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#1
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![]() "Radium" wrote in message oups.com... Hi: Can the Spin Exchange Relaxation Free Magnetometer be used to receiver distant AM radio signals in which the carrier frequency is 150 KHz? What if the carrier frequency is 44.1 KHz [for the same reason CDs use a 44.1 KHz sample rate]? 40 KHz? Thanks a bunch, Radium Radium, The simplest answer is no. The reason is that you specify 'distant'. The strength of a magnetic field decays rapidly with distance and for most practical purposes, 800 metres would be a maximum typical detection range for man made magnetic fields as opposed to natural fields like the earth's magnetic field. Man made fields can be many times thousands of times stronger than the earth's magnetic field at a local level, but the field strength decays rapidly as you move away from the source. A friends father experimented with a factory machinery control system using induction coils a foot long and about 8 inches in diameter wound with thousands of turns of thin copper wire. The maximum reliable communication distance with this set up was only 200 yards. This was 35+ years ago and detection techniques have improved considerably. The reason for the experiment was to try and develop a control system that could work in the presence of very high strength RF fields. This was superceded by the development of fibre optic cabling which was not susceptible to RF pickup. Communication using the magnetic field element of electromagnetic waves is best demonstrated by the 'molephone' devices used to communicate with cavers underground. See the following link for details and try googling cave rescue, underground communications, and molephone for more links. http://www.scavalon.be/avalonuk/technical/radio1.htm Squids and other highly sensitive magnetic field detectors can be used to detect the most minute distortions or changes in the earths magnetic field but are not suitable for communications use. It is possible to build a magnetometer at home that is so sensitive that it will pick up disturbances in the earth's magnetic field caused by solar activity for less than $100. This is not however going to be capable of receiving and demodulating 150kHz radio signals. It doesn't really matter what frequencies you want to receive, 44kHz, 150kHz, 150MHz or what the modulation method is, a diode (or two) and a tuned circuit are essentially at the heart of all receiving and demodulating systems. They are cost effective, reasonably efficient and they work. Why would you want to spend a million dollars to receive signals that can be picked up (probably a lot better) on a ten dollar consumer radio? Modulation methods, frequencies and bandwidths are chosen by commercial broadcasters to meet specific demands, e.g. limited bandwidth available for broadcasting, high fidelity music broadcasts, high efficiency powerful signals that can punch through interference, etc, etc. The basic rule is to get the job done as cheaply, efficiently and as quickly as possible. Mike G0ULI |
#2
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On Jul 5, 3:19 am, "Mike Kaliski" wrote:
"Radium" wrote in message oups.com... Hi: Can the Spin Exchange Relaxation Free Magnetometer be used to receiver distant AM radio signals in which the carrier frequency is 150 KHz? What if the carrier frequency is 44.1 KHz [for the same reason CDs use a 44.1 KHz sample rate]? 40 KHz? Thanks a bunch, Radium Radium, The simplest answer is no. The reason is that you specify 'distant'. The strength of a magnetic field decays rapidly with distance and for most practical purposes, 800 metres would be a maximum typical detection range for man made magnetic fields as opposed to natural fields like the earth's magnetic field. Man made fields can be many times thousands of times stronger than the earth's magnetic field at a local level, but the field strength decays rapidly as you move away from the source. A friends father experimented with a factory machinery control system using induction coils a foot long and about 8 inches in diameter wound with thousands of turns of thin copper wire. The maximum reliable communication distance with this set up was only 200 yards. This was 35+ years ago and detection techniques have improved considerably. The reason for the experiment was to try and develop a control system that could work in the presence of very high strength RF fields. This was superceded by the development of fibre optic cabling which was not susceptible to RF pickup. Communication using the magnetic field element of electromagnetic waves is best demonstrated by the 'molephone' devices used to communicate with cavers underground. See the following link for details and try googling cave rescue, underground communications, and molephone for more links. http://www.scavalon.be/avalonuk/technical/radio1.htm Squids and other highly sensitive magnetic field detectors can be used to detect the most minute distortions or changes in the earths magnetic field but are not suitable for communications use. It is possible to build a magnetometer at home that is so sensitive that it will pick up disturbances in the earth's magnetic field caused by solar activity for less than $100. This is not however going to be capable of receiving and demodulating 150kHz radio signals. It doesn't really matter what frequencies