All accessories are sourced from Taobao.
1. Aluminum tubing with an outer diameter of 8mm and an inner diameter of 6mm, priced at 17.5 yuan per 5 meters. The vendor ships the tubing in a coiled form approximately 250mm long, which needs to be straightened by the buyer. It won't be perfectly straight until the final product is made...
2) Two 20pF adjustable capacitors, only need one, for 2 yuan.
3. Aluminum strip, 1.2x20mm, 1 meter, only needing 10cm, 5 yuan.
4、Grippers, 6-12mm, 8 pieces, only need 1 piece, 7.6 yuan.
5. Cigarette holder head, 1.5, 1 piece, 10.2 yuan.
6. PVC pipe, 20mm diameter, 1.5 meters, at 2.94 yuan + 3 yuan shipping fee.
7、One 4x50mm screw and nut. 20mm PVC Ohm card, some zip ties. 5mm heat shrink tubing, 20mm. Some hot melt glue, not purchased, in stock.
Total of 48.24 yuan/RMB
Dimensions:
Power supply box connection method
Details of the power supply box
Bend an aluminum sheet at a 90-degree angle, and install the pipe head on one end. Calculate the distance between the power supply unit and the short circuit unit to be approximately 15mm. The short circuit unit should be about 100mm long.
On the other side of the aluminum sheet, drill two small holes and use self-tapping screws to fix it to the PVC pipe.
The end of the cigarette holder's lead wire is slightly smaller than the inner diameter of the aluminum tube, allowing two layers of heat shrink tubing to be neatly wrapped around it. The short circuit unit can then be securely attached on top.
In the short circuit unit, a small hole is drilled on one end. A section of insulated wire with a core is then inserted, and both ends are soldered: one to the cigarette head core, and the other to an adjustable capacitor. The other end of the adjustable capacitor is fixed to the short circuit unit using a clamp.
Use a 100mm aluminum sheet, shape it to resemble the image, drill a hole in the center, and create a shorting bar.
The power supply unit is pressed against the aluminum sheet, directly shorting out the mouthpiece and the power supply unit, eliminating the need for wiring.
Adjustment:
When adjusting, it's best to keep the feed line as far away from each unit as possible, otherwise it will affect the standing wave.
After assembly, simply adjust the shorting bar to the minimum resonant frequency, whether it's 2.0 or 3.0. As long as it's the current minimum, any offset in the center frequency is acceptable.
Once the shorting rod is properly installed, if the standing wave pattern is not ideal, increase the distance between the reflector and the feed unit. Regardless of how much the standing wave decreases, adjust it to the lowest possible value.
If the standing wave is still large, adjust (typically by shortening) the distance between the first unit facing the feed and the output unit until the minimum standing wave is achieved.
If the standing wave remains large, adjust (typically by shortening) the distance between the second and first inductive elements until the standing wave is minimized.
Currently, the entire wave's standing wave length is generally below 1.2.
Then, adjust the remaining references to match the distances specified on the drawing.
Vertical mounting, corresponding to U-segment vertical polarization.
When comparing to a previous setup using 2.8mm wire and directly soldering the feedline, with a 9-element Yagi antenna receiving the same signal from the same repeater, there was an increase of approximately 9 dBm in the received signal strength.
The signal strength has also improved significantly in both directions. The strongest signal is directed towards the unit's pointing direction.
Disadvantages:
1、Poor water resistance. The current solution I'm considering is to put a plastic bag around the power supply unit.
2. The PVC pipe is too flexible, and there is a visible bend when supported at the center point. In hot summer weather, it may become even more bent.
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