Quote from: aero on 07/22/2015 07:08 am@SeeShell - Your .png and .csv files data is/are up have been uploaded here:https://drive.google.com/folderview?id=0B1XizxEfB23tfm04QWNVVVVvT3gtcVAzRUp6T1BCLVpoV0EyeVVKR2ZxQkp2a3NKcUNPMU0&usp=sharingI uploaded my meep data request file/form to hopefully explain what the data is, although it needs more English and fewer Scheme statements. The inside big end is at row 15 and small end at row 216 of the csv files, and the total run meep time t = 13.054 (6527 timesteps).Thanks, interesting but not quite what we were looking to do. I'm still working out the antenna shape and placement and getting feedback like I said I was going to do on launching a Te mode. What I found out is a answer from a wonderful source that mretty much just lurks here. Of course doing it isn't as easy as it seemed to be and I'm not sure you can do it in a meep model. Quote from a email: "Your test setup looks great. If you use a 1/4 probe on the big end or little end you will launch a TM mode. If you use a 1/10 wave loop you will excite a TE mode at either top or bottom. I believe If you launch from the big end the net force will be toward the small end or vice versa launching from the small end as the reflected wave will be reduced by Q losses and will be smaller in magnitude than the launched wave. A loop on the side wall will excite either mode depending on orientation wrt the frustum z axis. All walls on the frustum look like a conductive ground plane. For low power testing ,with the sweeper , the sample port I would use a probe 1/4 wavelength from the side wall, variable probe depth for the needed coupling to put the SA sampler in its optimum resolution range. If you use a loop you should place it at a low impedance point or H plane max node. <End Quote>After hours of reading and several emails to people who are beyond my skills in antennas I would agree with this.Shell
@SeeShell - Your .png and .csv files data is/are up have been uploaded here:https://drive.google.com/folderview?id=0B1XizxEfB23tfm04QWNVVVVvT3gtcVAzRUp6T1BCLVpoV0EyeVVKR2ZxQkp2a3NKcUNPMU0&usp=sharingI uploaded my meep data request file/form to hopefully explain what the data is, although it needs more English and fewer Scheme statements. The inside big end is at row 15 and small end at row 216 of the csv files, and the total run meep time t = 13.054 (6527 timesteps).
Three types of antennas were used for simulations; dipole, monopole, and loop. For experiments, only monopole and loops were used. The dipole was used because of its simplicity, and ability to excite the E-fields within the cage. The loop was used because it is a magnetic antenna, and well suited to excite the H-fields.
Since the strongest E-fields created by the dipole are in the axial direction, to couple to a cavity it should be orientated in the same direction as the E-fields described by the mode configuration.
AxialAnt-06-exSx.csv; AxialAnt-06-eySx.csv and AxialAnt-06-ezSx.csv
Quote from: SeeShells on 07/22/2015 08:46 pmQuote from: rfmwguy on 07/22/2015 08:11 pmDIYer head's up. Copper flashing seems to be a cost-effect solution for frustum walls if you are not using mesh. As I was looking around for supplies, found this: http://www.acehardware.com/product/index.jsp?productId=1290779&KPID=984489&kpid=984489&pla=pla_984489A 10ft roll seems to be the smallest length. I'd recommend the 14 inch for frustum heights to 11 inches. I can say from experience that .021 thickness will not be self-supporting and an exoskeleton will be needed. When I switched to a magnetron, the 1/8 in square copper supports were not ideal. I'd move to 1/4 in copper struts or possibly tubing.Top and bottom plates on nsf-1701 were 1/2 oz copper clad pc board, again too flimsy for a 750g magnetron. Try the next size up. Solid copper plates would weigh too much, I stick with the pcb stuff, just make sure there are plated thru-holes or plenty of bolts to connect the 2 ground planes.Any metal above ground potential will be subject to plasma discharge, so "mind the gaps" p.s. Bonus points for anyone who knows that phrase...Had to do with electric trolleys I think. Before my time.One thing you need to be aware of in copper is that it's mixed with tin to prevent corrosion, 80-90% mix is normal and if not 99% pure copper it will cause more heating signal loss and not be as a good cavity.ShellPS:I'm still waiting (have some time) for my last piece of copper is holed out to my specs, was hoping to have a simulation run, it is 99% pure the same they use in waveguides.Shell, there are hundreds of copper alloys. Copper alloyed with tin is bronze. Copper alloyed with zinc is brass (both very generically speaking). What you are probably after is the highest possible electrical conductivity, which is commercially called 101 copper, or Oxygen Free High Conductivity (OFHC) copper.Both brass and bronze typically have drastically lower conductivity than OFHC copper. Waveguides are often brass for structural reasons (its much stiffer and harder than OFHC), and are often silver plated internally to enhance conductivity. Cheaper waveguides are usually aluminum.McMaster Carr (mcmaster.com) is a somewhat pricey but immediately available source for OFHC. Browse under "Raw Materials". They may even have perforated sheet.
