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Fisher Gold Bug Pro Coils on F75 and Vice-Versa


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While out on the Sawtooth adventure, Dee tried a GB Pro 5" coil on her F-75. Guess what.... it worked! Steve, any comments about that?

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I sold my F75 a while back but kept all the extra coils because they do work on the Gold Big Pro. The reverse would also be true. Work is a relative term. They are not optimized for the detector since the F75 is a 13 kHz detector and the Gold Bug Pro is a 19 kHz detector. However, the performance difference if any is minimal and many people would probably not see enough difference to matter. Fishers official position is "yeah, they work, but no guarantees".

That is the source of the confusion regarding aftermarket coils because coils not really specifically made for the Gold Bug Pro are being marketed as working on it.

My 13" Ultimate coil was made for my F75 but it appears to run just fine on my Gold Bug Pro and I kept it for that reason. I also have the little 6" elliptical concentric for the F75 and it appears to run fine on the Gold Bug Pro although no similar version is made for the Gold Bug Pro directly.

So bottom line is you can safely try Gold Bug Pro and F75 coils and not hurt the detector but may not get optimum performance. Teknetics T2 coils will not work on the F75 or Gold Bug Pro or vice-versa!

I suspect the big difference would show up in discriminate mode and skewed target identification numbers. As long as you run in pure all metal and do not use the target id numbers you are ok but beware using any discrimination at all as it is probably not accurate.

This is the official statement from Lead Engineer Dave Johnson at First Texas:

"The new Bug (and also Tek G2) are designed to work with the Tek "Greek series" (also known as "Frat Bros.") series DD searchcoils, which at this time (Nov 2010) consists of a 5 inch round and an 11 inch elliptical.

Some people have gotten creative and plugged in other searchcoils from the FratBros and F75 series just to find out what happens. Results have been mixed. Because of manufacturing variation in searchcoils some individual ones of a particular type may "work" and others may not work. The ones that "work" may in fact exhibit subtle performance deficiencies, or may seem to work fine today but not tomorrow.

FTP-Fisher explicitly un-recommends that people purchase anything other than searchcoils specified for use with these units. But if you have one of our other searchcoils anyway, there's nothing to stop you from plugging it in just to see what happens. It won't damage the machine. Note however that Tek T2 searchcoils flat out won't work, they're wired different."

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I had tried this a few years ago without much success but couldn't remember why. Today tried my 5"GB Pro coil on my f75 and it seemed to work ok, but when I put the f75 6" elliptical on the GB Pro it wouldn't ground balance. It may be my dirt, the ground phase reads,97,and that's what the gb reads also, if I manually GB up to 99.9 it is still out of bal. After doing this I now remember why it didn't work and I think it was the same for the larger coils also.

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We were in variable moderately warm to hot ground and the Ground Grab worked just fine.  It ground balanced much better than the GB2 was able to do.

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Yea , mine works that way, but the F75 coil doesn't  work on the GB P, it kinda works but won't ground balance.

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I think El Dorado is talking about the 5" DD and you are talking the small elliptical concentric Hobo. I have put the elliptical on my GB Pro and it bench tests well but I have not tried to ground balance it in the field. I will give it a go soon and report back, but being a concentric what you are saying does not surprise me.

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  • 3 months later...

one of the technical specifications of the the antennas is some thing called  impedance (the coil is an antenna ) which means the the resistance of the coil components to the inductive current caused by the electromagnetic spectrum introduced by the detected metal or the surrounding material and this impedance might be a inductive or capacitive or a mix depending at the nature of the coil ingredients and measured with a unite called OHM  any way these are a complicated technical details but the conclusion is if the impedance of any coils is matching the impedance of the other coil specified for using  with a certain detector then this 2 coils will work properly with the same detector this is due to the similarity of the coil impedance with the detector other components total impedance. the reason of the coil and other detector components should match is to transmit the scanning signal from the detector to the target with the max power and to pass the reflected induction due to this signal from the target to the detector circuitry with the max power too this comes under the  max power   transmitting theory. so the summary is equal impedance of the coils means working properly one instead the other.

                                   ;)  ;)  ;)  :blush: good luck  

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