you want to receive, 44kHz, 150kHz, 150MHz or what the modulation method is, a diode (or two) and a tuned circuit are essentially at the heart of all receiving and demodulating systems. They are cost effective, reasonably efficient and they work. Why would you want to spend a million dollars to receive signals that can be picked up (probably a lot better) on a ten dollar consumer radio? Modulation methods, frequencies and bandwidths are chosen by commercial broadcasters to meet specific demands, e.g. limited bandwidth available for broadcasting, high fidelity music broadcasts, high efficiency powerful signals that can punch through interference, etc, etc. The basic rule is to get the job done as cheaply, efficiently and as quickly as possible. Mike G0ULI Radio waves are made up of electric and magnetic fields. Couldn't the Spin Exchange Relaxation Free Magnetometer receive the magnetic portions of AM radio waves at the carrier frequencies I described? If not, why? Agreed, static magnetic fields tend to decay rapidly as you move away from them. However, alternating magnetic fields continue to propogate by generating alternating electric fields of the same frequency. These alternating electric fields, in turn, generate alternating magnetic fields. The cycle keeps repeating. |
#3
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In rec.radio.amateur.antenna Radium wrote:
snip Agreed, static magnetic fields tend to decay rapidly as you move away from them. However, alternating magnetic fields continue to propogate by generating alternating electric fields of the same frequency. These alternating electric fields, in turn, generate alternating magnetic fields. The cycle keeps repeating. Nonsense as stated. You have no understanding of the differences between: 1. A magnetic field 2. An electric field 3. An electromagnetic field. -- Jim Pennino Remove .spam.sux to reply. |
#4
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#6
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Radium wrote:
Couldn't the Spin Exchange Relaxation Free Magnetometer receive the magnetic portions of AM radio waves at the carrier frequencies I described? If not, why? Agreed, static magnetic fields tend to decay rapidly as you move away from them. However, alternating magnetic fields continue to propogate by generating alternating electric fields of the same frequency. These alternating electric fields, in turn, generate alternating magnetic fields. The cycle keeps repeating. This thread reminds me of situations where someone acquire a little knowledge of something and extrapolates it into areas of which they have an limited skill set for understanding them. Also reminds me of explaining things to my mother...but we won't go there. |
#7
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Radium hath wroth:
Radio waves are made up of electric and magnetic fields. Yep. Couldn't the Spin Exchange Relaxation Free Magnetometer receive the magnetic portions of AM radio waves at the carrier frequencies I described? If not, why? Nope. 1. The range of the magnetic field is limited. For example, you're not going to bounce (errr... refract) a magnetic fields off the ionosphere. 2. Magentometers use very big coils. Very big coils have lots of inductance. Resonant circuits with lots of inductance tend to resonate at very low frequencies. Figure on maybe 30Hz being the highest frequency detectable by a magnetometer. Most roll off even earlier to avoid 60Hz power line pickup. 3. Magnetometers are expensive. You're proposing using one as a replacement for a 5 cent silicon diode detector. If the technology doesn't get to you, the accountants will. Agreed, static magnetic fields tend to decay rapidly as you move away from them. However, alternating magnetic fields continue to propogate by generating alternating electric fields of the same frequency. These alternating electric fields, in turn, generate alternating magnetic fields. The cycle keeps repeating. Rubbish. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#8
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On 5 Jul, 22:25, Jeff Liebermann wrote:
Radium hath wroth: Radio waves are made up of electric and magnetic fields. Yep. Couldn't the Spin Exchange Relaxation Free Magnetometer receive the magnetic portions of AM radio waves at the carrier frequencies I described? If not, why? Nope. 1. The range of the magnetic field is limited. For example, you're not going to bounce (errr... refract) a magnetic fields off the ionosphere. 2. Magentometers use very big coils. Very big coils have lots of inductance. Resonant circuits with lots of inductance tend to resonate at very low frequencies. Figure on maybe 30Hz being the highest frequency detectable by a magnetometer. Most roll off even earlier to avoid 60Hz power line pickup. 3. Magnetometers are expensive. You're proposing using one as a replacement for a 5 cent silicon diode detector. If the technology doesn't get to you, the accountants will. Agreed, static magnetic fields tend to decay rapidly as you move away from them. However, alternating magnetic fields continue to propogate by generating alternating electric fields of the same frequency. These alternating electric fields, in turn, generate alternating magnetic fields. The cycle keeps repeating. Rubbish. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 I believe that the standard example of radiation referred to above is in error. I do not believe that radiation consists of fields of any sort but consists of ejected static particles in form of a swarm. I have asked the Eham forum to wade in on that one since it appears they have more scientifically molecular inclined members. The only cycle that repeates in radiation is the tank circuit of a diagmagnetic material which is resonant i.e. equal capacitance and inductance. Seems like the posts are relying on propagating fields which to me is an error. Regards Art |
