Apart from all the well-earned gratitude and respect for this excellent, very clear tutorial on E/H field probes, I gotta say, that's the finest hand-drawn image of an EM wave I've ever seen. @6:48
+w2aew I actually don't watch TV, well less than one hour per week. But I do watch your videos on YT and must admit that you have a talent to explain complex subjects in a simple way.Pleasant to watch and learn from someone that has been in business for many years.
+pat dhens Yeah, both are great. I really appreciate that they don't run too long. I can take in one of these with a cup of coffee in the morning and don't get that feeling I just sat thru a Calc II class.
100% agreed. I love this channel (w2aew). EEVblog, while also a great source of information, can be very tiring to watch after 5 minutes for us US based english speakers.
3 basically free probes I find very effective: 1. Simply cutting a small diameter coax cable flush and insulating the cut end with a thin layer of glue works very well for isolating noise down to individual trace level. 2. Same as 1 but allow the center conductor to stick out a bit. This would be similar to the E-field prob in this video. 3. Using small coax again, simply make a tiny loop from the center conductor back to the shield, and insulate. This very small loop is again handy for isolating noise to trace level (or close). If you are not seeing much of anything, do the common things to lower your noise floor: Turn on the preamp (if you analyzer has one), or use an external low noise amp, remove attenuation, reduce resolution bandwidth, reduce span if you want to increase the sweep rate.
At my work I had a set of 3 + 3 near field probes and an accompanying termination / 20 dB amplifier. But I made some of my H field probes using a gapped ferrite ring for some special situations. Since my retirement, I have built a few more to restore my lost abilities. But where I’m going with this introduction is that recently I bought an Aim I-prober model 520. And that is amazing! It is intended for H-field and for following very small traces. Not cheap, but for me worth every penny.
Nice job, it is a topic not usually addressed in these forums because of its' inherent complexities, yet you broke it down nicely and I think folks at all levels are able to take something away. You are definitely one of the top TH-camr's in this subject mattes, keep up the good work and thanks for taking the time to share your knowledge, it is most definitely appreciated. 73
Thank you Alan for another great class. Recently I ventured to assemble and search a little more about the magnetic loop antennas for use in my humble apartment ham radio station. The main problem I try to work around, is the excess of of QRM coming from the failure to proper grounding of my station. Recently built some magnetic probes and using a SDR dongle connected to HDSDR able to locate some sources of noise generation. Unfortunately I found that a lot of equipment in my country do not have an efficient control of EMI emission and therefore hinders much the practice of SWL. But how to persist is a positive feature in our hobby, still sniffing more noise sources and trying to eliminate them through changes in noise generating equipment. Thanks again for sharing. P.S: I'm sorry for my rusty English 73 PU2SRZ
As always, the best explanation I have ever heard. I have always been confused about free space impedance equals 377 ohms. OH... I get it after 50 years in the business. Thank you!!'
w2aew...I dont know if u read this. But Im depending on you so much these days. I am preparing for a interview and after watching your teachings, im confident ill crack the interview
Hi expert, I have watched many valuable videos what have been made out by you. It's really a good way to share your knowledge and skills with engineers who really interested. There is no such platform & nice man to share those matters in China. I hope I can be a such guy to do that.
Great. (really great, can not be better) And that's for all of your videos. So, hope you make another couple of hundred videos about whatever technical stuff. 30 years ago I could not have imagined someone is going to explain all this stuff.... ((well, do not move your tablet, sometimes you do, that's all))
Hi Alan, Thank you for making and sharing the videos. Regarding ~1:20 I believe these loops are not really "shielded". Across the gap at the top, you should have the same voltage difference (hence e-field) as for the feed of a loop made of a single conductor of the same size. I recently did a 3D EM simulation that also shows this. I can share screenshots if you like. I believe the coax shield is only kept in place to prevent cable waves on the feeding line. But this can be further analyzed.
Really, really useful explanation. I've just purchased some probes and now realise that they don't do what I thought!! However, I can use them correctly, abeit, not for what they were bought
Very clear and logical explaination about these 2 types of probes. As for all of your electronic basics videos a big THANKS and thumbs up as your videos help a lot in understanding *why* you have to do things the way they have to be done. Not just *that* one should do it this way. Thanks for sharing your knowledge on RF!
