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## Re: [TowerTalk] Funniest thing I've seen in weeks

 To: "Joe Subich, K4IK" Re: [TowerTalk] Funniest thing I've seen in weeks "Tom Rauch" Tom Rauch Wed, 30 Jun 2004 18:12:07 -0400
 ```> This would be true for ALL arrays.. the performance is proportional to the > aperture. Yagi-Udas just happen to be end fire arrays where the aperture > is in the same direction as the preferred propagation direction. There are > some subtleties in superdirective arrays, but, as you say, directivity/gain The electrical aperture or performance is NOT defined by the physical area an antenna occupies. The electrical aperture is defined only by gain and frequency, that's why it is more correctly called the *effective* aperture. For example, a Rhombic occupying an area of several wavelengths with 10dBd gain has the same effective aperture as a 10dBd Yagi occupying less than a wavelength on the same frequency. A longwire 20 wavelengths long can have less effective aperture than a dipole. When you throw a resistor in a given antenna, the electrical aperture decreases. I've noticed over the years many people think physical area makes an antenna more effective at receiving. The verbiage is something to the effect of "it's a darned good receiving antenna because it has a large capture area". That would only be true for size if you are talking about the antenna catching the wind, not radio signals. The capture area or effective aperture not only NOT determined by physical size, gain or effective aperture does not determine receiving S/N at HF. Directivity sets receiving ability, until efficiency is so low the receiver is no longer limited by external noise. It's the gain on transmitting and the directivity on receiving that matters, not the size. This is actually pretty important, because MANY people think 7dB of additional antenna gain improves the receiving and transmitting 7dB. The actual receiving change can be anything from zero to dozens of dB. If for example you have a 15 meter Yagi with 3dB of feedline loss and improve system gain 2dB by replacing the feedline, the receive S/N will remain the same. 73 Tom _______________________________________________ See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread [TowerTalk] Funniest thing I've seen in weeks, W0UN -- John Brosnahan Re: [TowerTalk] Funniest thing I've seen in weeks, Al Williams Re: [TowerTalk] Funniest thing I've seen in weeks, Jim Lux Message not availableRE: [TowerTalk] Funniest thing I've seen in weeks, Jim Lux Re: [TowerTalk] Funniest thing I've seen in weeks, Tom Rauch <= Re: [TowerTalk] Funniest thing I've seen in weeks, Jim Lux RE: [TowerTalk] Funniest thing I've seen in weeks, Keith Dutson Re: [TowerTalk] Funniest thing I've seen in weeks, GALE STEWARD Re: [TowerTalk] Funniest thing I've seen in weeks, Robert Shohet RE: [TowerTalk] Funniest thing I've seen in weeks, Keith Dutson