@MulletronI made some cylindrical cavity runs.....
Quote from: Star-Drive on 03/01/2015 03:57 pmQuote from: Notsosureofit on 03/01/2015 01:27 pmQuote from: Notsosureofit on 02/28/2015 11:49 pmThanks guys !So I have data for everything except the mode(s), and temp size for the flight cone.I need to use X numbers of 21, 26, and 77, respectively, for the proto, demo and flight cones to get those numbers. (w/o dielectric that is)What that means is TBD of course. There may be another variable involved, in or out of favor of a real effect.Realized this morning I'd been missing something after rereading Shawer's flight paper and the Magnetron "lock" time.Kicking myself for not recognizing a "Q multiplier circuit" (I've used enough of them) The long lock time (time constant) is the tip-off if this is what he's doing and the results are real. The trade off in that case is spectral purity vs the frequency stability of the oscillator since you track the cavity.Needs only a modest *10 for the proto and demo cases. The flight system needs *100 which is not out of the question at all.Again, this is pure speculation on my part w/o confirmation from Shawyer, but it puts the mode back in a reasonable range.Notsosureofit:Could you describe to me how one goes about building a "Q-multiplier Circuit" for a 1.90 GHz RF amplifier circuit? I've used the old Heathkit QF-1 Q-Multiplier for my old shortwave radio receiver back in high school, see: http://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_O-RX/QF-1/QF-1.pdf , but I've never thought to use one to enhance the Q-Factor of a microwave frustum cavity before...Best, Paul M."Q-multiplier" is the Heath term for adding feedback, short of oscillation, to an IF amplifier to narrow the bandwidthand enhance its "Q" as a filter. (had one on an HRO receiver in the 50's. HRO long gone but the Q-Multiplier is still in the pile somewhere)In the case of greater feed back you get an oscillator. (had a 220MHz re-entrant cavity oscillator at that time)The right feedback loop will improve the phase coherence of the oscillation and the "circuit Q". You pay for this with an increased time constant and are limited by the (thermal ?) drift rate of the cavity. The "flight" cavity might be heavily built for that reason ?Hopefully there is a radar guy (like Shawyer) on tap that could give a better explanation. (I'm pulling this out of memories of my misspent youth...)I was trying to remember something about radar systems (Russian ?) that had a dielectric resonator suspended in a microwave cavity.............
Quote from: Notsosureofit on 03/01/2015 01:27 pmQuote from: Notsosureofit on 02/28/2015 11:49 pmThanks guys !So I have data for everything except the mode(s), and temp size for the flight cone.I need to use X numbers of 21, 26, and 77, respectively, for the proto, demo and flight cones to get those numbers. (w/o dielectric that is)What that means is TBD of course. There may be another variable involved, in or out of favor of a real effect.Realized this morning I'd been missing something after rereading Shawer's flight paper and the Magnetron "lock" time.Kicking myself for not recognizing a "Q multiplier circuit" (I've used enough of them) The long lock time (time constant) is the tip-off if this is what he's doing and the results are real. The trade off in that case is spectral purity vs the frequency stability of the oscillator since you track the cavity.Needs only a modest *10 for the proto and demo cases. The flight system needs *100 which is not out of the question at all.Again, this is pure speculation on my part w/o confirmation from Shawyer, but it puts the mode back in a reasonable range.Notsosureofit:Could you describe to me how one goes about building a "Q-multiplier Circuit" for a 1.90 GHz RF amplifier circuit? I've used the old Heathkit QF-1 Q-Multiplier for my old shortwave radio receiver back in high school, see: http://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_O-RX/QF-1/QF-1.pdf , but I've never thought to use one to enhance the Q-Factor of a microwave frustum cavity before...Best, Paul M.
