10:00 onwards - Very helpful explanation of the electrical versus magnetic fields, and why and when the far field starts - thanks!
@w2aew4 жыл бұрын
Here's the one I did on Near Field (vs Far Field) probes: kzbin.info/www/bejne/maXcn6looNGHbLM
@Ziferten4 жыл бұрын
Build your own antenna! There's a ton of ham radio literature about log periodic antennas. No doubt it'd be a challenge, but I bet you could get it done under 100 USD. I specifically recommend the ARRL Antenna Handbook.
@mirmbloatbust47834 жыл бұрын
I agree with this, would make a neat video too. Although, the antenna may become somewhat big on those lower frequencies :P
@pyrokinetikrlz4 жыл бұрын
the difficult part is not building the antenna, but measuring how its gain changes with the angle and frequency, which you need for the EMC measurements. For measuring your antenna, you need one of the echo-less chambers.
@firstnamegklsodascb42774 жыл бұрын
aint nobody got time for that
@jafinch784 жыл бұрын
@@pyrokinetikrlz Right... was thinking can be done cost effectively other than tuning and standardizing with calibration certification or whatever the electronics test equipment industry uses.
@janbarthelmes17004 жыл бұрын
I'll suspect Andreas Spiess might be usefull there. He seems to have profound knowledge about antennas.
@johnwest7993 Жыл бұрын
Dave, I think you 'described' it without 'explaining' it. I always figured that a layman's explanation for the difference between near-field and far-field signals was that near-fields are the portion of the field that is close enough (at the speed of light,) to collapse back onto its source as the signal's source polarity reverses, while far-fields are the portion of the field that is not close enough to get back before the reversal, and thus is 'pushed away', and must continue on as free-space radiation, an effect that essentially turns an antenna into an electromagnetic-field 'pump'. This explains why longwave near-fields can extend a mile from an antenna, while microwave near-fields are centimeters or less.
@johnclawed3 ай бұрын
Damn good supplementary explanation.
@zetacrucis6814 жыл бұрын
Good one Dave. Being a physicist, I was gonna call you out on the H-field vs B-field thing but you included it in passing (which is plenty good enough!) 10:06 - nicely done!
@nonamemike71494 жыл бұрын
Zeta Crucis That section of physics is one i utterly failed at. Any chance of telling me what the function of this microwave part is? kzbin.info/www/bejne/eouvfpyLert-hK8
@eugenepohjola2584 жыл бұрын
Howdy. Nice presentation. Some comments. Near field. The E and H components are 90 degrees out of phase. Almost all field energy collapses back into the antenna periodically. Far field. The E and H components are in phase. The energy has broken free and travels forward. The intermediate field or the Fresnel field. The phase shift is between 90 degrees and 0 degrees. Some of the energy collepses and the rest propagates. What is the mechanism that splits the components into collapsing parts and propagating parts ? Collapsing takes time. Field lines closer to the antenna have time to collapse. Field lines farther away do not have time to collapse completely they will encounter the build up of the next half wave field at the antenna. The ends of the field lines disconnect from the antenna and interconnect to form loops that travel forwads. Regards.
@750kv84 жыл бұрын
Thanks for the explanation! Someone finally explains it in layman terms!
@eugenepohjola2584 жыл бұрын
@@750kv8 Thank you very much sir / ma'am. Check this wonderful clip: kzbin.info/www/bejne/kJK7nmmtltpgoMU I remeber from my college, eq. in Finland, days no teacher would explain what stuff is all about or what is the usefulness of stuff. Instead I just got a battery of math and theoretical physics stuffed down my throat. And was left bewildered. For myself I derive pleasure from dwelling on stuff until I am able to convey (in my mind) the point in clear language. Regards.
@johnclawed4 жыл бұрын
Thank you so much. I've seen textbooks that depict the E and M waves in phase, and other books that show them 90 degrees out of phase. I've asked physicists about that and never got a clear answer. I always thought it would make sense for them to be 90 degrees out of phase because then the energy of one field is at peak when the other is at zero, so the energy is converted from one to the other. But it also makes sense for them to be in phase at the antenna. You just wrapped it up, so thank you.
