20m Delta Loop.

This antenna is fed for vertical polarisation, to give a low angle of radiation for DX and also a nearly omni-directional radiation pattern (broadside is the best direction by about 3 dB).

I have built two versions of this antenna; one using coax as a monoband antenna for 20m as simulated below, and the second as presently used with 450 Ohm slotted ladder-line feeder for multiband use (20 and 15m).

In the monoband application, the impedance at resonance on 14.2 MHz of about 100 Ohms is transformed by a quarter wavelength of 75 Ohm cable (3.5m long) to give a good match ( better than 2 : 1) across the whole band. The 75 Ohm coax braid is connected to the lower side of the loop element. I don't use a balun as the antenna is not balanced, due to the offset side feedpoint, but do implement a coaxial choke at the 50 Ohm cable connection to the matching stub of 10 turns, 20cm diameter. The antenna is 7.71m per side, with the feed point 3/4 of the way down one side (5.78 m from the top) note; 3/4 * 1/3 wavelength = 1/4 wave, this is important to obtain vertical polarisation.

This antenna is also effective on 15m provided open wire feeder is used up to the antenna instead of coax. I have found 10m DX performance to be rubbish! Simulation confirms this.The pattern is rather directional on both the higher bands.

Drawing of antenna

The NEC4WIN95 design file;

CM Equilateral Delta loop for 20 meters, apex up.
CM Feed point 0.25 lambda from top corner for vertical polarisation
CM 2:1 75 ohm coax quarter wave-length match assumed.
CM G4EZT Tree supported antenna.
CE
GND Reference
UNITS Meters
Height 8.000
Over Ground 13 5 (Diel. - Cond. µSiemens)
Boundary Circular
F 14.200
GW 0 8 0.000 -3.854 0.000 0.000 0.000 6.675 0.002
GW 1 20 0.000 0.000 6.675 0.000 3.854 0.000 0.002
GW 2 8 0.000 3.854 0.000 0.000 -3.854 0.000 0.002
S 1 23 100 0
Coax 100

The SWR plot

The Zenith plot

The Azimuth plot.