Coil question for Reg

[Frank-S]

Reg,
I have been tinkering with coils for my VLF Technetic G-2. made a fue test
coils DD, and coplanar coils.the coils with best dept make a lot of noise,some
will detect my hand, also when I touch the controal box it detects my hand.
Is there a way to get ride of the excess noise maybe put a cap between coil
and controal box.
When I take a fue turns of wire off coils there is less noise but less dept.
Frank.

 

[Reg]

I suspect the noise and the ability to detect your hand is because of the lack of any shielding on the coil. You might try shielding the coil with somethng like conductive carbon paint and see if some of the noise and the detection of the hand subsides. The shield needs to be connected to the ground connection by using a fine wire.

I thought the housing of the detector is plastic. If that is the case, again, I suspect the lack of coil shielding is the culprit. No, there is no logical way to add a cap to the coil to the case to eliminate this noise. However, a cap of the right value might reduce the noise a little but this has to be added across the receive windings and should be a value such that the tank circuit of the receive winding and this cap resonate well above the resonant frequency of the detector. The cap will not take the place of the proper shielding of the coil and the shielding needs to be done.

All VLF coils need to be shielded and many if not most PI coils require shielding also. On a PI, detectors using a long delay may not need any shielding.

Reg

 

[Frank-S]

Thanks Reg,
You are right about the shield,its a test coil no shield.I use the same wire over and over
on each test coil so I dont shield each coil.I can remove a fue turnes of wire its almost like
useing a shield on a test coil.the controal box is plastic there is no shield inside.My old
Minelab Soverign had a shield inside the box.My old PI had no shield inside its box,I glued
a shield inside and grounded it.It did help.I have not made a test coil that goes deep, deep ,So
I dont finish it. Thanks again.
Frank.

 

[Reg]

Try to find some good stiff paper and coat it with some carbon based paint. Then add a thin wire by taping it to the painted side and when you want to shield a coil, simply attach the wire to the ground inside the coil housing and lay the paper on the coil.

Reg

 

[Frank-S]

Thanks Reg.
I can use that on my test coils.
Frank.

 

[Frank-S]

Reg.
On a US made VLF detector,is the ground positive or negative.
How can you tell what side of TX or RX is ground wiithout opeaning the detector.
Do you ground Tx or RX coil to shield in a VLF.
Thanks, Frank.

 

[Reg]

The ground is usually connected to the shield wire in the cable. So, look at the coil connector or the coil cable and find the bare wire which is the shield wire.

Reg