Had a chat with the test engineer at our factory. They made me a handful of these. They are tuned for 55hz. They don’t work. I can send them to you to play with if you want. They might work for 220v though… I only tested with 120v.
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They’ll work very close to a transformer’s primary - preferably with an armature around it 
Yes, want!
Wait, that’s not good bargaining technique.
Pardon me good sir, I see you have items that others might find desirable. Would you perhaps be interested in fair trade?
DM Sending now.
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Phone Company f-ed up my dsl line while installing neighbor’s connection. Hate being on phone. Too slow.
But…
Got them in. Thanks Amal!
Test1 220v air conditioner. Nothing.
Test2 480v in conduit. Nothing.
Test3 480v main switch panel. Note, requires arc flash protective gear to operate. Nothing
Test4 480v transformer. Outside housing dims approx 2ft x 3ft x 4ft tall. Pulls 200amps. Results Nothing.
Safe to say another direction will be needed.
Ah the glory of failure. It’s how we learn.
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Get rid of that safety rubbish 
I bet if you took the safety gear of, you would feel a tingle!
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You sure you’re not American?
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Hmmm. That’s a real bummer. I already tried a low Inductance coil with a larger 1F supercap. That didn’t work either. We can’t really go the other way with a larger inductor because we’re limited on space and there will be too much resistance in the wire. I’ll talk with Amal about it. Maybe I can crack one open and hook it up the the VNA to determine the actual resonant peak.
I also considered going to a flat pancake style coil such as the flex series use. I have absolutely no idea how those are wound (on a bobbin?) or how they retain shape without unwinding (superglue?).
I considered busting one open too, so I could check inductance. But, theyre such pretty little things. Such fine wire too. Finer than the 40awg I have.
What’s a VNA?
Here’s a video
They have a machine with two vertical plates that spin. They put a machined coil form on one of the plates, feed in the magnet wire, sandwich the two plates together, and then spin the whole thing while dripping adhesive on it radially until they’ve reached the correct number of turns.
It’s a real bitch to get them to do it at the quantities we need.
It’s a “Vector Network Analyzer”. Step up from an oscilloscope. You can use it to analyze antenna properties.
Wow, what a headache, was thinking of trying to start winding coils myself too, but seems like it’s really hard 
i am aiming for a 1.337 mH coil. cylindrical in shape to match the NExT tag and hopefully greatly improve read range 
Painfully hard at times, but awesome when you get it just like you want.
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It reminds me of my similar (failed) experiments I did ages ago.
As far as I remember 55Hz - or sound frequency in general, doesn’t like to travel in air as EM wave.
The flux goes through the ferrite, but it only jumps the air gap once the freq goes higher.
Even the kHz range would be only few millimeters, if that.
There is a formula of calculating air gaps for loops with and w/o ferrite core, but of course I don’t remember it. 
please correct me if I’m wrong. 
but now I thing that a contactless LED blinky would need xxkHz range at least.
EDIT: without power source
I might dig out the plasma ball to sniff some O3 again =)
I was thinking the other day,
I wonder if you could build a led implant with the right coil to light up when you go thru the EAS anti theft gates at stores
I’m not sure if it’s really apples to apples though, since if memory serves its an acousto-magnetic system…
But still, it’s a giant coil pumping power into a localized field… could be worth a shot
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imagine if it sets of every anti theft gate at any store 
then trying to explain it to the security guard you’re chipped
Lol oh I don’t need to imagine,
Anyone that’s worked in retail long enough, and run out of fucks to give has discovered the game / war
“Where can I hide a hard/soft tag on my coworker to mess with them”
The trick is multiple at a time, making it much harder to isolate which article of clothing it is
Normally you can hide soft tags super easy, but you just pass things over the sensor Matt and it deactivates them, or hard tags that always work, but are bulky
My personal favorite was I broke a had tag and took the guts out and slipped it inside the bungee hem of his coat
so next up is implant a tag while your co worker sleeps?? 
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So I’m getting there, bought myself a Chinese LCR meter, well 2 since the first was just garbage 
my self made antenna coil is in the 1.337mH range. but i have trouble with fine-tuning to get to that sweet-spot.
What I currently do: integrate antenna in the whole reader circuit, put a probe on the antenna to my oscilloscope. Then I remove or add windings until the amplitude of the sinus is at a maximum.
currently the read range is about 2-3 cm with NeXT.
so is this the way? or … looking for advice