Quote from: rfmwguy on 07/22/2015 08:11 pmDIYer head's up. Copper flashing seems to be a cost-effect solution for frustum walls if you are not using mesh. As I was looking around for supplies, found this: http://www.acehardware.com/product/index.jsp?productId=1290779&KPID=984489&kpid=984489&pla=pla_984489A 10ft roll seems to be the smallest length. I'd recommend the 14 inch for frustum heights to 11 inches. I can say from experience that .021 thickness will not be self-supporting and an exoskeleton will be needed. When I switched to a magnetron, the 1/8 in square copper supports were not ideal. I'd move to 1/4 in copper struts or possibly tubing.Top and bottom plates on nsf-1701 were 1/2 oz copper clad pc board, again too flimsy for a 750g magnetron. Try the next size up. Solid copper plates would weigh too much, I stick with the pcb stuff, just make sure there are plated thru-holes or plenty of bolts to connect the 2 ground planes.Any metal above ground potential will be subject to plasma discharge, so "mind the gaps" p.s. Bonus points for anyone who knows that phrase...Had to do with electric trolleys I think. Before my time.One thing you need to be aware of in copper is that it's mixed with tin to prevent corrosion, 80-90% mix is normal and if not 99% pure copper it will cause more heating signal loss and not be as a good cavity.ShellPS:I'm still waiting (have some time) for my last piece of copper is holed out to my specs, was hoping to have a simulation run, it is 99% pure the same they use in waveguides.
DIYer head's up. Copper flashing seems to be a cost-effect solution for frustum walls if you are not using mesh. As I was looking around for supplies, found this: http://www.acehardware.com/product/index.jsp?productId=1290779&KPID=984489&kpid=984489&pla=pla_984489A 10ft roll seems to be the smallest length. I'd recommend the 14 inch for frustum heights to 11 inches. I can say from experience that .021 thickness will not be self-supporting and an exoskeleton will be needed. When I switched to a magnetron, the 1/8 in square copper supports were not ideal. I'd move to 1/4 in copper struts or possibly tubing.Top and bottom plates on nsf-1701 were 1/2 oz copper clad pc board, again too flimsy for a 750g magnetron. Try the next size up. Solid copper plates would weigh too much, I stick with the pcb stuff, just make sure there are plated thru-holes or plenty of bolts to connect the 2 ground planes.Any metal above ground potential will be subject to plasma discharge, so "mind the gaps" p.s. Bonus points for anyone who knows that phrase...
Quote from: Prunesquallor on 07/23/2015 12:55 amQuote from: leomillert on 07/22/2015 08:00 pmTo all those proposing to use Thruster in the name, I reiterate what rfmwguy said:Quote from: rfmwguy on 07/22/2015 06:10 pmElectromagnetic Drive or Reactor seems safe, perhaps a little better than Thruster since we're not 100% sure its pushing rather than pulling.What could the possible difference be between "pushing" and "pulling"?A sign
Quote from: leomillert on 07/22/2015 08:00 pmTo all those proposing to use Thruster in the name, I reiterate what rfmwguy said:Quote from: rfmwguy on 07/22/2015 06:10 pmElectromagnetic Drive or Reactor seems safe, perhaps a little better than Thruster since we're not 100% sure its pushing rather than pulling.What could the possible difference be between "pushing" and "pulling"?
