Co-axial coils

[Frank Wallis]

Has any one ever made one for a PI detector
Regards Frank

[Eric Foster]

Re: Co-axial coils

Hi Frank,

The very first PI's for archaeological use had coaxial coils; outer transmitter winding with inner receive. This was to give less ground signal from the near surface. There was no balancing, as it is not needed when sampling the signal in the off period. In the 1970's I started using mono coils for simplicity in most treasure hunting applications. Later, I went back to coaxial coils when I built a PI discriminator. These were balanced, as the discriminator looked at what was happening just after the TX was switched on, as well as at switch off. Comparing DD with coaxial on a PI, the DD seems to have some performance advantages i.e. it is quieter on bad ground and has a wider front to back response pattern.

Eric.

[Frank Wallis]

Re: Co-axial coils

Hi Eric
Many thanks for info on co-axial coils
The co-axial you described has just two windings TX RX is that correct.

Regards Frank Wallis

[G.Gueorguiev]

Re: Co-axial coils

Dear Mr. Foster
I would like to see a real Disc-Pi design ... if it is possible! So I've got one Disc-Pi mashine designed and manufactured by Nedialko Jordanoff, which is working better than Pulse Star II pro.
Best regards,
G.Gueorguiev

[Eric Foster]

Re: Co-axial coils

Hi Frank,

Initially I used two windings, then went to a stacked coaxial for the discriminator. This is like a sandwich, with the TX in the middle and separate RX's above and below. Later I tried a coplanar coaxial, which seemed to be just as good and made for a thinner coil. Both of the latter were balanced.

Eric.

[Frank Wallis]

Re: Co-axial coils

Hi Eric
Many thanks for your info
Regards Frank Wallis