Ve6fi Amateur Radio
20 Meter Antennas
These four antennas are
mounted on a 150 ft tower
which has a 24 inch face.
The extra wires on this tower are for a wire log antenna
20 Meter 5 element Yagi at 150 ft.
This is a 20 meter homebrewed 5 element monoband yagi on a 46 foot boom. It has a integrated boom of three inch and two inch tubular aluminum.
This yagi is shown here ready to be raised to the 150 foot level on a 24 inch tower in 1996. It was put up by Denis and Evan themselves three days before the CQ WW contest. Things get done faster just before contests!
The rotator for this antenna is a large prop pitch rotator and it is designed to turn at 1/2 rpm. A shock absorber/damper is used between the prop pitch and the mast driving the antenna to remove any sudden stops and starts. The prop pitch motor is now a 100 volt DC motor with it's power source is located at the base of the tower. We usually park this antenna on Europe or on Japan.
20 Meter five element beam at 110 ft
It is a typical 5 element monobander on a 36 foot 3 inch diameter boom. The feed system is an OWA (Optimized Wide Array). From the picture you can see that the first director is close to the driven element. This brings the feed point up to 50 ohms. It is fed directly with 50 ohm coax and utilizes a coaxial wound balum.
This antenna is mounted at the 110 foot level and is pointed on the Caribbean. Both the 20 meter monobanders are on the same tower.
The 20 meter tower is located some 500 feet away from the building and is fed with 1/2 inch foam transmission line and switched at the base of the tower.
Another 5 element 20 Meter OWA Beam at 70 ft
This 20 meter was built and installed in 2005. It is on a 36 foot boom and the picture below shows how it side mounted on a 24 inch tower. The rotator used is an Alfa Spid, which has the feature where one can adjust the stop in the clockwise direction and the stop in the counterclockwise direction so that the boom does not contact the tower. The offsetting brackets are made off 2 X 2 X 3/16 inch galvanized steel. The Alfaspid is mounted on the bottom bracket and there is a wooden bearing on the top bracket. These Alfaspid rotators work in a reliable manner even in the cold weather.
This antenna is mounted at the 70 foot level of a 150 tower.
Log Periodic Antenna
This is one of the largest antennas that we have on site. It is a Telex Hygain LP 1001 model which covers a frequency range of 3.7 Mhz. to 30 Mhz. with an SWR of less than 2:1 This antenna is mounted on a 70 foot unsupported boom which is a triangular aluminum tower section 12 inches per side. The mast is a 12 inch pipe that attaches to a rotator at the base of the 100 foot tower.
I have modeled this antenna with Ezenec and it is equivalent to a 3 element Yagi on any particular frequency. The main advantage of the log antenna is that you do not have to switch antennas.
While we can use this antenna on 20 meters we usually use it as a second antenna for 40 meters during contests.