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#980 by Vesc on 06 Apr, 2016 03:55
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Please search for the posts by Frobnicat (preferably using "Google Advanced Search", who has thoroughly dealt with this, including frame-indifference, and the issues you discuss. Frobnicat has a lot of posts discussing this in previous threads.
OK, I'll bite. Frankly I don't get the objection. ...
ok, found this article:
http://forum.nasaspaceflight.com/index.php?topic=37438.msg1369806#msg1369806
Now I get it. Yes. I don't see this as constant acceleration for constant power in. But then even from SR I didn't see how acceleration could be constant either if mass is increasing and force is not. That's just basic SR coupled with Newton's first law. A variant of the rotating EMDrives I've also seen proposed as a perpetual motion machine was the "infinite oscillator". Two EMDrives that are cross coupled so that they oscillate in distance between them by using gravity to attract to each other, storing up the electrical energy produced by the motion induced by gravitational acceleration and then prior to collision, switching each device "on" to drive them apart until the stored electrical power is consumed and then back off again, thus completing the cycle. -
#981 by kml on 06 Apr, 2016 04:43
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The missing side walls are reality. Deal with it and maybe learn something?
Just don't be reckless and hurt yourself, man.
Thanks for the thought.
Just maybe accept there is something going on in Roger's cryo thruster that is not understood by most here? Roger is a 30 year microwave engineer, so don't believe his design is unsafe.
Everything we know about frustum design says there is no way that open sided frustum would work. Yet there it is, staring us in the face, saying you sure you know what is going on inside me?
BTW most of my testing is done at 78mW to 10W with only very brief periods of a few seconds at 100Ws. Never get closer than 1m to the Rf amp or frustum at any time. Nice to have an Rf amp that steps in 1dBm increments from 78mW to 100W, that reports both forward & reflected power and is driven by dial up freq gen at 1kh resolution. Means I know what is exciting the frustum and can easily dial up past settings.
Don't envy those maggie builders as there is almost no way to know what is happening to the drive freq, power, cavity Q, forward & reflected power as it is all over the spectrum and the frustum is pulling the maggie freq into it's resonance but with a power penalty of phase shifted reflected Rf due to the pulling. Then altering maggie power, alters Freq due to pushing. Not an easy beast to control, if at all.
Missing side walls? The picture appears to show conductive metal on all sides. Why do you call it open sided? -
#982 by Vesc on 06 Apr, 2016 04:48
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One more thought. Frobnicat admits waste heat is produced. I don't think heat loss is trivial or should be considered trivial in this case and is probably key to why this cannot be a unity or over-unity device, ever. If you are putting in exactly 1kW and getting 1N in return AND waste heat *from the device itself* then you are by definition under unity. I would posit that you cannot increase your angular momentum by any amount and achieve over unity because there would be more energy lost to waste heat than could be converted to thrust! On the other hand *if* the device is indeed harvesting vacuum energy then this is not wasted heat, this is heat gained through conversion, i.e. the difference between a motor and an engine! But now we're back to preferred reference frames again.
What a hoot to speculate that zero CMB Anisotropy is the preferred frame. This is like canoeing down a river in a current too swift to paddle upstream and would engender a "preferred" direction of travel to the EMDrive. Or to use another nautical analogy, it'd be like sailing w/o a keel. You could still get to anywhere in the universe by going the long way round, provided you don't hit the zero anisotropy 'doldrums' prior to arrival! And there is probably a mathematical proof out there that says exactly that would happen first! -
#983 by zen-in on 06 Apr, 2016 05:40
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So why the missing side walls in Roger's SC cryo EmDrive thruster?
Just maybe the top and bottom Rf mirrors (let's call them what they are) direct & beam the microwave photons from end to end without letting them hit the side walls?
If so there should be a BIG effect on reducing eddy current losses (no side walls), boosting Q (desired goal is increased cavity discharge time) to harvest the max momentum transfer (maxed number of Rf mirror reflections) from a short initial Rf excitation pulse.
