EEVblog
ฝัง
- เผยแพร่เมื่อ 6 ก.พ. 2019
- How to make your own magnetic H-field EMC probe out of semi-rigid coax for $10 that performs identically to a $300 commercial probe!
Search for "Low noise amplifier" and "semi-rigid rg402" on ebay.
Forum: www.eevblog.com/forum/blog/eev...
Bitcoin Donations: 38y7DE8HEHNj8fGDtUr4PkCn9nWxiorvvy
Litecoin: ML7oQokTwB38bgzzjLDbRV97HKAHuwRfHA
Ethereum: 0x11AceA38DCA9DbFfB4F35f3F746af65F9dED28ce
EEVblog Main Web Site: www.eevblog.com
The 2nd EEVblog Channel: / eevblog2
Support the EEVblog through Patreon!
/ eevblog
AliExpress Affiliate: s.click.aliexpress.com/e/c2LRpe8g
Buy anything through that link and Dave gets a commission at no cost to you.
Stuff I recommend:
kit.com/EEVblog/
Donate With Bitcoin & Other Crypto Currencies!
www.eevblog.com/crypto-currency/
T-Shirts: teespring.com/stores/eevblog
Likecoin - Coins for Likes: likecoin.pro/@eevblog/dil9/hcq3 - วิทยาศาสตร์และเทคโนโลยี
Now build a additional spectrum analyzer for 10 bucks and every one is happy ;-)
Would a SDR make a decent spectrum analyzer? I guess most have a more limited range though.
It would definitely work, although you'd have to be careful about the input signal level as they saturate easily, it also takes a good amount of time to sweep a large bandwidth.
Yes a HackRF would have more than enough frequency range although slow sweep (but then do we care?). They are a bit 'deaf' though. Can't hurt to try though can it?
Test it with RTLSDR for 10$
Dave should probably do a video with $165 handheld spectrum Analysers from rfexplorer.com
One of the best videos in a while!
@qashqai q Spot on. I'd rather have Dave post rarer, but higher effort content.
I don't watch the mailbags anymore, they seem to become a chore for him. Teardowns are a hit or miss really. Dave sometimes does too little research. Though that correlates with "off-the-cuff" slogan.
RicoElectrico Correct, I do practically zero research, that's the way I've always done videos and have built my channel from nothing doing that.
@@EEVblog How about more DIY expensive tools that work as well as the professional ones. Stickin' it to the man. How about an active oscilloscope probe next? Or a DIY Hewlett Packard 547a current tracer? I could probably use one but not enough to justify $200 on ebay
Totally agree .. high quality content .. stick it to the fat cats Dave .. maybe build a differential probe next from Ebay parts .. there are a ton of broke engineers and hobbyists out there
Yes sir. An RF probe came to mind from an old set of computer external speakers... that'd be about as cost effective. SDR ideas don't seem bad for cheap spectrum analyzers especially if there is an oscilloscope plugin... though I've figured a set of attenuators for the range and profiling the SDR well to know its range of performance to characterize the limitations so you don't blow it up. Probably a current limiting input thingamajiggy too. Normalizer dohicky would be impressive. Least that's what comes to mind. I was also wondering about making a leveling head for the cheapo signal generators since they're so cost effective. Trips me out how cheap some of the modules are and how like this detailed video demonstrates using the hardline or rigid or I guess it's called semi-rigid cable... can be used to make decent kit alone basically or with a or some modules. So much, I just ordered a range of modules, plus some, to make an Antenna Analyzer or looks like is going to be a VNA using Erik's latest modularized version he notes on the SoftwareControlledHamRadio groups.io post on Analyzer Comparison since seems impressive: github.com/erikkaashoek/Tapr-VNA
Another solution for your rubber coating: buy ABS filament for 3d printers and solve it in acetone. Then you can use a brush to apply it. The acetone vaporizes on its own at >20°C and only the ABS is left
I'm looking forward to next video "Build a $100 DIY Spectrum Analyzer"
It might not be $10, but the W7ZOI homebrew SA was a good design/project from the '90's, rebooted here:
hfsignals.blogspot.com/p/specan-reboot-of-w7zoi.html
I have done that (500 MHz) , is a lot of work, by the time it was finished I had a few real SA's. www.pa4tim.nl/?p=1643 , it is a while back so the page is in Dutch, newer projects etc are in English.
