DIY cable detector

[panoss]

I want to build a DIY cable detector (I don't wanna buy one, even though there are cheap ones).
e.g I have a cable coming out of a wall and I want to find out where it ends.

I tried this one, but no...it  can't detect a cable.
So (trying to avoid building a bunch of 'detectors' that don't work), have you tried something that you could suggest me building?
I 'm thinking about this one (creates a signal which is fed to the cable being detected. An AM reciever picks up the signal. Original article here), what do you think?
Or this one.
Or this one (on page 2).
Has anyone tried any of these? (or something else and worked fine)

[CopperCone]

seanb said he plugged in wire to his motorcycles ignition coil and used a AM radio

[panoss]

Ok, but I was thinking about something...more...descend... ...or let's say, more 'professional'.

[CopperCone]

hard to beat the power and cheapness of a motorcycle coil for something as crude as cable finding. Apparantly strong enough to work outdoors to find underground shit iirc.

I kinda want to make a box with a ignition coil mechanism to work as a transmitter with some kind of way to adjust coupling (maybe big resistors?).

I think that using a small hand held radio as a receiver is pretty professional.

Otherwise some kind of sparkgap transmitter I guess.

[Marco]

What's the point in RF? Won't you be detecting based purely on capacitive coupling until you get to UHF? If it's capacitive any way, might as well stick to audio frequency.

I'd build the one which alternates between 2100 and 2200 Hz. Build the receiver into metal box connected to circuit ground, so your body can provide the capacitance to earth it needs to work when you hold it. Also has the benefit of not being airwave polluting, which seems relevant in the HAM forum.

[panoss]

Ok I 'll built the one that alternates between 2100Hz and 2200Hz.
The receiver is just an audio amplifier with A1 (Antenna),  C1 and R1 in it's non inverting input, right?
So I can replace it with an LM386 amplifier, right?
Something like the circuit in the attachment.

[CopperCone]

What's the point in RF? Won't you be detecting based purely on capacitive coupling until you get to UHF? If it's capacitive any way, might as well stick to audio frequency.

I'd build the one which alternates between 2100 and 2200 Hz. Build the receiver into metal box connected to circuit ground, so your body can provide the capacitance to earth it needs to work when you hold it. Also has the benefit of not being airwave polluting, which seems relevant in the HAM forum.

marco I think its so that you can get a reasonable idea of where it is even if its going through a conduit or underground I think.