To all those proposing to use Thruster in the name, I reiterate what rfmwguy said:Quote from: rfmwguy on 07/22/2015 06:10 pmElectromagnetic Drive or Reactor seems safe, perhaps a little better than Thruster since we're not 100% sure its pushing rather than pulling.
Electromagnetic Drive or Reactor seems safe, perhaps a little better than Thruster since we're not 100% sure its pushing rather than pulling.
Quote from: aero on 07/22/2015 11:50 pm...I wondered why that went quicker last night. Not quick but a little quicker. I guess you found out. Check it again, they are there now.I'm looking at the Yang/Shell Axial Antenna at Big Base case now: very unusual: the stress, and hence the force at the small base is practically zero. The stress at the big base is a central point stress from the antenna. Close inspection of this mode looks like another TM11 transverse magnetic mode but with drastically lower amplitude.QUESTION1: was the mesh kept the same as in the previous csv Yang/Shell case, and you are sure this is the stress at the small base and not outside it?Most important: QUESTION2: did Meep give you a Q value for this case ?Thanks
...I wondered why that went quicker last night. Not quick but a little quicker. I guess you found out. Check it again, they are there now.
Quote from: Rodal on 07/23/2015 12:27 amQuote from: aero on 07/22/2015 11:50 pm...I wondered why that went quicker last night. Not quick but a little quicker. I guess you found out. Check it again, they are there now.I'm looking at the Yang/Shell Axial Antenna at Big Base case now: very unusual: the stress, and hence the force at the small base is practically zero. The stress at the big base is a central point stress from the antenna. Close inspection of this mode looks like another TM11 transverse magnetic mode but with drastically lower amplitude.QUESTION1: was the mesh kept the same as in the previous csv Yang/Shell case, and you are sure this is the stress at the small base and not outside it?Most important: QUESTION2: did Meep give you a Q value for this case ?ThanksHe emailed me saying the Q was something like 57,000+ but was worried about the antenna position, I said run it if you want but I was still doing research into the antenna and had questions out to ppl who had 40 years + in this field. It's not one I would want to make.Shell
Quote from: SeeShells on 07/22/2015 03:17 pmQuote from: aero on 07/22/2015 07:08 am@SeeShell - Your .png and .csv files data is/are up have been uploaded here:https://drive.google.com/folderview?id=0B1XizxEfB23tfm04QWNVVVVvT3gtcVAzRUp6T1BCLVpoV0EyeVVKR2ZxQkp2a3NKcUNPMU0&usp=sharingI uploaded my meep data request file/form to hopefully explain what the data is, although it needs more English and fewer Scheme statements. The inside big end is at row 15 and small end at row 216 of the csv files, and the total run meep time t = 13.054 (6527 timesteps).Thanks, interesting but not quite what we were looking to do. I'm still working out the antenna shape and placement and getting feedback like I said I was going to do on launching a Te mode. What I found out is a answer from a wonderful source that mretty much just lurks here. Of course doing it isn't as easy as it seemed to be and I'm not sure you can do it in a meep model. Quote from a email: "Your test setup looks great. If you use a 1/4 probe on the big end or little end you will launch a TM mode. If you use a 1/10 wave loop you will excite a TE mode at either top or bottom. I believe If you launch from the big end the net force will be toward the small end or vice versa launching from the small end as the reflected wave will be reduced by Q losses and will be smaller in magnitude than the launched wave. A loop on the side wall will excite either mode depending on orientation wrt the frustum z axis. All walls on the frustum look like a conductive ground plane. For low power testing ,with the sweeper , the sample port I would use a probe 1/4 wavelength from the side wall, variable probe depth for the needed