The Thrust curve that is there after the Rf pulse ends is due to retained cavity energy slowly decaying, yet still capable of generating force. The less the losses in the cavity during the decay time (from no eddy currents induced in the missing side walls), the longer the cavity energy will remain active and generate force.
I consider these two images as being major breadcrumbs from Roger to DIY EmDrive researchers/builders. Would suggest the missing side walls will also work with non SC cryo frustums. However the end plates need to be very good Rf mirrors that can very accurately direct and beam the microwave photons back and forth between the 2 Rf mirrors without touching the side walls.
I don't understand why everyone is saying there are missing sidewalls. The picture below shows metal walls. The metal might be mumetal or it could be hastalloy with YBCO + substrate + Silver. That is how 1st gen YBCO cable is made. Mr. Shawyer may have had some pieces of plate manufactured for him. It is usually made in long cables about 4 mm wide. The second photo shows a small section of AMSC's (formerly American Superconductor) 1st gen YBCO cable. The YBCO is encapsulated inside the metal with Fine Silver bonded to one side. I have read papers where the alloy used was called Hastalloy. I don't know if that is what AMSC used. It is not suitable for AC operation above 60 Hz and is anisotropic.
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#984 by mwvp on 06 Apr, 2016 05:52
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Just maybe accept there is something going on in Roger's cryo thruster that is not understood by most here? Roger is a 30 year microwave engineer, so don't believe his design is unsafe.
It is beyond my comprehension of how, using Maxwell's laws and waveguides work, that a hollow resonator with those dimensions could sustain a high-Q resonance. It seems more likely that Shawyer's photo is of an incomplete model, and you're thinking that "microwave-photons" are trapped bouncing between well aligned mirrors.
My understanding is that a momentum integral, the Poynting vector, can be attributed to fields, and will seem to ricochet between sidewalls and the ends of a waveguide. The ray-like integral is just a notion; reality is each point in space has an electric and magnetic component, following Maxwell's equations. As the frequency increases, the guide wavelength shortens, like a compressing bellows or spring. Or as the diameter/width is reduced, the guide wavelength or K-vector lengthens. The K vector may be longitudinal, the Poynting vector diagonal, and the E and B fields for each bit of polarized vacuum are spinning appropriately to give us the psychological notion of P and K vectors. Sure momentum and wavelength are real, a real consequence of the properties of each point's field-value in space.
Now if you have a sub-wavelength hole, greatly attenuated energy can still make it out. The attenuation is proportional to the impedance differences between the cavity, and free space. With a giant gaping hole, I can't conceive of a boundary impedance difference to support any high-Q resonance.
From the little I know of QM, the probability amplitude of detecting a photon calculates commensurate with field strength amplitudes, and rather than impedance you can use refractive index but you get the same result.
If I'm wrong about this, then either its possible to simulate such a cavity using Meep, Feko or Comsol, or Shawyer can update us on Maxwells' equations. -
#985 by FattyLumpkin on 06 Apr, 2016 06:34
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Probably a conductive polymer on the sides (mostly transparent)
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#986 by Cinder on 06 Apr, 2016 06:39
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It seems more likely that Shawyer's photo is of an incomplete model
(Agreeing: ) Interpreting a still picture is one thing, observing a live experiment is another. -
#987 by TheTraveller on 06 Apr, 2016 07:34
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I don't understand why everyone is saying there are missing sidewalls. The picture below shows metal walls.
Metal walls? Suggest you zoom into this image and have another look at the right side semi transparent glued on membrane and the sensor wire penetrations.
The full test setup is also attached.
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#988 by TheTraveller on 06 Apr, 2016 07:37
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TheTraveller
...Please, I implore you to whip up a simple hanging rotational test platform like the one I did and show the world the 8mN of force in action!...
I'll study your test setup and consider your request.
Please understand the only people I need to convince are my potential customers and they will only believe it works when shown it working to their face. I expect to redo the 0.4N force tests in high vac MANY times. -
#989 by A_M_Swallow on 06 Apr, 2016 09:21
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The thruster does not need side walls to work.
