Fan Loop?

[W9PSK]

Ok, guys. I always ask my antenna questions over on the other site, so I figured I'd give you guys a chance to answer one. I am planning on putting up an 80 meter loop skywire antenna. It's a full wave horizontal loop fed with 450 ohm ladderline. I got to thinking the other day that maybe I could create a loop within a loop type of antenna. The outside loop would be a full wave on 80 meters; the next loop, inside that 80m loop, would be a full wave 40 meter loop; and then the third loop would be a full wave 20 meter loop. If you look at the antenna from the top, it would look like three squares inside of each other, with a single feed point set up the way they set up fan dipoles. Are ya getting the picture? How do you think this would work?

[N8YX]

Probably not too well. You're going to be dealing with some interesting reactances as a result of the even "resonance" multiples, and I don't think your tuner is going to effectively cancel them out especially at higher frequencies.

You could get away with just one loop, cut to accommodate the lowest frequency you plan to use.

Or is a radiation angle which changes with increasing frequency what you're after?

[W9PSK]

I just want something that is going to work and work well. I've done some research on this 80m skywire antenna, and know it's a good one, but I was wondering if modifying the design to make it into a fan loop skywire (Yes, I am making up that name just in case it turns out to be a brilliant idea that I can market and make millions on. :D) would work.

[W9PSK]

My drawing totally sucks, but this is basically what the antenna would look like. The antenna itself would be horizontal and the ladderline would be vertical.

[N8YX]

I just want something that is going to work and work well. I've done some research on this 80m skywire antenna, and know it's a good one, but I was wondering if modifying the design to make it into a fan loop skywire (Yes, I am making up that name just in case it turns out to be a brilliant idea that I can market and make millions on. :D) would work.

In a fan dipole configuration, one can get away with what you're proposing. Things change when you close the ends of the loop(s).

You could stack multiple loops in a configuration that will give you optimum takeoff angles for each desired band then use a latching relay system to connect each to your open-wire line. Bear in mind that if the circumferences of each loop differ more than a very small amount (0.5%) you're probably going to need to adjust the matching network with each loop change.

A neat way to do this would be to construct a band-tracking/memory preset circuit for each. Or use separate, independently tunable matching networks at each feedpoint.

ETA: I would make the loops horizontal and the feedline vertical. You're not going to gain anything with a multiloop, horizontal broadside array unless you make one or more of the elements parasitic and use them to focus the radiated beam.

[WØTKX]

Just use it multi-band with a tuner. Make it as big and as high as you can. Trust me.

I miss my 460' loop, the dipole is OK, but the loop was quieter. The DX lobes kicked ass on 20, 17 and 15. Mine was suspended by 6 pulleys, and I could slide the whole loop to change the feed point and tweak the direction of the lobes. All it took was listening to specific DX pileups with the speaker on the roof, and I slid it back and forth. Ended up being fed about 1/4 of the length of a side closer to a corner.

One thing you can do is open one side opposite the feed point, and make it tune better on lower frequencies. This will change the pattern though...

Have you registered (free) at http://www.cebik.com

This you must do, find the Tales and Technical section, then read his stuff on loops. Well, everything, actually.

Specifically, these topics... links require login!

Notes on All-Band Use of Horizontal-Plane Loops(10-28-1997)
A 40-Meter Star (04-13-2003)
Horizontally Oriented, Horizontally Polarized Large Wire Loop Antennas (03-29-1999)
Horizontal Loops: How Big? How High? What Shape? (10-21-2004)
Half-Wavelength Interrupted Loops: Their Evolution and Uses (03-01-2008 ) (pdf)


Note: Antennex.com owns this stuff now, as W4RNL is an SK.
So all rights reserved blah blah, and you will get some spam for
expensive goodies from Antennex.com. Worth it though.

[KJ3N]

You could get away with just one loop, cut to accommodate the lowest frequency you plan to use.

This would be my suggestion.

Or is a radiation angle which changes with increasing frequency what you're after?

He'll get it, whether he wants it or not.

[N8YX]

He'll get it, whether he wants it or not.

Right, but stacking the loops and selecting one based on frequency used and height above ground will mitigate this somewhat.

[N9FE]

You'd light up the shack like a christmas tree with rf, And cancel each other out.

[KJ3N]

Right, but stacking the loops and selecting one based on frequency used and height above ground will mitigate this somewhat.

If you want nothing but NVIS, sure.

I prefer a different path. ;)