Help with 58khz coil

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Its definitely going to be a thick coil with 1,200 turns on a 10 x 100mm ferrite rod
Also I have seen pictures of these devices with a lot less copper wire such as the one here:

from what I know, it only has 1 layer and its on a ferrite rod
Do you know how they used less copper and achieved the same effect?
 
1200 turns with 1mm dia wire will be enormous.

Dan71 said:
Do you know how they used less copper and achieved the same effect?
Click to expand...
I don't know.
I assumed that what you wanted was a coil which was resonant at 58kHz.
Maybe the one with the thick wire is just a non-resonant coil and they batter it with a very high current.
I am just guessing here because I have never had anything to do with this type of equipment before.

JimB
 
From what I could tell, the sensor is basically a diode and another antenna. So, you have a modulated carrier at one of the ISM frequencies and if the modulation is detected, the alarm goes off.

I had an early RFID card and there was a diode(s) and 4 antennas. The F was swept and it causes a dip in signal strengthe at the reciver. That was translated into a "code".

At that point in time, the card I had in my pocket set off the anti-theft devices. Easy to defeat, if you know where the tag is.
One company put the tag in the ferrite in the line cord. Another company put it inside the power tool.
 

Hi. I was trying to create a jammer for the devices for experimental reasons, not the tag itself
Thanks.
 
If the system is 58Khz ( there are 2 main types, 58khz aka AM and 8.2Mhz aka RF) you can pulse
an electromagnetic field specifically, it will jam the system and prevent it from detecting
the tags..
though some systems have jammer detection and of course there are ways to bypass that

I also couldnt take the ferrite out of the tag as it would be powerful enough.
Thanks.
 
Nigel Goodwin said:
RF begins where ever you want to start using it (even audio type frequencies, or sub-audio)
Click to expand...
ITU regulations for radio services begin at 9khz... there are radio systems that operate below 9khz, and they are unregulated (and very difficult to get any usable range out of with any reasonable amount of power. the US Navy had an ELF system that operated on 76hz during the cold war. spelunkers have built radio systems for communicating between a cave and the surface that operates in the 1-3khz range...
 
unclejed613 said:
spelunkers have built radio systems for communicating between a cave and the surface that operates in the 1-3khz range...
Click to expand...

Cave rescue also use low frequency radio systems, as I recall laying long wires on the surface above the caves.

We actually know the one of the guys who runs the local cave rescue, and there's been some discussion about him bringing one in to see if we could make something similar - we've helped him with various things so far (at work we both used to be cavers).
 
unclejed613 said:
i used to live down the street from a store that had a rfid anti-theft system, and as it turned out it operated on 13Mhz, not 58khz....
Click to expand...
Hi. There are many systems out there..
The main company making 58Khz systems is Sensormatic
Their systems are actually very popular around where I live
Though of course RFID is starting to be used
 
There was an LF radio system developed by John Hay (G3TDZ) which gave good results in the limestone caves of North Yorkshire.
I think it may have used SSB on around 76kHz (from bad memory).

Having just called it a radio system, I have a feeling that the transmission medium was more magnetic than electro-magnetic.

JimB
 
Two very interesting articles, thanks. The trapped boys got a lot of airtime here in Australia but not one mention of the technical expertise needed to communicate.

Mike.
 
Hi, I made the coil today and it works quite well except that it doesnt have much range.
if I upped the volts would that give it a little bit more range?

Also many thanks for the help.
 
Dan71 said:
if I upped the volts would that give it a little bit more range?
Click to expand...
a coil on a linear form is not going to have much range. if you might have noticed, the coils in the store are in containers that are 3ft high x 2ft wide x 4 inches deep... the coils are "pancake" coils where it's on a flat surface and one end of the coil is at the center, and is laid down in a spiral and the other end of the coil is at the outside... very similar to the antenna coils of the RFID tags
 
Hi, It is not my point to create a huge coil like the stores use.
I wanted to create a jamming device for that frequency and I was able to.
I upped the voltage and it gave me the results I needed.
Thanks.
 
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