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On Sat, 14 Nov 2009 22:23:05 -0800 (PST), Art Unwin
wrote: Cebic found when comparing different style programs that some behaved well in certain circumstance where others did not. True. When circumstances dictate that I pay attention and I'm in a good mood, most programs behave normally. However, when circumstances are not so favorable, such as last week when I replaced my septic tank, all of the software I was using literally stunk. Fact is that most users use fractional wavelength designs, usually a half wavelength, that is not resonant at repeatable points where the area around the datum line of a sine wave is never equal when generated around a tank circuit. Last time I checked, the definition of a half wave automagically includes any external or magical factors that might change its length. For example, if you submerge the antenna under water, the increased dielectric constant will cause the half wave length to somewhat shorten. While the previous length has changed, the new shorter length is still a half wavelength. The reason for this is "voltage over shoot" which gets smaller with every cycle but never disappears. Overshoot can easily be fixed with a Cutts Compensator. http://en.wikipedia.org/wiki/Cutts_compensator Every time you cycle your antenna, the recoil tends to make the barrel climb a bit. This is the cause of the overshoot. A suitable Cutts Compensator attached opposite the feed point should help prevent overshooting the target. Thus when programs are used based on fractional wavelength radiators the results will never show 100% accountability and in fact efficiencies derived will be in the order of 92%! 95.718% of all statistics are wrong. If you're using single digit accuracy and single digit significant figures, 92% rounded off is equal to 100%. If the radiator is of a wavelength then one is not using a "fudge" figure in the calculations and then becomes possible to attain total accountability with efficiency of 100%. regardles of what type program is used. Half wave wire dipoles do tend to be resonant somewhat shorter than the free space wavelength. That's due to sales and value added tax placed on antennas by the government. You'll always come out a bit short when dealing with them. However, the last time I checked, the cut length was only about 5% shorter than the free space half-wave length. Did the antenna tax increase to 8%? If one is to use exact equations, as are Maxwell equations, then one must also use measurements that are also exact and repeatable and that is definitely not fractional wavelengths! My antennas are exact and repeatable. Not only that, I can also repeat my mistakes every time. What one gains from this aproach is that any radiator of any shape, size or elevation can provide figures in the order of 100% as long as the radiator is a multiple of a wavelength where it is resonant at exact and repeatable measurements. Perhaps. If you buy your antennas out of state or on eBay, you can avoid paying the 5% antenna length tax. However, you are required to pay Use Tax on any out of state purchases where the vendor neglected to collect the antenna tax and forward it to the Calif Franchise Tax Bored: http://www.ftb.ca.gov/current/usetax.shtml If anybody can give pointers that refute the accuracy of the above I would be very interested in hearing them Why? You haven't proven your point, demonstrated the phenomenon, or otherwise provided anything worth tearing apart. For all I know, your antennas are shorter than expected because of magic, enchantment, sloppy construction, mis-measurement, or all the aforementioned. Anyway, the problem is easily solved. Just increase your AC power line voltage about 5% and your numbers should increase by the same amount. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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