Garrett Groundhog

[Qiaozhi]

Does anyone here know the internal coil configuration of the Garrett Groundhog?
This is a 1970s VLF/TR detector that was the machine for finding gold. Its frequency of operation is 15KHz.
In particular, I would like to know the inductance of the TX and RX coils, and whether the tuning capacitors are contained within the search head or on the PCB.

[Carl-NC]

I can try, but it will be Sunday-Monday time frame.

[Qiaozhi]

I can try, but it will be Sunday-Monday time frame.

Thanks Carl.
No rush - my question is connected to the pistol detector investigation we're doing in the RS Forum. I'm trying to establish if it's possible that the original coils are being used in this design.

[Carl-NC]

Here's what I get:

TX -- pins 1/4 -- R=31.64 -- L=2.37mH -- fo=119kHz
RX -- pins 2/3 -- R=247 -- L=14.44mH -- fo=79.5kHz

So it appears there are no caps enclosed.

- Carl

[Qiaozhi]

Here's what I get:

TX -- pins 1/4 -- R=31.64 -- L=2.37mH -- fo=119kHz
RX -- pins 2/3 -- R=247 -- L=14.44mH -- fo=79.5kHz

So it appears there are no caps enclosed.

- Carl

Thanks Carl,

This is really useful information. Please can you also tell me if this coil is a concentric or a DD type?

[Carl-NC]

Appears to be concentric.

[Unregistered]

Here's what I get:

TX -- pins 1/4 -- R=31.64 -- L=2.37mH -- fo=119kHz
RX -- pins 2/3 -- R=247 -- L=14.44mH -- fo=79.5kHz

So it appears there are no caps enclosed.

- Carl

I know this maybe silly question.. but how can one determine if cap enclosed or not.
are you using o.scope to test or .. can one with simple test method judge if cap is enclosed or not. I have coil to test and wish to know.

[Carl-NC]

This head is for a 15kHz detector, and since the coils have self-resonances at much higher frequencies, I assume there are no internal caps. But I may be wrong, they might have some internal C and the rest in the control box. One way to check is to wind a basic coil of the same size & inductance and see if the resonance is similar.

- Carl

[Qiaozhi]

Hi Carl,

Hopefully this is the last question on this subject.

What is the diameter of the coil housing?

[Carl-NC]

I think Garrett calls it a 7-1/2" coil, but the TX coil is 6-3/4" at most.