Quote from: Notsosureofit on 02/28/2015 11:49 pmThanks guys !So I have data for everything except the mode(s), and temp size for the flight cone.I need to use X numbers of 21, 26, and 77, respectively, for the proto, demo and flight cones to get those numbers. (w/o dielectric that is)What that means is TBD of course. There may be another variable involved, in or out of favor of a real effect.Realized this morning I'd been missing something after rereading Shawer's flight paper and the Magnetron "lock" time.Kicking myself for not recognizing a "Q multiplier circuit" (I've used enough of them) The long lock time (time constant) is the tip-off if this is what he's doing and the results are real. The trade off in that case is spectral purity vs the frequency stability of the oscillator since you track the cavity.Needs only a modest *10 for the proto and demo cases. The flight system needs *100 which is not out of the question at all.Again, this is pure speculation on my part w/o confirmation from Shawyer, but it puts the mode back in a reasonable range.
Thanks guys !So I have data for everything except the mode(s), and temp size for the flight cone.I need to use X numbers of 21, 26, and 77, respectively, for the proto, demo and flight cones to get those numbers. (w/o dielectric that is)What that means is TBD of course. There may be another variable involved, in or out of favor of a real effect.
Quote from: Star-Drive on 03/01/2015 08:35 pmDIYFAN:Once the test series we are working on is finished, I will suggest to Dr. White that we try the use of the more readily available NiFeCo mu-metal from McMaster-Carr (See: http://www.mcmaster.com/#mu-metal-foil/=w4hfa3 ) for such a test. However I think we will have to copper plate the side of the mu-metal facing the interior of the cavity with about 10 microns of copper or silver to keep this large OD end-cap from greatly reducing the Q-Factor of the copper frustum. Mu-metal resistivity is much higher than copper...Best, Paul M.I couldn't find magnetic permeability values for mu metal close to the GHz range, except the frequent warning (also included in the Wikipedia article) <<The high permeability makes mu-metal useful for shielding against static or low-frequency magnetic fields>> (bold added for emphasis).I wonder what is the relative magnetic permeability of mu metal in the GHz range, and how effective it will be for the purposes described by Aquino.
DIYFAN:Once the test series we are working on is finished, I will suggest to Dr. White that we try the use of the more readily available NiFeCo mu-metal from McMaster-Carr (See: http://www.mcmaster.com/#mu-metal-foil/=w4hfa3 ) for such a test. However I think we will have to copper plate the side of the mu-metal facing the interior of the cavity with about 10 microns of copper or silver to keep this large OD end-cap from greatly reducing the Q-Factor of the copper frustum. Mu-metal resistivity is much higher than copper...Best, Paul M.
Maybe Dr. Rodal will tell me what the resonant frequency should be for the cylindrical cavity with dielectric that I posted data for earlier today?
Quote from: Notsosureofit on 03/01/2015 05:08 pmQuote from: Star-Drive on 03/01/2015 03:57 pmQuote from: Notsosureofit on 03/01/2015 01:27 pmRealized this morning I'd been missing something after rereading Shawer's flight paper and the Magnetron "lock" time.Kicking myself for not recognizing a "Q multiplier circuit" (I've used enough of them) The long lock time (time constant) is the tip-off if this is what he's doing and the results are real. The trade off in that case is spectral purity vs the frequency stability of the oscillator since you track the cavity.Needs only a modest *10 for the proto and demo cases. The flight system needs *100 which is not out of the question at all.Again, this is pure speculation on my part w/o confirmation from Shawyer, but it puts the mode back in a reasonable range.Notsosureofit:Could you describe to me how one goes about building a "Q-multiplier Circuit" for a 1.90 GHz RF amplifier circuit? I've used the old Heathkit QF-1 Q-Multiplier for my old shortwave radio receiver back in high school, see: http://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_O-RX/QF-1/QF-1.pdf , but I've never thought to use one to enhance the Q-Factor of a microwave frustum cavity before...Best, Paul M."Q-multiplier" is the Heath term for adding feedback, short of oscillation, to an IF amplifier to narrow the bandwidthand enhance its "Q" as a filter. In the case of greater feed back you get an oscillator. The right feedback loop will improve the phase coherence of the oscillation and the "circuit Q". You pay for this with an increased time constant and are limited by the (thermal ?) drift rate of the cavity. The "flight" cavity might be heavily built for that reason ?The "Q multiplier" effect comes from the calculation of the loaded resonator Q, as f/2 times the loop gain phase slope. "Loaded-Q represents the width of the resonance curve, or phase slope, including the effects of external components. In this case the Q is determined mostly by the externalcomponents." In typical references that I found, ie. low noise frequency sources, the loaded Q is between 20% to 50% of the unloaded Q.So for the "Shawyer" type application, to get a maximized loaded Q in a cavity oscillator, one should maximize the loop gain phase slope. (use the highest gain-bandwidth amp you can find ?)
