Coil Signals in a Vintage TR/VLF Detector

[Mike D.]

Hello Everyone,

I am new at this and am trying to learn a few things. Have purchased some 'Vintage' detectors and am tracing out the schematics for them.

Does anyone know what a good receive coil signature should look like on an O-scope for a transmit/receive VLF unit?
I have an old VLF unit that appears to work in both Ground Balance-All Metal and Discriminate modes.

However it's receive coil trace is almost identical to its transmit signature and 180 degrees out of phase.
The coil also shows some evidence of having some kind of components internal to its' housing other than just wire and shielding.

Did manufacturers historically not induction balance their coils or do I possibly have a broken coil?
Again, the detector does function and will discriminate iron objects from non-ferrous items.

Thanks.

 

[Reg]

Your coil is most likely fine.

Reg

 

[Mike D.]

Thanks Reg for your reply.

Just not the signal I expected.
I have wound concentric coils in the past and was able to get fair nulling on the scope, but this unit's coil and circuit seem unique.

 

[Carl-NC]

In the absence of any targets, the RX coil should have no signal on it. Make sure it is far from any metal when you're measuring.
Lotsa schematics & other info on geotech1.com.

 

[Mike D.]

Thanks Carl-NC
I have copies of most of the GeoTech site schematics and many notes.
Great site, and salute to the detector manufacturers that have allowed some of their circuits to be displayed.
Mike D.

 

[aspk]

n/t