Category: About antennas
About antennas
Amidon cores info
About SWR, and antenna resonance
I see many questions About antenna impedance/resonance ect.
in simple words about the complicated.
Z -complex impedance
R – active resistance
X – reactive impedance (j – is the imaginary unit, and is used instead of
i
in this context to avoid confusion with the symbol for electric current.)
Z=R+(-)jx
Swr 1:1.0 – 50=50+(-)0
remember swr this is unnecessary indicator.
Antenna Resonance in simple words this jx =0 (and then you see real antenna impedance)
For example:
Dipole z=50ohm on 7100, but z = (R)70-(jx)20, and we have for example swr 1,2
But real resonance for example on 6900 where minimum jx = +2.5 and R = 65.
Swr on 7100 ~1.2
Swr on 6900 ~1.2 BUT 6900 its antenna resonance.
UR4UNR
Double OCFD all HAM bands antenna
All band very effective antenna. Double OCFD invV.
SWR less than 2:1 on all HAM band – 80m 40m 30m 20m 17m 15m 12m 11m 10m 6m
Balun system – 1:4 voltage transformer + 1:1 current choke. Amidon core FT240-K. Silverplated wire 1.3mm
Antenna wire – 4mm copper
Tilted Terminated Folded Dipole
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
