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Excuse my Ignorance
- Thread starter Tico
- Start date
motion-based discrimination. It started with the Bounty Hunter Red Barron that George Payne designed and with the first model we got the term SPD (for Synchronous Phase Discrimination). Before this time we only had BFO-Discriminators and conventional TR-Discriminators. Actually, the BFO models were pretty much dying off in favor of the TR and TR-Disc. models and then the VLF offerings we had.
BFO's are Frequency change designs at a fixed volume (loudness).
TR (Transmit/Receive) detectors, also known as IB (Induction/Balance), were more popular because they provided a more easily discerned Loudness change and operated at a fixed frequency. Their quick-response and more descriptive audio response made them more popular.
Trash was a problem and we soon had Discriminating circuitry n both the BFO and TR designs. However, not only was common trash a problem, but the detector's response or "touchiness" to coil/ground variations was a bit of a challenge to deal with. It was very important to maintain a VERY uniform coil-to-ground relationship. Raising or lowering the coil from the height where tuned caused a false 'beep' or a nulling effect. When discrimination levels were increased to knock out unwanted foil and bottle caps and such, up to pull tabs, there was even more bias (more ground rejection) and they became even squirrelier to operate.
VLF (Very Low Frequency) circuitry gave engineers the edge they needed to add another adjustment control to let us "cancel" or "ignore" or "balance' out the ground mineral signal. This meant we could raise or lower the search coil a bit and not have to deal with falsing. We also handled "bad ground" easier and got fantastic depth of detection .... on ALL metal targets. Ferrous and non-ferrous.
Needing some way to help deal with common trash and identify iron from non-iron, etc., manufacturers designed the dual-mode VLF/TR-Disc. models. A ground compensating All Metal search mode, and then we could switch to a "conventional" or "traditional" TR-Discriminate mode to help classify the located target. One of the problems was that when in the standard TR-Disc. mode we didn't get the same depth of detection as we got in the ground balanced All Metal (VLF or GEB or GB etc., etc.) mode. Another of the several problems we had was that since these new models operated in he VLF range (most from about 1++-to-20 kHz) instead of the more common 50 kHz to 100 kHz range, they were much more "touchy" to any change in coil/ground position.
What many hobbyists wished for was a design that would ignore or balance out the ground signal AND discriminate most unwanted trash, such as foil or pull tabs. That's what the Red Baron gave us, but it came with some of its own sets of problems. To work, the detector's search coil had to be swept at a very exaggerated sweep rate in order to get the ground signal, target signal, and then analyze and process out the ground signal and pass along the target signal. "Rocket Speed" is perhaps a very appropriate term to describe the very first VFL-Discriminators (GEB-Disc. in White's lingo).
Through the years they have managed to slow the sweep speed down on even the better models that handled high mineralization, and they also brought us the dedicated slow-motion (2-filter type) discriminators that had a quick response and could be (had to be) swept slowly for best performance.
Since these designs (GEB-Disc.) required a certain amount of sweep speed in order for them to work, they became known as motion discriminators. The "conventional" TR-Disc. design s didn't require the constant sweep speed sort of signal processing. Unfortunately, there is one other unfortunate 'glitch' that came with motion-based discrimination compared with the good old TR-Disc. and that is that the conventional TR-Discrimination is what I refer to as a "true progressive" discrimination, while the motion-based discriminators have trouble with some types of iron trash.
Whereas the TR-Disc. models will PROGRESSIVELY reject targets based upon their metal make-up and size and shape, the motion GEB-Disc. models don't. TR-Discriminators will easily reject common iron nails, iron hair pins, and iron/magnetic material bottle caps. Not the aluminum screw caps, but the old-style, pry-off bottle caps also known as "crown caps" due to their crimply outer edge. While most iron nails and similar iron trash isn't too much challenge for modern discriminators, the bottle caps (rusty or not) can be a real pain in the arse!
Some models, such as White's Classic ID, Classic III SL and IDX Pro, for example, do one of the best jobs out of the more recent offerings, and the XL Pro (and those models it drew from) featured the Bottle Cap Reject feature that "audibly" gave a broken-up or sputtery audio response to help classify them. Most models, however, are likely to give a good hit on them and it takes some operator techniques to classify them as the ferromagnetic trash that they are.
So, that's sort of a rundown that might help you to understand the difference between what we HAD and what we HAVE to use.
Monte
BFO's are Frequency change designs at a fixed volume (loudness).