@randomdodads4 жыл бұрын
This was a very good video about EM radiaton. Thanks Dave!
@cheyenneriver16373 жыл бұрын
Excellent! Dave = walking electronics encyclopedia!
@DrMarkVaughan2 жыл бұрын
You were asking about lower freq antennas. Mil461 describes designs for biconical antennas that cover the lower end of the radiated field. Not overly difficult to make. I don’t believe they detail it also requires a 4:1 balun. The bigger wide range hyperlogs are practically a log periodic crossed with a biconical of course.
@1231trainfan4 жыл бұрын
EEV Community....thank you for your Arrogance!! I asked why the testing is done but I received not one response. Thank you!!
@byronwatkins25654 жыл бұрын
This "E field" probe is actually an electric potential (voltage) probe. Electric potential is a scalar and has no direction. In isotropic materials B and H are always proportional to each other. In fact it is quite difficult to find or to engineer materials having tensor magnetic susceptibility; materials having tensor electric susceptibility are numerous. In free space E=cB and B=mu H, but in materials mu is larger than 4pi X 10^-7. So whether we call the magnetic component of EM waves B or H is purely theoretical other than the proportionality constant with E.
@redknight3442 жыл бұрын
both are voltage probes then, since the H field probe mesaures the strenght of the H field with the voltage induced in the loop antenna as a probe.
@johnclawed3 ай бұрын
@@redknight344 Well, you wouldn't say a light meter is really a voltage probe because it converts light into voltage, or that a bathroom scale really measures distance because it converts weight into linear deflection.
@gincoba4 жыл бұрын
Hi Dave! Go for Schwarzbech, good antennas, and fair prices! But it depends if you want an antenna just to cover 30 to 250 or 300 MHz. In this case go for a biconical antenna. If you want to cover the band from 30 MHz to 1GHz with a single antenna, go for a so called hybrid antenna, the union of a biconical and log antenna, otherwise called bi-log. Happy EMCing!
@mohamedlanjri Жыл бұрын
If you look at the datasheets of those expensive antennas you'll apreciate how much variation is on parameters like the antenna factor, antenna gain, directivity and so on. The reason for those prices, apart from high quality materials that imporve the performance, are the calibration data that you get with them in order to be able to calculate with accuracy radiated and received power (Basically same concept as you explained in your video about why Fluke meteres are so expensive). So basically you're buying parameters to fill in your Friis ecuation, and certifications needed if you want to be a EMC certification lab. I think you can build your own antenna but you'll end up with the same problem of having several cheap antennas that cover all the frequencies range, the only advantage I see is that you won't need to switch from one antenna to other while sweeping the entire band.
@MrTomasMaliauka4 жыл бұрын
It would be iteresting to understand the difference between near field (NFC) and far field devices. As you said in one of your videos, near field devices work only in close proximity and in magnetic fields more like transformator with air core. I like your tutorial type videos.
@v12alpine4 жыл бұрын
HAM here. Look up Mag loop receiving antennas. Highly directional. 50khz to 50mhz with a 3ft loop.
@andhanwer4 жыл бұрын
0.005% efficiency @50khz with 3ft loop ham there back to drawing board
@v12alpine4 жыл бұрын
@@andhanwer That's why there's a preamp right at the loop. They work fine.
@johnclawed4 жыл бұрын
Excellent. Thank you. Now, a little more on the difference between H and B would be nice.
@leandroebner14053 ай бұрын
Oh yes!!!
@Mystickneon4 жыл бұрын
Dave, you have said in the past you're not a radio guy, but you should look into an antenna called the Quad Loop. Basically, a simple square(or any shape, really) antenna with a variable capacitor inserted at the feedpoint. I have built several of these(including the caps), and while the dimensions and cap values are important, they are not critical to function, as it's a tuneable antenna. Bonus: it has a fairly narrow(bilateral - dependent upon shape) gain pattern, so isolation is easier. One I manufactured for 20 meters(14MHz) measures only about 2/3 of a meter in its largest dimension. Getting down to 30MHz or low-VHF should not be a problem at all, and it would be even smaller. I used a simple SDR as a frequency domain analyzer to verify my tuning range, but I'm pretty sure you have one of those laying around the shop. As you tune the cap, you'll see the spike in the signals move around the frequency domain. Barring that, a coil of wire of the correct length or one wound around the correct ferrite rod will get you reception in high HF/low VHF. Or even lower - this is what most AM receivers use and I have seen those measuring only inches long; albeit with sometimes strange gain patterns, but it you put on in a Faraday Bucket(a cage with an open side), you may get good results. PS, I'm trying to get down to the site for the Solar Road demo in Baltimore and get some pics for you. I try to avoid that place, as it's all a "bad neighborhood"...
