Fan Dipole (Homebrew)
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| Frequency | 80m: 3.5-4.0 MHz, 40m: 7.0-7.3 MHz, 20m: 14.0-14.35 MHz, 10m: 28.0-29.7 MHz |
| Bands | 80m, 40m, 20m, 10m (typical set; any combination - 15m usually arrives free via the 40m wire's third harmonic) |
| Modes | SSB, CW, AM, FM, digital |
| Connector | single 50-ohm coax through a 1:1 current balun (choke) at the common feedpoint |
| feedpoint | all elements parallel on one feedpoint; 1:1 current choke strongly recommended |
Estimated (unverified): parts cost (build-dependent)
Dedicated-dipole performance on every chosen band for the price of wire and a balun: nothing in the signal path but copper, no tuner needed where you cut it right, and total honesty about what it is. The 40 m element's third-harmonic gift of 15 m is the design's charming free lunch.
The tuning afternoon is legendary: elements interact, every trim ripples, and wind-swung wires keep re-tuning themselves unless anchored. Bandwidth on 80 m is as narrow as any single dipole's, the feedpoint hardware carries several wires' weight, and each added band makes the next one harder to tune.
The best multiband wire you can build for the money, paid for in patience rather than dollars. Cut, hang, trim, repeat - and when it's done, it's a stack of real dipoles that owes nothing to anyone's matching network.
The fan dipole is multiband antenna design at its most disarmingly literal: if you want dipoles for four bands, hang four dipoles, and let them share one feedpoint. The physics that makes this work is impedance selection, on any given band, the resonant pair presents a low impedance and takes the power, while every other pair sits high-impedance and politely abstains. No traps, no loading coils, no matching network: on each band you are running an actual half-wave dipole, with an actual dipole's performance and bandwidth, through one coax and a 1:1 current choke that earns its place by keeping the paralleled wires' RF off your feedline shield.
The price is paid on tuning day, and every build guide tells the same war story. Elements interact: trim the 40 and the 20 moves; add a wire and the whole stack shifts slightly. The ritual is to start with the longest element and work down, to fan the pairs apart (angled apart vertically, spread by compass direction, or held off with spreaders) and then to anchor everything, because an element that swings in the wind is an antenna that re-tunes in the wind. The most famous interaction is also the design's best freebie: a 40 m element is resonant again near 15 m, its third harmonic (the same physics this site documents on the commercial Alpha Delta DX-CC) so most builders skip a dedicated 15 m wire and take the free band - noting that the harmonic lands slightly HIGH, so the CW end of 15 may want a tuner, and that adding a dedicated 15 m wire anyway is the classic mistake: the lab guidance says plainly not to parallel harmonically-related dipoles, because both pull low together and fight.
Against the alternatives, the fan dipole is the no-cleverness option, and that is its appeal: the off-center-fed school buys more bands per wire with transformer tricks and feedline radiation, commercial parallel dipoles pre-solve the tuning at a price, and the fan asks only wire, patience, and a free afternoon that may become two. What you get back is the quiet confidence of knowing exactly what is in the air: dipoles, plural, and nothing else.