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Text File  |  1991-02-03  |  6KB  |  241 lines
  1.  
  2.  
  3.  
  4.  
  5.                   +++++++++++++++++++++++++++++++
  6.  
  7.                   TERMINATED TILTED FOLDED DIPOLE
  8.  
  9.                   +++++++++++++++++++++++++++++++
  10.  
  11. |___  /.                                                   .
  12.  
  13. |    /    .                                                .
  14.  
  15. |   /.       .                                             .
  16.  
  17. |       .       .                                          .
  18.  
  19. |          .    / *.                                       .
  20.  
  21. |             ./    / .                                    .
  22.  
  23. |              *  ./     .                                 .
  24.  
  25. |              |    .       . /                            .
  26.  
  27. |              |       .     / ___                         .
  28.  
  29. |              |          . /     |                        .
  30.  
  31. |              |           /      |                        .
  32.  
  33. |              |                  |                        .
  34.  
  35. |                                 |                        .
  36.  
  37. |                                 |                        .
  38.  
  39. |                                 |                        .
  40.  
  41. |                                 |                        .
  42.  
  43. |                                 |                        .
  44.  
  45. |                                 |                        .
  46.  
  47. -----------------------------------------------------------.
  48.  
  49.       -A-                                                  .
  50.  
  51. |___  /.<--wood support                                    .
  52.  
  53. |    /    .                                                .
  54.  
  55. |   /.       .                                             .
  56.  
  57. |       .       .                                          .
  58.  
  59. |          .    / *.<-470 ohm resistor & wood supports on  .
  60.  
  61. |             ./    / .   either side                      .
  62.  
  63. |1:10 balun -> *  ./     .    -B-                          .
  64.  
  65. |inside plastic|    .       . /                            .
  66.  
  67. |tube          |       .-C-  / ___                         .
  68.  
  69. |              |          . /     |                        .
  70.  
  71. |50 ohm coax ->|    wood-->/      | _\ angle = 30 degrees  .
  72.  
  73. |              |   support        |                        .
  74.  
  75. |                                 |                        .
  76.  
  77. |                                 |                        .
  78.  
  79. |                                 |                        .
  80.  
  81. |                                 |                        .
  82.  
  83. |                                 |                        .
  84.  
  85. |                                 |                        .
  86.  
  87.                                                            .
  88.  
  89.                                                            .
  90.  
  91. distance between A and B = in meters 100/frequency (mhz)
  92.  
  93.  
  94.  
  95. space between wires (C) in meters = 3/frequency (mhz)
  96.  
  97.  
  98.  
  99. minimum height of lowest point = approx 10 meters
  100.  
  101.  
  102.  
  103.  
  104.  
  105. PARTS:
  106.  
  107.  
  108.  
  109. antenna wire: calculated length times 2 plus 10 percent
  110.  
  111.  
  112.  
  113.              -I used #12 prestolite 2-80 M13486/1-7
  114.  
  115.               This is neoprene covered military spec used
  116.  
  117.               in airborne hf systems.
  118.  
  119.               (I had contacts with a major supplier)
  120.  
  121.  
  122.  
  123. balun: PB-9 from Palomar Engineers (619) 747 3343
  124.  
  125.  
  126.  
  127. coax: RG58CU (this has stranded center conductor)
  128.  
  129.  
  130.  
  131. pulley: large enough to seat 1/4" rope and not jump out
  132.  
  133.  
  134.  
  135. rope: 1/4" nylon rope (yellow stuff), length - 150 feet max
  136.  
  137.  
  138.  
  139. wood: 1" by 1" by 10 feet long to make end and center
  140.  
  141.       supports (broken hockey sticks work best).
  142.  
  143.  
  144.  
  145. preservative: exterior wood stain or varnish to treat
  146.  
  147.               supports
  148.  
  149.  
  150.  
  151. HINTS: 1 meter = 39.37 inches, 3.281 feet
  152.  
  153.        make wood stress relief for resistor and balun
  154.  
  155.  
  156.  
  157. The above antenna is based upon the article in the 1988
  158.  
  159. publication of the WORLD RADIO TV HANDBOOK. In the article
  160.  
  161. they used a length of 15 meters which gave good results from
  162.  
  163. 3.5 mhz to 25 mhz. In my case I reduced this to 14.2 meters
  164.  
  165. to fit my space limitations. Also the balun is a 50:450 ohm
  166.  
  167. or a 1:9 ratio, this gives a possible swr of 1.1:1, not bad
  168.  
  169. in my books.
  170.  
  171.  
  172.  
  173. A quick rule of thumb to obtain the 30 degree angle is to
  174.  
  175. take your total length and divide it by 2, the figure you
  176.  
  177. have is the height that you must go up.
  178.  
  179.  
  180.  
  181. In my set up the low end is attached to the roof. The high
  182.  
  183. end is up a large tree, secured around the trunk and down
  184.  
  185. via a pulley to ground level. This permits me to hoist it up
  186.  
  187. and down with out going up the roof or tree. The sketch
  188.  
  189. below should give you an idea.
  190.  
  191.                                                            .
  192.  
  193.                                   Pulley                   .
  194.  
  195.                                    \|/                     .
  196.  
  197.                                                            .
  198.  
  199.                             .\------*==========            .
  200.  
  201.                        .     .\     |    /|\               .
  202.  
  203.                   .     .           |   rope tied around   .
  204.  
  205.                 |-\.                |   tree trunk         .
  206.  
  207.                 |                   |                      .
  208.  
  209.                / \                  |                      .
  210.  
  211.               /   \                 |                      .
  212.  
  213.              /_____\                | <-rope 1/4" nylon    .
  214.  
  215.              |     |                |                      .
  216.  
  217.              |     |                X <-end secured to tree.
  218.  
  219.              |_____|                    via large nail     .
  220.  
  221.                                                            .
  222.  
  223.                                                            .
  224.  
  225. Some of the smaller mechanical details have been left out
  226.  
  227. and I will leave theses these to your own creativity. If you
  228.  
  229. have any queries leave me note.
  230.  
  231.  
  232.  
  233.                            Happy antenna farming
  234.  
  235.                                                .......Frank
  236.  
  237.  
  238.  
  239.  
  240.  
  241.