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Does any detector's transmit/receive coil's 3 dB bandwidth affect any target's induced or return signal characteristics or signatures?
- Thread starter calfrope
- Start date
Larry (IL)
Well-known member
I think that would be a good project for an EE and he could answer his own question. 
Ok here goes..
Thele 3DB bandpoint is the level of the signal from peak down to 3db and allows one to plot a banwidth of transmit signal and therby gives you some idea of the power in a signal, 'if you do that you would be able to also get some idea as to the sensitivity of recieiver as it tell you about how broad or wide the front end of the reciever would be in order recieve a reflection or signal a metal object would give off. Now this implies that the signal is a composite of even and odd harmonics and impure enough to put power evenly across the spectrum at the 3db down point of the tranmit signal.
This holds true for a single frequency metal detector... Now in the todays multi frequency detectors the transmitter puts out signal power at several points in frequency on the spectrum. Most multi frequency transmitters are set up to generate discrete frequencies at several points. Because of this a multi frequency detector my not put out adequate power at each of frequncies. Minelabs therefore use a method of selecting which frequencies are optimal and use them based on a calibration run when setting up the MD at startup. The ennviornment and mineralization being different each time causes the RX to detect the TX Freq that are optimal in power and then auto notches the TX and RX based on the calibration run. In addition the detectors ciircuits can be set to notch out portions of the spectrum know to elicit certain responses from target objects, Some MD TX simply push out a power signal modulated with white noise and use the notches of a sawtooth reciever to pick signals to respond to...
So the answer is it depends...
Thele 3DB bandpoint is the level of the signal from peak down to 3db and allows one to plot a banwidth of transmit signal and therby gives you some idea of the power in a signal, 'if you do that you would be able to also get some idea as to the sensitivity of recieiver as it tell you about how broad or wide the front end of the reciever would be in order recieve a reflection or signal a metal object would give off. Now this implies that the signal is a composite of even and odd harmonics and impure enough to put power evenly across the spectrum at the 3db down point of the tranmit signal.
This holds true for a single frequency metal detector... Now in the todays multi frequency detectors the transmitter puts out signal power at several points in frequency on the spectrum. Most multi frequency transmitters are set up to generate discrete frequencies at several points. Because of this a multi frequency detector my not put out adequate power at each of frequncies. Minelabs therefore use a method of selecting which frequencies are optimal and use them based on a calibration run when setting up the MD at startup. The ennviornment and mineralization being different each time causes the RX to detect the TX Freq that are optimal in power and then auto notches the TX and RX based on the calibration run. In addition the detectors ciircuits can be set to notch out portions of the spectrum know to elicit certain responses from target objects, Some MD TX simply push out a power signal modulated with white noise and use the notches of a sawtooth reciever to pick signals to respond to...
So the answer is it depends...
Carl-NC
Active member
calfrope, the TX coil bandwidth has practically no effect on target response. The RX coil bandwidth can, but in modern digital detectors it can easily be calibrated out. Ground mineralization can have a far greater effect on target ID.
edjcox, I'm sorry, but your answer is way, way.... WAY... off.
edjcox, I'm sorry, but your answer is way, way.... WAY... off.