Quote from: deltaMass on 08/02/2015 08:27 am@The Traveller: For the 3rd time, can you tell me the meaning of the y and x axes here, and the units usedApologised, didn't see the other requests.The bottom x axis are the 0.5 units of the black marks on the table the pointer moved over. To gen more data points I estimated when the pointer was midway between the major black marks. The upper y axis are seconds as I frame by frame stepped the video.
@The Traveller: For the 3rd time, can you tell me the meaning of the y and x axes here, and the units used
Quote from: TheTraveller on 08/02/2015 08:40 amQuote from: deltaMass on 08/02/2015 08:27 am@The Traveller: For the 3rd time, can you tell me the meaning of the y and x axes here, and the units usedApologised, didn't see the other requests.The bottom x axis are the 0.5 units of the black marks on the table the pointer moved over. To gen more data points I estimated when the pointer was midway between the major black marks. The upper y axis are seconds as I frame by frame stepped the video.Please confirm: the vertical (y) axis is time in seconds? (so max about 120 secs)the horizontal (x) axis is distance in tick marks? (so max about 31 marks)
Quote from: deltaMass on 08/02/2015 08:44 amQuote from: TheTraveller on 08/02/2015 08:40 amQuote from: deltaMass on 08/02/2015 08:27 am@The Traveller: For the 3rd time, can you tell me the meaning of the y and x axes here, and the units usedApologised, didn't see the other requests.The bottom x axis are the 0.5 units of the black marks on the table the pointer moved over. To gen more data points I estimated when the pointer was midway between the major black marks. The upper y axis are seconds as I frame by frame stepped the video.Please confirm: the vertical (y) axis is time in seconds? (so max about 120 secs)the horizontal (x) axis is distance in tick marks? (so max about 31 marks)My bad incorrect quote. Went back and checked the calcs. Have edited the post.
Quote from: deltaMass on 08/02/2015 08:44 amQuote from: TheTraveller on 08/02/2015 08:40 amQuote from: deltaMass on 08/02/2015 08:27 am@The Traveller: For the 3rd time, can you tell me the meaning of the y and x axes here, and the units usedApologised, didn't see the other requests.The bottom x axis are the 0.5 units of the black marks on the table the pointer moved over. To gen more data points I estimated when the pointer was midway between the major black marks. The upper y axis are seconds as I frame by frame stepped the video.Please confirm: the vertical (y) axis is time in seconds? (so max about 120 secs)the horizontal (x) axis is distance in tick marks? (so max about 31 marks)I need to review that chart. Did it when was almost asleep and after a big pain pill. Will do so tomorrow and do the whole sequence as having an early night. Have deleted my earlier reply as it is probably not correct.
Quote from: flux_capacitor on 08/01/2015 03:13 pmYang's frustum has the following dimensions:- cavity length (m): 0.24- big diameter (m): 0.201- small diameter (m): 0.1492In particular, the big end is smaller than the height, not larger.There is no resonance I can find for those dimensions at 2.45GHz. Can get TE012 resonance at 2.51GHz
Yang's frustum has the following dimensions:- cavity length (m): 0.24- big diameter (m): 0.201- small diameter (m): 0.1492In particular, the big end is smaller than the height, not larger.
Db = 0.247 m Ds = 0.114425 m L = 0.24 mr1= 0.211022 mr2= 0.455515 mCone half-angle = 15.44 degrees
Quote from: rfmwguy on 08/02/2015 02:07 amNSF-1701 3rd static temp test video. I learned the IR gun is not useful at 3 feet. Also the quick drop of temp when mag cycles off is false reading. Regardless, saw some interesting arcing at full power at 1 minute duration. Frustum itself remained at low temp. Mag went to about 160°C.Digital cameras can be modified to record in the IR spectrum. http://www.lifepixel.com/ IR is normally filtered out so that you can't go peaking under peoples clothes.
NSF-1701 3rd static temp test video. I learned the IR gun is not useful at 3 feet. Also the quick drop of temp when mag cycles off is false reading. Regardless, saw some interesting arcing at full power at 1 minute duration. Frustum itself remained at low temp. Mag went to about 160°C.
