Ve6fi Amateur Radio
160 Meter Antennas
This is a 160 meter antenna which is a shunt fed vertical. A 72 foot Trylon tower with a 6 element 15 meter mono bander mounted on the top is used as the radiating element. Information on this type of antenna was obtained from ON4UN Low Band DXing book. (Chapter 9-71). The electrical length is 92 degrees but it is reduced by 5 degrees because of the 6 element beam on the top.
The gamma match incorporates a #8 cable bolted to the tower at the 62 foot elevation. The distance of the cable from the tower is 12 inches. A 500 pico farad variable capacitor was put in series with the gamma rod (wire) to tune out the reactance. The capacitor and the distance of the wire from the tower were adjusted for minimum SWR. The amount of the capacitor required was 150 pfd.
The capacitor used was rated at 4.5 KV. With 150 pfd of capacity the Impedance at the capacitor terminals is 580 ohms. At 2 KW of power the peak voltage will be 1000 volts. Even with an SWR of 2.0 to 1, the voltage will not exceed the 4.5 KV rating.
The pictures shows an enclosure around the capacitor which will keep the insects and dust from accumulating between the capacitor plates.
We initially installed seven ground radials all .125 wavelengths long. They run on the ground and are made from #22 paired insulated wire. The ground bar is located in the pedestal located at the base of the gamma match for the loaded tower (vertical)
The transmission line length back to the radio room is about 300 feet. I used 3/4 inch CATV 75 cable for the transmission line. (Not too much loss there!)
160 meter Dipole
The dipole is a full sized dipole mounted around 120 feet between two towers and favors the north-south direction. This dipole is about 350 feet from the radio room and again 3/4 CATV foam cable is utilized.
At present we do not have too much for receiving antennas for 160 meters. What we have is a fair amount of intermod noise generated on the site. After that source is located and cleaned up we hope to install a K9AY loop and possibly a permanent Beverage antenna.