simplest antenna that could provide operation on all HF bands
is a Delta Antenna. The antenna made in the shape of Delta needs
minimum points for installation, does not required grounding like
a vertical does and the antenna is not critical to nearest objects.
The antenna does not required high mast for installation. If the
antenna made as one band one it may feed direct through a coaxial
cable. However for multiband operation the antenna is required
a matching device at its feed-points.
For a long time I use to a Delta Antenna for 80- meter
(perimeter is 84 meters) on amateurs bands from 80 to 10 meters.
Two upper points of the antenna are fixed at the roof of a five-storey building third point (feed-points of the
antenna) is fixed on the balcony on the third floor. Wires
from the feed- points are going into my shack and connected to
an ATU. The ATU may be connected to transceiver by coaxial cable
of any length. Figure 1
shows design of the delta antenna. Figure 2 shows schematic of the ATU.
ATU consists of a broad band balanced RF transformer
T1 and Pi circuit that match antenna impedance to impedance of
the feeding coaxial cable. Figure 3 shows design of the balanced transformer. The transformer
may be connected to the antenna and to matching circuit according
to variant 1 or variant 2. It is depends on antenna placement
(so on to antenna impedance on the bands) and to parameters of
the transformer. Practice shows best variant for your antenna
Inductor L1 has 13 turns coiled on 45 mm OD, length
of winding is 70 mm. It is coiled by enameled wire in diameter
of 2... 2.5- mm (10- 12 AWG). Taps made from 2, 2.5, 3 and 6 turns
counting from the left side (according to the schematic on Figure 2) of the L1.Capacitors at the matching
device are composed from several fixed capacitors and one variable
capacitor switched in bridge makes the fine tuning.