Quote from: TheTraveller on 07/12/2015 10:54 pmQuote from: rfmwguy on 07/12/2015 10:51 pmQuote from: TheTraveller on 07/12/2015 10:28 pmJust to throw another log on the fire in Bringing Light into the Dark.In the 2010 Chinese paper, Prof Yang discloses the equation they use to calculate cavity Q. Yes that is right, they don't measure Q, they calculate it from their in-house developed equation.Search for equation 14 in the 2010 paper:http://www.emdrive.com/NWPU2010translation.pdfQuoteThe quality factor of this resonator under no load can be calculated by the following equation:Qu=∫|H|2dv/h/2∫|nxH|2ds+tgd∫|H|2dv = (14)Where tg is the electric loss within the cavity, n is the normal vector of the wall, s is the cavity surface area, v is the volume of the cavity.Who will be the 1st to post an Excel spreadsheet that duplicates Prof Yang's equation?Sorry mr t, this is an arbitrary equation of limited value imo. One must ask why estimate when one can measure.My point is this equation is what the Chinese use when they quote device Q. They don't, as far as I know, measure the quoted devices Q.Seems like it mr t...with all the proper gear in their lab, why they chose not to measure is beyond me.
Quote from: rfmwguy on 07/12/2015 10:51 pmQuote from: TheTraveller on 07/12/2015 10:28 pmJust to throw another log on the fire in Bringing Light into the Dark.In the 2010 Chinese paper, Prof Yang discloses the equation they use to calculate cavity Q. Yes that is right, they don't measure Q, they calculate it from their in-house developed equation.Search for equation 14 in the 2010 paper:http://www.emdrive.com/NWPU2010translation.pdfQuoteThe quality factor of this resonator under no load can be calculated by the following equation:Qu=∫|H|2dv/h/2∫|nxH|2ds+tgd∫|H|2dv = (14)Where tg is the electric loss within the cavity, n is the normal vector of the wall, s is the cavity surface area, v is the volume of the cavity.Who will be the 1st to post an Excel spreadsheet that duplicates Prof Yang's equation?Sorry mr t, this is an arbitrary equation of limited value imo. One must ask why estimate when one can measure.My point is this equation is what the Chinese use when they quote device Q. They don't, as far as I know, measure the quoted devices Q.
Quote from: TheTraveller on 07/12/2015 10:28 pmJust to throw another log on the fire in Bringing Light into the Dark.In the 2010 Chinese paper, Prof Yang discloses the equation they use to calculate cavity Q. Yes that is right, they don't measure Q, they calculate it from their in-house developed equation.Search for equation 14 in the 2010 paper:http://www.emdrive.com/NWPU2010translation.pdfQuoteThe quality factor of this resonator under no load can be calculated by the following equation:Qu=∫|H|2dv/h/2∫|nxH|2ds+tgd∫|H|2dv = (14)Where tg is the electric loss within the cavity, n is the normal vector of the wall, s is the cavity surface area, v is the volume of the cavity.Who will be the 1st to post an Excel spreadsheet that duplicates Prof Yang's equation?Sorry mr t, this is an arbitrary equation of limited value imo. One must ask why estimate when one can measure.
Just to throw another log on the fire in Bringing Light into the Dark.In the 2010 Chinese paper, Prof Yang discloses the equation they use to calculate cavity Q. Yes that is right, they don't measure Q, they calculate it from their in-house developed equation.Search for equation 14 in the 2010 paper:http://www.emdrive.com/NWPU2010translation.pdfQuoteThe quality factor of this resonator under no load can be calculated by the following equation:Qu=∫|H|2dv/h/2∫|nxH|2ds+tgd∫|H|2dv = (14)Where tg is the electric loss within the cavity, n is the normal vector of the wall, s is the cavity surface area, v is the volume of the cavity.Who will be the 1st to post an Excel spreadsheet that duplicates Prof Yang's equation?
The quality factor of this resonator under no load can be calculated by the following equation:Qu=∫|H|2dv/h/2∫|nxH|2ds+tgd∫|H|2dv = (14)Where tg is the electric loss within the cavity, n is the normal vector of the wall, s is the cavity surface area, v is the volume of the cavity.
