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On 28 Jan 2005 12:48:52 -0800, "art" wrote:
Most people have added an amplifier only to find out that the difference in signal was very small. Thus many people deride the value of a 'silly' db gain whereas DX'ers say that a single db extra is a lot ! Fact is that most long distance signals on 20 metres come in at angles of 11 degrees or less where as the 'normal' antenna has a TOA of around 14 degrees. So where a dxer points to the extra 1db gain as being everything in fact it is the lowering of the TOA that comes with the extra gain. In my opinion if one designs his antenna for a lower TOA say 10 to 11 degrees then even tho its gain may well be below the dxers choise( a very long boom or stacked antennas) the lower TOA with less gain will show little difference to the antenna of choics because the lower edge of the radiation lobe will follow the same line and any extra gain provided will have the same effect of adding an amplifier which is minimal compared to the ability of capturing signals that arrive at low angles. I believe it is time for antenna designers to concentrate less on obtaining gain and instead concentrate more on lowering the TOA. without the need of excessive real estate requirements. What say ? Art Someone correct me if I am wrong, but isn't gain derived by narrowing focussing all the energy into a more narrow path? Besides, TOA is important to the location of an antenna in respect to its relative position to the ground and the surrounding terrain. I have heard that people surrounded by mountains prefer a 1/4 whip on their cars for 2 meters and up when trying to hit repeaters due to its higher angle of radiation, but in the flat areas, the preferred antennas are the 5/8 wave etc due to its horizontal gain. Being on the side of a hill, I can't use an antenna at roof-top level with a low angel of radiation as there isn't enough power to get the signal through the miles of land mass under my neighbor's houses. I did an experiment when I first received my General license to see if I could sign into the GA SSB NTS Net. I rolled out a spool of wire on the ground approximately 1/4 wave for 3975 kc. Without a tuner I was able to get acceptable SWR and checked into the net. I wasn't the strongest signal but I did well enough to hold several QSOs. It wasn't as good as my dipole when I raised one, but it worked better than my 40 meter dipole at the time. I believe that a horizontal dipole will have about the same TOA as a vertical dipole when both are sufficiently high. However, the dipole is more bidirectional and the vertical is omni directional. Therefore the horizontal dipole may display some gain broadside over the vertical. I believe that Cecil's picture reinforces the idea that on HF especially, the TOA is largely affected by the antenna's elevation above ground. However, I was reading in CQ or QST last year about a DX operator who uses verticals near the sea and wins his contests because of his antennas. He finds the best location for his antennas near the ocean. I believe he said he had tried beams before but there is an ocean effect that makes the verticals better suited for his operations. That same vertical would be lousy for me as my house is on a hill that forms a very close valley. I used a Taylor Radio vertical years ago in this yard and it sucked. However, when I used it in Charleston and Jacksonville, it was fantastic (not near the ocean). Another DX operator suggests that most people will have a better chance of communicating with him if they use a slanted dipole pointed in the direction of their QTH. The angle of radiation and gain make it a great DX antenna. Different antennas work differently depending on their locations. I think your better question would be, what is the best antenna for my QTH and operating style? -- Buck N4PGW |
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