Dual band vertical antenna for 80 meter and 160 meter.
Because of the limited space available in my property, the only possibility to have a 80 meters and 160 meters antenna is to install a vertical. Then i decided to use a 22 meters Spiderbeam fiberglass mast with an insulated wire slightly wrapped around it. Verticals antennas need a lot of radials (especially if is shortened on 160m). Therefore i lay down as many radials as possible of various length of copper wire on the ground on all directions. The radials distribution plate is also grounded. At the base of the mast is a remote control box to switch between 160 meters band and 80 meters band.
The remote tuner
On 80 meters
The antenna is a full 1/4 wave for 3.500 MHz, therefore the vertical is directly feed through the K2 relay.
On 160 meters
As the antenna is too short, a low loss coil is inserted in series with the antenna need to be added. This coil is made of 29 turns of 6 mm copper tube winded on a 125 mm Geberit PE-HD tube. The signal goes through the K1 and K3 relay.
The relays
Depending on the power involved, those relays should have good high voltage switching capability.
- The K1 relay can be omitted.
- Lay down all radials before attempting to tune the antenna.
- Tune the 160 meters antenna resonance and impedance matching with the 2 coil connections.
- The 160 meters bandwidth is quite narrow.
- The 80 merers antenna can be also tuned on 30 meters band with your transceiver internal tuner.