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+ | ====== New Antenna for VK3RWO ====== | ||
+ | Ever since the VK3RWO repeater was installed it has had a VHF High band antenna for the 2M radio. | ||
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+ | Whilst this antenna has been performing OK, with the help of Dion, VK7DB I set about manufacturing a new 2M antenna for exactly 146.975Mhz. | ||
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+ | The antenna I started with was a 70 – 85Mhz antenna. | ||
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+ | Dion has a great experience in using MMANA-GAL modeling software. | ||
+ | The answer given was that I needed an end to end of 934mm. | ||
+ | The top element was to come down to the centre line, and the bottom element was to stop short of the centre line by 20mm. | ||
+ | {{ : | ||
+ | Photo 1: Cutting all complete…. | ||
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+ | The next hardest part was matching the antenna. | ||
+ | As we use 50 Ohms to the radio, and a Dipole is 292 Ohms (4 x 73ohm), a matching stub is needed. | ||
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+ | So an electrical quarter wavelength of 120.8 Ohm coax is needed. | ||
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+ | So. I needed a piece of RG63 that is 428mm long. | ||
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+ | Fortunately, | ||
+ | {{: | ||
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+ | Photo 2: The screen of the AA-1000 | ||
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+ | So after finding the correct length, I had to thread it back into the dipole and attach the braid to the top element and the centre conductor to the bottom element | ||
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+ | {{ : | ||
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+ | Photo 3: The terminating of the coax. | ||
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+ | So after gluing a piece of pvc pipe over the termination point and covering it in heavy walled heatshrink (it also has glue in it), it was time for a test. | ||
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+ | {{: | ||
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+ | Photos 4 and 5: Screen shots of the AA-1000 showing the resonance of the antenna. | ||
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+ | Now All I have to do is take the antenna up the hill and install it onto the repeater. | ||
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+ | {{ : | ||
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+ | Photo 6: The finished product. |