You had time to build it to scale and to paint it!!!
Only two coats!
@@EEVblog I believe this would do a better job coating it than the spray-can version: www.amazon.com/Performix-11602-6-075815116024-Plasti-Dip/dp/B000ZN1T16/ref=sr_1_9?keywords=plastidip&qid=1549645102&sr=8-9
@@altersami9660 yeah... I saw the name Plasti-DIP ... and a spray can, and I was like... what? Plasti-Dip is supposed to be a thing you *_DIP_* into, not spray on.... silly people, giving them a market for this.... (I mean, I suppose there are probably use cases where dipping is impossible and the spray is useful. But for this use case? Dipping seems entirely appropriate. Ah well.)
I may actually join the discussion over on the forum. We have billions of these DIY H-field probes in our lab of varying qualities. Might be rather entertaining to post a picture of all of them.
Please do!
I came here to say this is one of your best videos in a while and am amazed to see how many others are saying the same thing. I couldn't believe you peeled back that Tekbox cover; thanks for doing that!
It's funny that I don't have any use for the probe but found it so entertaining.
For all those wondering the weird round package is a type 86 plastic package, and the amplifier, which has only GND, IN, OUT, is a MSA0486.
That faint thudding at the end of the video is Tekbox executives jumping out of the windows.
Need more of these typ of videos
Great, now I just need a Spectrum analyzer :|
You scope likely has FFT
@@EEVblog or cheap RTL dongle or HackRf will work.
As SpecA’s go, you can likely get the Rigel jobbie that Dave was using for ~1500 $USD or less. That’s serious coin, but WAY cheaper than an equivalent unit a decade ago...
Yeah about $20 for the RTL SDR + Spektrum (free)
www.rtl-sdr.com/poor-mans-spectrum-analyzer-with-an-rtl-sdr-and-noise-source/
@@samuelcomeau Install it with Pothosware. Dead easy.
I got loads of those RF amps sitting around, they're handy because you can use a buck converter and set the output voltage to calibrate gain with them, no need to use an attenuator.
You don't need plasti-dip for probe coating, use electrical tape. It almost looks like the cheaper one could be prototyped in strip board if the need was urgent enough. For a cheap spectrum analyzer, attach a 10 MSPS SPI ADC to a raspberry pi, write some code to perform FFT on the data using the GPU and pipe the output to a graphing utility to get an approximation of a spectrum analyzer.
Use the PastiDip in the non-aerosol can or liquid electrical tape and you will be much happier.
Also, you can make the very small loops from very small diameter coax. The coax does not need to be rigid, and if you put some steel wires or small fiberglass/carbon-fiber rods along side the coax for the small loop, it will add the needed rigidity. Use heat shrink over the coax and stiffener for the straight part and dip/paint on the liquid tape over the loop.
The small loop can be even more finicky to cut and solder, so short the end of it back over the coax before bending it into the loop, then solder the whole end back to the shield to make the loop. To cut the gap in the middle, you only need to make a single slice, and when you dip it or brush on the tape, it will fill that slot and Robert is your mother’s brother.
You know you need to take this to the next level right?
First you use a 3d printer as x/y scanning platform for the board (printer can be fed gcode for movements from pc via usb) and then record the data from the oscilloscope via for example python integration with scope (usb again). Recording the spectrum on each position in a grid and display everything in a nice overlay on a photo of the board. User could then either see a sum/max of all the emissions or scroll through the spectrum and visualize a frequency slice in the overlay. Now that's sexy!
Yes, I said that in the previous video.
There is a product out there that is an array of loops in a paper sheet size bed. Its multiplexed and scanned into an analyser. You can put an image of the pcb layout over the scan data to give you an RF 'heat' image. Think its made by Emscan.com from memory.
@@simonbaxter8001 I know. I've used one. This is cheaper and more fun...
That coax looks like they just dipped normal braided shielding and dipped it in some solder.
That is exactly what they did.
Thats how many places make semi-rigid in the smaller coax styles. Very common.
we've always called that soldered braid stuff "semi-rigid" coax. Solid copper outer shield was called "rigid" ..
Yes, it's semi-rigid.
