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20M Coil-Loaded Dipole for Limited Loft Space - Loading Coil Construction

Built a coil-loaded 20M dipole using 1.5L water bottles as forms, similar to what M3UKD documented. Started with 6m wire per element, wound 15 turns on each bottle then trimmed until analyzer showed resonance at 14.1MHz. The bottles worked perfectly as coil formers - cheap and effective.

After testing with my IC-7300, first contact was OK2AOP in Czech Republic at 808 miles running only 10W! SWR stayed flat around 1.5:1 across the entire 20M band. Anyone else experimented with different coil formers or turn ratios for loading coils?

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  • Michael Torres
    Michael Torres

    Great work! I've used similar coil loading techniques but found close-wound coils on smaller forms give better Q. Your bottles probably have more distributed capacitance than optimal. Try 4-inch PVC p

  • Excellent first homebrew antenna! I'm just getting into HF and limited by apartment constraints. What gauge wire did you use and how did you calculate the initial coil inductance? My MFJ analyzer shou

  • Lisa Chen
    Lisa Chen

    Built something similar last year - used FT-140-61 ferrite cores instead of air-wound coils. More compact and higher Q factor, though more expensive. Your setup proves that simple solutions work great

Featured Replies

Great work! I've used similar coil loading techniques but found close-wound coils on smaller forms give better Q. Your bottles probably have more distributed capacitance than optimal. Try 4-inch PVC pipe with tight windings - you'll get better efficiency and bandwidth.

Excellent first homebrew antenna! I'm just getting into HF and limited by apartment constraints. What gauge wire did you use and how did you calculate the initial coil inductance? My MFJ analyzer should help with tuning but I'd like to start closer to target.

Built something similar last year - used FT-140-61 ferrite cores instead of air-wound coils. More compact and higher Q factor, though more expensive. Your setup proves that simple solutions work great. Did you notice any bandwidth compression compared to a full-size dipole?

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