desired radio frequency of the remote to be read.  I’m just verifying here that this is incorrect (?).  Is the mu metal to be wrapped around the offending source, once identified, of the RFI?  
  I identified a store that sells the mu metal for a few dollars, but it’s in Evanston, an hour drive for me in Oak Park.  The stuff costs 5$/roll online but $30 to ship, so I thought perhaps a drive there and pick the brain of the store staff might be worthwhile, but if I can’t identify the source of the RFI and it needs to be applied to said source then no point 

I bought a TeddyPardo power supply for my main system to replace my modem and router power supply.  Gave them the specs and cable info. The power supply  I received has two outlets - 12V the other 19v with 2 different connection types. Came with very high quality cables. Have been sitting on them for some time.  I’ll install this weekend.

I learned about TeddyPardo off this forum. Everything about them is stellar, website, their questions to me to double check info and their unit & cable build quality. Sent photos of the cheap power supply that came with my modem and router. That closed out the loop for exchange of needed information 

As previously posted, a Trifield EMF meter is indispensable for finding sources of RFI. Routers with wifi the worst, hard drives and transformers can be pretty bad.

Good move.

Proper shielding is always a good thing but may not be needed so much or at all  if the problem can be addressed by simply relocating affected components and/or the source of the EMI. 

@mahler123 said:

 I placed the transmitter -relay device on the floor next to the rack.  Previously it had been on the top half of the rack, and then placed on top of a surround that is wall mounted at near the same height.  The RFI light is off now and the Universal Remote works again.

Me thinks you found the source of the RFI. If you want to verify, I would suggest you place the transmitter -relay device back on the rack. Unplug all the associated A/V equipment from the 120Vac AC mains outlets. Then check for the presence of  RFI.

If you are using a surge protector plug strip, or a power conditioner with surge protection, unplug it as well from the AC mains wall outlet.

.

First off, I would like to thank everyone who has tried to help here.  My last post sounded snarky and ungrateful.

  Second, a new development.  I placed the the transmitter -relay device on the floor next to the rack.  Previously it had been on the top half of the rack, and then placed on top of a surround that is wall mounted at near the same height.  The RFI light is off now and the Universal Remote works again.

  There is a small window behind  and above the rack .  I am wondering if there has been an increase in RFI from the external environment (I live on a Flight Path for O’Hare Airport, for one thing).  However I don’t understand why the living room remote would not be effected, as the two systems are in parallel on different levels of the home.  Perhaps the weather updated windows in the living room are better for screening RFI?  I am just speculating.

  The floor location isn’t ideal-it might get kicked or placed back on the rack by my wife or someone else-but for now I will leave it there

+11 @mapman Mu metal foil is designed to shield sensitive devices. & Etc. There is also a carbon based paper I believe. that you can use.

We use cases designed to cover transformers in our designs that help greatly.  As we manufacturer tube products, tubes almost always impart noise in the sound.  In some systems, you can hear the noise, in others no noise.  We use a horn system to hear if there is noise.  Using any RFI rejection always helps.

As @jea48 mentioned, the RFI could be coming from somewhere else in the house.  What is upstairs, directly above the MFR-260?  And by any chance are you using a cellular 5G internet access point in the house?

Just a thought...

@mahler123 ,

Not sure if this is any help.

From the owner manual:

Page 4
5. Observe the Status LED of the MRF-260. If it is glowing or flickering you must relocate the MRF-260 to a location where the LED doesn’t flicker.

If your installation location simply doesn’t offer you any choice
and you are detecting interference everywhere you place the
MRF-260, you have two last resort options:

a. Remove the MRF-260’s antenna. This will reduce the
range enormously, but may still be enough for this client.

b. Admit defeat and install the two piece MRF-350 base
station, which can have the RF Antenna module remotely located (even in another part of the house).

 

7. Once you have found a location that is absolutely free of RFI
with everything on, test to see if the range is adequate and that macro reliability is perfect. Start with the antenna angle set to 45 degrees and positioned so that the long side of the antenna is facing the customer’s favorite seating position.

When testing, set both the remote and the MRF-260 to the same
valid RF ID#. Keep in mind that zero (0) is not a valid RF ID#.
Watch the Status LED on MRF-260 - it should light every time
you press a button on the remote. This confirms that the signal
was received and understood perfectly. If you repeat any button
press multiple times and the Status LED lights correctly every
time, you have no interference and a very reliable installation. If
some of the presses do not light the Status LED, you still have
some RFI. Your best strategy is return to step 3 and try to find a
better location for the MRF-260.

8. Now that the location is fixed, connect each of the emitters to
the appropriate IR output and run the cable to the appropriate
component. Do not attach the emitters to the front panel yet!

https://www.urc-automation.com/product/mrf-260/

The only other thing I can think of if the RFI is coming from something within the house is to turn off every circuit breaker in the electrical panel except the one that feeds the wall wart for the MRF-260. Then check for RFI. 

