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Balanced from unbalanced via a 100 ohm Q section - followup
Someone asked me how this antenna worked after I had built the Q section
from two pieces of 50r coax side by side, using the centre conductors as an open wire feeder equivalent. The shields being joined at each end but nowhere else.. (There should be grounded at the bottom end and at some neutral point at the top - if any) The antenna is a almost equilateral triangular shaped single quad loop with base/feed about 4 metres off the ground. The "almost" being the horizontal/top section is about 8 metres in length. Well it works! I dont have enough of a power supply at the moment for doing any extensive on air tests. VSWR was 1.4:1 without much excursion at the band edges. This is what 4NEC2 said it would be. In fact I didnt have to cut it after following the modelled dimensions. It was surprisingly wide band I guess from the higher feed Z (rather than using a single 75r section) I have only just moved here and there is a lot of noise about at various times of the day. (S7-9) I have heard stations across the US and maybe some Spanish speaking. Waiting for a PSU to arrive so I can try a little harder. I didnt notice any VSWR changes or a change in feedline radiation (through PC/stereo spkrs etc) by coiling the coax at the base of the Q section. Indeed I did it because I was at risk getting tangled in the coax going to the trash can! I expect high radiation angles BTW. Cheers Bob W5/VK2YQA East Texas. |
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