Quote from: Star-Drive on 03/01/2015 03:57 pmQuote from: Notsosureofit on 03/01/2015 01:27 pmRealized this morning I'd been missing something after rereading Shawer's flight paper and the Magnetron "lock" time.Kicking myself for not recognizing a "Q multiplier circuit" (I've used enough of them) The long lock time (time constant) is the tip-off if this is what he's doing and the results are real. The trade off in that case is spectral purity vs the frequency stability of the oscillator since you track the cavity.Needs only a modest *10 for the proto and demo cases. The flight system needs *100 which is not out of the question at all.Again, this is pure speculation on my part w/o confirmation from Shawyer, but it puts the mode back in a reasonable range.Notsosureofit:Could you describe to me how one goes about building a "Q-multiplier Circuit" for a 1.90 GHz RF amplifier circuit? I've used the old Heathkit QF-1 Q-Multiplier for my old shortwave radio receiver back in high school, see: http://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_O-RX/QF-1/QF-1.pdf , but I've never thought to use one to enhance the Q-Factor of a microwave frustum cavity before...Best, Paul M."Q-multiplier" is the Heath term for adding feedback, short of oscillation, to an IF amplifier to narrow the bandwidthand enhance its "Q" as a filter. In the case of greater feed back you get an oscillator. The right feedback loop will improve the phase coherence of the oscillation and the "circuit Q". You pay for this with an increased time constant and are limited by the (thermal ?) drift rate of the cavity. The "flight" cavity might be heavily built for that reason ?
Quote from: Notsosureofit on 03/01/2015 01:27 pmRealized this morning I'd been missing something after rereading Shawer's flight paper and the Magnetron "lock" time.Kicking myself for not recognizing a "Q multiplier circuit" (I've used enough of them) The long lock time (time constant) is the tip-off if this is what he's doing and the results are real. The trade off in that case is spectral purity vs the frequency stability of the oscillator since you track the cavity.Needs only a modest *10 for the proto and demo cases. The flight system needs *100 which is not out of the question at all.Again, this is pure speculation on my part w/o confirmation from Shawyer, but it puts the mode back in a reasonable range.Notsosureofit:Could you describe to me how one goes about building a "Q-multiplier Circuit" for a 1.90 GHz RF amplifier circuit? I've used the old Heathkit QF-1 Q-Multiplier for my old shortwave radio receiver back in high school, see: http://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_O-RX/QF-1/QF-1.pdf , but I've never thought to use one to enhance the Q-Factor of a microwave frustum cavity before...Best, Paul M.
Realized this morning I'd been missing something after rereading Shawer's flight paper and the Magnetron "lock" time.Kicking myself for not recognizing a "Q multiplier circuit" (I've used enough of them) The long lock time (time constant) is the tip-off if this is what he's doing and the results are real. The trade off in that case is spectral purity vs the frequency stability of the oscillator since you track the cavity.Needs only a modest *10 for the proto and demo cases. The flight system needs *100 which is not out of the question at all.Again, this is pure speculation on my part w/o confirmation from Shawyer, but it puts the mode back in a reasonable range.
