Ferrite Coil receiver

I am currently refitting a robot lawn mower.

This is my first project with anything remotely involved with radio type electronics.

The robot lawnmower has an electric fence wire that has a signal of approx 6kHz going around it.

I need to detect this that I can keep the robot in the perimeter.

I am ok designing a circuit for amplification etc but I need a resonant coil and capacitor
to pick up.

There doesn't seem to be coils just to buy of the shelf??? I am in the UK.

How many henries should I use? Where can I get them? Do I have to wind my own?
If so how many turns of wire should I use??

Thanks for any help.

Just wind 50 turns of 0.25 enamelled wire around a 20cm diam saucepan and make sure you add a pencil below the winding so you can remove it.
Tape up the coil and you have the pick-up coil.

So how many henrys would this be? and what size capacitor would I need to produce the right resonant frequency?

You are not trying to make a resonant circuit. You pick up the 5kHz and amplify it with with type of circuit:

**broken link removed**

If you go here there is a calculator. Enter the frequency the capacitor and it will give you the inductor size. Example: .006 Mhz, 1 Ufd = 70 Uh.

https://www.daycounter.com/Calculators/LC-Resonance-Calculator.phtml

You can then go to the air core calculator page (samr site) and get a coil for 70 Uh.