I've been around electronics for quite a while, but I never knew the real relationship between the electric field and the magnetic field. This honestly blew my mind.
Those nicely insulated ones would make a nice addition to my test bench. Nice bit of information, it brought back memories of using a home made sniffer probe to track down offending noise in mobile radio installations before fancy noise reduction circuits. I am giving away my age. Hi Hi. 73 Leo. k1zek.
Thanks Alan. That was quite useful... but it would have been nice to also see perhaps just a simple circuit that you could have demonstrated the sensitivity of these probes. Just a simple oscillator maybe with some different resistors that you could change out to show the current sensitivity and maybe another to show the voltage sensitivity. What are the frequency responses of these types of probes?
+ElmerFuddGun Frequency response of these probes vary by their size and construction - you'd have to consult the datasheets. Small ones can be useful up to several GHz.
wow, man, I got a long way to go. thank you. this is another hole in the pocket soon. got my huntron last year, few months ago got my PRC 2000 and polar toneohms 950 a few weeks ago. when is this bleeding is going to stop.
Excellent teaching video. Can you add some comments or technically explain the reactance area of the near field "inside" a large solenoid antenna. (say 60 cm in diameter). It is the area where E and H fields are unpredictable. I am looking to find an answer but I can't.
I have very basic knowledge in this topic, but I saw once a nice experiment made by Jeri Ellsworth "Magnetic Loop Antenna Current and Voltage Distribution", maybe it will help You: th-cam.com/video/adJp1zO9qfo/w-d-xo.html
Best explanations. Thank you. For EMI testing, it is mainly for far field. It would be interesting to see the correlation between near field probing vs real EMI testing. Is there any way to build a far field (home) setup for pre-compliance testing?
The correlation between near-field measurements and far field measurements is not going to be consistent. Signals observed in the far field will be observable in the near-field, but may be predominantly E field or predominantly H field - it depends on a number of factors such as the impedance of the circuit creating the emission, etc. In other words, near field measurements are not good predictors of far field behavior - but far field signals can often be located using near-field measurements.
Thanks for the great explanation! Very educational! I would like to ask one question regarding detected harmonics: Are those harmonics can be translated in RF (if there is some RF module fitted in) chain and transmitted to an antenna, potentially causing RF interference? Thanks in advance for answering.
I never knew that these things existed! They certainly are a handy tool but for me, I would rather connect those probes to a signal tracer... I only work with audio equipment and finding noisy resistors, well there's no better way to find them than using a probe like that. I have been planning to try using a head from a cassette deck but I haven't got around to it yet...
I'd be interested to learn about the use cases and potential traps for using an LNA with nearfield probes too. Another terrific episode, Alan! I learn a LOT of stuff from you and your videos tend to hit just the right subject at just the right time for me. I can't tell you enough how much I appreciate your outstanding work and effective teaching style.
+EweTwoughb In most cases, a spectrum analyzer is going to have enough sensitivity and dynamic range to use the near field probes without an LNA. Exceptions to this are when you can't physically put the probe very close to the radiating device.
Nice video, thanks for making it. I see that Beehive and Tekbox both offer wideband amplifiers to complement their probes. Do you recommend such an amplifier for the EMI probes? Are the received levels often so low that you need one if your spectrum analyzer doesn't have a builtin one? Or is there another reason for using one?
+Electronic Eel A preamp is often needed when using these probes with an oscilloscope. When using a spectrum analyzer, it really depends on how low the noise floor is on the analyzer, and if it includes a preamp of its own.