....The oscillator model is the same as the tuned amp model w/ the cavity used as a filter in the feedback loop. In a quick search, I was only able to find one worked out example of using feedback to increase the loaded Q of an oscillator over that of the unloaded Q. www.zen22142.zen.co.uk/Design/vcqmswo.pdf
Quote from: aero on 03/02/2015 06:03 amMaybe Dr. Rodal will tell me what the resonant frequency should be for the cylindrical cavity with dielectric that I posted data for earlier today?Please fill-in the following data (question marks ? below) for the cylindrical cavity with a dielectric section having the same diameter as the cavity's ID and located at one end of the cavity:GEOMETRYInner Diameter of cylindrical cavity = ? meters (cavity has a constant, same diameter throughout)Total Inner Length of cavity = ? meters (Length including dielectric length)Length of dielectric section = ? metersCONSTITUTIVE PROPERTIESRelative electric permittivity of dielectric = ? (dimensionless) (for HD PE it is reported as 2.3)Relative magnetic permeability of dielectric = ? (dimensionless) (1 ?)Relative electric permittivity of empty section = ? (dimensionless) (air or vacuum ?)Relative magnetic permeability of empty section = ? (dimensionless) (air or vacuum ?)FREQUENCY of interestThere are an infinite number of resonant frequencies for a resonant cylindrical cavity. What resonant frequency are you referring to? ? (The lowest natural frequency? )
Quote from: Rodal on 03/02/2015 12:17 pmQuote from: aero on 03/02/2015 06:03 amMaybe Dr. Rodal will tell me what the resonant frequency should be for the cylindrical cavity with dielectric that I posted data for earlier today?Please fill-in the following data (question marks ? below) for the cylindrical cavity with a dielectric section having the same diameter as the cavity's ID and located at one end of the cavity:GEOMETRYInner Diameter of cylindrical cavity = ? meters (cavity has a constant, same diameter throughout)Total Inner Length of cavity = ? meters (Length including dielectric length)Length of dielectric section = ? metersCONSTITUTIVE PROPERTIESRelative electric permittivity of dielectric = ? (dimensionless) (for HD PE it is reported as 2.3)Relative magnetic permeability of dielectric = ? (dimensionless) (1 ?)Relative electric permittivity of empty section = ? (dimensionless) (air or vacuum ?)Relative magnetic permeability of empty section = ? (dimensionless) (air or vacuum ?)FREQUENCY of interestThere are an infinite number of resonant frequencies for a resonant cylindrical cavity. What resonant frequency are you referring to? ? (The lowest natural frequency? )I just printed these numbers out from my program so this is what I used when generating the posted data. Inner diameter of cylindrical cavity, 0.08278945,m total inner length of cavity, 0.1224489,m Length of dielectric section 0.027282494103102, m Relative electric permittivity of dielectric =1.76Relative magnetic permeability of dielectric = 1 Relative electric permittivity of empty section = vacuum (a meep program option)Relative magnetic permeability of empty section = vacuum I know that the dielectric constant of hdpe is 2.3. I will make some runs later using that value but for now I am using 1.76.The resonances I'm looking for are those at the peaks of the force/power curves above, near 1.8 Ghz, 1.9 GHz and 2.4 GHz using an electric source, and about 2.3 GHz with the magnetic source.It could be that there are no resonances in those frequency ranges but everything we know right now says that there will be.And thanks.
