two coils in one housing

[Koala]

I think someone had put a large DD and small DD in the same housing. looks neat.

https://www.youtube.com/watch?v=O00taPZ2Sns&feature=youtu.be

[Nandor]

Why he connects the 9volt battery to the coil? Is that a relay switch for the coils?

[Koala]

Why he connects the 9volt battery to the coil? Is that a relay switch for the coils?

Yes

They have also started another one with a standard double pole double throw switch. Details on the MD4U.4U site somewhere.

[SGS]

AKA made such a coil two years ago. Switch the frequencies from the menu, not by battery 9V.

https://postimg.org/image/4emely5gb

[Koala]

AKA made such a coil two years ago. Switch the frequencies from the menu, not by battery 9V.
https://postimg.org/image/4emely5gb

Cheer I was not aware of this

An explanation here

http://z13.invisionfree.com/IrishMetalDetecting/ar/t2763.htm

"Next project in development - 2SF work with 4D coils - big DD and small DD - all in one housing (patented). Also 2 frequency detector. But, depend on the soil condition operator can choose different modes:
- one coil / one frequency
- two coils / one frequency
- one coil / two frequency
- two coils / two frequency
What are the advantages of this?
When we are in contaminated sites with many irons - need small coil and high frequency. OK, we choose to work with small DD coil and high frequency.
If you need a depth greater purpose in a clean place - choose big DD coil and a low frequency.
But the icing on the cake will be the joint work of both coils simultaneously both frequencies Much better identification and much better performance in all type of soils."