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Hi All,
I just received the Backpacker I recently purchased and began playing with it. For those of you who don't know much about this brand of detectors, they are built on the principle of "off resonance". There are several models out but all work basically the same. The backpacker is a compact version that is small and light weight.
Now, the down side of this type of detector is the fact it is ground sensitive and as such, they do not work well in heavily mineralized ground since the ground signal causes strong changes much like a metal object does. Off resonance works on the principle that a resonant signal is injected into a tuned coil that is tuned at a slightly different frequency. By adjusting the amount the two are off in resonant frequencies, one can discriminate out different objects. Objects will either provide an increase in amplitude or a decrease depending upon the type of metal and the amount the coil resonance is off from the main signal.
Fortunately, the Backpacker was made in two versions, a manual type and an automatic version. I received the automatic version. This unit has a form of autotune that tries to keep the threshold constant. I suspect it works quite well as it is in low mineralized ground.
Unfortunately, the ground here is really bad, so even with the standard autotune feature, the detector has little depth.
Well, I found I could change the autotune speed easily so I did and that made the little detector work much better. What I need to do is to figure out just where I want to mount another pot and add one for the autotune. Then I need to figure out how to increase the gain of the circuitry. The reason for the need for increased gain is the autotune reduces the gain as well as reduces the ground response. Fortunately, increasing the autotune speed reduces ground problems much more than it reduces target signals, so there is a net gain if I can add a gain increase for the target response.
So, does anyone out there have a schematic for the Backpacker they are willing to share? I sure could use one. It would make things a lot easier and faster. I feel with a little work, this little detector would make a great iron killer even in tougher ground since it does a great job of ignoring iron.
Reg
I just received the Backpacker I recently purchased and began playing with it. For those of you who don't know much about this brand of detectors, they are built on the principle of "off resonance". There are several models out but all work basically the same. The backpacker is a compact version that is small and light weight.
Now, the down side of this type of detector is the fact it is ground sensitive and as such, they do not work well in heavily mineralized ground since the ground signal causes strong changes much like a metal object does. Off resonance works on the principle that a resonant signal is injected into a tuned coil that is tuned at a slightly different frequency. By adjusting the amount the two are off in resonant frequencies, one can discriminate out different objects. Objects will either provide an increase in amplitude or a decrease depending upon the type of metal and the amount the coil resonance is off from the main signal.
Fortunately, the Backpacker was made in two versions, a manual type and an automatic version. I received the automatic version. This unit has a form of autotune that tries to keep the threshold constant. I suspect it works quite well as it is in low mineralized ground.
Unfortunately, the ground here is really bad, so even with the standard autotune feature, the detector has little depth.
Well, I found I could change the autotune speed easily so I did and that made the little detector work much better. What I need to do is to figure out just where I want to mount another pot and add one for the autotune. Then I need to figure out how to increase the gain of the circuitry. The reason for the need for increased gain is the autotune reduces the gain as well as reduces the ground response. Fortunately, increasing the autotune speed reduces ground problems much more than it reduces target signals, so there is a net gain if I can add a gain increase for the target response.
So, does anyone out there have a schematic for the Backpacker they are willing to share? I sure could use one. It would make things a lot easier and faster. I feel with a little work, this little detector would make a great iron killer even in tougher ground since it does a great job of ignoring iron.
Reg