A Three - Element Yagi Mini-beam Using Hamsticks

by Russ Wilson VE6VK      ve6vk@cadvision.com

INTRODUCTION

Rick NE8Z and I were having a very long discussion about minibeams and credit for suggesting the use of hamsticks must go to Dr. Rick. I thought it was a great idea and well worth building one. I needed something light, easy to install and reasonably efficient with some directivity. Almost immediately I started building the boom and the feed point insulator and then ordered the hamsticks. After lots of experimenting the results are shown below.

DESIGN CHART

BOOM = 12 feet (365.76 cm) x 1-1/4"(3.175 cm) diameter aluminum tubing [4' sections, (121.92 cm)]

BOOM ELEMENT SPACING:

• Driven Element to Director spacing = 5' 9" (175.25 cm)
• Driven Element to Reflector spacing = 6' 3" (190.5 cm)

DIMENSIONS FROM BOOM TO TIP OF HAMSTICK ROD:

• Reflector = 7' 6.5" (230 cm)
• Driven Element = 7' 2" (218 cm)
• Director = 6' 9" (205.5 cm)

DIMENSIONS OF HAMSTICK ROD (WHIP) FROM END OF HAMSTICK COIL:

• Reflector = 3' 8.3" (112.5 cm )
• Driven Element = 3' 3" (98.5 cm )
• Director = 2' 10.4" (87.5 cm )

CISA Pictures

	MEASURED IMPEDANCE USING OMEGA BRIDGE = 48 ohms at 15 feet off the ground. FEEDING = 1 wavelength of RG58U and a 1:1 balun FREQUENCY COVERAGE = 14.070 to 14.295 flat TOTAL WEIGHT (INCLUDING CARRYING TUBE) = 12 lbs.   Note: I color code my Hamsticks for ease of assembly.

CONSTRUCTION

The support for the minibeam is 22 feet high and is constructed of telescoped aluminum. This support also has a 40M hamstick installed on the top utilizing an insulator and matching coil. The vertical uses the support, the beam, and boom for the ground plane. The base has to be matched to 52 ohms. Two coax cables are used, one for the beam and one for the vertical. The antennas are switched with a coax switch at the rig end. The vertical is tuned to 7.250 and if it is found necessary to QSY lower in frequency, a clip and extension is used as a capacity hat for the purpose.