Microwaves are dangerous to people, and possibly other electronics, so the thruster needs operating in an earthed metal container.
The diagrams show the microwaves spreading out from the transmitting aerial.
I suspect the shape of the container does not matter so it could be an oblong box or a metal tube. These can be purchased cheaply off the shelf. How far do the walls have to be from the centre of the beam of known frequency to ensure that less than say 1% is absorbed? -
#990 by Rodal on 06 Apr, 2016 11:47
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(Mod note - first sentence removed per site rules)
The missing side walls are reality. Deal with it and maybe learn something?
Just don't be reckless and hurt yourself, man.
Thanks for the thought.
Just maybe accept there is something going on in Roger's cryo thruster that is not understood by most here? Roger is a 30 year microwave engineer, so don't believe his design is unsafe.
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1) whether your belief is correct that Mr. Shawyer's tested "cryo thruster" is meant to have no metal side walls during operation
2) whether it would be safe for DIY like you to contemplate resonance-testing an EM Drive with no metal side walls
This would be a most essential and helpful clarification, since safety (your safety and the safety of every possible DIY) should be priority number one. It says so on the first page of each of these threads.
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#991 by frobnicat on 06 Apr, 2016 12:03
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Please search for the posts by Frobnicat (preferably using "Google Advanced Search", who has thoroughly dealt with this, including frame-indifference, and the issues you discuss. Frobnicat has a lot of posts discussing this in previous threads.
OK, I'll bite. Frankly I don't get the objection. ...
ok, found this article:
http://forum.nasaspaceflight.com/index.php?topic=37438.msg1369806#msg1369806
Now I get it. Yes. I don't see this as constant acceleration for constant power in. But then even from SR I didn't see how acceleration could be constant either if mass is increasing and force is not. That's just basic SR coupled with Newton's first law. A variant of the rotating EMDrives I've also seen proposed as a perpetual motion machine was the "infinite oscillator". Two EMDrives that are cross coupled so that they oscillate in distance between them by using gravity to attract to each other, storing up the electrical energy produced by the motion induced by gravitational acceleration and then prior to collision, switching each device "on" to drive them apart until the stored electrical power is consumed and then back off again, thus completing the cycle.
Breaking my silence for once. A "over unity" scheme does not need constant acceleration with constant power, it needs constant force with constant power input. Because acceleration is relative (what you say of acceleration in SR depends on reference frame, from the spacecraft itself there is no decrease in acceleration at constant force...) there is always a great confusion with interpretation in delta kinetic energy. And a force can be applied at constant velocity, no acceleration, as in a tractor pulling a plow at constant velocity (wrt to ground), as in a turbojet thrusting for a plane moving against aerodynamic drag at constant velocity (wrt to air mass). Such a force F applied at a given constant velocity V relative to a support will release a power of FV if F is in same direction as V and will absorb a power FV in the opposite direction. More generally the power given from the thrusting system at constant velocity V wrt to some support will be the scalar product F by V (the power given is negative, ie absorbed, if vector are opposite directions). The power will not change any kinetic energy as we are talking constant velocity, so it must go elsewhere. I'm heavily insisting on that because it seems hard to get through, as many want to think as the emdrive as some kind of "electric energy to kinetic energy converter". This is not the principle of the proposed overunity scheme.
The proposed scheme derives from the fact that (most of) the claims so far measure a thrust against a proportional restoring force, a spring or such, and damped, being that after a short transient of acceleration (as expected from a force) the system stabilizes (more or less) in a static equilibrium (as expected from a constant force). In other words, the proposed device is claimed to give a constant force (at least for a few tens of seconds) for a constant power input when acceleration is 0, ie at constant velocity (of 0 wrt ground). So far so good, that's what we would expect from a thruster after all.