Great Video Thanks you might have an answer for me. I am interested in building Loop antennas for HF band. Do you want the XL and XC to equal 377 ohms of Z radiating coil loop IE for 10 watt W=I^2*Z and W= E^/Z where Z=377 Ohms....I=(10/377)^.5=0.162 A......E=(10*377)^.5= 61.4 V RMS I assume.????? the input coil will have to match the the input loop of 50 ohms to the output loop 377/50 7.45 to 1 transformer primary to secondary ratio ???? so input coil Z= 50 I=10/50)^2= 0.442 A.... E=(10*50)^.5=22.56 V...input Z voltage=22.56 V output Z voltage= 61.4 V ratio of 2.72 why does this ratio not match. 2.72 ^2= 7.4 close to ratio 7.45 So transformer impedance is also square law???? people on you tube are saying they are getting several thousand volts across an RF coil with only 100 W input Why???? if you could help me figure this out. ????? thanks N7RBC
Yes, of course you can use a spectrum analyzer - that's what I was demonstrating in the video (the MDO4000 scope has a built-in spectrum analyzer). You can use a scope too, but the sensitivity won't be as good.
Nice video. Where'd you get that plot of impedance vs FF distance? I thought it's always 377 Ohm, irrespective of how close you are to circuit impedance. A GTEM cell can go to DC, and if you place the field probe within the septum, the impedance (E/H) is still 377, even though the septum Z0=50 Ohm, all the way down to essentially DC. I thought E/H would be 50 Ohm, but after hours of researching, it's always 377. Maybe this only applies to within a TEM line.
This plot of the wave impedance is in several references as applied to radiating elements. Without doing the research, I suspect that since the TEM line isn't radiating that the E/H relationship may revert to the impedance of the medium (air), thus 377 ohms. Although, I can certainly see the argument as to why the E/H impedance would be 50 ohms, since the voltage/current creating this field is from a 50 ohm source. Hmmm - a good question for the next time I run into my old EM Field professor...
The near field probes are often used effectively to detect emissions from PCB assemblies. Would these probes be as effective to detect the sources of emission in Power Electronic equipment of > 50 KVA rating, like a UPS or a VFD?
+qwaqwa1960 Not really - because it is very difficult to obtain any useful calibration on these probes, plus it would be difficult to quantify the effective radiation efficiency of the radiating structure on the PCB. Most use cases are where you're searching for the source of an emission that was already reported in the far field.
At 1:41 you said E field probe are sensitive to orientation. I think that you meant to say that H field probes are sensitive. Thanks for your time and great videos..
Re making your own H probe, could you use thin coax instead of bare wire to implement E shielding? Or maybe a foil wrapper around the coil :-) A little Faraday cage...
Hi! Great video. I want to recreate this type of measurement. I could find the probes, but not the cable you used. Could you provide a link where to get the connector cable? Thanks!
The connector on these probes is an SMB. You can use an adapter to go from the SMB to a suitable connector such as BNC and then use an ordinary BNC test cable.
Wow! This was such a great video!! One thing that wasn't clear to me is how do you connect the probes to your MDO? I saw that Beehive doesn't sell a cable with a BNC ending. Do you use the "BNC probe adapter 0309-0006" and connect it to the scope with a BNC male-male cable? What would you recommend? Thanks!
Such a great video, thanks for the demo. Just one question, do you purchase any amplifier with the yellow probes? I'm trying to measure the transients on a SIC-MOSFET and the measurement is getting coupled with some noise, so I want to find a good place (less noisy) in the design to perform the measurement. Thanks in advance!
+Mihail Dimitrov I notice this a lot. Have no idea why folks do that. A person freely gives information out and someone does not like it? Only tells me one thing.........
Thanks Alan for the very interesting video. In principle, is it possible to measure the energy radiated from the circuit by measuring both E and H at the same point (as ExH is proportional to energy, Poynting vector )? Did you use the FFT mode in the scope to measure the frequencies?
+esmaeil nam Not really - the probes aren't really calibrated, and they're not very precise in measuring the field in the same location - since the fields are falling at a rate of 1/r^2 or 1/r^3, there can be huge differences in measured strength with very small radial distance errors. The scope I used has a spectrum analyzer built in, but you could use the FFT on a scope channnel.
@@tejeshwvardhan1165 HFCTs are typically used at frequencies under 200MHz, and are designed specifically to have the "wire under test" pass through it, so that you're measuring just the high frequency content of the current on that particular wire. The H-Field probe shown in this video is typically used at much higher frequencies - up to several GHz - and thus won't have as much sensitivity at the lower frequencies associated with PD. They're mainly used as "sniffer" probes to look for the source of an RF emission.
