Finished the Bandero II build - Part1 - The Head

I started with the coil, my reason being if I could not do that then there was no point doing much else. I used a stick = half the coil circumference (you can see one in the pics), built just the oscillator, and got winding. At 10KHz, broke the stick, opened up the coil, measured it....exactly half, 5KHz.    I work day to day on the 1Ghz area but the principles are the same. Doh! wound another to measure 20.1 KHz, opened up, 10.5 Khz (because the buck coil will take care of that odd 500hz. :

Did much the same for the Rx coil. Fixed the Rx coil to a lump of wood, spread the Tx coil around it. By careful distortion of the Tx coil got almost zero op from the Rx coil. Then wound a buck coil over the top of the Rx coil, adjust etc, and ended up with just 50mV at the output of the Rx pre-amp so changed the 100ks for 200ks to get a bit more front end gain.

I fixed the coils in place with cable ties and tie bases, The hotmelt in the pics is just to stop the coil moving now it is in position. Now I know somebody is going to throw their toys out of the pram and say that the shape of the coils means there will be dead spots, and maybe there are BUT in testing I found none and besides, as you swing the head how do you think you are going to find them ? You aint.

My build target for the whole thing was $20.00 and I was well under. The case for the head is a plant pot tray from the garden centre. It has a  disc of PCV facia borad inside ( strong and very light). The two are held together with plastic screws from my kitchen re-fit. The clear pillars were cut from arcylic rod (Ebay) . The coils were fixed the a disc of plastic  - left over from a window re-fit.

The fixing on the top was from a chandlers (Ebay) - it is used to hold an awning on a boat, I just tapped it to take one of those kitchen screws, so no metal in the head.

Ongoing testing is proving it up to a foot so far. Disc mode is excellent, bit of weird instability in Metal mode, still fixing that.
More to come on the (very changed) electronics.
 

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Wonder what ever happened here?

March was a Long time ago.

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Well I went out and then I posted a few questions. Nobody answered/helped so it stays in the garage for now.
Qs are:
Ground balance - I was attempting a very rutted track; is this a bad thing ? Got a lot of false stuff.
Could my coil be crap ? It is ok in free air, good range etc. What should I expect/hope for ?
Electronically, it does all it should.

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Shield ? you mean shield the top and sides connected to 0v ? (or maybe an out of of phase osc??) How does that help ? I am interested, not querying your advice.
Is it anti-magnetic shielding I need ie a ferrous shield ? I am able to obtain a lot of copper adhesive tape. I thought maybe tin foil ? The copper tape makes a great solder contact with the foil. I laso wondered if my coil shape was a problem - I adjusted it until I got zero pick up ie a 100% null so it is an odd shape; a bit like a circle with four or five dents.
thanks

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aaa! a short while. I'm trying to get up from my desk

Hi all.

At first I thought it was joke but it seriously I think it's something weighs much as a large brick 

1: the transmitting coil to be perfectly circular.

2: plastic in the reaction with grass produces electrostatic fields which kills the sense of creating something like this

3: try to use calculators to designing coils - it is full of them. eg. induction calculators, resonance calculators... etc.

4: throw it to the trash and make a new one 



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