And like to play on the VHF / UHF ham, most prefer to do their own antenna system, and more than a two, because the V / U section, good or bad for the transceiver antenna effect is very large, and also the cable loss very powerful, which requires the antenna to have the largest possible gain.
Who wants to gain the largest possible antenna, but we must go to the most common effect of a good Yagi or HB9CV, which is directional, in order to randomly change the direction of the receiver, then had to install rotary motors, but still often miss the other in different directions ham sent signal. What we need is a 360-degree monitor / communications antenna.
The most basic omnidirectional antenna is 1 / 4 wavelength ground network antenna, its gain is 0DB, then there are 1 / 2, 5 / 8 wavelength (3DB), there is a high gain antenna fiberglass, but they both use coaxial cable or other forms of doing, there size is too long, adjust the trouble and other issues.
Recently there are many places you can see the introduction SLIMJIM antenna, generally well received, I must try.
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----==== Making ====----
1 This antenna is really very simple, though it is even more than the J antenna retrace period, but significantly increased the mechanical strength of the antenna, making 2 m section of the vertical antenna can be better.
(2) I chose to purchase materials or the spirit of easy, cheap / light principle, VHF because of large size, single-slot aluminum alloy, cross-section of about 12mm, to the store to buy 3.2 m aluminum material enough to spend $ 5. (Pick a bit thick material)
3 Prepare two small alligator clips were welded at one end of the 50 Au wire and the wire, then of course the other side of the transmitter plugs.
4 in the A / B / C / D Department of four dimensions, the two wings of steel saw blade to saw kerf slot, be careful not to saw off the bottom slot.
5.A/B/C/D four to retrace the site, the sawing of joints of the wings to take one side of the pliers gently clip this, so turn back, the side of the wing into the buckle on the other side of the wing in two.
6 Finally, the Ministry of the gap left 25mm, to remove the extra slot sawing, to find a diameter of about 10mm, length greater than 5CM insulation materials such as wood, buckle at the open end into the slot, the use of insulating tape winding fixed.
7 in Europe with alligator clips 50 clip in the diagram feed point X / Y, the whole antenna with insulating tape fixed on a wooden stick, and stand in a relatively open area, standing waves can be measured, and adjust the alligator clip at the antenna site, making the standing wave minimum. no friends standing wave form, the method can be used to receive the signal, reception 145MHz near the signal, look at the S point of the receiver until the receiver up to the S point.
8 In the adjusted antenna feed point marking, aluminum alloy with two self-tapping screws screwed into the slot where, while the feeder core / net-side to remove alligator clips, cut short in the self-winding tapping screws, the last tightening, like my antenna feed point, network access at a distance of 75mm at the bottom, then the core at a distance of 90mm at the bottom, the measured standing wave minimum is 1.1.
9 antenna set up, can not be directly fixed iron pipe, the first fixed on a stick, then stick the antenna fixed to the iron rod.
10 This high gain antenna radiation because it is very low elevation, about close to the level of radiation and 5/8GP elevation of about 30 degrees.
11 quickly try, I used the moment to do a good job of this antenna and 1 / 4 compared to net GP, and achieved remarkable results. Resonance of the antenna at 145MHZ, 128 in the vicinity of the aircraft received signal is also received Italy think of a good signal.
please Click hereto get our dipole antenna
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