Linear-Loaded Multi-Band Fan Dipole

by Johan
(Cape Town, South Africa)

Basic configuration of a multiband fan dipole (Source: VE2RMP.org)

Basic configuration of a multiband fan dipole (Source: VE2RMP.org)

Good day Claude. I am in Cape Town, South Africa and I have come across your interesting and informative subject of "Short Ham Antennas for HF With Linear Loading". I have typical space constraints and I am keen to try this design in my roof. There is just one aspect that I am not sure about: is there an ideal or recommended space between the top and bottom element? I was also wondering if this design could be "clustered / stacked" to create a fan dipole / multi-band option? I am considering those lovely e-books that you have. Thank you for your service to amateur radio. Regards, Johan.

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by: Claude - VE2DPE

Thank you for the kind words about my website. They are very much appreciated.

I used 450 ohm ladder line to experiment with linear-loaded dipoles on HF. The space between conductors is about 3/4 in. This allows enough capacitance to reduce the overall length (wing span) of the dipole to something "manageable." Also, ladder-line ensures a uniform distance between conductors, making the capacitance equal all along the entire length of each side of the dipole.

On the other hand, if you decide to use single wires, you will likely end up with a wider and irregular distance between the wires where, "wider distance" will mean less capacitance resulting in a longer dipole wing span... and unequal capacitance on each side of the feedpoint resulting (electrically) in an off-center fed dipole!

Yes, it’s possible to make a multi-band "fan dipole" using the linear loading technique for each band (the 15-meter band can be skipped because it will be covered by the third harmonic of the 40-meter dipole). The presence of other antennas in the immediate field of the 40-meter linear-loaded dipole will likely detune it a little. You might have to adjust its length to bring it back to where you want it to resonate. You will have to experiment and it will involve some "trial & error" work but, it's a feasible scenario nonetheless.

I hope I have answered your questions.

Enjoy!
--
73 de VE2DPE - Claude
www.HamRadioSecrets.com

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73 de VE2DPE
Claude Jollet
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Notre-Dame-des-Prairies, Québec, Canada J6E 1M9

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