antenna room is limited by balcony or attic you need think about
a small antenna. Below you find a description of small antennas
for HF amateur Bands 40- 10- meter.
a family of shortened dipole antennas with spiral loads on the
ends. However the antennas can provide good result on the bands.
Figure 1 shows design of the shortened dipole antenna with spiral loads for the
10 meter band. MMANA file for the antenna you may download at:
2 shows SWR of the antenna. Figure 3 shows DD of the antenna.
As you can see DD of the shortened antenna is almost similar to
DD usual dipole antenna, so it is not shown for others antennas.
Spiral loads of the antenna made
like a rectangle, distance between sides is 10- cm, first horizontal
and vertical side is 10 cm long, then
sides grow according to winding. Antennas for 30- 10- meter Band
were simulated with length in 2- meter, main vibrator was simulated
from aluminum tube in diameter of 16- mm, gamma match simulated
from aluminum tube in diameter of 10- mm. Distance between vibrator
and gamma match is 10- cm.
Spiral loads may be made
from aluminum or copper wire in 1- 2- mm diameter. Antenna may
be tuned in usual way- with length of gamma match and capacitors
(match the input impedance) and with length of the spiral load
(tune to resonance).