Thanks for the comments and suggestions.
I would suspect a typical antenna's Q would be 1, being energy in per cycle would equal energy lost (radiated) per cycle so no need to measure Q.
1st at very low power it can sweep the output frequency back and forth, by varing the Rf gen frequency, looking for the lowest VSWR around my spreadsheets calculated resonate frequency as lowest VSWR is the same thing as the highest return loss.
For this application, it doesn't matter that the Rf amps output impedance is not calibrated to any standard. It only matters that the VSWR reported by the Rf amp, when driving the cavity, is as low as possible as that means the input and output impedances of the 2 devices are as closely matched as possible and that the cavity will accept the max Rf energy it can, while rejecting the min Rf energy it can.
Further by doing real time monitoring of the VSWR, while the Rf amp is driving the cavity, my embedded micro controller can detect when conditions inside the cavity have changed and the Rf gen's frequency needs to be adjusted to stay in the middle of the cavities resonance curve.As an ex ham, I don't see why an antenna can't have a bandwidth measured at it's -3dB points as determined by converting the measured VSWR change, caused by deliberate Rf gen frequency change, into return loss dB change to determine the -3dB points from the peak return loss or lowest VSWR.
Quote from: TheTraveller on 07/12/2015 09:14 pmThanks for the comments and suggestions.Your welcome. Very happy to help - can't wait to see your drive work and figure out how its doing it.Quote from: TheTraveller on 07/12/2015 09:14 pmI would suspect a typical antenna's Q would be 1, being energy in per cycle would equal energy lost (radiated) per cycle so no need to measure Q.Not exactly. Best case is a tuned, long, thick conductor. A dipole is around 70 ohms, free space is 377 or so; antennas have an (evanescent) near field, which isn't radiated. The thicker the conductor or antenna width, the wider the bandwidth.The antenna has an effective "radiation resistance". An AM radio ferrite loop antenna is a "high Q" antenna. They're called "electrically short" antennas. Typically poor radiation resistance to dielectric/ferrite/conductor loss. So your ferrite bar & tuning cap may have a Q of 100, and IIRC radiate < 5% of its power and make 95% heat from its losses.You can tune up the transmitter and coax to an electrically short antenna for very low VSWR, and it will still suck because the energy isn't going to be radiated so much as heat the little antenna.Quote from: TheTraveller on 07/12/2015 09:14 pm1st at very low power it can sweep the output frequency back and forth, by varing the Rf gen frequency, looking for the lowest VSWR around my spreadsheets calculated resonate frequency as lowest VSWR is the same thing as the highest return loss.I think high reflected power for high return loss (say, -3db). A low reflected power (-20db) I suppose you might call high because its a bigger negative number, but -3db is 1/2 and -20db is 1/100. But its been a long time...Quote from: TheTraveller on 07/12/2015 09:14 pmFor this application, it doesn't matter that the Rf amps output impedance is not calibrated to any standard. It only matters that the VSWR reported by the Rf amp, when driving the cavity, is as low as possible as that means the input and output impedances of the 2 devices are as closely matched as possible and that the cavity will accept the max Rf energy it can, while rejecting the min Rf energy it can.I would be shocked if it isn't 50 ohms.Quote from: TheTraveller on 07/12/2015 09:14 pmFurther by doing real time monitoring of the VSWR, while the Rf amp is driving the cavity, my embedded micro controller can detect when conditions inside the cavity have changed and the Rf gen's frequency needs to be adjusted to stay in the middle of the cavities resonance curve.As an ex ham, I don't see why an antenna can't have a bandwidth measured at it's -3dB points as determined by converting the measured VSWR change, caused by deliberate Rf gen frequency change, into return loss dB change to determine the -3dB points from the peak return loss or lowest VSWR.As with the difference between the dipole and the AM ferrite loop, or a tiny BaTiO:Zr dielectric puck for GPS. You can tune the coax to a Z-matched high-Q network fine, with VSWR meter. But does it really give you the Q of the network if you've got a length of un-tuned coax going to it, and the cavity feed and transmitter are also not perfectly matched?Several variables involved, but the largest probably is the resonances and anti-resonances of the high-Q cavity. I think its best to put on a monitoring port. 1/16" hole with a tiny wire, maybe only 1/16" in, far from the feed point. But I've never messed with cavities before.
