EEVblog #1178 - Build a $10 DIY EMC Probe

[floobydust]

It's 10 turns of #34AWG wire (0.16mm dia.) on a 1.5mm form, like a toothpick.
The murderous part is soldering the coax on one end, and the brass Faraday shield on the other. It was too flimsy, even with lots of epoxy.

If I was to revisit this, I would just buy a 0603 chip air-core RF inductor and solder to it or make a slim pcb for the probe. I also was looking at adding a balun because the grounded (to spectrum analyzer) shield easily shorts to your PCB under test.
The R&S probe has an exposed, grounded bare metal tab which causes drama, sparks etc. for noobs.

A big area probe like OP, I do not find useful. Aside from finding an unshielded inductor or SMPS transformer gapped-core spewing flux, I'm usually looking at smaller things for EMC.

[joeqsmith]

Link to articles of the probes I handmade and use.   I use these without any sort of preamplifier.   They are good enough that I can normally isolate things to a single trace.   

https://www.eevblog.com/forum/rf-microwave/ferrite-bead-pcb-track-current-probe/msg1723385/#msg1723385

[wilfred]

I don't have a multi $1,000's spectrum analyser but I do have a Digilent Analog Discovery. Could you make meaningful measurements about a circuit with such limitations? Or with some other inexpensive device. One question I had was could you measure bypass effectiveness and therefore evaluate changes/improvements where needed? Even if only on a single or double layer board.

[Radiosonde]

These are mine...nice for rf development and comparing shielding.

Gesendet von meinem SM-J730F mit Tapatalk

[Mortymore]

I had an EMC DIY probe made a long time ago, out of RG58 cable and with a 50 resistor placed in the ring, if I recall correctly, from an Elektor magazine article. At the time I had some fun finding the horizontal sweep frequency of computer CRT monitors.

This weekend I built 2 EMC probes, Dave Jones inspired. Not yet terminated since I don't have liquid electrical tape, but they are partially insulated with heat shrink tube. The soldered joint is naturally still exposed.

Attached a photo showing the radiated signal from a 100 MHz crystal oscillator. The graph has a 100MHz CF and a 10MHz span.

EDIT: Attached the article "H-field sensor" from Elektor UK magazine December 1994. This probe is 50 terminated at the tip.

[bitwelder]

Hackaday post on a DIY EMC probe (https://hackaday.com/2019/04/24/a-diy-emc-probe-from-semi-rigid-coax-and-an-sdr/)
based on an article on rtl-sdr.com (https://www.rtl-sdr.com/creating-an-emc-probe-using-an-rtl-sdr-and-semi-rigid-coax/),
inspired by Dave's video

[jemangedeslolos]

Hello,

Nobody tried to design EMC probe directly on PCB ?
With the ridiculy low price we can have this day, it will be interesting

[EEVblog]

Nobody tried to design EMC probe directly on PCB ?
With the ridiculy low price we can have this day, it will be interesting

No point, you can buy a complete set for US$46
http://s.click.aliexpress.com/e/bMu5qeBI

[German_EE]

I'm OK with almost everything that is involved with building the Jim Williams probe including winding the coil. The only sticking point is the two slits in a very small tube, far too small to use a hacksaw. How do I carry out this step?

[G7PSK]

I have just made one of these using the rigid coax as Dave showed with a wide band RF amplifier. I tried it with a Nooelec nesdr smartee dongle have not found any near fields yet but it makes one heck of an antenna from comercial FM upwards have not had time yet to find it's upper limits.

[David Hess]

I'm OK with almost everything that is involved with building the Jim Williams probe including winding the coil. The only sticking point is the two slits in a very small tube, far too small to use a hacksaw. How do I carry out this step?

Hobby shops sell "razor" or "snap" saws (1) which use much thinner saw blades than hacksaws.  Thin slitting saws or abrasive disks on a rotary tool like a Dremel are another option but operation can be tricky unless the work piece and rotary tool can be anchored firmly.

(1) Search for "atlas snap saw".

[Gromitt]

I'm OK with almost everything that is involved with building the Jim Williams probe including winding the coil. The only sticking point is the two slits in a very small tube, far too small to use a hacksaw. How do I carry out this step?

Hobby shops sell "razor" or "snap" saws (1) which use much thinner saw blades than hacksaws.  Thin slitting saws or abrasive disks on a rotary tool like a Dremel are another option but operation can be tricky unless the work piece and rotary tool can be anchored firmly.

(1) Search for "atlas snap saw".

Or, as you are in Germany, search for 'Roco Bastelsäge' or 'Roco 10900' (They are the same thing, Roco makes them for Atlas)