@@tejeshwvardhan1165 OK. I haven't used HFCTs myself. They do generally want the wire of interest to pass through the center. Note that there are many different types of ferrites, all which have different permeabilities vs. frequency. The particular ferrite "mix" is chosen based on the frequency range of the application.
Interesting topic, would have liked a bit more info on what kinds of problems these fields cause and of course how to resolve such problems. Something I can Google I suppose ;) As always well done and thanks! As always - making us think and grow ;)
One of the main problems is meeting emissions standards, which place limits on acceptable levels. e.g. your product can't interfere with peoples AM/FM radios, TVs, etc. Also your products emissions can in some cases be strong enough to cause itself to not operate properly.
I just use a sniffer with a metal Tip and metal ground then I just try to match my cascade analysis in the chain when I debug. Do you not like that style sniffer or are you strictly trying to catch fields ?
Does this technique of investigation requires same oscilloscope than yours ?( will a ordinary oscilloscope or a spectrum analyser will do the job ?) thank you
Apart from all the well-earned gratitude and respect for this excellent, very clear tutorial on E/H field probes, I gotta say, that's the finest hand-drawn image of an EM wave I've ever seen. @6:48
You are one of the greatest human beings who has ever lived.
+Afrotechmods Your channel is one of a few that I've tried to model my videos after.
+w2aew +Afrotechmods I have learned a great deal from both of your youtube channels! Thanks!
+w2aew I actually don't watch TV, well less than one hour per week. But I do watch your videos on YT and must admit that you have a talent to explain complex subjects in a simple way.Pleasant to watch and learn from someone that has been in business for many years.
+pat dhens Yeah, both are great. I really appreciate that they don't run too long. I can take in one of these with a cup of coffee in the morning and don't get that feeling I just sat thru a Calc II class.
+w2aew Hey can you make a video on smith charts thx in advance
Not the nervous fumbling around and pinched-ball voice from the EEVblog. How beneficial!
100% agreed. I love this channel (w2aew). EEVblog, while also a great source of information, can be very tiring to watch after 5 minutes for us US based english speakers.
What an elegant explanation of near and far field impedance!
3 basically free probes I find very effective:
1. Simply cutting a small diameter coax cable flush and insulating the cut end with a thin layer of glue works very well for isolating noise down to individual trace level.
2. Same as 1 but allow the center conductor to stick out a bit. This would be similar to the E-field prob in this video.
3. Using small coax again, simply make a tiny loop from the center conductor back to the shield, and insulate. This very small loop is again handy for isolating noise to trace level (or close).
If you are not seeing much of anything, do the common things to lower your noise floor: Turn on the preamp (if you analyzer has one), or use an external low noise amp, remove attenuation, reduce resolution bandwidth, reduce span if you want to increase the sweep rate.
All good tips, thank you.
At my work I had a set of 3 + 3 near field probes and an accompanying termination / 20 dB amplifier. But I made some of my H field probes using a gapped ferrite ring for some special situations. Since my retirement, I have built a few more to restore my lost abilities. But where I’m going with this introduction is that recently I bought an Aim I-prober model 520. And that is amazing! It is intended for H-field and for following very small traces. Not cheap, but for me worth every penny.
Nice job, it is a topic not usually addressed in these forums because of its' inherent complexities, yet you broke it down nicely and I think folks at all levels are able to take something away. You are definitely one of the top TH-camr's in this subject mattes, keep up the good work and thanks for taking the time to share your knowledge, it is most definitely appreciated. 73
Thank you Alan for another great class.
Recently I ventured to assemble and search a little more about the magnetic loop antennas for use in my humble apartment ham radio station.
The main problem I try to work around, is the excess of of QRM coming from the failure to proper grounding of my station. Recently built some magnetic probes and using a SDR dongle connected to HDSDR able to locate some sources of noise generation.
Unfortunately I found that a lot of equipment in my country do not have an efficient control of EMI emission and therefore hinders much the practice of SWL.
