VLF Magnum Build

[Qiaozhi]

Try moving your shaft (left-right) near to working coil to determine position at which you cannot detect your shaft any-more. Then this is the right position/distance.

Gary, this is not true because Magnum is motion detector and the shaft not moves relative to coil. However the RX preamp sees a signal from metal shaft and you should reduce the gain to avoid its saturation. To avoid reduction of sensitivity, make the clevis tubing from wooden rod long about 250 mm.

Actually, you are both correct.

For a motion detector, the shaft does not move relative to the search coil. Therefore it will not be detected when in use. But, it will negatively affect the sensitivity of the detector. Also, if the angle between the coil and shaft is altered in any way, the balance of the coil will be upset.
Now ... having said that ... read the following text from Carl:

"The Magnum is a VLF design with ground balance and a TR discriminate mode, but lacks a motion ground balance/discriminate mode. Thus far it is the most advanced hobbyist metal detector project I've come across, amazing considering the date of publication. In 1980 the Magnum would have been a fairly advanced metal detector, just one step behind the motion discriminators that were introduced only 2 years prior."

As you can from the text, and by simply looking at the schematic, the Magnum is not a motion detector.

[mikebg]

Try moving your shaft (left-right) near to working coil to determine position at which you cannot detect your shaft any-more. Then this is the right position/distance.

Gary, this is not true because Magnum is motion detector and the shaft not moves relative to coil. However the RX preamp sees a signal from metal shaft and you should reduce the gain to avoid its saturation. To avoid reduction of sensitivity, make the clevis tubing from wooden rod long about 250 mm.

[WM6]

Regarding the Support Shaft from the Search Head to the Control Box. How far, safe distance does my Support Shaft have to be from the Search Head if use an aluminium shaft?

Try moving your shaft (left-right) near to working coil to determine position at which you cannot detect your shaft any-more. Then this is the right position/distance.

[baht7]

Regarding the Support Shaft from the Search Head to the Control Box. How far, safe distance does my Support Shaft have to be from the Search Head if use an aluminium shaft?
I found a cheap chinese Floor mop that is collapsible and was thinking it would ease my transportion area.

I know this will be a lame question for you guys, but bare with me.

In the Magum build project, is that 4 inch Pick Up coil on top or underneath the Search Coil...hahahahahahahah.
I warned you.

Gary N Bangkok