@TheEmbeddedHobbyist4 жыл бұрын
When testing in the chamber if we got within 3db of the limit or so, we would have to take the kit outside and retest at the points that got too close to the limit line. As reflections off the chamber walls could be making our test sample appear better than it is. This means you may o ly need to a few test frequencies out side. We used to get problems outside as the test site was 6 miles for a small city with its airport so quite a lot of rf noise. Also on damp days electric fences can be heard clicking away over a very wide spectrum. So even looking at a single frequency outside could take up quite a long time. And ho boy their time is a lot of money.
@MrTomasMaliauka4 жыл бұрын
I am totally not a EM radiation hobbyist ... I have never heard abaut near field zone, where separate electric and magnetic fields are converging in to a point where they become an electromagnetic field/ radio wave. Very interesting info. Could you make more video tutorials about EM fields and radio wave basics? Maybe viewers could build up some kind of cool and usefull radio devices after these tutorials...
@Unsensitive4 жыл бұрын
I had to learn the basics about Nearfield effects of RF transmitters for MRI Safety. It's absurd that a Magnetic Resonance Imaging scanner, designed for imaging humans, can cause RF burns. If a patient has any part of their body within 5mm of the inside bore of the MRI scanner, nearfield effects are possible. This would be like building a car with holes on the floor, then blaming the driver then they lose a foot by putting it through the hole. Hoping to understand better from this video :)
@tubastuff4 жыл бұрын
Back in the bad old days in Silicon Valley, I recall that VDE certification and testing was performed in an empty steel warehouse (probably originally intended for agricultural produce). It was an expensive process.
@manishbhatt13994 жыл бұрын
Hello We can see the peaks with near field H probe on our board. How we can ensure that this peaks will effects our product compliance testing (CISPER22)which is tested at far field(>3m)?
@joshuaflores8648 Жыл бұрын
I'm having a hard time understanding the correlation between the impedance, and distance. How is the impedance measured?
@AngDavies4 жыл бұрын
Bit of a weird suggestion, but would it help if you immersed the antenna in a tank of distilled water? Seems to have a fairly consistent permittivity of about 80, and a relatively low loss factor at 100mhz (~5e-3) The impedance mismatch would lead to a ~4.4 dB loss due to reflection, but the wavelength in the water Is Lower by a factor 9 which would bring it close to the 30mhz you needed? Even tap wateright work, should have a skin depth measured in meters, which seems workable Don't the antennas in mobile phones to a similar thing to reduce the needed length, but with better dielectrics than water? Just a random thought, not an EE
@chrisjones87414 жыл бұрын
Hmm, interesting idea! Would love to hear feedback from someone who would know.
@johnclawed4 жыл бұрын
Why do many other videos put lambda in the denominator? Distance can't be the reciprocal of a distance unit, but it's not a one-time typo, when a lot of lecturers say the same thing.
@shanieboi864 жыл бұрын
E fields are divergent, they radiate outwards from a source, so its like having a net. H fields are curl, they effect orthagonal to current vector, this is why orientation matters. Its kinda like measuring the rotation on intimately tiny hoolahoops
@milantrcka1214 жыл бұрын
Antenna: 30 to 1000MHz (ex-or) cheap. One precludes the other.
@antoineroquentin22974 жыл бұрын
13:24 the e-field has a polarization though. The probe needs for example 3 orthogonal antennas to have an isotropic response in this regard.
@johnclawed4 жыл бұрын
I'm not sure but I think the E-field is only polarized in the far field.