What I'm proposing is to put this phenomenon of constant thrust at constant power and constant velocity to do work on a generator (a mechanical energy to electric energy converter). Well, the overunity then appears immediatly for a propellantless system thrusting above 1/c = 3.33 µN/kW, because at a constant velocity above the inverse of this figure_of_merit (and the inverse of something that is above 1/c is a velocity that is below c, hence physically attainable, at least in principle), at such a velocity V wrt to the generator that recovers some power (I illustrate the case on a rotating shaft, but could be linear all the same), then one sees that the mechanical power output by the thrusting system is FV while the electric input is F/figure_of_merit<FV, given that we chose V such that V>1/figure_of_merit.
The only caveat I see is if the phenomenon somehow "knows" its velocity relative to what it is pushing, or more generally that it "knows" some kind of absolute velocity, and that the "figure_of_merit" is different depending of V, even while acceleration=0. Different constant velocities (wrt to what ?) would yield different figure_of_merit, in such a way to render such overunity scheme impossible. Notice that, the higher the figure_of_merit as measured in some frame (say, the lab) the lower the range of velocities around this hypothetical 0 velocity frame is allowed before the figure_of_merit is degraded. Basically, an hypothetical 1N/kW Emdrive thruster in the lab could certainly not thrust at such performance above 1km/s (wrt to the lab) in all directions. If there is such a thing as an aether defining a priviledged physical reference frame against which the phenomenon is "pushing" or "grabbing", one would indeed see a very strong directionality of the efficiency of the effect, presumably relative to the stars, and one would see such strong directionality all the more with higher figure of merit. At 1N/kW measured in the lab, the directionality could hide only if the aether wind wrt the lab would be below 1km/s. Such an "aether" would clearly be earth bound, as no other thing that is not earth bound moves at such small pace relative to labs on earth. Which would ask the applicability to deep space use of an effect that depends on an earth bound (or any local planetary) field to reach its nominal efficiency. What I'm saying is that, should static experiments show consistent results (we are far from that) and dynamical experiments show some kind of lowering of figure_of_merit when velocity wrt lab is higher, say for instance that figure_of_merit is shown to be always below 1/velocity (as is the case for other means of propulsion, when taking into account all the flows, see link below), then we would understand that the system is indeed unable to be used in overunity schemes, but also that it is pushing on the walls of the lab or some other nearby part, and is useless as a mean of revolutionary deepspace propulsion, where there are no walls to push on.
For the full constant velocity treatment please refer to https://forum.nasaspaceflight.com/index.php?topic=39004.msg1461319#msg1461319
To be fair, only the most extravagant claims of figure of merit in the 1N/kW range and above would make it practical to put such "power harvesting property" (of constant power constant thrust at constant velocity propellantless propulsion) in a reasonably sized box. Given the efficiencies in conversion and the difficulty to put material at 2km/s tangential speed, I guess the practicallity of such device would start with 2N/kW and above. At 5N/kW there is no question it is possible, the frustum is solid state after all (and the RF generator can be put near the axis...). With mega engineering I see a solution also to extract continuous excess power from the overunity scheme with only 0.1N/kW with two contra-rotating rings in LEO... power would have to be beamed elsewhere... don't know if it would be more economical that massive spatial solar infrastructures...
On the other hand, practical engineering and potential tremendous economic impact apart, the theoretical "problem" of the apparent over unity remains even for figures of merit as low as 4µN/kW, even though we can't really build devices with macroscopic parts approaching relativistic relative velocities needed. Thank you for reading.
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#992 by Monomorphic on 06 Apr, 2016 12:14
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Metal walls? Suggest you zoom into this image and have another look at the right side semi transparent glued on membrane and the sensor wire penetrations.
My analysis of this image is that the side walls are metal. What appears to be a wire penetrating inside the cavity is actually a reflection from outside (circled in red). Those bolts, circled in green, are highly unlikely to be screwed into clear glass or plastic. The "glue" seen everywhere is probably to keep the cryogenic fluid from penetrating into the cavity through the cracks around the bolted metal.
