Such an antenna was developed for professional communication, but then it became popular among radio amateurs.
Depending on the length of the structure, such an antenna can operate in the frequency range up to 2 – 30 MHz, that is, in almost the entire HF range. In this case, any tuning of the antenna to the frequency is not required, it works the same in the entire frequency range.
T2FD antennas are available in various lengths. The most popular lengths are 28 m (regular) and 14 m (short). But there are other lengths as well. The T2FD antenna is 28 m long and operates in the frequency range from 3 to 30 MHz, covering all shortwave amateur bands except 160 m.
But there is also an extended version of the antenna with a length of 56 m. Such an antenna is slightly less popular among amateurs due to its large size. But thanks to its size, it covers the entire HF range and allows you to work both for reception and transmission in all amateur bands. Continue reading Tilted Terminated Folded Dipole
Dipole its symmetric system with ~72ohm in center.
Wiki:
The dipole is any one of a class of antennas producing a radiation pattern approximating that of an elementary electric dipole with a radiating structure supporting a line current so energized that the current has only one node at each end.
The most commonly used is the center-fed half-wave dipole which is just under a half-wavelength long. The radiation pattern of the half-wave dipole is maximum perpendicular to the conductor, falling to zero in the axial direction, thus implementing an omnidirectional antenna if installed vertically, or (more commonly) a weakly directional antenna if horizontal
A half-wave dipole antenna consists of two quarter-wavelength conductors placed end to end for a total length of approximately L = λ/2. The current distribution is that of a standing wave, approximately sinusoidal along the length of the dipole, with a node at each end and an antinode (peak current) at the center (feedpoint)
How to build half-wave dipole antenna for hf:
1.Need 2 copper wire 1-4mm diameter and λ/4– use this table:
Wavelength table
Band
MHz
λ
λ/2
λ/4
160 meter
1,81 MHz
165,75 Meter
82,87 Meter
41,44 Meter
80 meter
3,6 MHz
83,33 Meter
41,66 Meter
20,83 Meter
60 meter
5,35 MHz
56,07 Meter
28,04 Meter
14,02 Meter
40 meter
7,1 MHz
42,25 Meter
21,13 Meter
10,56 Meter
30 meter
10,1 MHz
29,70 Meter
14,85 Meter
7,43 Meter
20 meter
14,15 MHz
21,20 Meter
10,60 Meter
5,30 Meter
17 meter
18,1 MHz
16,57 Meter
8,29 Meter
4,14 Meter
15 meter
21,2 MHz
14,15 Meter
7,08 Meter
3,54 Meter
12 meter
24,95 MHz
12,02 Meter
6,01 meter
3,00 Meter
10 meter
28,4 MHz
10,56 Meter
5,28 Meter
2,64 Meter
Note that the shortening factor of the wire is not included in the table. So the antenna will be about 5% shorter in reality.
2. Balun 1:1 (without balun you will be have many common mode. Balun need for current symmetry and choke commonmode)
Balun 1:1 (without balun you will be have many common-mode. Balun need for current symmetry and choke common-mode)
Balun:
Balun is an electrical device that converts between a balanced signal and an unbalanced signal. Our dipole its strongly balanced device, our coax its unbalanced device.
Balun materials:
Wire copper or silverplated (much better) 0.5-0.7mm 100-300wt
Core:
FT140-43 – 1-10 mhz 10-24 mhz30-54mhz
FT140-52 – 1-3 mhz3-30 mhz54mhz
Wire copper or silverplated (much better) 1.2-1.5mm 500-1000wt