@antoineroquentin22974 жыл бұрын
@@johnclawed but i'm sure ;)
@linuxsquirrel3 жыл бұрын
I was wondering this too. I guess the probe is single-ended (i.e. not differential), and it's just measuring the field with respect to ground, not the gradient. kzbin.info/www/bejne/iWOaq56VfM9spLc seems to confirm this.
@Impulsetech368 ай бұрын
You explained that the E field and the H field move 90 degrees relative to each other and later in the video that the H field is a round loop surrounding the conductor. For the E field I understand well perpendicular to the conductor, but how can the H field be at 90 degrees from E if it is a round loop as per your animation?
@DiyMech4 жыл бұрын
Welcome to EMC hell !!, wait till you package it in your designed box, send it to the very expensive test house and it leaks like a siv, both radiated and conducted. keep up the excellent vids
@outsideworld764 жыл бұрын
Design with EMC in mind and avoid hell.
@DiyMech4 жыл бұрын
@@outsideworld76 they did, supposedly 🤣🤣🤣🤣🤣🤣
@ZomB19864 жыл бұрын
4:25 You asked, these are also far-field antennas: www.saelig.com/product/M00154004.htm (1/8.33th of the price of the log antenna). Is this what you're looking for? Edit: they have an even smaller version nowadays: www.saelig.com/tem-cells/tbtc0.htm to test cellphone-sized devices. Edit2: random quote: "The wave travelling through the cell has essentially a free-space impedance (377 W) (sic), thus providing a close approximation to a far-field plane propagating in free-space."
@threeMetreJim4 жыл бұрын
Does Australia allow you to do your own certifications? It used to be allowable in the UK if done by a 'competent' person and using calibrated equipment and done to the correct standards. You still had to hire calibrated equipment and the process is very time consuming, so in the end might not be much savings as compared to having it done by a professional test house. I'm going back to the mid nineties here - I worked somewhere where they decided to self certify a custom built power supply for use in their own equipment. Due to EMC rules, it became very costly for the small independent electronics manufacturer to supply ready built equipment as everything needed to have EMC compliance in addition to complying with electrical safety standards.
@bobwhite1374 жыл бұрын
Not to be pedantic or anything :) but your hand drawing of E and H fields would be propagating in the other direction. The direction is given by the Poynting vector S = E x H. The animation which you placed over it (very cool by the way) had the direction correct.
@cvillf46942 жыл бұрын
Hi Dave, how about the 10m, 3m and 0.3m for 30Mhz, 100Mhz and 1Ghz respectively?, how were they calculated?. Thanks!
@ewafelber1658 Жыл бұрын
The obvious answer is that they were calculated using the speed of light. But I have another doubt. The far field starts quite close according to Dave explanation. From the Antenna, HF and propagation knowledge one can get, that far field region depends on frequency and the size of the antenna, which is not mentioned here. And as already said - starts very close
@funkyironman694 жыл бұрын
Thanks Dave, never heard about wave impedance before.
@N0SSC4 жыл бұрын
Have you looked into magnetic loop antennas for 30MHz? I don’t think they’re commonly used for EMC hence nothing really being available, but they’re as easy to build as a mag NF probe. Not sure if they can result in an FCC/IC/etc compliant measurement though.
@wyattsnare94003 жыл бұрын
Please explain the process of near field with mathematical transformation to obtain far field.
@macro8204 жыл бұрын
Can't wait to see a video doing far field measurements
@R2AUK4 жыл бұрын
The "far field probe" is basically a regular antenna. I doubt that you can buy a cheap log-periodic antenna for HF (3-30 MHz). Firstly, because of the wavelength the antenna will be huge. Secondly, because these antennas are manufactured for amateur radio operators. This market is really crazy, a piece of wire with a ferrite core can easily cost 100-200 USD. If you need an HF antenna the cheapest and simplest option is to make one. There are many articles online that explain how to make a dipole, two element yagi and wideband variations of these antennas. From personal experience it takes one Saturday to make a dipole or two element yagi if you never tried this before. However you will need some free space, about 30ft of 22 AWG wire, a 10m fishing rod (two for yagi) and an antenna analyzer / SWR meter. The FAA-450 from Electroparts is a good product in terms of price/quality and it covers 0.5-450 Mhz. Also it's an open hardware project by EU1KY amateur radio operator.