IF RFI is gone turn on one breaker at a time and then check for RFI. Repeat process until you find the culprit causing the RFI. 

.

There is an RFI indicator on the relay part of the remote.  It is on constantly.  The same relay unit is in the upstairs unit and the RFI indicator is never one.

  I have switched remotes as I indicated in posts above between the 2 systems.  No change.

   The tools that I have seen for measuring RFI, in YT videos, don’t isolate the RFI to a single source.  They basically say “There is RFI in the room” and the user then has to try turning of appliances, lights, etc.  I know that I have RFI because the indicator on the unit is on, and I’ve tried all the solutions, to no avail.  So buying another tool that will inform me that I have RFI isn’t in the cards.

At the risk of asking a possibly really stupid question: Have you absolutely ruled out that you might have a defective universal remote? Have you tried using it in your other system?

Identify the source of the crud before launching-in to any RF shielding or RF snubbing effort. Start with what tosnc suggests.

@mahler123,

Are you sure it is RFI and not EMI interference? You will measure a lot of EMI in front of the breakers in the electrical panel. (metal panel door open). Especially large running loads like the outdoors central air conditioner unit, and refrigerator, and other such motor loads when running. It is normal. There is a large EM, Electromagnetic field present around the loaded breakers. 

.

@mahler123 I’m curious… how is the RFI affecting your system audibly? Are its effects clear to you?

I use Synergistic Research’s Tranquility Base Carbons with excellent results (in full disclosure I am a dealer for them). They are not inexpensive, but they project an electromagnetic field around components to deflect ambient EMI/RFI and suck out trace EMI/RFI within components. In a highly resolving system, these bases add critical improvements in lowering noise floor, removing high frequency hash, and increasing coherence and spatial presentation. 
 

I currently use six of them in my reference system. 

Fusebox.  It must have been autocorrected. 
Tried switching remotes, no changes.

Tried turning off lights and unplugging everything in the basement, even the components that I want to control with the remote, to see if that changed the RFI indicator, and none of them did.

  What exactly is the Mu Metal supposed to be placed on, if not the Radio switching station?

@mahler123 said;

 I also have a surround sound system on the main floor; same AVR, same universal remote, and no RFI.  

Did you try using the main floor level remote in place of the one in the basement?

What is the "firebox" in the basement?

.

Trifield EMF Meter Model TP2 is a handy tool to source EMF pollution.  

@mahler123 shielding the RF receiver will not work.  It needs to receive a 418MHz from the remote control to act as an RF to IR controller.  It uses 418MHz narrowband to limit the effects of RFI. Try unplugging everything electronic in the basement and turn off any LED or fluorescent lights and see if that helps.  If it does add things back one at a time to determine the source of the RFI. 

https://ebay.us/m/Fc9vst
 

thanks map man that’s helpful.  My remote control sensor detector is shown in the link above.  So should I try wrapping the my metal over the antenna or the entire unit?  And should the aluminum wrap go over the my metal, or under, or does it matter?

Mu metal foil is designed to shield sensitive devices.    I use it to shield my phono step up transformer which picks up audible noise from nearby HVAC devices otherwise.  Low level devices like step up transformers in a phono stage are most sensitive.   Line level devices like preamps are less problematic.  
 

“

Mu-metal can be used for RFI (Radio Frequency Interference) shielding, but its effectiveness depends on the frequency of the interference. [[1]](https://www.eevblog.com/forum/projects/mu-metal-for-shielding-rf/) Here's a breakdown:

**1. How Mu-Metal Works for Shielding:**

*   **High Permeability:** Mu-metal is a nickel-iron alloy with very high magnetic permeability. [[2]](https://eureka.patsnap.com/blog/mu-metal/)[[3]](https://www.spinquanta.com/news-detail/mu-metal-shield-in-quantum-computers-explained) This means it can easily attract and redirect magnetic field lines.
*   **Shielding Mechanism:** It doesn't block magnetic fields but provides a low-reluctance path, diverting them around the shielded area. [[4]](https://en.wikipedia.org/wiki/Mu-metal)[[5]](http://www.mu-metal.com/faqs.html)
*   **Low-Frequency Shielding:** Mu-metal is most effective at shielding against static or low-frequency magnetic fields. [[2]](https://eureka.patsnap.com/blog/mu-metal/)[[6]](https://resources.pcb.cadence.com/3d-electromagnetic-simulation/2022-the-impact-of-rf-shielding-effectiveness-on-interference-mitigation)

**2. Mu-Metal and Radio Frequencies:**

*   **Up to 100 kHz:** Mu-metals provide interference control of H-fields (magnetic fields), DC or AC, up to approximately 100 kHz. [[5]](http://www.mu-metal.com/faqs.html)
*   **Reduced Permeability at Higher Frequencies:** The permeability of mu-metal alloys decreases significantly near 1 kHz. [[5]](http://www.mu-metal.com/faqs.html)
*   **Conductivity for Higher Frequencies:** Mu-metal is conductive and *can* potentially shield higher frequency (RF) fields in the 1-100 kHz range. [[5]](http://www.mu-metal.com/faqs.html) However, it's primarily designed for low-frequency magnetic fields. [[5]](http://www.mu-metal.com/faqs.html)
*   **Not Ideal for High RF:** For frequencies above 100 kHz, highly conductive materials like copper, aluminum, or conductive coatings are generally more effective for RF shielding.

