LRC, oscilloscope, ohm meter, soldering iron, is that enough?

[punagold]

I am going to try to make an enlarged DD for my Garrett ATX. I have been learning about how to use an oscilloscope and now have a much better understanding on the basics, although I am not yet sure how to to measure the self resonant frequency, so any guidance there will be greatly appreciated.

Will the above tools be enough to deal with the electrical half of the coil construction? Not sure if I need a pulse generator or can I just use my ATX to generate the pulse? Or is that risking destroying my detector? If I need a pulse generator, do I need a frequency counter to first take accurate measurements of the ATX?

Sorry for all the dumb questions, But I am trying to get a handle on the equipment that I will need to buy before I start this project. I am planning on buying ITMD very soon, but I am hoping to get some of these basic questions answered in the meantime.

I'm not sure if I'm biting of more than I can chew, but is it really that difficult to make a bigger coil that will work good? This has got to be do-able. I'm not shooting for more depth, I just want something like a 22" x 6" to speed up sweeping a large open beach.

Thanks again.

[Silver Dollar]

The equipment you have should be enough. You want to try and match the resistance and inductance.
The problem is that there sometimes are other components in the coil like caps or amplifiers. It helps if
someone has disassembled or X Rayed the stock coil.

I have found that even if you get everything right and think you have built a good coil it doesn't work as
well as a factory one. The shielding might contribute to that or the residual voltage might be wrong.

Some people seem to have no problems and others (like myself) can't seem to make a good one.

Do you have a 22" housing to use? I've found some housings do not have much room so the winding's have
to be exactly the right size to fit and be able to move for nulling. Thick shielding might make them not fit.
Also the crossover points can be too high so the coil does not fit inside the housing.

Loose winding's can make for micro-phonics but solid winding's can have fit problems, etc.

You have the cost of the wire, cost of the housing, cost of the connector, cost of the cable,
cost of the sheilding and cost of the epoxy too. The good epoxy costs $30 for a pint!

So although it's fun to experiment it can take a long time and cost a lot to make a new coil. You might
be better off buying one if you actually want to go out and use it some time in the near future...

[punagold]

Thanks Silver Dollar,

I don't have the equipment yet, but I do plan on buying soon. I just want to make sure I get the correct stuff before I start. That way I can have a better estimate of the cost before I start too.

Someone posted the schematics for an infinium DD, which also works on the ATX, so I am going to use that as my starting point.

As far as housing, I am a semi-skilled surfboard/paddleboard maker. I should be able to make just about any shape housing that I desire. I am striving for large and ultralight to use strictly for dry/wet sand. In doing so, it will probably be a little delicate but that is okay cause I can be careful about banging rocks and don't have to worry about the surge from waves. I've got coils for the water.

I have a supply of epoxy, a cable and connector. Planning on buying some litz wire and the resistor. I also have tons of fiberglass and even some carbon fiber, but my carbon is too stiff to wrap a coil. It would make good cross bracing though.

My big expense is the equipment. My big concern is blowing my ATX while testing the coil during and after construction. I could buy the big so called mono coil for $500+, but I really want a big long skinny DD. That is only obtainable by making my own or I can wait for one of the PM coils after they get their plugs manufactured. I'm not in a big hurry, but would like to get something in my hands in the next 6 months or so.

[Silver Dollar]

Well there is some good info in this thread; http://www.geotech1.com/forums/showt...Infinium/page2

I don't think you can hurt anything as long as you keep the resistance of the coils the same as stock.
PI machines are pretty forgiving as the normal mode is shorting the coil...