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#993 by SeeShells on 06 Apr, 2016 13:21
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I thought the same thing at first but what bothers me is nothing else shows up in the reflections, like wires, a bit of a conundrum.Metal walls? Suggest you zoom into this image and have another look at the right side semi transparent glued on membrane and the sensor wire penetrations.
My analysis of this image is that the side walls are metal. What appears to be a wire penetrating inside the cavity is actually a reflection from outside (circled in red). Those bolts, circled in green, are highly unlikely to be screwed into clear glass or plastic. The "glue" seen everywhere is probably to keep the cryogenic fluid from penetrating into the cavity through the cracks around the bolted metal.
Shell -
#994 by Monomorphic on 06 Apr, 2016 13:31
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I thought the same thing at first but what bothers me is nothing else shows up in the reflections, like wires, a bit of a conundrum.
I can see the reflection of the white plastic bar. I also see no evidence of internal reflections along the sharp edge of the glue. If the surface were partially transparent, there should be a faded outline.
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#995 by sghill on 06 Apr, 2016 13:37
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Why would he have a large hole in the top small plate?
Top-mounted waveguide entrance? A simple top vent that doesn't affect operation?
Looks about 20-30mm sized IMHO.
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#996 by meberbs on 06 Apr, 2016 13:43
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I thought the same thing at first but what bothers me is nothing else shows up in the reflections, like wires, a bit of a conundrum.Metal walls? Suggest you zoom into this image and have another look at the right side semi transparent glued on membrane and the sensor wire penetrations.
My analysis of this image is that the side walls are metal. What appears to be a wire penetrating inside the cavity is actually a reflection from outside (circled in red). Those bolts, circled in green, are highly unlikely to be screwed into clear glass or plastic. The "glue" seen everywhere is probably to keep the cryogenic fluid from penetrating into the cavity through the cracks around the bolted metal.
Shell
I believe the angles of the wires are deceptive in that picture. Looking closer, I believe they are much more in the foreground than the initial impression I had. There is also a reflection of a window or something in the top corner which clearly indicates that is a reflective surface.
It is worth repeating: Do not try any "missing side" frustums as part of a DIY, this is something that requires expert assistance to keep it done safely. Even the best RF engineers in the world (designing radars etc.) still end up with lots of energy going in all sorts of undesired directions. It simply would be impractical to get a reasonable Q with the amount of energy that would radiate away. You can have sidewalls with some small % loss from reflections of fields off them, or 100% loss by fields passing through a nonexistent side and radiating away. (simplified description, but it is the basic idea) -
#997 by Rodal on 06 Apr, 2016 13:44
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First, thank you for taking your valuable time and break your silence. We miss you!...
Please search for the posts by Frobnicat (preferably using "Google Advanced Search", who has thoroughly dealt with this, including frame-indifference, and the issues you discuss. Frobnicat has a lot of posts discussing this in previous threads.
OK, I'll bite. Frankly I don't get the objection. ...
ok, found this article:
http://forum.nasaspaceflight.com/index.php?topic=37438.msg1369806#msg1369806
Now I get it. Yes. I don't see this as constant acceleration for constant power in. But then even from SR I didn't see how acceleration could be constant either if mass is increasing and force is not. That's just basic SR coupled with Newton's first law. A variant of the rotating EMDrives I've also seen proposed as a perpetual motion machine was the "infinite oscillator". Two EMDrives that are cross coupled so that they oscillate in distance between them by using gravity to attract to each other, storing up the electrical energy produced by the motion induced by gravitational acceleration and then prior to collision, switching each device "on" to drive them apart until the stored electrical power is consumed and then back off again, thus completing the cycle.
Breaking my silence for once. A "over unity" scheme does not need constant acceleration with constant power, it needs constant force with constant power input. Because acceleration is relative (what you say of acceleration in SR depends on reference frame, from the spacecraft itself there is no decrease in acceleration at constant force...) there is always a great confusion with interpretation in delta kinetic energy. And a force can be applied at constant velocity, no acceleration, as in a tractor pulling a plow at constant velocity (wrt to ground), as in a turbojet thrusting for a plane moving against aerodynamic drag at constant velocity (wrt to air mass). ...
and are always thankful for your valuable contributions.