Quote from: Ricvil on 07/12/2015 04:12 amNice. The graph shows the mixing of the modes as a function of cavity shape.There is a choice of frequency, and dimension on graph. Any specific motivation?No idea.Quote from: Ricvil on 07/12/2015 04:12 amI'm looking for a configuration when there is one hybrid mode, followed by any other mode very close.Why? Because I think there is another thing interacting with the electromagnetic field of cavity.This thing probally will have a very small coupling with the electromagnetic field.To enhance this coupling I need:- A mode excited by a source puting the max energy on cavity- At least one second mode with frequecy very close to the first but not excited by the source.In this situation, when a small region of the cavity has its electromagnetics properties changed to anything different of vacuum (epslon0 and mu0), then this little "scatter" region triggers a very strong perturbation called "ghost mode".In waveguides "ghost modes" are caused by deformations or imperfections on waveguide, but in principle, any "pertubation" can cause this effect.This "ghost modes" can in some situations, reflect almost all power flux in the waveguide, and the "scatter" will be under very strong radiation pressure.I don't know if this case can be considered also a type of Fano resonance, but I think if I want some type of interaction of the field inside of cavity with some "other thing", I would try to maximize this interaction with this setup.To me this thing is the axion field/particle. To others can be particles from "quantum vacuum" or a space-time flutuactions, but the result of the ghost mode arising is the same, change the incidence of electromagnetic radiation on the walls of cavity.I had to look up ghost mode and Fano reasonance, interesting stuff to know. Perhaps explains why putting a dielectric in the frustrum is a bad thing. Dielectric loss aside, it could cause ghost modes if there are nearby modes available. Lots of google hits on microwave/klystron windows pertaining to ghost modes. Wikipedia notes microwaves are associated with Fano resonance. A 1958 paper by Jaynes http://bayes.wustl.edu/etj/articles/ghost.modes.pdf notes that microwave ghost modes have a similarity to localized imperfections in crystalline periodic structures (such as dopants) leads to bound states that overlap the conduction band. If that Fano resonance too? I'll have to absorb that awhile. I have no idea how that could conjure axions out of the qv.
Nice. The graph shows the mixing of the modes as a function of cavity shape.There is a choice of frequency, and dimension on graph. Any specific motivation?
I'm looking for a configuration when there is one hybrid mode, followed by any other mode very close.Why? Because I think there is another thing interacting with the electromagnetic field of cavity.This thing probally will have a very small coupling with the electromagnetic field.To enhance this coupling I need:- A mode excited by a source puting the max energy on cavity- At least one second mode with frequecy very close to the first but not excited by the source.In this situation, when a small region of the cavity has its electromagnetics properties changed to anything different of vacuum (epslon0 and mu0), then this little "scatter" region triggers a very strong perturbation called "ghost mode".In waveguides "ghost modes" are caused by deformations or imperfections on waveguide, but in principle, any "pertubation" can cause this effect.This "ghost modes" can in some situations, reflect almost all power flux in the waveguide, and the "scatter" will be under very strong radiation pressure.I don't know if this case can be considered also a type of Fano resonance, but I think if I want some type of interaction of the field inside of cavity with some "other thing", I would try to maximize this interaction with this setup.To me this thing is the axion field/particle. To others can be particles from "quantum vacuum" or a space-time flutuactions, but the result of the ghost mode arising is the same, change the incidence of electromagnetic radiation on the walls of cavity.
