dumb question?

[Anonymous]

i have a question probaly a dumb one but curiousity is killing me . i was sitting here the other night looking at all these vintage detectors hanging on my wall (about 12 of them ) and was looking at the shafts and the loops. the ones from the 60's and early 70" the loop has metal bolts holding it to the metal shaft, the some bit newer ones still have metal bolts but the loops are bolted to a short plastic piece on the end of the shaft.. question is if the loop will pick up metal on both top and bottom of loop how does this metal not effect the detector.. with this piece of metal rite there? confussed .

 

[Anonymous]

Older detectors were not as powerful and I understand bolts were made of metals that did not interfer.Also once explained the metal does not move on its own, but only movement when coil moves..All I know is I would replace them with plastic screws myself..Just seems it has to have an influence..Do remember the biggest advanced facet on newer detectors is their ability to go deeper...

 

[Anonymous]

yea dan but these detectors had nothing to with motion they were tr and bfo operation. and the meteal on them is aluminum and brass bolts or stainless ones and these metals drive us crazy in the feild. whish some had the answer on this.

 

[Anonymous]

Most likely if you take the coil off the pole and have it away from the metal shaft its mounted on and then tune the detector to a medium point to zero beat then tune it slightly to a slow motor boat when you move the coil back toward the metal shaft ( pole )
it normally mounts to you will get a swing in signal from the coil being near the pole.
With most beat frequency detectors the tuning is set near the zero beat with the detector coil exposed to the nearness of the metal shaft. It the shaft was made of wood and had a metal bolt through it the same thing in the tuning of set point for motor boat with being mounted with the metal bolt.
Now the detector being tuned to a certain setting ( motor boating) while its coil is mounted on a metal pole or with a metal bolt it gets a new response ( I guess you can say a total ) different signal when exposed to a metal object near it besides the already near item like the pole or bolt that has become part of the tuned circuit and moves along with the coil and is now only affected by the contact or nearness of new metal objects. ( or minerals etc ) Trying to explain without electronics technicalities.
In summary the metal that the coil is attached to becomes part of the tuned circuit when the detector is tuned to near its operating beat frequency. Any other metal object placed near the coil will then react . The pole and or bolts are not coils or energized with the electronics of the circuits though. But only in a sense become part of the tune up so to speak. There is a limit though as to how much the coil will can match up to with out becoming useless.
HH
Dan R.

 

[Anonymous]

Sounds reasonable to me Dan and good explanation...As I use newer units my bolts are all non-metal..

 

[Anonymous]

You got that right I use newer units myself those bfo's are ancient.
All my stuff uses plastic type bolts and non metal poles. Your correct though in your response about movement of the coil ( or in an other way ) moving metal parts relative to the coil. even on the old unit. Movement between coil that is relavent to any metal parts will show up as a signal also, even on a bfo.
HH
Dan R.