Fan Loop?

[W6EM]

The multi loops with a common feed should act just like dipoles do, except with higher impedances at resonance. IOW, the reactances will go up when the particular loops aren't resonant.

Now, as to parasitic radiators, it is the spacing that would mess up that idea, since different wavelength spacings would be necessary for each loop.

Here's a thought. How about an all-band "loop screwdriver?" Four support points being long springs with pulleys on each. Route the loop wire through the pulleys around to a small bi-directional winch at the feedpoint. The winch would pull in or pay out wire, thus shrinking or expanding the loop. Insulators added to keep the loop floating.

[W9PSK]

The multi loops with a common feed should act just like dipoles do, except with higher impedances at resonance. IOW, the reactances will go up when the particular loops aren't resonant.

Now, as to parasitic radiators, it is the spacing that would mess up that idea, since different wavelength spacings would be necessary for each loop.

Here's a thought. How about an all-band "loop screwdriver?" Four support points being long springs with pulleys on each. Route the loop wire through the pulleys around to a small bi-directional winch at the feedpoint. The winch would pull in or pay out wire, thus shrinking or expanding the loop. Insulators added to keep the loop floating.

Hmmmm. From a mechanical standpoint, that would require the springs to be just the right length and have just the right tension. Otherwise, there would either be too much pull or not enough pull. Also, wouldn't I end up creating a coil that would alter the antenna's characteristics when it wound up the wire for the higher bands? It sounds too complicated to figure out for a guy like me.

[W6EM]

Hmmmm. From a mechanical standpoint, that would require the springs to be just the right length and have just the right tension. Otherwise, there would either be too much pull or not enough pull.

Well, sagging and taughtness would need some adjustment. Perhaps surgical tube instead of the springs. That stuff is quite elastic and can be cut to adjust the tension so as to be just enough when on the lower frequencies and real tight when on the higher bands.

Also, wouldn't I end up creating a coil that would alter the antenna's characteristics when it wound up the wire for the higher bands? It sounds too complicated to figure out for a guy like me.

The coiled-up wire feed point would be where you attach one leg of the feed, so the effects of coiled up wire would be negligible. And, you'd have to run bare wire for it to work with a sliding contact point.

Nah, not too difficult, but a lot of work and ingenuity. Try the concentric multiloop idea you had. It should work like a fan dipole as those loop impedances will change as the paralleled, fan dipole ones do. Just would be a problem with parasitic elements due to the different wavelengths requiring different spacings band to band.

[N5RLR]

I'm exhausted at the moment but I'll toss this in for consideration: Carpet Loop Antenna [click]

Feed with ladder- or window-line. Adapt the switch-tapped coil idea with heavier-gauge wire for transmitting; use relay(s) at the feedpoint. You'd have to twiddle with a tuner, but you should be able to put a signal on the air in much of the spectrum. ;)