Hmmmm.. can I throw a brick? Been thinking about the findings of yesterday, while there is still something that is bothering me...What is nice to see is that dr. Rodal's calculations do also match the graphical recreation i've made of the obtained results. So that confirms for me that the way to calculate the dimensions is most likely a correct one.What keeps bothering me is the starting values as the calculations do not take the top/bottom cylindrical parts of the cavity into calculation. Consequently, the half cone angle obtained from the drawing is not the one that is calculated.So.. I've adapted the YANG drawing further to match the calculation method better. What's needed is the angle going from top to bottom, without consideration of cylindrical parts.I've redone the drawing and added the new half cone angle : 10.8°I do not know if the good doctor would like to check the new angle and see if that would match better or worse ?
Shawyer's frustum design rules are:1) Small end to be as small as possible to have cutoff just below it's guide wavelength. For TE01 mode and 2.45GHz the min small in diameter, in air, is 148.7m diameter. As you can see the Prof Yang small end diameter at 149.2mm is 0.5mm bigger than the minimum. That gives the frustum a bit of breathing room if the external freq needs to increase for tracking or a wide magnetron output bandwidth.
weekly interactive particleyou can't go peaking under peoples clothes.Sometimes poor spelling is an advantage
Quote from: TheTraveller on 08/02/2015 07:44 amQuote from: flux_capacitor on 08/01/2015 03:13 pmYang's frustum has the following dimensions:- cavity length (m): 0.24- big diameter (m): 0.201- small diameter (m): 0.1492In particular, the big end is smaller than the height, not larger.There is no resonance I can find for those dimensions at 2.45GHz. Can get TE012 resonance at 2.51GHzThey were surely wrong dimensions, based on the assumption Yang's drawings had the correct proportions. ..
Quote from: TheTraveller on 08/02/2015 07:44 amShawyer's frustum design rules are:1) Small end to be as small as possible to have cutoff just below it's guide wavelength. For TE01 mode and 2.45GHz the min small in diameter, in air, is 148.7m diameter. As you can see the Prof Yang small end diameter at 149.2mm is 0.5mm bigger than the minimum. That gives the frustum a bit of breathing room if the external freq needs to increase for tracking or a wide magnetron output bandwidth.Yes, that is Shawyer's rule.But it makes no sense.It has been known for over 2 decades that "Due to the absence of sharp cut-off frequencies ..., the interior of the frustum can support nontrivial field amplitudes, even in regions of relatively small electrical cross section"Electromagnetic plane wave excitation of an open-ended conducting frustum, IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 42, NO. 5, MAY 1994. 699I also have attached Doctor Rodal's report on the matter that should make your mind once and for all, as it is made obvious that truncated cones show an absence of sharp cut-off frequencies and that continuing the cone beyond the small diameter at which cut-off would occur (according to the cylindrical formula with is inapplicable to the cone) leads to significantly higher amplitudes of the electromagnetic fields.To everyone reading this, don't take Shawyer's rules as actual rules. Take them with a pinch of salt and research before trusting what he says.This particular rule, which is nonsensical, has hindered development, because people wouldn't test lower small diameters (which are good) just because Shawyer claimed without any basis that it wouldn't work.
Quote from: TheTraveller on 08/02/2015 07:44 amQuote from: flux_capacitor on 08/01/2015 03:13 pmYang's frustum has the following dimensions:- cavity length (m): 0.24- big diameter (m): 0.201- small diameter (m): 0.1492In particular, the big end is smaller than the height, not larger.There is no resonance I can find for those dimensions at 2.45GHz. Can get TE012 resonance at 2.51GHzThey were surely wrong dimensions, based on the assumption Yang's drawings had the correct proportions. But what is your analysis of Rodal's revised numbers for Yang's frustum having TE012 resonance at 2.45 GHz:Quote from: Rodal on 08/01/2015 10:20 pmDb = 0.247 m Ds = 0.114425 m L = 0.24 mr1= 0.211022 mr2= 0.455515 mCone half-angle = 15.44 degreesAccording to you, the cutoff dimension, just below the guide wavelength for TE01 mode at 2.45GHz = 148.7 mmBut Rodal's small end for Yang's frustum is now at 114.42 mm. Your advice?
...But please yourself and ignore microwave industry practice, Shawyer & Prof Yang.