Your contributions to the Conservation of Energy problem with the EM Drive have withstood the test of time. In that sense, they are a classic in the annals of the EM Drive thread.
Yes, essentially the steady state response of a dynamical system with viscous damping and zero stiffness, as occurs for example in liquid lubrication between moving parts. A viscous force synchronous with the velocity of the object but opposite in direction to it. If such force is also proportional to the velocity, as for a simple mechanical viscous damper, the applied force F may be related to the velocity v by the equation of motion
F = m dv/dt +cv
where c is the damping coefficient, F is the applied force, m is the mass of the single degree of freedom system, v is the velocity and t is time. The constant "c" representing damping has units of newton per (meters per second). (*)
When the acceleration dv/dt times the mass m is negligible compared to the product of damping times velocity cv, we have, as you state:
F ~ cv
a force proportional to the speed.
Experimenters using a teeter-totter device with viscous damping, as some DIY people reporting in this thread, would measure such a steady-state response (if the inertial force m dv/dt becomes negligible compared to the viscous force cv, such that F ~ cv). Please note that these DIY teeter-totters have the EM Drive hanging at one end, so their teeter-totter are at least a two-degree of freedom system (teeter-totter beam rotating around pivot point and EM Drive rotating around hanging point).
There can also be friction damping and hysteretic damping in a problem. Strictly speaking, a system being acted upon by Coulomb damping is nonlinear. Under the influence of Coulomb damping, the amplitude decays linearly with a slope of ±((2μmgωn)/(πk)) where ωn is the natural frequency. As a linear approximation, one can model friction damping with an "equivalent viscous damping" F ~ cv
see: https://engineering.purdue.edu/~deadams/ME563/lecture2010.pdf
for example
The linear air track used by another DIY probably has some small frictional force that can be modeled as a coefficient of damping. I suggested to measure the coeffcient of friction by using a fine-threaded screw to lift the track at one end (starting at a perfectly horizontal inclination) such that the angle of friction (at which it starts to slide) can be measured with the EM Drive and all attendant equipment resting on the air track.
Finally, concerning the damping coefficient for aerodynamics (**), both the the coefficient of drag and the coefficient of lift play a role, in general, for arbitrary angle of attack ( the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving), see for example:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670030344.pdf
http://www.iawe.org/Proceedings/EACWE2013/E.Mattiello.pdf
The aerodynamic damping coefficient being a function of the Reynolds number, the angle of attack, the coefficient of drag, and the coefficient of lift.
_________
(*) since the stiffness k is zero, the term k*x (where x is the displacement) is zero
(**) not necessarily negligible for the forces (microNewtons to milliNewtons) that EM Drive experimenters are measuring when testing at ambient conditions instead of a partial vacuum -
#998 by rfmwguy on 06 Apr, 2016 13:44
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Why would he have a large hole in the top small plate?
30 mm is the standard hole size for magnetron injection into a consumer microwave oven.
Top-mounted waveguide entrance? A simple top vent that doesn't affect operation?
Looks about 20-30mm sized IMHO. -
#999 by Rodal on 06 Apr, 2016 13:51
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The safety warning concerning the fact that the near field behavior is very different from the far-field also applies for magnetron injection of radio frequency microwaves:Why would he have a large hole in the top small plate?
30 mm is the standard hole size for magnetron injection into a consumer microwave oven.
Top-mounted waveguide entrance? A simple top vent that doesn't affect operation?
Looks about 20-30mm sized IMHO.
(Mod note - image removed after 3rd appearance)
and there are safety standards that preclude humans being near operation of such devices without side walls at high enough power:
(Mod note - image removed after 3rd appearance)
Please be safe !
as remarked by meberbs...Even the best RF engineers in the world (designing radars etc.) still end up with lots of energy going in all sorts of undesired directions. ...
and are always thankful for your valuable contributions.