Worked example: a half-wave dipole for 14.100 MHz cuts to about 10.1 m end to end (wavelength 21.3 m), and at 10 m over average ground its main lobe peaks around 30 degrees of take-off. Change frequency, height and ground below and every figure recomputes. Server snapshot, refreshed every 5 minutes. The tool below is live.
Cut it, hang it, and see what it actually does: the vertical lobe that sets your take-off angle, the horizontal lobe that says where it is pointing, and the dB you have towards the DX you care about. Height, ground quality, feedline and harmonic operation are all in the maths.
1 · Band and site
Everything below recomputes as you change these.
2 · Antenna
Sixteen models, all solved the same way.
3 · How you have put it up
4 · The two lobes
Vertical lobe elevation cut through the main direction
Horizontal lobe azimuth cut at the take-off angle
5 · The DX you are aiming at
Great-circle bearing, hop count and the angle the path needs — then what your antenna gives at exactly that angle and bearing.
6 · Height is the biggest lever
Radiated power against height and elevation angle, for this antenna on this ground.
Height map white line: take-off angle · orange: your target angle
Side view at this height
7 · Feeding it
Bandwidth, what the coax eats, and how much of your power actually leaves the wire.
SWR across the band
Feedline and losses what reaches the antenna
8 · Cut list
Start 2% long and trim to resonance.
9 · Every band at a glance
Same antenna, same height in wavelengths, every band.
10 · Questions people actually ask
Short answers, from the same maths this page runs on.
11 · Take it with you
One link, every setting.
Share this exact antenna
The link carries every setting, so the page opens on what you are looking at now.
What it does
Models sixteen wire and beam antennas, from a plain dipole to a Moxon or a four element Yagi, and gives you the cut lengths, the vertical and horizontal patterns over real ground, the take-off angle, feed impedance and SWR, feedline loss and the decibels that actually land on six DX paths.
Data and refresh
Nothing to refresh: there is no feed behind this one. Every figure is computed in your browser from what you type, so it works offline and the same inputs always give the same answer. The Copy link button carries your whole setup in the URL.
How to read it
Start with the take-off angle and the height map, which draws that angle against height from 0.05 to 1.5 wavelengths. Lock a reference trace and compare a second antenna against it, check the SWR curve inside the 2:1 window, then use the band table to see what fits the space you actually have.
Who it is for
Anyone deciding how high to hang a wire, whether raising the dipole is worth the afternoon, which of two antennas to build this winter, or what a dipole cut for 40 metres really does on 15.
What it cannot tell you
The model puts an idealised current on an idealised wire over flat, uniform ground. Your garden is none of those things. It does not know about the fence, the gutter, the neighbour's satellite dish, or the tree that detunes the far end when it rains, and all of those move a real pattern further than the difference between two of the antennas offered here. Treat the numbers as a way of comparing choices against each other, not as a promise about what your analyser will read on the day.
Using it in practice
Change one thing at a time and watch the take-off angle rather than the gain. Height is almost always the biggest lever available to you: raising a dipole from a quarter wave to a half wave over ground does more for DX than any amount of arguing about wire type. When the model gives you a cut length, cut long by a few per cent and trim, because every real installation ends up slightly shorter in resonance than the arithmetic says. And check the harmonic view before you buy a second antenna: the one in the air may already work the band you want.
Frequently asked questions
How accurate are these patterns?
The model puts a sinusoidal current on every segment, adds the image below ground weighted by the Fresnel reflection coefficients, and integrates the hemisphere for gain; Yagi parasitic currents come from the classic mutual impedances. On the textbook cases it lands where it should: 2.1 dBi for a dipole in free space, 8.4 dBi for a half wave dipole over perfect ground, 5.1 dBi for a quarter wave vertical, about 8.2 dBi with 25 dB front to back for a three element Yagi. It is not NEC. The Moxon comes out near 15 dB front to back instead of the 25 to 30 dB it shows in practice, because the model does not capture the coupling between the folded tips.
How high should I put my dipole?
Use the height map. Around half a wavelength up, the main lobe sits near 30 degrees, which is what you want for DX; at a tenth of a wavelength it points almost straight up, which is NVIS and fine for regional work. Height also moves the feed impedance, roughly 22 ohms at 0.1 wavelength and 95 ohms at 0.3, which is why the SWR changes when you raise the antenna.
What is the take-off angle and why does it matter?
It is the elevation angle of the strongest lobe. A signal leaving at 10 degrees reaches much further per hop than one leaving at 40. The DX target cards show the angle each path needs, from a hop model with the F2 layer at 300 km, next to the angle your antenna actually produces.
Does it take my ground into account?
Yes. Choose poor, average, good or sea water and the reflection coefficients change with it, which moves both the gain and the take-off angle. Sea water gives the lowest angle, which is why coastal stations do so well on DX.
Can I use an antenna cut for one band on another?
That is what the harmonic chips are for: the cut frequency is separate from the operating frequency, so you can cut for one band and work another. A dipole cut for 145.300 MHz used on 435.900 MHz is 1.44 wavelengths long: the take-off angle drops from 30 to 10 degrees, three lobes appear, the resistance rises to about 93 ohms and the SWR sits near 3.7 to 1.
Why does the same antenna score differently on two bands?
Because everything that matters is measured in wavelengths, not metres. Ten metres of mast is a third of a wavelength on 30m and a full wavelength on 10m, so the same wire that fires straight up on the low bands puts a low lobe out on the high ones. That is also why the cut list changes length band by band while the shape of the pattern changes with height.