Most of the ham who like to play VHF / UHF, most like to do itself to do antenna, but more than one pair, because in the V / U segment, the antenna is very much affected by the transmission and receiving effect, and the loss of the cable is also It is very powerful, this requires antenna to have a big gain as much as possible. Who also wants to make a gain as much as possible antenna, but our most common effect is a good eight wood or HB9CV, they are directional, if they want to change the reception direction, they have to load the motor, but often missed Signals from other direction ham. What we need is an antenna that can listen to / communications 360 degrees.
The most basic full-to-directional antenna is a 1/4 wavelength of the ground antenna, its gain is 0dB, then 1/2, 5/8 wavelength (3dB), and the high gain is the FRP antenna, but they use It is still in other forms of coaxial cables, there are problems such as too long, adjusting trouble.
It can be seen in many places in many places, and it is generally reflected in good reflection. Of course I have to try.
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1. This antenna is really simple, don't look at it, it is more foldful than the J-type antenna, but it has significantly increased the mechanical strength of the antenna, which can be better upright when doing 2 meter antenna.
2. I choose the material or the principle of easy to buy, the price is cheap / light, VHF is large, with an aluminum alloy single slot, with a cross section of about 12mm, to the aluminum alloy material store to buy 3.2 meters, spend 5 yuan. (Pick a little bit)
3. Prepare 2 small crocodile clamps, soldered on one end of 50 Euro line and the network cable, and the other end is of course a plug of the transmitter.
4. In the four sizes of A / B / C / D, the two wings of the single slot are shown by the steel saw blade, and pay attention to the bottom side of the single slot.
5. A / B / C / D four points to fold back, gently clip the two wings of the saws of the saws, make it folded back, on the other side of the two wings.
6. Finally, at the notch department left 25mm, the extra single slot saws, find a diameter of about 10mm, the length of insulation is greater than 5 cm, such as the wood bar, insert the single slot at the opening, and wrap the fixed tape with insulating tape .
7. 50 Euro line with crocodile clips in the figure of the feed point X / Y, fix the antenna whole with the insulating tape, stand in the air, you can measure the standing, adjust the crocodile clip The part on the antenna makes the standing wave smallest. With friends who have a standpoint table, you can receive a signal of 145MHz, and see the S point of the receiver until the received S point is received.
8. Mon the marker at the feed point of the adjusted antenna, screw in the single slot with the two aluminum alloy, and take the feeder core / NAND to the crocodile clip, and stripped a small piece of entangle On the screw, finally tighten it. My antenna feed point, the network is connected to the bottom 75mm, and the core is at the bottom of 90 mm, and the standing wave minimum is 1.1.
9. When the antenna is erected, it cannot be fixed directly with the iron tube. First fix it on a wooden bar, and then secure the wooden rod on the iron antenna rod.
10. The reason why this antenna gain is that its radiation elevation angle is very low, approximately approximately 30 degrees of radiation angle of 5 / 8gp.
11. Try it quickly, I used this antenna and 1/4 land GP comparison to use it for a while, and I have achieved a significant effect. Harmony is in the antenna of 145MHz, and it has received it when receiving 128 aircraft signals. Thoughtful good signals.
The material should not be cut, wait for the shape, then remove the excess part.
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