@schitlipz4 жыл бұрын
Hi Dave, Would you please do a video about how a near field becomes a far field -- specifically the details of what is needed to "spit out" the energy rather than have it fold back in. (And maybe a word of how quanta and classical physics really throw a bum-wrench in the understanding of wireless transmission.) I feel like I should understand those particular things thoroughly, but I don't. I only fake it and have always let the equations do the work for me in the past. It would be really nice to have a better conceptual model of radio transmission. It's all about that mysterious place in the in-between --- the near-to-far transition. In any case, a Merry Christmas! to you and yours and may 2020 bring good fortune to you all.
@chrisfuller12682 жыл бұрын
How are you defining the wave impedance differently for E and H?
@Korystuwatch42 Жыл бұрын
So the Electric Field probe is just another half of a capacitor?
@openyourmind72884 жыл бұрын
When you say far field, are you referring to radio waves?
@EEVblog4 жыл бұрын
Yes, they become electromagnetic waves. Radio waves are electromagnetic waves.
@openyourmind72884 жыл бұрын
Ok, so how would you go about measuring the electric field of a plasma globe?
@EEVblog4 жыл бұрын
@@openyourmind7288 Why? Maybe with an ESD electric field tester perhaps if you wanted to measure a surface spot? The electric field has to be defined over a given surface area. You have to know what, how and why you want to do this first before answering that question.
@andhanwer4 жыл бұрын
@@openyourmind7288 first you become a freemason
@Lloyd334 жыл бұрын
I'm sure you were saying something for the first 5 or 6 minutes of this video, but I was too distracted by that 4 CPU socket motherboard on the shelf behind you.
@strange67x4 жыл бұрын
I hope everything is okay out there, because of the fire. This is not good at all. Hoping everything will go out fine, I just saw that video with a koala and a fireman in the news. Love, Markus
@electronic79794 жыл бұрын
Helpful information
@jackjackson51374 жыл бұрын
might be worth getting a nanoVNA as it covers the frequency range you're looking for and would let you characterize different antennas from aliexpress
@MLX14014 жыл бұрын
14:55 Any idea what certain episode is this clip from? Not a doctor but could take a look O_O
@750kv84 жыл бұрын
Thanks for the explanation! So I guess, as an extreme example, when I build and run a ZVS flyback (which I have), most of the low voltage side circuit, with the MOSFETs and caps and chokes etc. mostly emit H-field, and the HV output of the flyback emits mostly E-field, when it's not arcing, just... held up into air like that... And I guess the output emits mixed fields, both E-field and H-field when arcing.
@thedevilinthecircuit14144 жыл бұрын
Could you adapt a standard TV VHF (30-300 MHz) log-periodic antenna for your testing purposes?
@dhpbear24 жыл бұрын
10:10 - I have a stupid question? The H-Field is horizontal, S-Field is vertical--relative to WHAT?
@johnclawed4 жыл бұрын
That's E not S. E is vertical if the radio wave is "vertically polarized" which depends on antenna orientation, since the convention is to refer to polarization in terms of the electric field. If a waveguide is used then it also depends on its orientation (which can be twisted), and as it happens the magnetic field follows the wider side of a waveguide, so it is vertically polarized when the opening looks like it is horizontal.
@jafinch784 жыл бұрын
Great video Dave! Nice overview and good range of information. I've wondered how to make the complete test setup in the most cost effective way since I've done the SDLC work for lab test equipment and apps in pharma other than the RFI/EMI/EMC testing per the whatever the range of FCC and more standards are required in the World, CE/UL/etc.?. I still need to read into the range of standards.
@friedmule54034 жыл бұрын
15:01 Last time I saw a smile like that on anyone, was when at boy was told he could eat as much candy he would! :-)
@ChristianHenriksenNorway4 жыл бұрын
@EEVblog Did you find this antenna eventually?
@benjaminargenziano58514 жыл бұрын
What about a teardown and review of a Keysight PA2203 power analyzer?
