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On Sat, 26 Feb 2011 07:30:00 -0800 (PST), Wimpie
wrote: Hi Wimpie, This may require another approach then you should use in a professional environment. If you prefer that, Edaboard.com (just an example) is a more suitable place. Now the result is a professional reaction of Norbert: Curious combination of conflicting sentiments, there. What is suitable, and how should we recognize it? Radiation resistance (no coupling with other objects) will be about 1 mOhm. There are many source for computation, I chose one that closely agrees with several at hand. Perhaps I made an entry error, so I will take the opportunity to examine that possibility he Rr = 80 · pi² · (dl/lambda)² 80 · 9.87 · (2/80)² 790 · (0.025)² 790 · 0.0006 0.49 Ohm Of course, the possibility of mis-entry remains, and cross checking is helpful given an in dependant validation. If I examine my text further it uses as an example a smaller loop at a lower frequency dl = 1m F = 1MHz (lambda = 300) resulting in Rr = 0.0084 Ohm which is roughly 10 times your computed radiation resistance for a larger loop at a smaller wavelength. Now, having said that, and examining my text for further possibilities of error, I find that, yes, I made an error. My computation was based for an electric dipole, not a loop. Let us examine the Rr for a loop from the equation from the same source: Rr = 320 · pi^6 · (r/Lambda)^4 320 · 961 · (1/80)^4 307,645 · 2.44^-8 0.0075 Ohm This, too, is very different from your calculation, but certainly that error is eclipsed by my own first reckoning. However, what does this say about efficiency based upon the original design (but computed for another)? However, I did first ask Norbert for the equation used and the parameters entered. Testing those results did not appear to be appealing in the face of contradicting testimonial. It should come as no surprise that many testimonials are tested here. Testimonials stand or fall in such tests, and those tests are retested (as has given rise to this and your response). Curiously we entered into this with how the loop has superior qualities over the standard dipole, and then the same loop is cited as being very inefficient. How such contradictions are held within the space of a short thread is certainly a denial of engineering professionalism, but denial is not the standard of merit that is typically lauded in this forum. A hearty defense of wounded ego raises suspicion even further. One consequence of that demurral brings us to a rather remarkable insight in comparing the radiation resistance of the electric dipole to the loop within the same spread of the loop (and in certainly a smaller volume of space). The electric dipole enjoys 60 times more radiation resistance that certainly impacts efficiency to the same degree. This, of course, presumes no further errors in computation or application. 73's Richard Clark, KB7QHC |
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