8

Yes, this works fine. It is often called a "fan dipole". There are separate resonant dipoles for each band, all fed from a common point. The wires should be separated by a foot or more. If you have enough tie points at the ends, you can run them in slightly different directions. The resonant dipole will have a low impedance, around 50 Ohms. The non-...


5

If I were making an antenna like that, I would add the extra 10" (25cm) first anyway, because when you come to tune it it's much easier to trim the wire than it is to add wire to it later. Also, because the antenna is an inverted V (a kind of dipole - a balanced antenna) and you are using coaxial cable to feed it, you should consider using a balun at the ...


3

I don't know how much of an impact it might make, but you might try moving the trap resonance to be outside the 20m band. Trap losses are highest at the trap's resonant frequency because at this frequency the current circulating between the inductance and capacitance is at a maximum. Thus, ohmic losses within the trap are maximized. At resonance is also ...


3

The length is measured between the center and the end insulator. I'd further add: don't overthink it. Common practice is to cut the wire a bit long, then iteratively make it shorter until you get a good match at your target frequency. Things like proximity to ground or other conductive objects can cause some deviation from the idealized conditions used by ...


3

When a dipole is less than a 1/4 wavelength above ground, the image antenna formed by the reflection from the ground creates destructive interference at low angles, making the antenna quite useless for DX. At 40 meters, a quarter wavelength is about 35 feet, more than the current 23 feet at apex. The effect will be diminished if you are not also able to ...


3

Maybe a little, maybe a lot. It depends on the particular geometry of that wire. Your best bet would be to either build it and see, or use some simulation like NEC to predict what will happen. But consider: aluminium wires supporting the center of the antenna are not that different from the conductive feedline that's already there. Provided your wire runs ...


2

It's very difficult to predict. If your siding were an infinite, perfectly conducting plane, then the results would be the same as if you had another inverted V, positioned as if mirrored through the plane of the siding, but fed in antiphase. This is called an image antenna. What this does depends on the distance between your antenna and the siding. It's ...


2

NEC4.2 comparison of an inverted V, center-fed dipole with a linear center-fed dipole: AUTHOR EDITS: The apex angle in my plots here is mislabeled. The correct value is 120°. The graphic below compares the elevation pattern gains at 90° azimuth intervals for these two configurations; posted in response to the comment of rclocher3.


1

My quick opinion is that this looks reasonable. A trapped dipole will likely have a smaller bandwidth than a regular dipole. A short simulation is what is required to be sure. You're getting 5% bandwidth at 40 m (the traps don't load it very much at 40 m) which is normal. And to be generous 1% at 20 m. The traps are working on the high impedance tips of the ...


1

The formula for calculating the end-to-end length of a half-wavelength center-fed dipole is in feet: 468÷f in meters: 143÷f where f=frequency in MHz. That is measured "from loop to loop"; that is, after the extra wire you allow for the wire loops inside the end insulators is twisted back on itself and soldered. Between the center of the center insulator ...


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