But how to persist is a positive feature in our hobby, still sniffing more noise sources and trying to eliminate them through changes in noise generating equipment.
Thanks again for sharing.
P.S: I'm sorry for my rusty English
73 PU2SRZ
As always, the best explanation I have ever heard. I have always been confused about free space impedance equals 377 ohms. OH... I get it after 50 years in the business. Thank you!!'
w2aew...I dont know if u read this. But Im depending on you so much these days. I am preparing for a interview and after watching your teachings, im confident ill crack the interview
Good luck with your interview!
@@w2aew thank you Sir!!
Good stuff, I am now smarter than before! 😁
Hi expert,
I have watched many valuable videos what have been made out by you.
It's really a good way to share your knowledge and skills with engineers who really interested.
There is no such platform & nice man to share those matters in China.
I hope I can be a such guy to do that.
great attitude, man!
wish you all the best
My favorite channel!
We always learn nice things on this chanel that we do not see elsewhere. Nice Video
Great. (really great, can not be better) And that's for all of your videos. So, hope you make another couple of hundred videos about whatever technical stuff. 30 years ago I could not have imagined someone is going to explain all this stuff....
((well, do not move your tablet, sometimes you do, that's all))
Hi Alan, Thank you for making and sharing the videos.
Regarding ~1:20 I believe these loops are not really "shielded". Across the gap at the top, you should have the same voltage difference (hence e-field) as for the feed of a loop made of a single conductor of the same size. I recently did a 3D EM simulation that also shows this. I can share screenshots if you like. I believe the coax shield is only kept in place to prevent cable waves on the feeding line. But this can be further analyzed.
Really, really useful explanation. I've just purchased some probes and now realise that they don't do what I thought!! However, I can use them correctly, abeit, not for what they were bought
Very clear and logical explaination about these 2 types of probes. As for all of your electronic basics videos a big THANKS and thumbs up as your videos help a lot in understanding *why* you have to do things the way they have to be done. Not just *that* one should do it this way. Thanks for sharing your knowledge on RF!
I took me a while to get it but this may help others. What you need to do is thread the loop on the direction of the magnetic field.
I've been around electronics for quite a while, but I never knew the real relationship between the electric field and the magnetic field. This honestly blew my mind.
When is "RF for dummies" coming out? You have a the uncanny ability to extract the perfect amount of information out of complex topics. Thanks again!
Man, what a clean explanation, kudos!
great explanation
Your handwriting is amazing.
+kuro68000 Thank you!
+w2aew Would it be possible to make a video on Smith charts?
+yiannis lhzl That's a big topic area - and would require several videos. I do have it on my list though.
+w2aew
Smith chart video would be awesome 👍🏻
What are Smith charts?
Those nicely insulated ones would make a nice addition to my test bench. Nice bit of information, it brought back memories of using a home made sniffer probe to track down offending noise in mobile radio installations before fancy noise reduction circuits. I am giving away my age. Hi Hi. 73 Leo. k1zek.
Thank you for another wonderful video and the time to share articles and references..
Thanks Alan. That was quite useful... but it would have been nice to also see perhaps just a simple circuit that you could have demonstrated the sensitivity of these probes. Just a simple oscillator maybe with some different resistors that you could change out to show the current sensitivity and maybe another to show the voltage sensitivity. What are the frequency responses of these types of probes?
+ElmerFuddGun Frequency response of these probes vary by their size and construction - you'd have to consult the datasheets. Small ones can be useful up to several GHz.
gracias por la gran aportacion de sus videos . con mis mejores deseos este bien ud, mister
Great, Great, Great video. Thanks a million for sharing your valuable experience with us.
Thanks for this wonderful video .... it clear all my doubts regarding E and H field antennas...
Reading others' comments it seems you've been commended graciously already, but I want to add my little thanks to the list. Liked and subscribed!
Im developing a product , that is why i watch this , especially back to basics parts :)
wow, man, I got a long way to go. thank you. this is another hole in the pocket soon. got my huntron last year, few months ago got my PRC 2000 and polar toneohms 950 a few weeks ago. when is this bleeding is going to stop.