@rauldxjr4 жыл бұрын
Dave! Big fan here greetings from CA! Funny I was just watching your mini series on DIY NFP last week and built my own. Thought I'd let you know it worked GREAT! Quick question though, where did you get your enclosure? Does a shielded enclosure work better for these applications? Many thanks friend and keep up the great work!
@h7opolo4 жыл бұрын
i thought something was off about you since you leave keys in the door lock. at 9:25 you show you can't spell "wavelength"
@michelfeinstein4 жыл бұрын
It could be an interesting video of you trying to DIY a log periodic + bowtie antenna... I bet there are some tutorials out there, maybe The Signal Path can help also
@robfinch99524 жыл бұрын
Can’t you build one DIY? Or is compliance of it the problem?
@MedSou4 жыл бұрын
*Very informative ,Thank you* 👍👍👍👍👍
@chrisw14624 жыл бұрын
30-300 MHz log periodic? It's not going to be cheap, because it'll be quite large. The bowtie is a great antenna for 300 MHz, because it's relatively small, and it's bandwidth is almost 100 MHz. It allows the log perodic section to start just below 400 MHz, which makes it smaller, too. At 30 MHz, the bowtie's bandwidth drops to 10 MHz, and it would be something near 24 ft wide. It saves you about a foot each way (width and length) on the log-periodic-only (30-300 MHz) version (vs. a 30-40 MHz bowtie plus 40-300 MHz log-periodic). Not enough space savings to justify the extra materials and work, really, and either way - Huge. It's not hard to make your own log-periodic antenna. There are a few log-periodic design programs around. Here's one site that gives all the details and a calculator: hamwaves.com/lpda/en/index.html, though you'd have to use larger square tubing and 1/4" aluminum tubing for those lengths. If that's just too huge, you could try a Fan Dipole. They're very popular with Amateur Radio people who just can't afford one of those huge beam antennas, and you can make it out of wire and roll it up for storage when you don't need it, or just leave it flat on the wall.
@electricspark78873 жыл бұрын
Hello sir make video about antenna impedance matching design.
@WacKEDmaN4 жыл бұрын
30Mhz antenna is gonna be quite large....how about just using some tuned wire?...(2.377m for each side of a dipole!)
@stephenbell92574 жыл бұрын
The trouble with dipoles is that you have to adjust the length for each frequency if you want to get calibrated results. This quickly gets very, very tedious if you are testing multiple frequency ranges
@nux39604 жыл бұрын
I like Tool :)
@flos2514 жыл бұрын
Step 1: Press the like button under the video. Step 2: Watch the video.
@thekaiser43334 жыл бұрын
EEVblog is now 800% better than Batteriser.
@EEVblog4 жыл бұрын
Haters: Step 1: Press the dislike button Step 2: Partly watch the video and jump to silly conclusion Step 3: Leave valueless comment
@pnjunction56894 жыл бұрын
@@EEVblog And as we all know, jumping to conclusions is best performed on a "jump to conclusions mat".
@GertStegeman4 жыл бұрын
Milton wants his stapler back.
@andrewandrosow47973 ай бұрын
the cheap Chinese antenna may has a "random" gain. You must calibrate it in open air - it would better to do it on open field not in a town or a city
@MollyWi4 жыл бұрын
Just get a bunch of coat hangers and tune it. :)
@mannesq4 жыл бұрын
So is it correct to say that an SPI signal will mainly produce E field (high and fast voltage variations but low current) while the switching node in a converter will rather produce H field (big currents involved)?
@Matt-bt7ej4 жыл бұрын
Heres another vid thats pretty useful on the subject... kzbin.info/www/bejne/maXcn6looNGHbLM
@johnclawed4 жыл бұрын
Yes except that it is big /changes/ in current that would produce the alternating H field that is relevant here. A large constant current would produce a constant magnetic field like a magnet, and wouldn't be measurable with that probe, and wouldn't form a radio wave when combined with the E field beyond the far field distance. For more on magnetics, and measuring constant magnetic fields with a different kind of probe, see the AppliedScience video on the BH Curve.
