EMI RFI detector/measuring equipment?

Sarra · July 10, 2022

I'm posting this in the hobby section, because that's what this is going to be, if I end up finding something worth getting. I'm not a licensed elechicken, nor am I a contractor, nor am I trying to prove that tin foil hats are, indeed, necessary (that SHOULD already be common knowledge, but I digress [paypals $20 to Jay for copyright use]).

But, I'm considering getting into HAM radio, and I would like to know if my Microwave is barfing out RFI. I'd also like to know if my neighbor's ancient VTECH cordless phone is flobbing out RFI, as well (actually, I don't, I don't want to go anywhere near that phone, it's from like 2003).

Is there a reasonable, portable piece of equipment that can do basic EMI/RFI detection, that I can use to tinker with at my house? I don't need FCC Lab Grade test equipment, just something I can use when I board and wandering around my house, to see if there's an issue that I could fix, and maybe make life a little easier if I do get HAM licensing.

RollyShed · July 10, 2022

51 minutes ago, Sarra said:

I'm considering getting into HAM radio, and I would like to know if my Microwave is barfing out RFI.

What do you know about electronics?

You don't say what country you are in or how much you are willing to pay so a guess at what you can buy.

I'd suggest reading -
https://en.wikipedia.org/wiki/Spectrum_analyzer

Then do some more Googling.
Cost?
$50 - $2000
How about a PRO ISA-730, ISP-730 Desktop Spectrum Analyser, 150 kHz → 3 GHz, possibly $1000

A few mentioned here -
https://www.keysight.com/us/en/products/spectrum-analyzers-signal-analyzers.html

The microwave cooker, yes, there will be some leakage but it should be minimal
A phone by definition emits a signal though it definitely isn't interference as far as it is concerned.
As for it being 2003, what's the matter with that? I see the manual for one phone we have is dated 2011. Does it work? Yes. So what is the matter with that?

RollyShed · July 10, 2022

41 minutes ago, offweek said:

Any SDR should be able to do this. A cheap one should be sufficient

https://www.rtl-sdr.com/rtl-sdr-spectrum-analyzer/

I didn't spot that one. Certainly looks like the way to go and affordable.

H713 · July 18, 2022

The cheap crappy solution that I keep in my backpack is an RTL-SDR. Otherwise, you really need a spectrum analyzer to do this properly, PLUS the right type of antennas for testing. The RTL-SDR isn't a real spectrum analyzer - it can kinda-sorta act like one, but you're going to be limited to viewing relatively narrow parts of the spectrum at a time (don't expect to see too many harmonics at once) and it won't do too much below 30 MHz. You won't be looking at EMI from a typical offline SMPS with one. The Analog Discovery II has as spectrum analyzer in it as well, but it's pretty bandwitdh limited on the top-end. You won't see anything the 2.45 GHz band, that's for sure. There's also the TinySA handheld spectrum analyzers, but I've never used one and can't promise it isn't a complete POS.

You will also be surprised by what the biggest sources of EMI are. It probably isn't your microwave, probably isn't your neighbor's cordless phone, etc. Cheap LED lights and cheap power supplies from who-knows-where that don't meet EMC standards tend to be the big problems in my experience. Fluorescent tubes, being a gas discharge, tend to be pretty noisy as well.

On 7/9/2022 at 9:53 PM, RollyShed said:

What do you know about electronics?

You don't say what country you are in or how much you are willing to pay so a guess at what you can buy.

I'd suggest reading -
https://en.wikipedia.org/wiki/Spectrum_analyzer

Then do some more Googling.
Cost?
$50 - $2000
How about a PRO ISA-730, ISP-730 Desktop Spectrum Analyser, 150 kHz → 3 GHz, possibly $1000

A few mentioned here -
https://www.keysight.com/us/en/products/spectrum-analyzers-signal-analyzers.html

The microwave cooker, yes, there will be some leakage but it should be minimal
A phone by definition emits a signal though it definitely isn't interference as far as it is concerned.
As for it being 2003, what's the matter with that? I see the manual for one phone we have is dated 2011. Does it work? Yes. So what is the matter with that?

Spectrum Analyzers tend to be more in the $500 - $100,000 range, though that isn't to say there aren't things that are a little cheaper (maybe you could find something usable for $50), and it certainly isn't to say you can't find something a whole lot more expensive.

As a warning, EMI is a complicated issue, and if you think it's as simple as buying some equipment and pointing it at a device, you're wrong. That's how the media portrays it, how the people spreading misinformation about 5G network systems do it, but that doesn't make it right. There are a lot of things that are very counter-intuitive, and a good deal of physics that a lot of people have a really hard time wrapping their head around. Finally, some EMI problems are really hard to find and really hard to solve, and even RF engineers will sometimes spend weeks or even months troubleshooting an interference issue. It's not black magic, but unless you know E&M fields like the back of your hand, it will feel like it.

Sarra · July 18, 2022

5 hours ago, H713 said:

The cheap crappy solution that I keep in my backpack is an RTL-SDR. Otherwise, you really need a spectrum analyzer to do this properly, PLUS the right type of antennas for testing. The RTL-SDR isn't a real spectrum analyzer - it can kinda-sorta act like one, but you're going to be limited to viewing relatively narrow parts of the spectrum at a time (don't expect to see too many harmonics at once) and it won't do too much below 30 MHz. You won't be looking at EMI from a typical offline SMPS with one. The Analog Discovery II has as spectrum analyzer in it as well, but it's pretty bandwitdh limited on the top-end. You won't see anything the 2.45 GHz band, that's for sure. There's also the TinySA handheld spectrum analyzers, but I've never used one and can't promise it isn't a complete POS.

I'm going to start out with the RTL-SDR. I'm not an engineer, but I'm not opposed to learning. I don't want to become an engineer, but if I have to...

5 hours ago, H713 said:

You will also be surprised by what the biggest sources of EMI are. It probably isn't your microwave, probably isn't your neighbor's cordless phone, etc. Cheap LED lights and cheap power supplies from who-knows-where that don't meet EMC standards tend to be the big problems in my experience. Fluorescent tubes, being a gas discharge, tend to be pretty noisy as well.

The microwave is actually problematic. It keeps burning the paint off near the door, which then causes sparking, and then we have to touch up the paint. Last time, I sanded down the entire area and repainted it and it seems to be working better... And our neighbor did used to have a really bad phone. When they had it off the charger, it would essentially knock the entire block's WiFi offline. Figured this out when I called them and my WiFi dropped off, and after the call, the WiFi came back up. I bought them a new cordless phone, and the problem stopped entirely.

5 hours ago, H713 said:

Spectrum Analyzers tend to be more in the $500 - $100,000 range, though that isn't to say there aren't things that are a little cheaper (maybe you could find something usable for $50), and it certainly isn't to say you can't find something a whole lot more expensive.

As a warning, EMI is a complicated issue, and if you think it's as simple as buying some equipment and pointing it at a device, you're wrong. That's how the media portrays it, how the people spreading misinformation about 5G network systems do it, but that doesn't make it right. There are a lot of things that are very counter-intuitive, and a good deal of physics that a lot of people have a really hard time wrapping their head around. Finally, some EMI problems are really hard to find and really hard to solve, and even RF engineers will sometimes spend weeks or even months troubleshooting an interference issue. It's not black magic, but unless you know E&M fields like the back of your hand, it will feel like it.

If I can justify something to myself (this is going to let me spend 700 hours of my time fine tuning something), then the price is somewhat irrelevant. Either way, eventually this will be a project for me. Though I'm 99% sure that the actual cause is the GPU in my gaming/editing machine, but I could be wrong.