The Cheapest Near Field EMI Probes from Amazon

The Cheapest Near Field EMI Probes from Amazon

I wanted some near field (EMI) probes for my Tiny SA Spectrum Analyzer. But I didn't want to pay $200+ for probes for a $60 tool. A quick search on Amazon turned up this set of 4 for less than $6.

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Gear I use:

Soldering Station: Sealody ???????

[bblod]

From what I've read, all the probes will have a similar frequency response. The larger probe is used to sniff out the signal and then you move to a smaller probe to narrow down exactly where that signal is coming from. Good for finding interference in a circuit.
☮️

[IZMTW]

Thanks for sharing the video.
Not sure why you keep inverting the names. H field probe is the circular one, the one that picks up the magnetic field. E field is the pointy one, sensing the electric field. The two fields by the way are not 90 degrees out of phase, is just the vectors representing the fields that are at a 90 degree angle in space, but the two fields actually propagate in phase, ie at a moment in time they are both zero for example.
I’m about to build some myself but having those super cheap ones available make it non senso to build them.
Best wishes

[technovideo]

In an electromagnetic wave, the electric field (E field) and the magnetic field (H field) are in phase and perpendicular to each other.

[caltech-wirewizard]

Paul I love your videos. Paul makes excellent videos in an easy to understand format especially for the novice / hobbyist. However, I feel this one needs a little polishing. I’m not trolling here. My aim is just to get your viewers back on track where you made a few errors and to fill in some information that you missed that’s important, relevant & on-point with your video.

ERROR:
1) At 1:31 The probes with the Loop are the “H Field” probes & the short stubby one is the “E Field” Probe.

BACKGROUND:

The reason there are several probes with the Loop (H Field) is to narrow down where the RF radiation is coming from.

SCENARIO:
Perhaps you have a circuit where it’s leaking excessive RF. But there are 2 components in close proximity to each other (E.g. a Coil & Crystal) The larger H-Field probe is very sensitive and you’d get similar results regardless of which component the probe is placed by. Whereas, using the smaller H-Field probe will be much more discriminating and give you better relative results as it relates to Field strength. Which leads to point 2 below.

ERROR:
2) At 5:39 It’s not that’s it’s “too small”. (It’s operating as designed) When you use the smallest H-Field (Loop) probe, you may not pick up a signal strong enough to be detected by a Spectrum Analyzer. (Not even on my $6k Rohde & Schwarz SA) In that case, you need to use a Low Noise, High Gain, Wideband, RF Pre-Amplifier between 10-30db gain, at (9kHz-6GHz) In-fact, an RF Pre-Amplifier is an essential tool for any EMI Pre-Compliance testing. RF Pre-Amplifiers can be purchased between $20-$50 on eBay. Or on Amazon for about $15.

BACKGROUND:

PRO TIP: * IMPORTANT *
When using an RF Pre-Amplifier, be very careful not to over-drive your Spectrum Analyzer’s inputs. You may “blow-out” the Front-End of the SA. (This is particularly true for the tinySA & tinySA Ultra since these don’t have any input protection circuits)

tinySA Maximum Input: +10dbm
tinySA Ultra Maximum Input: +6dbm

To overcome this, use “Signal Attenuator(s)” following the output of the RF Pre-Amplifier. An SMA Attenuator Kit can be purchased on Amazon for about $45.
(Kit of 6 Attenuators, 1, 2, 3, 6, 10, 20 db reaching 42db in 1 db increments)

Now in reality, if you’re losing the probe signal in the noise-floor, (around -80 to -95db), amplifying it by 30dbm, will raise the signal by that much (-65 to -50db) enough so you’ll see the signal. So it’s unlikely you’re going to over-drive your SA’s inputs.

Nevertheless, you should still have an SMA Attenuator Kit in your toolbox anyway. In my humble opinion.

ERROR:
3) I’m sorry Paul, but at 7:14 you made an error. They are “NOT” 90-degrees out of phase. I’ll explain why. In ALL radio frequency (RF) electromagnetic waves, the electric field (E) and magnetic field (H) are perpendicular to each other, meaning they have a 90-degree “ANGULAR” difference. This doesn’t mean that they are out of phase by 90-degrees. (Perhaps that’s what’s tripping you up ?) To put it another way, imagine a 3D model with an X, Y, & Z axis. With X representing time and Y & Z representing Amplitude. Now, place the E-Field running flat going out the backside along the Z-Axis & then place H-Field running flat up the Y-Axis both starting and being joined at the Origin (zero), both oscillating at the same frequency. Because they are oscillating at the same frequency, both reach their maximum and minimum values at the exact same moment in time and have no phase difference between them; they oscillate together. Hence, “In Phase”.

If the electric (E) and magnetic (H) fields are significantly out of phase, it would not be considered an RF signal now would it?

This is precisely why the H-Field probe must be in the correct orientation to pick up the magnetic field (H) part of the wave.

I hope this helps some Viewers.

[englishrupe]

A very happy New Year to you. Thanks for the have now shot up to over 12 bucks, because of the "learnelectronics" factor...lol. They perform remarkable well, considering. I am one of those that made my own by following the EEVBlog DIY video. Those work well, too. Thanks, mate, and stay well....and happy.

[FridayHouseXYZ]

Thank you for the explanation and example! Also thank you for proving some sites will stoop to price gouging lol nevertheless these probes are very handy. Happy new years! Love the breadboard design!

[dominicread]

I tensed up at 1:10 - I thought there was going to be blood!
I bought a similar set. Mine had 6 pieces, including an even bigger loop probe and a combined loop and stub probe. I found that the 2 smallest loop probes were faulty (the SMA connector was not even touching the PCB) but I still got what I needed for very little money.
I hadn't thought about using the VNA as a 'spectrum analyzer' - so glad I saw this.
I agree with IZ0MTW - when you say 'E' I shout 'H' and vice versa.

[brokenworld]

I believe you have the terms the wrong way round. The larger loop is the H field, the small tipped one is the E field.

[EnergyTRE]

very much so. thanks friend. not a bad bang for the buck. hard not to find over priced items 😂

[davidmoran]

A piece of rectangular wave guide is good to explain the E and H propagation at 90° polarization. I used to work on navigational RADAR too many years ago, and wouldn't even be able to climb the stick anymore.

[wlvradio]

Happy New Year! What stand are you using for the TinySA? All the Best! 73 DE W8LV BILL

[warrenbaker]

In looking at probes on Amazon, there are half-shield and full-shield probe sets. Can you tell me what the difference is from an application standpoint?

[bblod]

Are you the guy who said not to aim a knife at yourself? That slip was close.
Yeah, I shut down my brain for the holidays, only using basic systems for life support 🤣

[MrBC]

I sent you a show idea via email. It involved setting an RTC using bluetooth and your phone. A button-free solution to set an RTC accurately with a minimum of interaction.

[AJBK]

Here's and Idea for a very quick video (YouTube short) Blink a single LED!
I have a few shorts now doing this and want to encourage others to join in.

[farisikhmal]

real question, can we find short circuit on multilayer pcb using this method ?

[dsfryda]

Ya they already raised the price to $12 bucks already...LOL

[paranoidzkitszo]

23bucks(Canadian) now.... better returns than that of the markets...

[nigelsheridan]

Happy New Year, thank you for all the informative videos. 73 MM0NJS