Quote from: rfmwguy on 07/11/2015 07:09 pm...Here is where they went wrong...under no industrial RF standard does anyone measure Q on return loss, S11. It is done on S21, forward power in the frequency domain for cavities. I stand by my claim that "Specsmanship" was used to create an unnaturally large Q, either by unfamiliarity or intent.Note that S21 requires a 2 port measurement, input and output (note the sampling port on the frustums will provide the output). I'd bet a six-pack of craft beer that realistic Qs are in the 4 digit range for both shawyer and yang. And yes Doc, Yang should have used the -3dB points below 0 insertion, not -3dB above best return loss...not RF types IMHO.rfmwguy, a big thanks from me, and a big applause, for clarifying this issue: you are 100% right. The Q should be measured using two port S21.All Q measurements using S11 are suspect: everybody should take with a grain of salt the reported Q's from different EM Drive researchers, unless the procedure to measure the Q is detailed and they have used S21.
...Here is where they went wrong...under no industrial RF standard does anyone measure Q on return loss, S11. It is done on S21, forward power in the frequency domain for cavities. I stand by my claim that "Specsmanship" was used to create an unnaturally large Q, either by unfamiliarity or intent.Note that S21 requires a 2 port measurement, input and output (note the sampling port on the frustums will provide the output). I'd bet a six-pack of craft beer that realistic Qs are in the 4 digit range for both shawyer and yang. And yes Doc, Yang should have used the -3dB points below 0 insertion, not -3dB above best return loss...not RF types IMHO.
Quote from: Rodal on 07/12/2015 05:51 pmQuote from: rfmwguy on 07/11/2015 07:09 pm...Here is where they went wrong...under no industrial RF standard does anyone measure Q on return loss, S11. It is done on S21, forward power in the frequency domain for cavities. I stand by my claim that "Specsmanship" was used to create an unnaturally large Q, either by unfamiliarity or intent.Note that S21 requires a 2 port measurement, input and output (note the sampling port on the frustums will provide the output). I'd bet a six-pack of craft beer that realistic Qs are in the 4 digit range for both shawyer and yang. And yes Doc, Yang should have used the -3dB points below 0 insertion, not -3dB above best return loss...not RF types IMHO.rfmwguy, a big thanks from me, and a big applause, for clarifying this issue: you are 100% right. The Q should be measured using two port S21.All Q measurements using S11 are suspect: everybody should take with a grain of salt the reported Q's from different EM Drive researchers, unless the procedure to measure the Q is detailed and they have used S21.Hence, why I ignored them and calculated the change in energy required for a given thrust, rather than a thrust given the reported stored energy based on Q. I don't trust the data.Todd
Quote from: WarpTech on 07/13/2015 03:59 amQuote from: Rodal on 07/12/2015 05:51 pmQuote from: rfmwguy on 07/11/2015 07:09 pm...Here is where they went wrong...under no industrial RF standard does anyone measure Q on return loss, S11. It is done on S21, forward power in the frequency domain for cavities. I stand by my claim that "Specsmanship" was used to create an unnaturally large Q, either by unfamiliarity or intent.Note that S21 requires a 2 port measurement, input and output (note the sampling port on the frustums will provide the output). I'd bet a six-pack of craft beer that realistic Qs are in the 4 digit range for both shawyer and yang. And yes Doc, Yang should have used the -3dB points below 0 insertion, not -3dB above best return loss...not RF types IMHO.rfmwguy, a big thanks from me, and a big applause, for clarifying this issue: you are 100% right. The Q should be measured using two port S21.All Q measurements using S11 are suspect: everybody should take with a grain of salt the reported Q's from different EM Drive researchers, unless the procedure to measure the Q is detailed and they have used S21.Hence, why I ignored them and calculated the change in energy required for a given thrust, rather than a thrust given the reported stored energy based on Q. I don't trust the data.ToddShawyer uses unloaded cavity Q for his Force calculations as the cavity is never attached to nor filled with anything to alter it's unloaded status. The unloaded Q is all there is. As I see it, it's like a LC circuit that never drives / is connected to anything but just sits there doing it's resonate thing and has its stored energy topped up, from time to time, to replace the parasitic energy loss.So loaded cavity Q measurements have no place in the EMDrive world as the cavity is never loaded. It is a 1 port cavity.Unloaded cavity Q can be calculated by 1 port S11 return loss measurements based on the side frequencies that are 3 dB down from the return loss peak. It can also be calculated, in real time, by my Control & Measurement System, based on the Rf amps VSWR output.
