Help Setting up Surf 1.2 PI

[apulmax]

I have made a new coil from PTFE INSULATED EQUIPMENT WIRE, 7/0.15
10" internal diameter with 21 turns. I have a resistance of 2.9 ohms across the coil (out of circuit) I have set the offset to 0v after I noticed that I soldered in C13 the wrong way round. I put every component in carefully as not to get polarities wrong and still managed it I binned the cap and used a new one just in case I fried it.
Anyway, I set the trimmer (delay) to the mid point but am getting slow pulsing through the speaker, I think someone referred to this as "ringing". To get the resistance to around 1.6 ohms I need to put a resistor in parallel which will block the coil, so what now?

I have ordered an inductance meter to give me an idea of the inductance of the coil.
I have a Caltek CS10H Scope which I have never used, so if anyone is willing to tell me where to connect it and use it to set this detector up, I would appreciate it very much

[UFO]

Sure, connect the two wires of your Caltek CS10H Scope to two wires on the oscilloscope.
Plug the Caltek CS10H Scope into the wall to power it up. You should see a squiqley line on the screen, you will need to adjust some dials, to make the line even more wavy.
When it gets hard to read turn it back some more. You can then turn some more dials until you get the desired inductance reading you desire.
I once made a .300uH coil out of 600' of cat5 that was only 2 ohms.

Whatever you do, make sure you strip the plastic insulation off that PTFE wire.

I hope this clears things up for you.

[apulmax]

Thanks for the info UFO, it was very helpful.
Strip off the insulation from the PTFE wire? That's the first time that has been mentioned.
If the insulation is stripped off that will make it one solid coil of wire with no resistance at all, surely?
I have 21 turns and it measures about 1.6 ohms with an inductance of 340uH which is about what they say the coils should read.

[Lord Dracon]

what? yes your right there you need some form of insulation on the wire, that is to stop it shorting out between turns! .. i tend to use enamel coated copper wire for my coils..

[Lord Dracon]

Here is a link to something different (if you wish to try it) re surf PI coil made by ApBerg using coax cable

http://www.geotech1.com/forums/showthread.php?t=16322

[UFO]

Thanks for the info UFO, it was very helpful.
Strip off the insulation from the PTFE wire? That's the first time that has been mentioned.
If the insulation is stripped off that will make it one solid coil of wire with no resistance at all, surely?
I have 21 turns and it measures about 1.6 ohms with an inductance of 340uH which is about what they say the coils should read.

I was being extremely sarcastic, tongue in cheek.

Keep the insulation, the instructions for the scope was jibberish.

I think you are well on your way now to a nice coil, you don't "need" the scope although it would be nice.

I don't know if it was mentioned in this thread or not, but one of those variable pots rigged up for the dampening resistor works great. You can just tune to maximum depth, and then measure later with your inductance to see what it is for curiosity sake.

[apulmax]

Sorry, a bit slow off the mark regarding the insulation, (old age creeping in)

I have ordered a 10k pot for making up a variable dampening rig

At the moment my kit is not working, it stopped out of the blue. The scope is showing the the pulse going into U4 (4093) but not coming out of it, so I am suspecting the 4093 has died. I have ordered another 4093 so when that arrives I will know if my diagnostics are correct or way off