Actually the right term for this stuff is "handflex." Examples of semi-rigid coax would include the 0.086" and 0.141" cables with the solid tinned-copper shield that you see in commercial spectrum analyzers and other RF gear. It is not meant to be formed by hand and often breaks when you try.
Good noise floor for the couple dollar pre-amp.
I've seen worse from decent commercial jobs.
You can also make a quick and dirty e-field probe by cutting away some shield leaving a very short stub of the solid core conductor then insulating against shorts.
Even if you don't have a specan these tools are useful with an oscilloscope (you will need the preamp). If it has fft like most dso do then that is a bonus.
Home made H-felds are great, beat the old emco kit any day of the week
That piece of coax is beautiful.
Not sure why you have a few thumbs down. A huge money saver that will give the same performance. This is great Dave. Thank you yet again
The thumbs down will be from the company that makes the probes or from people who bought the probes and now feel like they wasted their money.
I built an EMC probe for less than $8, using a toraial core coil and soic op amp. I needed to measure current WITHOUT physically touching the current-carrying conductor. Torrid core coil to the rescue! You can see it, and the printed circuit board CAD files that I offer as "open source", on my MeWe page @ Esp and IoT
Welcome to the world of radio frequency hobbyists / radio amateurs!
We knew this all the time. I made such a probe years ago and used it many times, it is also useful to tap off some signal from an oscillator coil to measure the frequency using a counter, to tune a transmitter amplifier while constructing/experimenting, etc etc.
Yes, they are quite common.
Is it also usefull for making measurements in Audio circuits? I'm thinking off finding noise sources in the 1khz to 40khz range.
Afaik RF is much higher then what interferes with audio ...
For that I have a different probe that has a coil with some more turns at the end.
Just a length of RG58 with a BNC at one end (for the scope) and a coil made from .5mm enamelled wire that I threaded through a length of insulation tube (4-5cm), ends pulled together so it forms a small loop.
Finished with some heatshrink to cover the solder joint to the end of the cable.
Experiment with the number of turns depending on the signal pickup level you need and the high-frequency response. For this region it should not be a problem to have like 20-40 turns, but of course it will no longer work so well in the MHz range.
We knew this all the time, I made one years ago. Well why didn’t you take the time and effort and put it up on TH-cam and not wait for other people. With your sort of attitude no wonder the young people are not coming into amateur electronics. Why are your sort so protective of knowledge?
@@KidCe. Just use a normal flat coil for that and either a cheap oscilloscope or a cheap audio amplifier. Or search for "superprobe".
We always made our own probes like this. You can make them more selectable by adjusting the size of the loop.
Well, that came in handy! Things ordered, now the waiting begins. Thanks a lot!
Looking forward to the E-field probe.
Thanks again Dave. Way cheaper and super easy. You’re the man!!! Gonna build my own.
Thanks, Dave! Very good.
The guys at tekbox spent houndres of hours on r&d for this thing to work properly.
Dave botches something together in 10 minutes and it works just as fine if not better than the pro kit. :D
R&D, or D&M (design & marketing)? :P
Research & Development
Getting those curves that are individual, and that are a true reflection on the device, as opposed to lucky try and it worked. Plus the whole repeatable manufacture thing that means you can interchange probes, and not have to run a calibration on each new one you get, just use the curve supplied, which is well within a specified tolerance spread.
In my book, this is a proper tear down.
Great work.
Great video Dave! The blue coating on the outside of the TekBox probes is likely a low-pressure overmold, which is the same material used on strain reliefs for cables, etc.
That's the kinds of videos we are here for. Thank you!
I think you might be slightly wrong about the commercial probe coating. I feel like they did a grippy gritty transparent conformal coating to help adhesion of the blue shmoo.
Possibly
Great video as always, Dave. We’re dealing with an EMC issue on a project right now..
love all your videos, but i have a preference on EMC/EMI things, keep it up
Good job Dave!
Great video! This is the kind of content that I really like, this is definitely worth the patreon subscription.
Brilliant dialogue, very entertaining and informative. Many thanks for sharing
Great video! Waiting for Part 2 with a little EMI pre-testing howto!
Frigging amazing hack! Everyone is going to build one. Thank you Dave, really
Very instructive - thank you!
Great Video. Top marks for peeling back the rubber.
Dave's videos are really fun to watch. Few other channels can do the same.