Thank you for the video and the notes, very interesting.
Thanks heaps for the super informative video! Also Dave from EEVblog has a good "follow up" video on H & E field probes
Excellent teaching video. Can you add some comments or technically explain the reactance area of the near field "inside" a large solenoid antenna. (say 60 cm in diameter). It is the area where E and H fields are unpredictable. I am looking to find an answer but I can't.
I have very basic knowledge in this topic, but I saw once a nice experiment made by Jeri Ellsworth "Magnetic Loop Antenna Current and Voltage Distribution", maybe it will help You: th-cam.com/video/adJp1zO9qfo/w-d-xo.html
how beautifully insane this concepts become at milimeter wave frequencies.....
Great video as always. I might try making a shielded loop using some RG-174 coax with a split shield at the far side of the loop (single turn).
+Herbert Susmann That's a popular and effective way to make a h-field loop. You might want to add a few ferrites at the tail too.
Beautifully explained. Thank-you very much.
Thanks for sharing the wonderful video tutorial and The technical content was precise and apt to the point.
Pleasure watching this insight! Brilliant
Thanks again for this great explanation. Would be also interesting to see how you solve such electrical- or magnetic Field issues on the board.
Best explanations. Thank you. For EMI testing, it is mainly for far field. It would be interesting to see the correlation between near field probing vs real EMI testing. Is there any way to build a far field (home) setup for pre-compliance testing?
The correlation between near-field measurements and far field measurements is not going to be consistent. Signals observed in the far field will be observable in the near-field, but may be predominantly E field or predominantly H field - it depends on a number of factors such as the impedance of the circuit creating the emission, etc. In other words, near field measurements are not good predictors of far field behavior - but far field signals can often be located using near-field measurements.
Great, thanks for sharing.
Very nicely explained!! Looking forward to watching more videos from you.
Really informative video! Thank you for the clear and concise explanation.
Thanks again for another informative video.
Awesome video Alan. Learned a great deal, Thanks
Thanks for the great explanation! Very educational!
I would like to ask one question regarding detected harmonics:
Are those harmonics can be translated in RF (if there is some RF module fitted in) chain and transmitted to an antenna, potentially causing RF interference? Thanks in advance for answering.
I never knew that these things existed! They certainly are a handy tool but for me, I would rather connect those probes to a signal tracer... I only work with audio equipment and finding noisy resistors, well there's no better way to find them than using a probe like that. I have been planning to try using a head from a cassette deck but I haven't got around to it yet...
amazing review, ty
Many have a hard time with electric vs. magnetic fields. Both thumbs up.
Fantastic as usual. Do these probes need an amplifier to get the most out of them?
A preamp is most useful when using the probes with a scope. When using a spectrum analyzer, it depends on the analyzer performance and signal level.
I'd be interested to learn about the use cases and potential traps for using an LNA with nearfield probes too.
Another terrific episode, Alan! I learn a LOT of stuff from you and your videos tend to hit just the right subject at just the right time for me. I can't tell you enough how much I appreciate your outstanding work and effective teaching style.
+EweTwoughb In most cases, a spectrum analyzer is going to have enough sensitivity and dynamic range to use the near field probes without an LNA. Exceptions to this are when you can't physically put the probe very close to the radiating device.
Nice video, thanks for making it.
I see that Beehive and Tekbox both offer wideband amplifiers to complement their probes. Do you recommend such an amplifier for the EMI probes? Are the received levels often so low that you need one if your spectrum analyzer doesn't have a builtin one? Or is there another reason for using one?
+Electronic Eel A preamp is often needed when using these probes with an oscilloscope. When using a spectrum analyzer, it really depends on how low the noise floor is on the analyzer, and if it includes a preamp of its own.
