Hi! Any distance is fine as long as it's larger than the distance between the trace and the ground plane for it to act as a microstrip. Else, a coplanar waveguide calculation of trace impedance should be used

Great question! The value of the series inductor is determined by the Q-factor and the frequency range of LISN. As a result, it's standardized as 50uH for CISPR32 (domestic/industrial) and 5uH for CISPR25 (automotive). You can use an AC LISN to measure emissions on DC lines, but not the other way round. However, you'd have to make up your own wiring because AC LISNs typically come with AC plugs and sockets rather than banana plugs.

I don't see how that would be possible. RF power and sensitivity are measured on a modulated signal (i.e. GSM or LTE or 5G NR) and VNAs cannot modulate/demodulate signals.

I can see why this may be confusing. The harmonics apply to electric vehicles because they can affect the power station, which is external to the vehicle. It is not the same when we consider ESD, because ESD can only cause damage to the vehicle. The R10 does not care about the vehicle itself. It only cares about the external equipment and the safety of other road users.

Great question! Clause 6.10.4 of R10 details the reasons why ESD is considered out of scope. Reading it between the lines, R10 is focused on the safety of a moving vehicle and since ESD can only happen on entry/exit while the vehicle is stationary, this means that in the event of ESD no safety hazard can happen. So, it's out of scope. But for obvious reasons, most ESA manufacturers I worked with would not be satisfied with this answer. Then they would either apply ISO 10605 for automotive ESD or the conventional EN 61000-4-2. Notably, automotive ESD test levels are higher and go up to +-15kV contact, +/-25kV air. I believe, the Ford standard requires that as well as SAE J1113/13, so this is why EN 61000-4-2 is often applied instead, with +-4kV contact and +-8kV air. This tells the manufacturer that the product can handle some ESD, and doesn't require the manufacturer to go above and beyond of what's needed to get the product into the market.

why fix something that isn't broken :)

That's correct, thanks!

Hey, thanks! Afraid that's just how internet works - slow during the day, fast at night. Fibre optic is probably the best option in the market right now. en.wikipedia.org/wiki/Internet_bottleneck

Thank you!

😀

Great to hear! Enjoy the channel :)

Hmm, does the interference still occur when a laptop is powered from a battery supply rather than mains? Also, is the laptop connected to the plasma cutter in any way, i.e. RS232 or Ethernet? I'd expect a plasma cutter to produce a lot of conducted emssions, but not as much radiated.

​@@DrEMC-sf8rxI've tried it both ways, connected to power supply and running only off battery. The laptop is connected to the control board of the CNC machine via USB. I've tried running a ground wire from the z axis mechanism to the plasma cutter case. That didn't seem to help. Then I ran a ground wire from the z-axis mechanism to the case of the power supply next to the control board. That seems to help a little. Most people connect their control boards to older computers with metal cases via the parallel port. But I use a cheaper card (similar to an Arduino) and it doesn't have a parallel port option. Using an older computer with a metal case and a parallel port seems to be a key factor in reducing HF interference. It is also recommended to ground the cutting table itself to an outside ground rod. I haven't tried that yet. I recently picked up an optiplex 960 which is an older computer tower with a metal case. I also picked up a shielded USB cable to run to the board. I should get a chance to test out the new setup in the next day or two. From what I understand the torch lead from a plasma cutter acts as a large HF antenna. I'm thinking about buying some Faraday fabric and using it to shroud the work lead.

@@roberthosking7524 I think it's a lot simpler than you think. The interference is most likely conducting via the USB port that you mentioned. Try a USB isolator, such as this one - it should fix the problem :) hifimediy.com/product/usb-isolator/

​@@DrEMC-sf8rx great - I'll get back to you after testing and let you know how it worked. Thanks. I think you might be correct on this. When the machine was freaking out the laptop it was chiming with a connect and disconnect USB sound.

@@Hollywood4Fun yes, please do! It's always fun to debug these :)

Hey, a plane wave is an approximation that is designed to simplify mathematics. A true plane wave cannot physically exist at any frequency. However, if we sample a 15kHz wave from distance 2D^2/lambda with a small loop antenna, then it will look like a plane wave to us, due to the antenna aperture being much smaller than the wavefront. Hope it makes sense?