**3. When to Use Mu-Metal for RFI:**

*   **Low-Frequency Magnetic Fields:** Use mu-metal when the dominant interference is from low-frequency magnetic fields (e.g., power lines, transformers).
*   **Combination with RF Shielding:** When both high and low-frequency fields are present, mu-metal can be used in combination with other RF shielding techniques. In these cases, grounding the mu-metal and using proper RF shielding practices is important. [[5]](http://www.mu-metal.com/faqs.html)

**4. Limitations:**

*   **Saturation:** Mu-metal can saturate in strong magnetic fields, reducing its shielding effectiveness. [[2]](https://eureka.patsnap.com/blog/mu-metal/)[[4]](https://en.wikipedia.org/wiki/Mu-metal)
*   **Brittleness:** It's a brittle alloy and can be damaged by stress or impact. [[2]](https://eureka.patsnap.com/blog/mu-metal/)
*   **Cost:** Mu-metal is relatively expensive compared to other shielding materials. [[2]](https://eureka.patsnap.com/blog/mu-metal/)
*   **Skin Depth:** At higher frequencies, the skin effect becomes important. [[7]](https://www.eastcoastshielding.com/metal-rf-shielding-guide-optimize-applications.php)  The skin depth is the depth to which an electromagnetic wave penetrates the material. [[7]](https://www.eastcoastshielding.com/metal-rf-shielding-guide-optimize-applications.php)  Thinner layers are sufficient for higher frequencies.

**5. Alternatives for High-Frequency RFI Shielding:**

*   **Copper:** Excellent conductivity, easy to manufacture. [[6]](https://resources.pcb.cadence.com/3d-electromagnetic-simulation/2022-the-impact-of-rf-shielding-effectiveness-on-interference-mitigation)
*   **Aluminum:** Lighter than copper, sufficient high-frequency shielding. [[7]](https://www.eastcoastshielding.com/metal-rf-shielding-guide-optimize-applications.php)
*   **Steel:** Effective for low-frequency magnetic fields due to its high magnetic permeability. [[7]](https://www.eastcoastshielding.com/metal-rf-shielding-guide-optimize-applications.php)
*   **Conductive Coatings:** Can be applied to various surfaces.
*   **Faraday Cages:** Enclosures made of conductive mesh or solid metal, effective at blocking electromagnetic radiation.

**In summary:** Mu-metal is a good choice for shielding low-frequency magnetic interference. [[3]](https://www.spinquanta.com/news-detail/mu-metal-shield-in-quantum-computers-explained)[[7]](https://www.eastcoastshielding.com/metal-rf-shielding-guide-optimize-applications.php) For higher frequency RFI, other materials like copper or aluminum are generally more effective. [[1]](https://www.eevblog.com/forum/projects/mu-metal-for-shielding-rf/) When dealing with a combination of both, a layered approach using mu-metal for the low frequencies and a conductive material for the high frequencies can be optimal. [[3]](https://www.spinquanta.com/news-detail/mu-metal-shield-in-quantum-computers-explained)

---
Learn more:
1. [Mu-Metal for shielding RF - EEVblog](https://www.eevblog.com/forum/projects/mu-metal-for-shielding-rf/)
2. [Mu Metal: The Ultimate Protector Against Magnetic Interference - Patsnap Eureka](https://eureka.patsnap.com/blog/mu-metal/)
3. [Mu-metal Shield in Quantum Computers Explained \[2025\] - SpinQ](https://www.spinquanta.com/news-detail/mu-metal-shield-in-quantum-computers-explained)
4. [Mu-metal - Wikipedia](https://en.wikipedia.org/wiki/Mu-metal)
5. [MuMetal Relative Permeability](http://www.mu-metal.com/faqs.html)
6. [The Impact of RF Shielding Effectiveness on Interference Mitigation - PCB Design & Analysis](https://resources.pcb.cadence.com/3d-electromagnetic-simulation/2022-the-impact-of-rf-shielding-effectiveness-on-interference-mitigation)
7. [Choosing the Right Metal for RF Shielding: A Detailed Guide to Optimize Performance Across Diverse Applications](https://www.eastcoastshielding.com/metal-rf-shielding-guide-optimize-applications.php)”