Quote from: flux_capacitor on 08/02/2015 10:18 amQuote from: TheTraveller on 08/02/2015 07:44 amQuote from: flux_capacitor on 08/01/2015 03:13 pmYang's frustum has the following dimensions:- cavity length (m): 0.24- big diameter (m): 0.201- small diameter (m): 0.1492In particular, the big end is smaller than the height, not larger.There is no resonance I can find for those dimensions at 2.45GHz. Can get TE012 resonance at 2.51GHzThey were surely wrong dimensions, based on the assumption Yang's drawings had the correct proportions. ..No, they were the dimensions that I had correctly based on the assumption that the small diameter for Yang was obtained based on the cut-off condition for the small end. And TheTraveller's calculation actually confirms it:<<There is no resonance I can find for those dimensions at 2.45GHz. Can get TE012 resonance at 2.51GHz>>The 2% difference between 2.45 GHz and 2.51 GHz is completely and utterly negligible compared to the other differences we are talking about: compared to the difference between 6 degrees and 15 degrees for the cone half-angle or compared to the uncertainties in having to eyeball the dimensionless ratio equations from Yang's chart.On top of that, the result TE012 resonance at 2.51GHz is obtained by TheTraveller from an Excel spreadsheet using very simplified ad-hoc approximate formulas that do not respect the boundary conditions of the problem while the solution for TE012 2.45GHz resonance uses Wolfram Mathematica to solve the exact solution to the problem using Legendre Associated Functions and Spherical Bessel functions.Taking into account the above considerations, the 2% different ad-hoc TE012 resonance at 2.51GHz means a complete agreement with the dimensions provided, because the 2% difference is completely within bounds.___________________________________________The issue at hand (determination of Yang's geometry) has to do with whether L=24cm provided by Yang in her paper is correct, and if so, whether the other (one and only one available to choose) parameter to consider should be the small diameter (based on cut-off), or the cone half-angle (determined from drawings), or some other parameter like D/L (determined from drawings), etc.One cannot obtain dimensions from Yang's schematic drawings, one can only obtain dimensionless ratios: angles and ratios, that's it.For L=24 cm and f=2.45 GHz, you cannot satisfy both that the diameter of the small base be above cut-off for an open waveguide AND satisfy the cone half-angle from Yang's drawings . They are in violent conflict with each other. Something got's to give. This has to be clearly understood: we have mathematical relations to satisfy here, they are mathematical constraints. You cannot satisfy all the dimensionless ratios from Yang's drawings and simultaneously satisfy the cut-off condition at the small end and simultaneously satisfy L=24 cm and simultaneously satisfy the D/L vs frequency relation.
...I'd like to insert one other thing here as well, having been in the middle of this as one of the builders. First I understand the why of your calculations and how you arrived at them. Numbers don't lie, but liars and the deceiving will number. That said I think we need to at least make sure that the cone angle for Yang's frustum is correct, better than just taking it off of Yang's drawings which have been proven to be not quite accurate. How do we know that the drawing wasn't modified to fit the page ie: shortening or lengthening the image changing the cone angle? How can we even know who drew this and in what program? PCPaint? The answer is, we truly cant. That throw the angles and ratios under question as well.Unless you are aware of a designed numerical conditions and guides that promotes this anonymously vague thing called thrust (don't think any here are) we still are poking the bear in the dark. How can I design something to optimize thrust when we don't even know what causes it and then throw in the misleading facts and figures from other builders and we have a real corundum on our hands. (ack, Shell runs screaming into the woods here) Numbers don't lie, but confusion in reported numbers or intentional misreporting of them makes for bad designing.I'm not going to throw bricks or mash up my frustum with it but I have much to do in the building of the test stand and I'm gonna sortta float for awhile seeing if better numbers come forth.Shell
Quote from: leomillert on 08/02/2015 12:48 pmQuote from: TheTraveller on 08/02/2015 07:44 amShawyers claim is not without basis, it is based on microwave industry experience. A waveguide operated below cutoff will not propagate an EM wave. If the small end operates below cutoff there is no EM wave to bounce off the small end, then the big end, then the small end, then the big end, etc.But please yourself and ignore microwave industry practice, Shawyer & Prof Yang.
Quote from: TheTraveller on 08/02/2015 07:44 am