coupling to put the SA sampler in its optimum resolution range. If you use a loop you should place it at a low impedance point or H plane max node. <End Quote>After hours of reading and several emails to people who are beyond my skills in antennas I would agree with this.ShellHere you have a Master of Science thesis on the RF fields excited by dipole and loop antennas inside a stainless steel wire mesh cage :http://epublications.marquette.edu/cgi/viewcontent.cgi?article=1011&context=theses_openBesides the obvious interest in the simulation of the mesh, notice the considerable effort in modeling antennas.Quote Three types of antennas were used for simulations; dipole, monopole, and loop. For experiments, only monopole and loops were used. The dipole was used because of its simplicity, and ability to excite the E-fields within the cage. The loop was used because it is a magnetic antenna, and well suited to excite the H-fields. For our case, the TMagnetic modes have an axial electric field, hence excited by the dipole antenna. To excite a TElectric field which has a magnetic axial field, a loop antenna is needed.Quote Since the strongest E-fields created by the dipole are in the axial direction, to couple to a cavity it should be orientated in the same direction as the E-fields described by the mode configuration. The author used numerical simulation of electromagnetic fields, using The Numerical Electromagnetics Code (NEC) for simulation of the electromagnetic fields inside the cage and Matlab for post-processing of the results from NEC.Showing once again that it is usual for researchers to use other codes to post-process data. (Ditto for post-processing Meep data).
I'm curious as to why the capable engineers at EagleWorks are finding Q-values around 5,000 to 6,000, and yet around here there's a lot of talk about Q-values ten times higher?
I think I've lost track of all the DIYers now. Let's see:1. TheTraveller2. SeeShells3. rfmwguy4. Mulletron (?)5. klm(?)Is this on the wiki?http://emdrive.wiki/Main_Pagehttp://emdrive.wiki/BuildingI guess it's a dirty dozen so farIs the wiki link not supposed to be at the top of the page btw? - can't find it.
Quote from: Rodal on 07/23/2015 12:27 amQuote from: aero on 07/22/2015 11:50 pm...I wondered why that went quicker last night. Not quick but a little quicker. I guess you found out. Check it again, they are there now.I'm looking at the Yang/Shell Axial Antenna at Big Base case now: very unusual: the stress, and hence the force at the small base is practically zero. The stress at the big base is a central point stress from the antenna. Close inspection of this mode looks like another TM11 transverse magnetic mode but with drastically different amplitude.QUESTION1: was the mesh kept the same as in the previous csv Yang/Shell case, and you are sure this is the stress at the small base and not outside it?Most important: QUESTION2: did Meep give you a Q value for this case ?ThanksEverything about the run was identical except the antenna. The csv files are the same size aren't they? If something were changed likely they would change size. And really, the bases should be in the same place they were previously. I looked at this data set with HDFview. But note that the row numbers I gave you I had 1 added, to start at 1 like the csv matrices, instead of 0 as HDFview uses. If you also added 1, that would be the problem. The model skin is three matrix rows thick, adding an extra 1 would make the small base row be inside the skin.It was also the same 58 mm antenna centered quarter wavelength from the inside face of the big base but rotated 90 degrees to an axial orentation. Note that 1/4 wave length is only slightly more than half of 58 mm, so the end of the antenna near the big base was about 1.5 mm away from the base, and excited with ez component although hy would have been more natural.Q? Yea, Q was ridiculously high, like 60 million and the resonant frequency was like 2.463 GHz, which I ignored and made the run at 2.45 GHz.
