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| Thread ID: 66696 | 2006-03-04 19:05:00 | Where should I point my Router Antennas? | kiwimate27 (9833) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 435455 | 2006-03-05 18:00:00 | In the olden days we used to call this "co-phasing"......is this not the whole idea of using twins? I don't think the laws of radiant energy can be or have changed for the newer frequencies, just made the application and engineering of them a little tighter and less tolerant of sloppy design/construction. We had a lot of leeway in low frequencies (11 meter, 10 meter) stuff that is not possible today. Using radiant values and solving for ¡ we often found that the distance from each antenna needed to be a value divisible by 2 of the wavelength of whatever freq we were using. ( ¡¹ ÷ þ² = r¸ ) We found that the radiated pattern was more at a right angle to the line drawn between the two antennas, and dropped off significantly to either side, or in parallel with the line drawn thru the two antennas. Actual gains in radiated pattern would go toward that "fore-to-aft" footprint at the expense of loss (or shadow) to the sides...this was assuming a good ground plane and/or mirror effect below the radiator(s) on non-ground plane effects antennas. I am assuming that in this case there is no appreciable ground plane effect and therefore loss of "off-the-top" signal..or off the tips of the antennas will probably be evident. With the mega- and giga- hertz freqs today, I can imagine that some of these antennas are pretty close to full wave or even multi-wave lengths...... Vertical polarization is probably best in this case, as you cited, whereas horizontal polarization will just cause drop-off to both ends of the radiators and make a lot of dead zones in coverage. ...just an old guy with old experiences and theories here.... -- Joe Vreeland |
SurferJoe46 (51) | ||
| 435456 | 2006-03-05 18:55:00 | Nice explanation there Billy :) OK, so all I do now is put two donuts over the antennas.... :thumbs: ;) |
Jester (13) | ||
| 435457 | 2006-03-07 02:51:00 | I was trying to keep it non-technical, Billy. I know the full clever system is called diversity. I have an idea that they don't use the full system (yet); just a couple of antennae going through a coupler to get two different path lengths for signals. (The new coming systems do use diversity). Joe: Those rubber duck antennae are each a collinear array -- probably two or three elements (to get a few dB by reducing the vertical component: flattening the doughnut). The two of them are definitely not intended to make a phased array. The object of that is to get gain from directivity. I've built big ones. Try 1.8 degree beamwidth at 26 MHz. On these boxes, it's to get more chance of getting a signal from any direction. They don't usually want horizontal directivity. When a quarter wavelength is 31 mm (for 2.4 GHz, and half that for 5GHz) it's very easy to get cancelation of signals on one antenna. Something metallic waving in the wind can cause the signal to drop out and in . |
Graham L (2) | ||
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