TR (Transmit/Receive) detectors, also known as IB (Induction/Balance), were more popular because they provided a more easily discerned Loudness change and operated at a fixed frequency. Their quick-response and more descriptive audio response made them more popular.
Trash was a problem and we soon had Discriminating circuitry n both the BFO and TR designs. However, not only was common trash a problem, but the detector's response or "touchiness" to coil/ground variations was a bit of a challenge to deal with. It was very important to maintain a VERY uniform coil-to-ground relationship. Raising or lowering the coil from the height where tuned caused a false 'beep' or a nulling effect. When discrimination levels were increased to knock out unwanted foil and bottle caps and such, up to pull tabs, there was even more bias (more ground rejection) and they became even squirrelier to operate.
VLF (Very Low Frequency) circuitry gave engineers the edge they needed to add another adjustment control to let us "cancel" or "ignore" or "balance' out the ground mineral signal. This meant we could raise or lower the search coil a bit and not have to deal with falsing. We also handled "bad ground" easier and got fantastic depth of detection .... on ALL metal targets. Ferrous and non-ferrous.
Needing some way to help deal with common trash and identify iron from non-iron, etc., manufacturers designed the dual-mode VLF/TR-Disc. models. A ground compensating All Metal search mode, and then we could switch to a "conventional" or "traditional" TR-Discriminate mode to help classify the located target. One of the problems was that when in the standard TR-Disc. mode we didn't get the same depth of detection as we got in the ground balanced All Metal (VLF or GEB or GB etc., etc.) mode. Another of the several problems we had was that since these new models operated in he VLF range (most from about 1++-to-20 kHz) instead of the more common 50 kHz to 100 kHz range, they were much more "touchy" to any change in coil/ground position.
What many hobbyists wished for was a design that would ignore or balance out the ground signal AND discriminate most unwanted trash, such as foil or pull tabs. That's what the Red Baron gave us, but it came with some of its own sets of problems. To work, the detector's search coil had to be swept at a very exaggerated sweep rate in order to get the ground signal, target signal, and then analyze and process out the ground signal and pass along the target signal. "Rocket Speed" is perhaps a very appropriate term to describe the very first VFL-Discriminators (GEB-Disc. in White's lingo).
Through the years they have managed to slow the sweep speed down on even the better models that handled high mineralization, and they also brought us the dedicated slow-motion (2-filter type) discriminators that had a quick response and could be (had to be) swept slowly for best performance.
Since these designs (GEB-Disc.) required a certain amount of sweep speed in order for them to work, they became known as motion discriminators. The "conventional" TR-Disc. design s didn't require the constant sweep speed sort of signal processing. Unfortunately, there is one other unfortunate 'glitch' that came with motion-based discrimination compared with the good old TR-Disc. and that is that the conventional TR-Discrimination is what I refer to as a "true progressive" discrimination, while the motion-based discriminators have trouble with some types of iron trash.
Whereas the TR-Disc. models will PROGRESSIVELY reject targets based upon their metal make-up and size and shape, the motion GEB-Disc. models don't. TR-Discriminators will easily reject common iron nails, iron hair pins, and iron/magnetic material bottle caps. Not the aluminum screw caps, but the old-style, pry-off bottle caps also known as "crown caps" due to their crimply outer edge. While most iron nails and similar iron trash isn't too much challenge for modern discriminators, the bottle caps (rusty or not) can be a real pain in the arse!
Some models, such as White's Classic ID, Classic III SL and IDX Pro, for example, do one of the best jobs out of the more recent offerings, and the XL Pro (and those models it drew from) featured the Bottle Cap Reject feature that "audibly" gave a broken-up or sputtery audio response to help classify them. Most models, however, are likely to give a good hit on them and it takes some operator techniques to classify them as the ferromagnetic trash that they are.
So, that's sort of a rundown that might help you to understand the difference between what we HAD and what we HAVE to use.
Monte
Hello Monte
Just a short note to say I appreciate all the technical and old hand experience that you share with the members of this and many other forums! Your thoughts are a good read, and may I add that I would be first in line to have you autograph your book whenever you decide to publish it. Many thanks again for being on the forum...................Hombre
Just a short note to say I appreciate all the technical and old hand experience that you share with the members of this and many other forums! Your thoughts are a good read, and may I add that I would be first in line to have you autograph your book whenever you decide to publish it. Many thanks again for being on the forum...................Hombre