I am rebuilding my HF station after a lightning strike.

I plan on doing a lot of BPSK31/BPSK63 work.

I want to build a dipole optimized for use on 14070/7080 KHz, and 3581 if possible.

These frequencies are not exact harmonic multiples of each other.

A dipole cut for 3581 operating in 20 meters would be 180 khz off resonance.

Would this be too much of a mismatch if I do not use an antenna tuner?

I want to avoid using an antenna tuner.

Would optimizing the antenna for some nearby or intermediate frequency be a good compromise?

Would an antenna just using 14070/7080 be a better solution?


I am located in EM95vs.
What kind of antenna pattern would get from the following antennas:
350-170 degrees mounted 32 feet above ground at center or 60-240 degrees mounted 45 feet above ground?

On Wednesday, September 19, 2012 11:26:28 AM UTC-5, ai8o wrote:
I want to build a dipole optimized for use on 14070/7080 KHz, and 3581 if
possible. These frequencies are not exact harmonic multiples of each other.

Even multiples don't work for single-wire dipoles. Only odd multiples work. A resonant dipole cut for 3581 would also be resonant around 10.7 MHz, 17.9 MHz, and 25.1 MHz. It would be *anti-resonant* around 7.16 MHz, 14.32 MHz, 21.5 MHz, and 28.7 MHz. Anti-resonance is worst-case for coax fed antennas.

You could build a fan dipole with a separate dipole per band or you could build an 80m dipole with traps for 40m and 20m.

A standard G5RV works well on 80m, 40m, and 20m with a tuner. A ZS6BKW could be optimized for 40m/20m operation by playing with the dipole length and matching section length.