27 lines
1.9 KiB
Plaintext
27 lines
1.9 KiB
Plaintext
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Do you have an old (or new) VHF/UHF TV yagi you'd like to put to a little more
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exciting use than TV reception? That antenna could be converted for scanner
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use with out too much trouble, and also be used to transmit 2 meter Amateur
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Radio. The un-modified antenna could be used without modification, but images
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and signal overload from TV broadcasters could be a problem. With the
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elements of the antenna unfolded to their normally extended positions, mark the
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longest elements (the hindmost elements) with a felt tip marker 21" from the
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boom, and the shortest elements (the foremost elements) at 16&1/2" from the
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boom. This should be done on both sides of the boom. After marking them, tie a
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string snugly from the mark on the rear boom to the mark on the fron boom as a
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cutting guide. Mark the remaining elements where the string touches them.
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Carefully cut off the excess lengths at the marks. The corner reflector (UHF)
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is modified as follows. Measure and cutoff all the corner reflector elements to
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16" lengths (total length). Saw off the boom directly in front of the closest
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element to the corner reflector (ie. leave one of the elements that is attached
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directly to the boom). This element will be the one connected to the feed line.
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The conversion is now complete. Determine the new center of gravity and drill
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a couple of new mounting holes. Remember that the antenna will be mounted 90
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degrees from its normally horizontal polarization, so that the elements are
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oriented vertically. If you can, feed the antenna with RG-8U. The antenna will
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need a 300 ohm feed, so a proper transformer will be required at the feed
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point. The antenna should be mounted on a 3' length of PVC pipe to prevent the
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mast from interacting with the elements. Although the antenna will exhibit gain
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and directivity at VHF and UHF, do not expect much in the 30-50 Mhz range. Good
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Luck!
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