Thank you for your comment! :) EN 301 908-13 is specific to E-UTRA UE, while EN 301 908-1 applies to any equipment on cellular IMT network. This includes UE as well as BS and all applicable radio access technologies (2G-5G, etc.). As a result, the testing to EN 301 908-13 is more strict as its detailed in a very specific manner per TS 136 508. For example, the lowest channel bandwidths, 5 MHz and the highest must all be tested, while in EN 301 908-1 we simply can pick the worst case. That alone increases the testing time 3x times. There are other differences.

@@DrEMC-sf8rx thanks!! That's good to know that it is more stringent than version 1.

It's just under 4 hours. One week sounds about right, but don't try to watch everything in one day. There is a small quiz at the end and the certificate of completion for these who are interested :)

This course is tailored specifically for RF/IoT products, and designed to provide a detailed ovderview of: a) the scope of RF testing b) standards and c) test setups. It's suitable for beginners, EMC test engineers, and managers as I've deliberately limited the amount of EM theory and PCB-level design guidelines in this course.

thanks for the correction

Sorry, I don't understand the question. What do you mean by EM r/a/t ?

@@DrEMC-sf8rx electromagnetic reflection/absorption/transmitance. So i want to test some materials sheet for shielding from electromagnetic interferance and i think i can accomplish this with a spectrum analyzer if so how to do so?

@@ajingolk7716 Ah! You'd need not just a spectrum analyzer, but also a signal generator and two wideband antennas to receive and transmit signals. But may I suggest that prior to making measurements, you may want to learn the EM theory and perhaps do some simulations in CST or HFSS where you got libraries of all common materials. This is a great resource to learn, in particular Topic 2 EM properties of materials: empossible.net/academics/21cem/

@@DrEMC-sf8rx great to know that a spetrum analyzer will help, for the signal generator can i use this board EV-ADF41513SD1Z?

Thank you! I design IoT products and such, so I have to get involved because it's a legal requirement to do qualification testing. But you could also simply work for the test house, and you will learn quite a lot about RF if you did that :)

@@DrEMC-sf8rx Thanks, we've got SAA locally here in Australia and I too am wanting to develop my own IoT products. Guess there's no harm in forwarding my CV to them.

@@TradieTrev Great idea! Once you get your hands on equipment you'll learn 10x faster :)

Thank you, well spotted! From 17:34 onwards, the average of SUM values in X, Y, Z should be taken, and then converted to dBm to get TRP. In my example, I obtained TRP for X, Y, Z separately, but indeed they cannot be averaged in dBm form. The difference is not large, but that is more accurate.

Sure! The main isssue was that the product has an HDMI interconnect cable and a 90degree RA HDMI plug. I noted that if I plug a display directly to the PC, even without a cover, then the emissions dissapear. That solution would be ideal, but it wasn't possible to actually do that. So the pass was achieved through a combination of: a) better quality HDMI cable, linked below, which removed the harmonics, and b) adding a ferrite clamp, which reduced the fundamental. These fixes are acceptable, because they can easily be implemented in production without a major change in design. A metalwork re-design would require a re-test on the other hand. kabeldirekt-store.de/en/products/hdmi-2-0-kabel-top-series-4k-8k-blau

@@DrEMC-sf8rx Hi Dr. Emc, can you share some knowledge why ferrite clamps work on shielded cable? Besides, why does it only reduces the fundamental frequency 148.5Mhz but not the higher harmonics?

@@TheZoro-ub1zm great question! As you've implied, the problem is that shielded cables are not so shielded after all. Magnetic fields penetrate metals with attenuation and create electric fields that propagate further. So, a thin sheet of metal won't stop strong magnetic fields even if it's reflective for electric fields! Of course, commerical cables are relatively thin, and this is why EM fields exist around them, which are the strongest at their fundamental frequency. ps. You can also watch my other video about EM shielding: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-4TaFm_Y_E2c.html

There's no such thing as 5mm wave technology. 5mm wavelength would be 60GHz frequency, which is currently not in used 5G, not even in Wuhan 🤡