#9
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In rec.radio.amateur.antenna art wrote:
On 5 Jul, 22:25, Jeff Liebermann wrote: Radium hath wroth: Radio waves are made up of electric and magnetic fields. Yep. Couldn't the Spin Exchange Relaxation Free Magnetometer receive the magnetic portions of AM radio waves at the carrier frequencies I described? If not, why? Nope. 1. The range of the magnetic field is limited. For example, you're not going to bounce (errr... refract) a magnetic fields off the ionosphere. 2. Magentometers use very big coils. Very big coils have lots of inductance. Resonant circuits with lots of inductance tend to resonate at very low frequencies. Figure on maybe 30Hz being the highest frequency detectable by a magnetometer. Most roll off even earlier to avoid 60Hz power line pickup. 3. Magnetometers are expensive. You're proposing using one as a replacement for a 5 cent silicon diode detector. If the technology doesn't get to you, the accountants will. Agreed, static magnetic fields tend to decay rapidly as you move away from them. However, alternating magnetic fields continue to propogate by generating alternating electric fields of the same frequency. These alternating electric fields, in turn, generate alternating magnetic fields. The cycle keeps repeating. Rubbish. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 I believe that the standard example of radiation referred to above is in error. Belief doesn't make reality. I do not believe that radiation consists of fields of any sort but consists of ejected static particles in form of a swarm. A hundred years or so of experments say that's utter, babbling, nonsense. I have asked the Eham forum to wade in on that one since it appears they have more scientifically molecular inclined members. Right. The only cycle that repeates in radiation is the tank circuit of a diagmagnetic material which is resonant i.e. equal capacitance and inductance. Seems like the posts are relying on propagating fields which to me is an error. I'd suggest fluphenazine and haloperidol. -- Jim Pennino Remove .spam.sux to reply. |
#10
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On 6 Jul, 20:15, wrote:
In rec.radio.amateur.antenna art wrote: On 5 Jul, 22:25, Jeff Liebermann wrote: Radium hath wroth: Radio waves are made up of electric and magnetic fields. Yep. Couldn't the Spin Exchange Relaxation Free Magnetometer receive the magnetic portions of AM radio waves at the carrier frequencies I described? If not, why? Nope. 1. The range of the magnetic field is limited. For example, you're not going to bounce (errr... refract) a magnetic fields off the ionosphere. 2. Magentometers use very big coils. Very big coils have lots of inductance. Resonant circuits with lots of inductance tend to resonate at very low frequencies. Figure on maybe 30Hz being the highest frequency detectable by a magnetometer. Most roll off even earlier to avoid 60Hz power line pickup. 3. Magnetometers are expensive. You're proposing using one as a replacement for a 5 cent silicon diode detector. If the technology doesn't get to you, the accountants will. Agreed, static magnetic fields tend to decay rapidly as you move away from them. However, alternating magnetic fields continue to propogate by generating alternating electric fields of the same frequency. These alternating electric fields, in turn, generate alternating magnetic fields. The cycle keeps repeating. Rubbish. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 I believe that the standard example of radiation referred to above is in error. Belief doesn't make reality. I do not believe that radiation consists of fields of any sort but consists of ejected static particles in form of a swarm. A hundred years or so of experments say that's utter, babbling, nonsense. I have asked the Eham forum to wade in on that one since it appears they have more scientifically molecular inclined members. Right. The only cycle that repeates in radiation is the tank circuit of a diagmagnetic material which is resonant i.e. equal capacitance and inductance. Seems like the posts are relying on propagating fields which to me is an error. I'd suggest fluphenazine and haloperidol. -- Jim Pennino Remove .spam.sux to reply.- Hide quoted text - - Show quoted text - Jim, In the past you have shown that you are not that smart and I see of no evidence of any change. Suggest you review "particles" in nuclear physics, tho I suppose some could see a swarm of particles as a "wave" tho certainly not in the electrical sense. Seems like you take comfort in harrassing people with statements that have no reality. I have the strong suspicion that you are also short in stature and thus have a macho feeling in hiding. I personally have proved that radiation is in particle form where you do not have the ability to prove anything. |
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