@pitti2602 Жыл бұрын
The switching node is actually high E field due to high dv/dt, while your input/output loop (depending on buck/boost) is high dI/dt and therefor high H field.
@udhayakumara40334 жыл бұрын
Can we use the antenna in open area test or do we need anechoic chamber? The aliexpress link is not working (at least for me)
@EEVblog4 жыл бұрын
Links work for me. You can use either an OATS or a chamber, take your pick. OATS is technically better.
@SkyhawkSteve4 жыл бұрын
If you test in an OATS facility, then you have to deal with all of the TV and radio stations in the area, as well as whatever smaller transmitters are near (probably wifi and the like). Dave was talking about emissions testing, but there is also the issue of immunity testing, where RF energy is directed at the device under test. In an OATS, this can get you in trouble with the FCC or the local equivalent.
@threeMetreJim4 жыл бұрын
@@SkyhawkSteve Does immunity testing matter for most consumer grade equipment? I'm thinking the FCC class B notice you often see, with the wording "This device must accept any interference received, including interference that may cause undesired operation."
@SkyhawkSteve4 жыл бұрын
@@threeMetreJim I've never designed consumer electronics, so I'm not sure about the specifics. FCC part 15 is the basic spec on emissions, which is that the device isn't allowed to interfere in the standard radio and TV bands, etc. (if I recall correctly, etc) Dealing with EMC regulations isn't for the faint of heart. For a small hobbyist selling a few items, it's not a concern. If you are selling a lot of stuff, you might be liable for any problems caused by your product or may have to provide replacements or refunds. This is when it's good to consult with an EMC test house and get their guidance. regarding immunity testing specifically.... that probably depends more on the type of product. If it's a toy, then it is no big deal if it stops working when someone uses a cell phone nearby. If there are safety implications, then you'll want to do whatever the industry standard testing is. Even concerns about customer satisfaction might be a good reason to do immunity testing... no one wants to deal with thousands of customers seeking refunds or replacements.
@-vermin-4 жыл бұрын
@@threeMetreJim There is no immunity compliance required in Australia only emission.
@1231trainfan4 жыл бұрын
What is the reason for near field and far field testing?
@PlasmaHH4 жыл бұрын
You have VNAs and all that stuff, just build one yourself and show us the process of tweaking the design... btw it would be fun to have a robot that runs evolutionary algorithms to bend and stack together some antennas...
@1231trainfan4 жыл бұрын
EEVblog why is this testing done? Is it necessary ?
@ACTlVISION4 жыл бұрын
totally random thought but I wonder if high precision H field probes could be made by 3D printing metal-infused PLA somehow
@nicolas_poli4 жыл бұрын
Hi Dave, I have always been suspicious about the drawings or animations that show the E and B parts of the EM fields in phase with each other. Indeed Faraday and Ampere equations that are part of Maxwell's equations precisely state that there should be a quarter wavelength shift between E and B when these contain only a single frequency. But I could never find *any* drawing actually showing the right representation. Do you have any clue? I may misunderstand something.
@EEVblog4 жыл бұрын
If you do the Maxwell business then that can popout for various polarisations. But for linear polarisation the phase angles are the same. And yes, I don't think I've ever seen it pictured that way either though. Maybe because it more confusing drawn that way? Don't know.
@TeslaLegend4 жыл бұрын
In free space E and H are always in phase. It is curl of E that is equal to the partial time derivative of B and in absence of lossy materials (i.e. real wave impedance) the E and H field will be in phase. If E and H were to be out of phase by 90º the time average of Poynting vecotor (E*conj(H))would be 0 and there would be no transmission of power
@nicolas_poli4 жыл бұрын
@@TeslaLegend I completely forgot the affect of the curl operator. You are right about the average power too. That's one more question answered I don't need to deal with. Thanks a lot!
@TeslaLegend4 жыл бұрын
@@nicolas_poli You are very welcome. Cheers.
@justpaulo4 жыл бұрын
I advise you to watch the following: kzbin.info/www/bejne/pHfXf3aGirKij6M I must warn you though it's a bit heavy on math, but well explained nevertheless.
@dosgos4 жыл бұрын
fmtunerinfo group has a bunch of antenna designers so they might have some ideas.