Thank you, you are a great teacher
Great Video Thanks you might have an answer for me. I am interested in building Loop antennas for HF band. Do you want the XL and XC to equal 377 ohms of Z radiating coil loop IE for 10 watt W=I^2*Z and W= E^/Z where Z=377 Ohms....I=(10/377)^.5=0.162 A......E=(10*377)^.5= 61.4 V RMS I assume.????? the input coil will have to match the the input loop of 50 ohms to the output loop 377/50 7.45 to 1 transformer primary to secondary ratio ???? so input coil Z= 50 I=10/50)^2= 0.442 A.... E=(10*50)^.5=22.56 V...input Z voltage=22.56 V output Z voltage= 61.4 V ratio of 2.72 why does this ratio not match. 2.72 ^2= 7.4 close to ratio 7.45 So transformer impedance is also square law???? people on you tube are saying they are getting several thousand volts across an RF coil with only 100 W input Why???? if you could help me figure this out. ????? thanks N7RBC
Is it possible to use an ordinary o'scope to do the sniffing? Maybe even a spectrum analyzer?
Yes, of course you can use a spectrum analyzer - that's what I was demonstrating in the video (the MDO4000 scope has a built-in spectrum analyzer). You can use a scope too, but the sensitivity won't be as good.
Sorry for my ignorance.
Nice video. Where'd you get that plot of impedance vs FF distance? I thought it's always 377 Ohm, irrespective of how close you are to circuit impedance. A GTEM cell can go to DC, and if you place the field probe within the septum, the impedance (E/H) is still 377, even though the septum Z0=50 Ohm, all the way down to essentially DC. I thought E/H would be 50 Ohm, but after hours of researching, it's always 377. Maybe this only applies to within a TEM line.
This plot of the wave impedance is in several references as applied to radiating elements. Without doing the research, I suspect that since the TEM line isn't radiating that the E/H relationship may revert to the impedance of the medium (air), thus 377 ohms. Although, I can certainly see the argument as to why the E/H impedance would be 50 ohms, since the voltage/current creating this field is from a 50 ohm source. Hmmm - a good question for the next time I run into my old EM Field professor...
Simply brilliant! Thank you..
Great demo
thanks
Excellent always..
Another great video, thanks.
Thanks for this video....
The near field probes are often used effectively to detect emissions from PCB assemblies.
Would these probes be as effective to detect the sources of emission in Power Electronic equipment of > 50 KVA rating, like a UPS or a VFD?
Certainly - just be wary of the voltage/insulation ratings if you probe near high voltage points.
Thanks Alan.
Now...is there any way to get an idea of the far field based on near field measurements? If so, video please :-)
+qwaqwa1960 Not really - because it is very difficult to obtain any useful calibration on these probes, plus it would be difficult to quantify the effective radiation efficiency of the radiating structure on the PCB. Most use cases are where you're searching for the source of an emission that was already reported in the far field.
At 1:41 you said E field probe are sensitive to orientation.
I think that you meant to say that H field probes are sensitive.
Thanks for your time and great videos..
Yeah, you're right! Sorry about that. I'll add an annotation to the video later.
No worries. Glad to help.
+Pokojni Tozo he (demonstrated and said) otherwise many times too, though. Thanks for pointing out. I must have missed :)
How can this be used to test the quality of shielding on coax cable used in HF ham radio stations ?
Re making your own H probe, could you use thin coax instead of bare wire to implement E shielding? Or maybe a foil wrapper around the coil :-) A little Faraday cage...
+qwaqwa1960 Yes - all possible. There are some good DIY examples in the links provided in the video notes.
Great Video again , very informative...
Well explained video.
Hi! Great video. I want to recreate this type of measurement. I could find the probes, but not the cable you used. Could you provide a link where to get the connector cable? Thanks!
The connector on these probes is an SMB. You can use an adapter to go from the SMB to a suitable connector such as BNC and then use an ordinary BNC test cable.
@@w2aew Hi! Thanks for the info, I will see to find the connector and cable.
Very helpful and informative, thanks for putting this together! :)
...yes I definitely learned a lot from this video. :)
Wow! This was such a great video!! One thing that wasn't clear to me is how do you connect the probes to your MDO? I saw that Beehive doesn't sell a cable with a BNC ending. Do you use the "BNC probe adapter 0309-0006" and connect it to the scope with a BNC male-male cable? What would you recommend? Thanks!
