Right with the ham that likes to play VHF/UHF for, great majority likes him to make aerial, and more than a pair two pairs, because be in V/U paragraph, aerial stand or fall is very big to sending and receive the influence of the effect, and the loss of cable is very fierce also, this should have generous gain with respect to need antenna.
Everybody wants to do gain to use up generous antenna, but our commonnest result is good not belong to 8 wood or HB9CV, they are tropism of in the right way, want to change the sentence that receives direction at will, still rotate so that install electric machinery, but the signal that often still missed ham of other and different way to be sent. What we need is can 360 degrees all-around monitor / the antenna of communication.
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The basiccest omnidirectional antenna is the earth mat antenna of 1/4 wavelengh, its gain is 0DB, it is 1/2 again, 5/8 wavelengh (3DB) , still have gain tall is antenna of glass reinforced plastics, but they are the other still form that makes with coaxial cable no matter, put in dimension to grow too, adjust the problem such as the trouble.
A lot of places can see those who have introductory SLIMJIM antenna recently, general report is favorable, I should try of course.
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1. this antenna is very simple really, do not see it even more than J antenna retrace a paragraph, but the mechanical strength that increased aerial apparently, OK when making line of 2 meters of Duan Tian better erect.
My choosing material still acts on 2. to be bought easily, low-cost / light principle, VHF because size is large, with aluminium alloy odd chamfer, sectional make an appointment with 12mm, buy 3.2 meters to inn of aluminium alloy material enough, cost 5 yuan. (pick a bit thicker material)
3. prepares 2 small crocodilian mix, respectively solder is on the core line of one aspect of the matter of 50 Europe line and reticle, another end is the plug that receives catapult of course.
4. is in A/B/C/D 4 dimension ministry, the saw blade that use steel the both wings saw kerf odd chamfer, the attention cannot curium the hemline of odd chamfer.
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5.A/B/C/D wants the place of retrace 4 times, curium seam among them at the same time both wings takes forceps to be placed gently, make when retrace, at the same time the ala buckles two wings that take across in.
6. leaves 25mm in breach ministry finally, curium redundant odd chamfer take out, look for a paragraph of diameter to make an appointment with 10mm, length is more than the insulating material of 5CM, be like batten, buckle the odd chamfer that is in into mouth end in, twine with insulating tape fixed.
The 50 Europe line that 7. takes crocodilian clip is placed in the feed in the graph to nod X/Y, secure aerial whole on club of a wood with insulating tape, stand in relatively hollowness place, can measure standing wave, adjust crocodile to be placed in day on-line place, make standing wave the smallest. Without the friend that standing wave expresses, can use the method that receives signal, receive 145MHZ around signal, see the S drop of receiver, nod till reception S most.
8. is adjusting the feed point point of good antenna to make mark, use from result screw with two aluminium alloy in the pigheaded chamfer that present sheet, at the same time the core line of make a present of / crocodile of upright take out places the network, pare one paragraph small is twined going up from result screw, screw finally, good. My aerial feed is nodded, the net is received in the distance bottom 75mm is in, core is received when be apart from bottom 90mm to be in, measure standing wave is the smalliest for 1.1.
When 9. antenna erect, cannot secure directly with iron pipe, secure first go up in club of a paragraph of wood, secure wooden club on the aerial lever of iron again.
The radiation angle of elevation that the reason with tall gain of 10. this antenna is it is very low, approach a level about, and the radiation angle of elevation of 5/8GP is 30 degrees about.
11. tries at once, I use this antenna that has made and GP of 1/4 earth mat a little while to compare, obtained apparent effect. Resonance is in this antenna of 145MHZ, also got the good signal that expect is less than when receiving the 128 plane signal around.
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Data is not cut good first, wait after breaking good figure, again take out of will spare part. |
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