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Tape measure antenna with hairpin match
A few days ago I constructed a tape measure type antenna for 2 meters.
It is a 3 element beam and uses a hairpin or beta match. Ran a return loss on it with the signal generator/spectrum analizer. The best return loss was about 149 Mhz instead of 146. Thought it may be because the tape AI used was 1/2 inch wide instead of 1 inch wide. I tried lenghtning the hair pin form 5 inches to 6 inches. This did not change the frequency of the return loss to any great ammount , but the RL went from around 20 or more db to 10 db. Did a little research on the hair pin match. From what I am getting out of this, and it is very rough, is that the length of the driven element does not make much differance in the actual resonate frequency of the antenna. It is mostly where it is placed on the boom and the other elements that determin the frequency of the antenna, but the length of the driven element is determined by the impedance of the transmission line to be matched and the impedance of the antenna/driven element. Is that mostly correct or did I miss something in my reading ? |
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