(hard): help needed to wire a PKE inductive receiver coil and measure it working.

Thread Starter

cndg

Joined Mar 31, 2013
6
I bought a bunch of these PKE receiver coils: https://www.aliexpress.com/item/32840317868.html
Screen Shot 2021-10-22 at 6.55.49 pm.png
which exactly match the part inside a PKE car alarm that I also bought.

My goal is to build an undersea personal remote-control so a scuba diver can wirelessly control foot-mounted thrusters from a bite-throttle on their regulator. I'm not interested in using sonar instead, and note that RF does not pass through sea. I've tested this - the car keyfob works fine through 2m of actual ocean, while no R/C remotes of any frequency get anywhere near the range I need.

I'm trying to read the coil signal without using the keyfob chip: https://ww1.microchip.com/downloads/en/AppNotes/01024B.pdf

Up-close, wired direct with no other components, it shows up just fine on my oscilloscope, however, at 2 meters (the max range I want), I cannot see any signal (note that the key-fob works fine past 3m or more). I gather the signal will be 1millivolt or less out there (but 5v or more when touching the transmitter antenna)

What do I need to do, so that I can detect any signal reliably at upto 2 meters range?

I gather that I need a 20pf capacitor in the circuit, and that my oscilloscope itself adds capacitance. Ultimately, an Arduino or similar MCU will drive the thrusters: should I be working now on some kind of amplifier and auto-gain-control ? If yes - what kind of things can work with such low signals that vary over such a great range?
 
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