Vertical antenna impedance matching

- An
**antenna**loading coil is an inductor placed in series with an**antenna**element in order to lower the**antenna's**resonant frequency. A standard dipole**antenna**is resonant if constructed with a length of one-half wavelength. A**vertical****antenna**(effectively half a dipole operating against a ground plane) is resonant at one-quarter wavelength. . Resonance may also be observed at each of the odd ... - A voltage feed (i.e., high impedance) antenna such as this end-fed monopole, have feed point impedance of a few Kohms. Since our feed line is 50 ohm, 9:1 bring it up to ~450 ohm, so within SWR of 2 to 3 range. Antenna couplers can deal with that. 9:1 unun is available from good people like Palomar Engineers and DX Engineering.
- The input
**impedance**of an ESA is capacitive and in order to provide the maximum transfer of power into the**antenna's**driving point a**matching**network may be required. The eﬃciency of the**antenna**and its**matching**network is expressed as: ηs= ηaηm (3) ηs=eﬃciency of system (i.e.**antenna**and**matching**network) ηm=eﬃciency of**matching**... - Loop
**Antenna**1 λon 15 m (approx.47.5 ft.) #12 AWG Wireman # 551 To**antenna**tuner via approx 51 ft. RG-8 Length not critical. Loop and pre-**matching**circuit Uses a ladder line as**impedance**transformer The length of the ladder line is approx. λ/2 at 21 MHz. Obtained from simulations. The 90 Ωloop**impedance**is transformed to about the same value ... - far-field radiation. In the next section, the input
**impedance**of the ILA is derived by assuming a sinusoidal current distribution on the**antenna**. 3.3 The Input**Impedance**of the Inverted-L**Antenna**Before applying Pocklington's equation to the Inverted-L**Antenna**(ILA), it is worth while to review the derivation for a z-directed current source.