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#2
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In article ,
Jim Thompson wrote: [....] But I vaguely recall a 5/8 wavelength antenna that had a good low-angle pattern. Unfortunately, the OP (is he still here?) was stuck with a box to short to even fit a 1/4 wave whip. I also think that this box could not be assumed to be resting on the ground If you squint at the ASCII art below, you will see more or less the radiation pattern of a 5/8 whip over a large ground plain. ................................. .................!............... ...........******!*****.......... ..........*......!......*........ ..........*......!......*........ ...........****..!..****...A..... ........*******..!..*******...... .....***.........!.........***... ...*.............!.............*B ******************************** If you don't have a large enough ground plain, the notch in the side labeled "A" starts to go away and the peak at "B" reduces. -- -- forging knowledge |
#3
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On Sun, 27 Feb 2005 17:52:52 +0000 (UTC),
(Ken Smith) wrote: In article , Jim Thompson wrote: [....] But I vaguely recall a 5/8 wavelength antenna that had a good low-angle pattern. Unfortunately, the OP (is he still here?) was stuck with a box to short to even fit a 1/4 wave whip. I also think that this box could not be assumed to be resting on the ground If you squint at the ASCII art below, you will see more or less the radiation pattern of a 5/8 whip over a large ground plain. ................................ ................!............... ..........******!*****.......... .........*......!......*........ .........*......!......*........ ..........****..!..****...A..... .......*******..!..*******...... ....***.........!.........***... ..*.............!.............*B ******************************** If you don't have a large enough ground plain, the notch in the side labeled "A" starts to go away and the peak at "B" reduces. -- The rain in Spain falls mainly on the plain ;-) ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice ![]() | E-mail Address at Website Fax ![]() | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
#4
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Still here, not quite sure who to believe, but enjoying the ride :-)
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#6
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Richard Clark wrote:
No amount of armchair philosophies about Thevenin's theorem will replace that loss. Thevenin's is a linear theorem. Large signal devices are not linear. (Hey, maybe triodes are, but I don't use them for PA's.) There is no armchair philosophy about Thevenin's theorem because it does not apply in the RF PA situation. Your's is a red herring. |
#7
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On Sun, 27 Feb 2005 10:16:19 -0700, Jim Thompson wrote:
On Sun, 27 Feb 2005 17:08:23 +0000 (UTC), (Ken Smith) wrote: In article , Cecil Moore wrote: Ken Smith wrote: At the point where it fails, the output goes to zero, I assume. If so, wouldn't that be the impedance as I've been defining it. Is an amp that fails at one minute with 100w FM better matched than an amp that fails at two minutes with 100w CW? No, you've got the concept backwards. Obviously the worst matched is the 1 o=minute case, next would be the 2 minute case and so on up to one which runs for about its MTBF at the connected load. This last case would likely be the one the designer was targeting. -- It's been thirty years since I "hammed". I was only interested in the electronics, not the talking, so I dropped out after I got a homemade solid-state 2-meter rig running. I did the same after putting together a HF setup. The electronics was fun, but the chirping was booorrring. But I vaguely recall a 5/8 wavelength antenna that had a good low-angle pattern. I didn't know the height affected the pattern that much. IIRC 5/8 wavelength seems to be what the AM stations around here. Though they'd load up a barn if it worked. -- Keith |
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