3/8 Wavelength Two-Band Marconi Aerial 160 80
This aerial functions as 3/4 wavelength self-resonant aerial on high band and as a tuned 3/8 wavelength aerial on low band. Low band resonance is established by adjustment of tuning capacitor. High band resonance is established by trimming length of A section. Capacitor is 250 pF, 2 kv (Johnson 154-1 or equivalent ). Separate radial ground wires are required for each band.
This is the Vertical I am working on at the moment. It is a 33Ft long for 40 metres and of courses work's well on 21. If you look at the bottom there is a Q coil 13 turn's of enamel wire to give 50 Ohm marching, another wire is connected to the feed which is on standoff brackets on the aerial. The wire is 17Ft long for 20. This aerial is connected to an extensive ground radial systems. Still working on this aerial to put more band's on it will let you know more soon.
Fig:1The sloping half-wave dipoles are used very successfully by a number of stations, especially near the sea. The half-wave sloper radiates a signal with both horizontal and vertical polarization components. Unless it is very high above the ground. You need not bother with the horizontal component, the low angle will be produced only by the vertical component. Due to the weight of the feed line, a sloping dipole will seldom have two halves in a straight line. For the vertical component the same rules apply as for the half-wave vertical: In order to exploit the intrinsic very low-angle capabilities, you must have a good ground around the aerial. Don't forget, the Fresnel zone (the area where the reflection at ground level takes place) can stretch all the way out to 10 wavelengths or more from the aerial! The sloping dipole with a relatively horizontal bottom quarter-wave wire yields almost the same signal as the straight sloping dipole. It is important to keep the top half of the sloping dipole as vertical as possible. Analysis shows the angle of the bottom half of the aerial is relatively unimportant. I have got link's in my aerial I plug in to bring in 160. of course it is on pulleys to drop it down quickly.