Shawyer uses unloaded cavity Q for his Force calculations as the cavity is never attached to nor filled with anything to alter it's unloaded status. The unloaded Q is all there is. As I see it, it's like a LC circuit that never drives / is connected to anything but just sits there doing it's resonate thing and has its stored energy topped up, from time to time, to replace the parasitic energy loss.So loaded cavity Q measurements have no place in the EMDrive world as the cavity is never loaded. It is a 1 port cavity.Unloaded cavity Q can be calculated by 1 port S11 return loss measurements based on the side frequencies that are 3 dB down from the return loss peak. It can also be calculated, in real time, by my Control & Measurement System, based on the Rf amps VSWR output.
Resolution of the Space-Drive Energy Paradox (version 6) Have at it @deltaMass and @wallofwolfstreet. I'm looking forward to your responses. https://www.dropbox.com/s/p86dvc8733h9iph/Desiato-Energy_Paradox-v6.pdf?dl=0Todd
Quote from: TheTraveller on 07/13/2015 04:27 amShawyer uses unloaded cavity Q for his Force calculations as the cavity is never attached to nor filled with anything to alter it's unloaded status. The unloaded Q is all there is. As I see it, it's like a LC circuit that never drives / is connected to anything but just sits there doing it's resonate thing and has its stored energy topped up, from time to time, to replace the parasitic energy loss.So loaded cavity Q measurements have no place in the EMDrive world as the cavity is never loaded. It is a 1 port cavity.Unloaded cavity Q can be calculated by 1 port S11 return loss measurements based on the side frequencies that are 3 dB down from the return loss peak. It can also be calculated, in real time, by my Control & Measurement System, based on the Rf amps VSWR output.Are you sure the EMDrive will never be "loaded"? Didn't Shawyer describe it as a motor/generator depending one which direction its moving? At rest, its RF-wise at equilibrium. If it moves backwards, it generates and a reflected wave will move towards your transmitter. Moving forward, shouldn't it present a greater load on the transmitter then?Perhaps any coax reactance (a coax with an unevent # of 1/4 wavelengths) will be absorbed/dwarfed by the cavity tuning, so perhaps S11 is good enough for tuning.However, wouldn't it be nice to sense each of the 3 modes in a TE013 frustrum at 90 degree points, and watch the amplitude modulations/traveling wave or Sagnac effect as it spins to or fro? Or configure the taps for phase rather than amplitude measurement to measure group velocity?Would be a good reality check for the FEA/FDTD simulations.BTW, I'm pretty sure the transmitter will have an isolator or circulator to protect the PA from VSWR damage. If it doesn't, it may be very easy to burn it out if its tuned at high-power while the cavity is tuned through its anti-resonance.
In the finite-difference time-domain method, the electric and magnetic fields are stored at different times (and different positions in space), in a "leap-frog" fashion. At any given time-step t during the simulation, the E and D fields are stored at time t, but the H and B fields are stored at time t − Δt / 2 (where Δt is the time-step size). This means that when you output the electric and magnetic fields from a given time step, for example, the fields actually correspond to times Δt / 2 apart. For most purposes, this slight difference in time doesn't actually matter much, but it makes a difference when you compute quantities like the Poynting flux \mathbf{E}\times\mathbf{H} that combine electric and magnetic fields together, e.g. for the output-poynting function. If what you really want is the Poynting flux \mathbf{S}(t) at time t, then computing \mathbf{E}(t)\times\mathbf{H}(t-\Delta t/2) is slightly off from this — the error is of order O(Δt), or first-order accuracy. This is unfortunate, because the underlying FDTD method ideally can have second-order accuracy.To improve the accuracy for computations involving both electric and magnetic fields, Meep provides a facility to synchronize the H and B fields with the E and D fields in time. Technically, what it does is to compute the magnetic fields at time t + Δt / 2 by performing part of a timestep, and then averaging those fields with the fields at time t − Δt / 2. This produces the magnetic fields at time t to second-order accuracy O(Δt2), which is the best we can do in second-order FDTD. Meep also saves a copy of the magnetic fields at t − Δt / 2, so that it can restore those fields for subsequent timestepping.