Quote from: aero on 03/02/2015 03:09 pmQuote from: Rodal on 03/02/2015 12:17 pmQuote from: aero on 03/02/2015 06:03 amMaybe Dr. Rodal will tell me what the resonant frequency should be for the cylindrical cavity with dielectric that I posted data for earlier today? ... snip ... ... snip ...GEOMETRICAL INPUT for cylindrical cavity:bigDiameter = 8.278945 centimeter;smallDiameter = bigDiameter; length = 12.24489 centimeter; dielectricThickness = 2.7282494103102 centimeter;You can verify this case directly from equation in Wikipedia http://en.wikipedia.org/wiki/Microwave_cavity#Cylindrical_cavityFirst four mode shapes and frequencies for Relative electric permittivity of dielectric =1 (No dielectric){{"TE", 1, 1, 0}, 2.12223*10^9}, {{"TE", 1, 1, 1}, 2.44998*10^9}, {{"TM", 0, 1, 0}, 2.77191*10^9}, {{"TM", 0, 1, 1}, 3.03019*10^9}First three mode shapes and frequencies for Relative electric permittivity of dielectric =1.76; dielectricThickness = 2.7282494103102 centimeter{{"TE", 1, 1, 1}, 2.31958*10^9}, {{"TE", 1, 1, 2}, 3.03479*10^9}, {{"TM", 0, 1, 2}, 3.47425*10^9}First three mode shapes and frequencies for Relative electric permittivity of dielectric =2.3; dielectricThickness = 2.7282494103102 centimeter{{"TE", 1, 1, 1}, 2.26774*10^9}, {{"TE", 1, 1, 2}, 2.93557*10^9}, {{"TM", 0, 1, 2}, 3.37114*10^9} Perhaps you are getting much lower frequencies because you are using Maxwell's equations in 2-D ?, and you are modeling the cavity as a flat plane bounded by a rectangle instead of 3-D cylindrical cavity under 3-D Maxwell's equations
Quote from: Rodal on 03/02/2015 12:17 pmQuote from: aero on 03/02/2015 06:03 amMaybe Dr. Rodal will tell me what the resonant frequency should be for the cylindrical cavity with dielectric that I posted data for earlier today? ... snip ... ... snip ...
Quote from: aero on 03/02/2015 06:03 amMaybe Dr. Rodal will tell me what the resonant frequency should be for the cylindrical cavity with dielectric that I posted data for earlier today? ... snip ...
Quote from: frobnicat on 03/01/2015 09:12 pmDr. March,I'm trying to model various aspects of the whole system to put upper bounds on thermal effects, and possibly also reconstruct the thrust(t) original signal from the distance(t) given in the charts. It would be a nice boost to this (amateur level) effort if you could confirm either :- That the flexure bearings have a stiffness of 0.007 in-Lb/deg ? Each ? Both together ? Do you know the exact model reference ?- That the vertical scale in the charts (indicated in µm, around 500) are relevant or not relevant.I ask this question because I find a contradiction between the stiffness around the vertical axis and the recorded deviation from the 30µN calibration pulses (at .007 in-Lb/deg the deviation of the linear displacement sensor would be above 40µm, at .014 in-Lb/deg still above 20µm). The readings amount for between 1 to 2.5 µm for the 30µN calibration pulses. So I'm stuck.While I'm at it : is the plane in which the arm rotates kept as horizontal as possible (ie the axis of rotation as vertical as possible) or is there a small slope voluntarily introduced leading to some pendulum effect against g (for stabilisation or tuning purpose) ? That could explain the varying deviation (in µm) for the same calibration pulses thrusts. Also wondered if this is what was implied in this post :Quote from: Star-Drive...These thermally induced actions to the left requires the torque pendulum's arm to move to the right to maintain the balance of the torque pendulum's arm in the lab's 1.0 gee gravity field, since we also use the Earth's g-field to help null the pendulum's movements....ThanksFrobnicat:To answer your question:" - That the flexure bearings have a stiffness of 0.007 in-Lb/deg ? Each ? Both together ? Do you know the exact model reference?"The two torsion bearings used in or torque pendulum are supposed to have a stiffness of 0.007 in-Lb/deg, +/-10% and is made by the Riverhawk Co. in New York USA. As to their model number find the data sheet for same attached. "- That the vertical scale in the charts (indicated in µm, around 500) are relevant or not relevant."The Philtec D63 fiber-optic displacement sensor measures distance from its target mirror in microns, so the numbers on the left hand side of the force plots measure the distance from the end of the fiber-optic laser head to its mirror target mounted on the torque pendulum arm. The data sheet for same is attached."While I'm at it : is the plane in which the arm rotates kept as horizontal as possible (ie the axis of rotation as vertical as possible) or is there a small slope voluntarily introduced leading to some pendulum effect against g (for stabilization or tuning purpose)?"The design of our Torque pendulum follows what JPL and Busek Co did at their respective facility, see attached report from Busek. We found that if we tried to keep the arm completely horizontal though that the pendulum's neutral point would wonder erratically and make alignments near impossible. So yes I balance the pendulum arm so there is always a slight tilt in it, however this tilt angle magnitude is not controlled as well as it probably should. Best, Paul M.