@normallyopen11904 жыл бұрын
I've never seen proper response curves for cheap log periodic TV antennas on eBay, nor someone take a VNA to one, but some claim to go down to 40-50MHz for FM radio. Might be some gaps between 230-400 MHz though? Other than that, DIY?
@eideticex4 жыл бұрын
The cheap antenna are easy to figure out. Usually take little more than basic geometry to compare the expected waveform to what the antenna is configured to be sensitive to. Since your talking cheap, you can safely assume there's only bare minimum signal processing if any and rely on physical characteristics.
@Chris_Grossman4 жыл бұрын
NO Corporation fm radio is 96 MHz to 108 MHz, ~50 MHz to 96 MHz was the old analog tv low band
@normallyopen11904 жыл бұрын
@@Chris_Grossman ITU region 1 is 87.5-108, ITU region 2 is 88-108, Japan starts lower? Not sure what FM broadcasting region starts at 96?
@hansurmann4 жыл бұрын
Very interesting information!
@ophello4 жыл бұрын
Your forum is down now...
@evrim734 жыл бұрын
kzbin.info/www/bejne/Z4Oal6GhoMyprqc System of a Down - Aerials on Eight Floppy Drives
@flos2514 жыл бұрын
😣 The moment when I am to early to read comments.
@erikwestrheim8044 жыл бұрын
NO worries Kreosan will upload the answer soon :0D
@rodrigomaero4 жыл бұрын
how about a video on a DIY antenna? maybe a livestream
@garthenar4 жыл бұрын
Got it. Building a near field probe
@keithking19854 жыл бұрын
I seen a guy in a video(not sure who it was) with one of those probes but instead of a ring at the top he had made his own with a English two pence piece!! (copper coin) he was using it to find stuff in a car engine!! cool...
@Chris_Grossman4 жыл бұрын
your web site is down
@1231trainfan4 жыл бұрын
Why is this testing done?
@alfaguppie4 жыл бұрын
EMC = ElectroMagnetic compatibility.. not conformaty
@doktor64954 жыл бұрын
For about 100 kHz up tp 30 MHz you have to use a rod antenna. www.schwarzbeck.de/index.php/de/antennen-de/monopol-stab-antennen
@smccain9533 жыл бұрын
Ha, I got the Back to the Future reference!
@rfmonkey49424 жыл бұрын
i periodically hang logs and by deduction i have a log-periodic !
@1231trainfan4 жыл бұрын
HELLO....ANYONE, What is the reason for near field and far field testing?
@johnclawed4 жыл бұрын
Testing is for compliance with regulations that forbid radio interference. If a device emits excessive unwanted EM waves then it would interfere with other radio signals.
@Motor_Cackle4 жыл бұрын
You'll want to build a biconical (modified cage dipole) like this: www.com-power.com/products/antennas/biconical-antennas/ab-900a Covers 25 to 300 MHz. The standard I used over the last 20 years for MIL-STD 461 testing has been the A.H. Systems SAS-540.
@norgerichard4 жыл бұрын
I love your videoes
@zeb41284 жыл бұрын
New EMC antennas are not cheap, the cheapest new one I found is www.rowielektronik.de/emv-emi-antennen/hta-2003-20-mhz-3000-mhz.html It comes with individual calibration data (antenna factor table). Of course you can try to buy used one on e-bay. Sometimes you can find bi-log for 200....500$.
@lawrencecole65274 жыл бұрын
Are you making bubble wands? They look like bubble wands.
@km54054 жыл бұрын
its compatiblity not conformity. rigid standards and all :-)
@EEVblog4 жыл бұрын
I'm old school.
@matthewlambermon-southam44184 ай бұрын
2π of 60Hz is about 800Km, fits between the top of the F-layer of the ionosphere and the lower part of the asthenosphere. Also the fundamental frequency that fits within this boundary (I.E 2π * 60) is equal to 376.99Hz....... WTF? I know its Ohms not Freq but still, nature loves a coincidence :-P Also, 376.99112 / 123 = 3.065 1, 2, 3.... 123... I kicked myself when I realized.