Antennas
Half Wave Dipole
- If a half wavelength of wire is cut at the centre and fed with RF power at
the frequency at which it is resonant it is called a half wave dipole
and has a feed point impedance of about 40-70Ω depending on height above ground
- A half wave dipole is a balanced antenna and needs a balanced feed.
This can be either typically coaxial cable and a balun (balance-to-unbalance transformer)
or 75 or 450Ω balanced line.
The loss due to the 6:1 mismatch (6:1 SWR) on 450Ω line is inconsequential
because this type of line is very low loss, though it needs to be matched to the Tx output