Simply use an adapter to convert from SMB to whatever you need to connect to the instrument
+w2aew Beehive has SMB to N and SMB to SMA cables available; those cables are double shielded. Pretty pricey but supposedly good to 6 GHz.
Such a great video, thanks for the demo. Just one question, do you purchase any amplifier with the yellow probes? I'm trying to measure the transients on a SIC-MOSFET and the measurement is getting coupled with some noise, so I want to find a good place (less noisy) in the design to perform the measurement. Thanks in advance!
Beehive does sell a preamp, but I don't have it.
Great explanation!!! way to go!! Thank you!!
Does this mean that whenever a receiver gets a signal inside the near field distance, it's really picking up reflections?
this was very helpful thank you
I don't know why there are someone who do not like such videos??? And vote dislike...? Thank you for your time and effort 73 de LZ1MOB
+Mihail Dimitrov I notice this a lot. Have no idea why folks do that. A person freely gives information out and someone does not like it? Only tells me one thing.........
Sad but it is the nature of some people.
Thanks Alan for the very interesting video. In principle, is it possible to measure the energy radiated from the circuit by measuring both E and H at the same point (as ExH is proportional to energy, Poynting vector )? Did you use the FFT mode in the scope to measure the frequencies?
+esmaeil nam Not really - the probes aren't really calibrated, and they're not very precise in measuring the field in the same location - since the fields are falling at a rate of 1/r^2 or 1/r^3, there can be huge differences in measured strength with very small radial distance errors. The scope I used has a spectrum analyzer built in, but you could use the FFT on a scope channnel.
please tell me about the right angle connector that you are using on probe? is it SMB or SMC?
It is SMB.
@@w2aew can you compare H field probe and high frequency current transformer HFCT?
They are used in power grid to test for partial discharge signal.
@@tejeshwvardhan1165 HFCTs are typically used at frequencies under 200MHz, and are designed specifically to have the "wire under test" pass through it, so that you're measuring just the high frequency content of the current on that particular wire. The H-Field probe shown in this video is typically used at much higher frequencies - up to several GHz - and thus won't have as much sensitivity at the lower frequencies associated with PD. They're mainly used as "sniffer" probes to look for the source of an RF emission.
@@w2aew HFCT upto 3Ghz are available. would love to see a video of ferrite core and their frequency response
@@tejeshwvardhan1165 OK. I haven't used HFCTs myself. They do generally want the wire of interest to pass through the center. Note that there are many different types of ferrites, all which have different permeabilities vs. frequency. The particular ferrite "mix" is chosen based on the frequency range of the application.
Très intéressant ... merci !
Nice vid!
Very good video!!!
Amazing info
Any good way to measure the frequency of 32.768kHz crystals with a E-field probe.?
Thanks so much! Interesting as usual
Learned a lot! 73
Do they work on Mixed Signal Oscilloscope? Also the yellow one, Does that comes with all accessories like cables and all??
Yes on the scope. No on the accessories.
Interesting topic, would have liked a bit more info on what kinds of problems these fields cause and of course how to resolve such problems. Something I can Google I suppose ;) As always well done and thanks! As always - making us think and grow ;)
One of the main problems is meeting emissions standards, which place limits on acceptable levels. e.g. your product can't interfere with peoples AM/FM radios, TVs, etc. Also your products emissions can in some cases be strong enough to cause itself to not operate properly.
I just use a sniffer with a metal Tip and metal ground then I just try to match my cascade analysis in the chain when I debug. Do you not like that style sniffer or are you strictly trying to catch fields ?
The near field sniffer probes are useful only when you're trying to track down sources if undesired RF emissions, not general debugging.
great, thanks
will someone please tell that what should be S parameters for two ports orthogonal measuring near magnetic fild probe for without DUT?
How can I measure high frequency magnetic field with Beehive Electronics 100B EMC Probe?
So cool，thank you very much
Thanks!
Does this technique of investigation requires same oscilloscope than yours ?( will a ordinary oscilloscope or a spectrum analyser will do the job ?) thank you
Any oscilloscope or spectrum analyzer that covers the frequency range of interest can be used.
Thank you!