Excellent! Thank you Dave. Videos like this are why I subscribe to EEVblog.
Love the enthusiasm. How about doing the E field probe next ?
Excellent idea!
Nice little project that one. Thanks for an great video.
13:29 It looks like a tool handle dip to me 4:14 the surface finish is rough, bumpy, and full of holes.
It's likely the same thing you used Plastidip and that shade of blue is one of the three shades they sell. It also comes in a can so you can dunk the part rather than spray it.
Just just dunk the PCB into the container, pull it out, and let it drip dry. Repeat the process to thicken the coat.
Bushougoma Looks like they also used some primer coating to make rough surface layer on PCB and make it stick.
Just another grand Video!
Very educative and interesting!
Keep it up! Good onya Dave :)
Nice video, one has to question why the commercial one’s are so expensive. It reminds me of when companies rub off chip numbers to hide how they are made. Probably also would reveal the company’s mark up vs actual part costs
I love RG402. Nothing better for DIY antennas
Awesome video, I like how you show that doing EMI measurements is easy. And in my electronics courses they said I'd never do that unless I go to university, yeah... Right.
You can make the H-field loop solder connection and shield cutting in many ways. There will be very little performance difference if you make it unsymmetric and just solder the center conductor to the shield on one side. Yeah, it won't be geometrically symmetric, but it will be electrically almost the same as the more complicated construction.
Excellent video. This was quite interesting and useful. Please do the video in compliance.
That was ace, enjoyed that. I was thinking u could 3D print a mould for the coating.
Fascinating! Thank you!
awesome davesome save. thank you👍
Very useful. Thank you.!!!
Very useful video, thanks
excellent video. I hope you make the follow up videos as you mentioned. I would also love to see a differential version of this instead of single ended. I think high end EMC probes must be differential to suppress common mode noise and enhance sensitivity. In the end it can be converted to single ended using a balun or something.
Someone asked if this can be used in audio frequencies, I think the voltage induced in that loop must be proportional to frequency as well as the loop area, so at audio frequency, the picked up voltage will be way below noise level
them cheap amps are perfect to use for RTL-SDRs aswell..infact you can use this probe on a SDR and find the same results!
Yes, they advertise them for that
Well done
*Very helpful, Thank you* 👍👍👍👍
Nice job Dave , Make more hack like this i love it .
That's pretty ridiculous. Cool video Dave!
39 dislikes are from EMC probe manufacturers lol
Now start mass production and sell it on Ebay for $50 and bundle it with calibration certificate "Calibrated by Dave".
A cal cert on a post-it note...
Dave thank you for this video really useful video so many applications, looking forward to an official diy PCB.
Cat nail scissors are excellent for stripping braid off small coaxes.
Thank You .
Awesome! Never knew there was just a trace and a plane to it
Nice little project :)
Interesting Dave, Cheers bud :-)
Beautiful!
Great video. In the pre-compliance process right now for an IVD device with the cheapest company on the planet.. I seriously hope it doesn't come down to me building one of these. Thanks.
Oh, nice. I saw the other EMC video and was thinking about 3d printing something and winding the head with the various reels of magnet wire I have here. I also have lots of rigid coax so winner, winner chicken dinner.
When I play our video at 2x speed you become an electronic squeaky madman!
Play it backward... Dave is dead...
I built one too. Works fine!
Great video Dave! Could you do a similar frequency domain analysis with an oscilloscope's FFT? Just to make it a lot cheaper and accesible, since it's a more common tool.
I would love a video on using FFT function to make these measurements. I think building one of these probes would be a lot of fun for $10. A spectrum analyzer is out of the question for me, and probably a lot of hobbyist, but I do got a scope with FFT.
You could potentially use fft on a scope, if you had a scope with 1+Ghz bandwith. A new 1Ghz scope is in the $10k vicinity. A hacked to 3.2Ghz Siglent spectrum analyzer is about $1700. A HackRF SDR is about $250, and I believe with the correct firmware sweeps 6Ghz rapidly. The lower cost devices would not be calibrated or have features like like tracking generator, so the hacked spectrum analyzer has some significant attractions. There are also PC based vector network analyzers, which add a lot of additional functionality, as they measure phase shift in addition to amplitude. A full duplex SDR + a ebay reflection bridge might be a usable vna with the right software.