Dr. March,I'm trying to model various aspects of the whole system to put upper bounds on thermal effects, and possibly also reconstruct the thrust(t) original signal from the distance(t) given in the charts. It would be a nice boost to this (amateur level) effort if you could confirm either :- That the flexure bearings have a stiffness of 0.007 in-Lb/deg ? Each ? Both together ? Do you know the exact model reference ?- That the vertical scale in the charts (indicated in µm, around 500) are relevant or not relevant.I ask this question because I find a contradiction between the stiffness around the vertical axis and the recorded deviation from the 30µN calibration pulses (at .007 in-Lb/deg the deviation of the linear displacement sensor would be above 40µm, at .014 in-Lb/deg still above 20µm). The readings amount for between 1 to 2.5 µm for the 30µN calibration pulses. So I'm stuck.While I'm at it : is the plane in which the arm rotates kept as horizontal as possible (ie the axis of rotation as vertical as possible) or is there a small slope voluntarily introduced leading to some pendulum effect against g (for stabilisation or tuning purpose) ? That could explain the varying deviation (in µm) for the same calibration pulses thrusts. Also wondered if this is what was implied in this post :Quote from: Star-Drive...These thermally induced actions to the left requires the torque pendulum's arm to move to the right to maintain the balance of the torque pendulum's arm in the lab's 1.0 gee gravity field, since we also use the Earth's g-field to help null the pendulum's movements....Thanks
...These thermally induced actions to the left requires the torque pendulum's arm to move to the right to maintain the balance of the torque pendulum's arm in the lab's 1.0 gee gravity field, since we also use the Earth's g-field to help null the pendulum's movements....
"- That the vertical scale in the charts (indicated in µm, around 500) are relevant or not relevant."The Philtec D63 fiber-optic displacement sensor measures distance from its target mirror in microns, so the numbers on the left hand side of the force plots measure the distance from the end of the fiber-optic laser head to its mirror target mounted on the torque pendulum arm. The data sheet for same is attached."While I'm at it : is the plane in which the arm rotates kept as horizontal as possible (ie the axis of rotation as vertical as possible) or is there a small slope voluntarily introduced leading to some pendulum effect against g (for stabilization or tuning purpose)?"The design of our Torque pendulum follows what JPL and Busek Co did at their respective facility, see attached report from Busek. We found that if we tried to keep the arm completely horizontal though that the pendulum's neutral point would wonder erratically and make alignments near impossible. So yes I balance the pendulum arm so there is always a slight tilt in it, however this tilt angle magnitude is not controlled as well as it probably should. Best, Paul M.
Quote from: Star-Drive on 03/02/2015 12:21 am"- That the vertical scale in the charts (indicated in µm, around 500) are relevant or not relevant."The Philtec D63 fiber-optic displacement sensor measures distance from its target mirror in microns, so the numbers on the left hand side of the force plots measure the distance from the end of the fiber-optic laser head to its mirror target mounted on the torque pendulum arm. The data sheet for same is attached."While I'm at it : is the plane in which the arm rotates kept as horizontal as possible (ie the axis of rotation as vertical as possible) or is there a small slope voluntarily introduced leading to some pendulum effect against g (for stabilization or tuning purpose)?"The design of our Torque pendulum follows what JPL and Busek Co did at their respective facility, see attached report from Busek. We found that if we tried to keep the arm completely horizontal though that the pendulum's neutral point would wonder erratically and make alignments near impossible. So yes I balance the pendulum arm so there is always a slight tilt in it, however this tilt angle magnitude is not controlled as well as it probably should. Best, Paul M.The torque pendulum arm had a slight tilt so that alignment was easier. The Philtec D63 fiber-optic displacement sensor measures distance from its target mirror by measuring the intensity of the reflected light. If the change in the center of mass reduces the pendulum arm tilt, the light intensity may increase. This would explain the negative slope of the baseline waveform (apparent movement closer) after the RF is switched off. It would be interesting to see what the thrust waveform looks like when the cavity is turned around.