Quote from: aero on 07/22/2015 11:50 pm...I wondered why that went quicker last night. Not quick but a little quicker. I guess you found out. Check it again, they are there now.I'm looking at the Yang/Shell Axial Antenna at Big Base case now: very unusual: the stress, and hence the force at the small base is practically zero. The stress at the big base is a central point stress from the antenna. Close inspection of this mode looks like another TM11 transverse magnetic mode but with drastically different amplitude.QUESTION1: was the mesh kept the same as in the previous csv Yang/Shell case, and you are sure this is the stress at the small base and not outside it?Most important: QUESTION2: did Meep give you a Q value for this case ?Thanks
Speaking of magnetrons and antenna matching, read a lot of design papers on microwave ovens lately. An empty microwave is designed for ideal match. Food or liquid changes impedance match, yet magnetrons are not recommended to be fired into an empty microwave cavity. Since therrs nothing to absorb the em, the radome/monopole heats up on the reflected or standing waves.Also read waveguide launchers for magnetrons are not designed for 50 ohms. One I read about was 550 ohms. In addition, standard mw magnetrons or designed to accept a mismatch up to 3:1 vswr. average mtbf is about 6k hours.Perhaps we see why spr cooled their magnetron, to bleed of heat due to high standing waves. Wonder if the dielectric insert at ew was perhaps a radiation "sink". so many questions, so few data runs...hope to fix that.
Quote from: Hauerg on 07/22/2015 08:06 pmACDAsymmetric Cavity DriveThis debate is actually not really helpful. The one who explains the physics correctly will give it a name in his paper, or do it democratically, but let's go back to science right now This for example: ghost modes in imperfect waveguideshttp://bayes.wustl.edu/etj/articles/ghost.modes.pdf
ACDAsymmetric Cavity Drive
Use a simple internal working name...and take a hint from the marketing gurus in big pharma...the BIG EASY TO REMEMBER MARKETABLE NAME...Brand it when there is a device that you want to have the masses interested enough in to fund it. Big companies may invest in it, but the masses still fund it, whether they want to ride on it or have it bounce reruns of Cheers to them from orbit.
Quote from: rq3 on 07/22/2015 11:31 pmQuote from: SeeShells on 07/22/2015 08:46 pmQuote from: rfmwguy on 07/22/2015 08:11 pmDIYer head's up. Copper flashing seems to be a cost-effect solution for frustum walls if you are not using mesh. As I was looking around for supplies, found this: http://www.acehardware.com/product/index.jsp?productId=1290779&KPID=984489&kpid=984489&pla=pla_984489A 10ft roll seems to be the smallest length. I'd recommend the 14 inch for frustum heights to 11 inches. I can say from experience that .021 thickness will not be self-supporting and an exoskeleton will be needed. When I switched to a magnetron, the 1/8 in square copper supports were not ideal. I'd move to 1/4 in copper struts or possibly tubing.Top and bottom plates on nsf-1701 were 1/2 oz copper clad pc board, again too flimsy for a 750g magnetron. Try the next size up. Solid copper plates would weigh too much, I stick with the pcb stuff, just make sure there are plated thru-holes or plenty of bolts to connect the 2 ground planes.Any metal above ground potential will be subject to plasma discharge, so "mind the gaps" p.s. Bonus points for anyone who knows that phrase...Had to do with electric trolleys I think. Before my time.One thing you need to be aware of in copper is that it's mixed with tin to prevent corrosion, 80-90% mix is normal and if not 99% pure copper it will cause more heating signal loss and not be as a good cavity.ShellPS:I'm still waiting (have some time) for my last piece of copper is holed out to my specs, was hoping to have a simulation run, it is 99% pure the same they use in waveguides.Shell, there are hundreds of copper alloys. Copper alloyed with tin is bronze. Copper alloyed with zinc is brass (both very generically speaking). What you are probably after is the highest possible electrical conductivity, which is commercially called 101 copper, or Oxygen Free High Conductivity (OFHC) copper.Both brass and bronze typically have drastically lower conductivity than OFHC copper. Waveguides are often brass for structural reasons (its much stiffer and harder than OFHC), and are often silver plated internally to enhance conductivity. Cheaper waveguides are usually aluminum.McMaster Carr (mcmaster.com) is a somewhat pricey but immediately available source for OFHC. Browse under "Raw Materials". They may even have perforated sheet.A good heads up, I'm having to have the final copper frustum which is OFHC drilled and used for wave guides. Looked at McMaster Carr (bought a lot of stuff over the years from them) and it doesn't seem the have the right copper perforated sheets for the final build.Thanks!Shell