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#1
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Hello:
Have the following questions regarding the typical Sloper antenna to be used from 30 MHz on down to the broadcast bands. Listening only. Would be mounted outside (high end at the house) a. Is the most sensitive direction along the axis, or perpendicular to ? b. If along the wire axis is most sensitive, Is there a meaningful difference in sensitivity for signals originating in the direction of the low end (low point being closest to signal origination, is probably the best way I have of delineating the direction)), or vice-versa ? Is the answer freq. dependent ? Thanks, Bob |
#2
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For practical receiving purposes, a sloping wire, in the midst of
buildings, can be considered to be omi-directional, even isotropic. Any variations in directivity, in either the vertical or horizontal planes, although they exist, are not measurable or noticeable. The random effect of the presence of a nearby building or buildings is greater than the direction in which the wire may or may not slope. Sensitivity is frequency dependent. It falls of rapidly when the length of the antenna is less than 1/6th wavelength at the lowest frequency of interest. Of at least as great importance is the grounding system. With ordinary garden soil you will need at least 5 or 6 shallow buried wires under the antenna, radiating from a common point in random directions. Ground wire length need be no longer than 1/12th wavelengths at the lowest frequency of interest. Lengths and numbers are very non-critical. A sloping wire or inverted-L is the best general-purpose antenna you can get. Just erect something, not forgetting the ground. ---- Reg, G4FGQ. |
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