This Dave! This is why we subscribe. Now, can you show how to build a DSA 815 for those of us that can't afford one? Haha
You can buy the cans of plasti dip, probably works better than the spray. Also, using a spray paint primer first might help it stick better.
As someone else said on the comments, I'd like to see how an oscilloscope FFT using this probe compares to the spectrum analyzer, for the ultimate thrifty EMI measurements!
Great video and the answer to my needs for a cheaper and accurate way to measure fields. I enjoyed the 2 layer/four layer computer boards comparison you did recently but shuddered at the $300.00 Tek probe kit price. I used to make sniffer probes for use in troubleshooting radio xmtrs and receivers which were of course uncalibrated. I consider what you taught us to do here to be close to calibrated. Thanks for the unselfishness.
Should be pretty close to the performance of the professional Tekbox one. I can do some more detailed measurements and comparison, but it's looks as close as you can get. Although with near field probes you aren't really dealing with absolute quantitative measurements.
Dave, thank you and here is a project request: Would you design, build and test the efficiency of a
a Joule Thief circuit. There have been many offerings but I have never see any commercial products. I recall you commented in the past about the LED in a similar circuit not having a current limiting resistor. Some of the offerings have run a long time on a battery. I have designed my own 1.5VDC non Joule Thief LED "flyback circuit that generates a sine wave that I thought might recharge the battery but did not even though LTSpice indicated that it might. I also have a LTSpice design that uses very little 1.5VDC battery current to drive a LED but I can't get it to run in the real world. Still trying........
Great idea! I just happen to have a box of surplus semi-rigid SMA jumpers (and some with 1 end off,) and 3 or 4 of those little amps, AND some ferrite cable clams, but no EMC probe! I'll do it!
BTW, that is braid on the coax cables, but it is saturated with something much like solder, ensuring 100% coverage.
I love this kind of videos comparations. More videos like that, please. Expensive VS Cheap. Who is gonna win?
Usually there is a performance difference, but in this case pretty identical!
@@EEVblog EEVblog I agree. But for a simple mortal like me and others learners, $10 to $300 makes a lot of difference.
Dave, you need an x-ray machine. Just saying :-)
Not possible to buy one here without a license.
@@EEVblog ugh. That sucks.
I like the type of x-ray machine bigclive uses ;)
@@zvpunry1971 Bigclive has an x-ray machine ?
Hahaha I have a lot of different x-ray models at home and didn't know it.... Hilarious
A good appropriate spray paint should do the same job nicely as the plastic dip here.
Was hoping you might go into this a bit deeper. Thanks!
In what way?
EEVblog not the poster but I loved the video but I would also love, maybe in a follow-up, how/why the probe is designed that way, why the symmetry and impedance matching are so important.
In any case, I'm loving the EMI/EMC series!
@@EEVblog I'd guess he meant it as "after watching the previous video, I was hoping you would dig deeper. Thanks for doing it! “ as that's what I feel too. And please keep them coming! :)
Is it possible to get any sort of useful reading with a scope? I've seen these used for locating dead ICs
More DIY!!!! Awesome !
Nice, thanks for sharing :-)
A PCB would be awesome
Excellent video, more diy stuff. The difference in price is shocking, electrons spontaneously felt off if they had any notice of value.
Those tiny amplifiers are the MAR series from minicircuits.com. They have been around since the late 1970's. This is the MAR-2 line.
www.minicircuits.com/WebStore/dashboard.html?model=MAR-2SM%2B
Please do a Rogowski Current Probe next!
Nice, I gave it a big thumbs up
it's a INA-02186 MMIC apparently.... got some MAR6 (little worse) gotta try it ASAP!!... thanks
Really great video, Dave. Thanks!! I know you might not like the request but since we are looking into bargain field probes....what options do we have out there for bargain spectrum analysers? Does Hantek offer anything? Something for the home hobbyist or person at home looking to tinker around or EE student looking to learn more practical application wise about fields. A DIY probe and amp set coupled with a bargain analyzer would be right powerful bit of kit for people like myself.
You could characterize the two amps for frequency response, that might be the only tech difference.?
I just missed a DaveCad with EM fields around the probe, so we can understand better how the fields convert to Volts into the probe, for the signal analyser
Love this