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#17
November 30th 15, 12:35 AM
posted to uk.radio.amateur,rec.radio.amateur.antenna
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Follow up to Spike ;Bent dipoles?
"Paul Cummins" wrote in message
k... In article , (FranK Turner-Smith G3VKI) wrote: If the dipole is now turned vertically, the nulls would be upwards and downwards and the horizontal radiation would be omni-directional. I've not tried this, but my gut feeling is that if the elements were at right angles you would get a combination of the two radiation patterns, hence some degree of directivity in the form of a null in the direction the horizontal element was pointing. The difficulty there being that if you consider the vertical element to be a monopole, and the horizontal element to be a grpundplane, then logic says that the signal will be stronger in the direction of the horizontal element. Think magmounts on cars, for example. This is making my brain hurt, more beer required. If you fold the dipole into a 90 degree "V" The lobe within the V will be concentrated while the other lobe will be spread across 270 degrees instead of 180. This looks like a gain in the 90 degree section of about 3dB. In the case of a Band 1 TV "X" aerial this would give 3dB gain plus the reflector's contribution (if any) at ground level. In the case here, with one leg vertical, the other horizontal the major lobe would fire at 45 degrees from horizontal, with a null at ground level in the direction the horizontal element was pointed. The magmount on a car is a different proposition. Here you have a vertical radiator just above the centre of a large horizontal metal sheet, plus the vertical is normally more than a quarter wave. 5/8 wave being a figure which springs to mind. -- ;-) .. 73 de Frank Turner-Smith G3VKI - mine's a pint. .. http://turner-smith.uk |
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