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Thanks - I guess I should have added some background I've tried top loading and it works but is unwieldy. I'm working on an variant of the St Louis vertical which does use a loading coil (at the bottom) Since this antenna starts with the assumption that a light weight portable mast will be used, a top load solution puts too much stress on the weak top whip of the pole. For example, the calculation of a top load cylinder is about 13" long by13" wide. I built on out of light weight aluminum window screen and it worked but dragged the top down. By contrast, using a length of 450 ohm ladder line, I hoped to build an easily transportable antenna with a better SWR range than the SLV. I'm iterating on the solution but still looking for some analytic approach. Tom W2TER Back to my "Yuri Blanarovich" wrote in message ... Does anyone have a good source for calculating the length of linear loads for a shortened 40 meter Vertical? I'm experimenting with a 20' vertical and a pair of 10' parallel lines moved the resonant point near the 7 Mhz band. Any suggestions? More elegant and efficient solution is to use loading coil placed abour 2/3 up the radiator. Best is to use top loading with hat or wire. Yuri, K3BU |
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