3-Element HF Yagi Design

Introduction

This page presents a series of 3-Element HF antennas that are easily constructed, "easily matched and easily tuned". By "easily matched and easily tuned" it is meant that, these antennas can be constructed and tuned on the ground. When the antenna is finally placed at height, there will only be a small decrease in F/B ratio. But the decrease is small and not worth trying to tune at height.

Note: The feed impedance for these yagi designs is 18-20 Ω. This means that a matching device will be necessary for the driven element, if you want to use 50/75 Ω coax or 75/300/450 Ω Ladder Line. See the web page on 2 and 3 Element Yagi Matching.

3-Element Parasitic Beam For 6 or 10 Meters	3-Element Parasitic Beam For 11, 15, or 20 Meters
Power Gain = 7.5 - 8.0 dB F/B Ration = 20 dB Radiation Resistance = 22 Ohms	Power Gain = 8.0 - 8.5 dB F/B Ration = 25 dB Radiation Resistance = 20 Ohms
Driven Element Length 475/F_MHz (ft) \|\| 144.8/F_MHz (m) Director Length 436/F_MHz (ft) \|\| 132.9/F_MHz (m) Reflector Length 505/F_MHz (ft) \|\| 153.9/F_MHz (m) Element Spacing 185/F_MHz (ft) \|\| 56.4/F_MHz (m)	Driven Element Length 473/F_MHz (ft) \|\| 144.2/F_MHz (m) Director Length 445/F_MHz (ft) \|\| 135.6/F_MHz (m) Reflector Length 501/F_MHz (ft) \|\| 152.7/F_MHz (m) Element Spacing 140/F_MHz (ft) \|\| 42.7/F_MHz (m)
Bandwidth for 1.75:1 SWR 1250 KHz at 10 Meters 2100 KHz at 6 Meters	Bandwidth for 1.75:1 SWR 450 KHz at 20 Meters 840 KHz at 15 Meters 1070 KHz at 11 Meters
Diameter of Elements 10 Meters = 1-1/2" 6 Meters = 1"	Diameter of Elements 20 Meters = 1-1/2" 15 Meters = 1" 11 Meters = 1"

The table on the right is similar to the table in Bill Orr's¹ book. I updated the table to include current references and metric dimensions. The antennas are separated into two groups and have slightly different gains. This is because the bands on the left (6 and 10 Meters) have a greater operating bandwidth (>3% at the design frequency). For these bands, the gain is lowered so that the antenna covers a larger bandwidth. Whereas, the bands on the right (11, 15, and 20 Meters) are much narrower (<3% at the design frequency) and can realize a higher gain and still cover the whole band with an SWR <= 1.75:1.

The antennas in the table are detailed below. For the most part, the text associated with each antenna is pretty generic. However, if there is anything specific about an antenna, it will be listed in the description

3-Element 6 Meter Antenna

The diagram below contains all the information you would need to build a 3-Element 6 Meter antenna. A General Coverage frequency (51.5 MHz) is selected as this provides the best coverage of the 6 Meter band. The SWR chart on the right show the General Coverage antenna's SWR performance, within the 6 Meter band. If you wish to use a center frequency above or below the General Coverage frequency, the Element Length .vs. Frequency chart can be used to determine new element lengths. The chart only lists the length of the driven and director elements. The Element Spacing can be kept the same, as there is very little change (2 inches) across the 6 Meter band. The spacing listed on the diagram is a good mean value.

The table below can also be used to determine Driven and Director elements for a frequency other than the General Coverage frequency. Just select your center frequency from the drop-down selector listed under the Frequency catagory. The dimensions for the Driven and Director elements, and the Element Spacing, will automatically be updated.

Gain	F/B Ratio	Rad. Res.	Frequency	DE Length 475/F_MHz (144.8/F_MHz)	Dir Length 436/F_MHz (132.9/F_MHz)	Ref Length 505/F_MHz (153.9/F_MHz)	Element Spacing 185/F_MHz (56.4/F_MHz)	1.75:1 SWR Bandwidth	Element Diameter
7.5 to 8.0 dB	20 dB	22 Ω						2,100 KHz	1"

3-Element 10 Meter Antenna

The diagram below contains all the information you would need to build a 3-Element 10 Meter antenna. A General Coverage frequency (28.75 MHz) is selected as this provides the best coverage of the 10 Meter band. The SWR chart on the right show the General Coverage antenna's SWR performance, within the 10 Meter band. If you wish to use a center frequency above or below the General Coverage frequency, the Element Length .vs. Frequency chart can be used to determine new element lengths. The chart only lists the length of the driven and director elements. The Element Spacing can be kept the same, as there is very little change (3 inches) across the 10 Meter band. The spacing listed on the diagram is a good mean value.

Gain	F/B Ratio	Rad. Res.	Frequency	DE Length 475/F_MHz (144.8/F_MHz)	Dir Length 436/F_MHz (132.9/F_MHz)	Ref Length 505/F_MHz (153.9/F_MHz)	Element Spacing 185/F_MHz (56.4/F_MHz)	1.75:1 SWR Bandwidth	Element Diameter
7.5 to 8.0 dB	20 dB	22 Ω						1,250 KHz	1-1/2"

3-Element 11 Meter Antenna

The diagram below contains all the information you would need to build a 3-Element 11 Meter antenna. A General Coverage frequency (27.1 MHz) is selected as this provides the best coverage of the 11 Meter band. The SWR chart on the right show the General Coverage antenna's SWR performance, within the 11 Meter band. If you wish to use a center frequency above or below the General Coverage frequency, the Element Length .vs. Frequency chart can be used to determine new element lengths. The chart only lists the length of the driven and director elements. The Element Spacing can be kept the same, as there is very little change (1 inch) across the 11 Meter band. The spacing listed on the diagram is a good mean value.

Gain	F/B Ratio	Rad. Res.	Frequency	DE Length 473/F_MHz (144.2/F_MHz)	Dir Length 445/F_MHz (135.6/F_MHz)	Refr Length 501/F_MHz (152.7/F_MHz)	Element Spacing 140/F_MHz (42.7/F_MHz)	1.75:1 SWR Bandwidth	Element Diameter
8.0 to 8.5 dB	25 dB	20 Ω						1070 KHz	1"

3-Element 15 Meter Antenna

The diagram below contains all the information you would need to build a 3-Element 15 Meter antenna. A General Coverage frequency (21.2 MHz) is selected as this provides the best coverage of the 15 Meter band. The SWR chart on the right show the General Coverage antenna's SWR performance, within the 15 Meter band. If you wish to use a center frequency above or below the General Coverage frequency, the Element Length .vs. Frequency chart can be used to determine new element lengths. The chart only lists the length of the driven and director elements. The Element Spacing can be kept the same, as there is very little change (2 inches) across the 15 Meter band. The spacing listed on the diagram is a good mean value.

Gain	F/B Ratio	Rad. Res.	Frequency	DE Length 473/F_MHz (144.2/F_MHz)	Dir Length 445/F_MHz (135.6/F_MHz)	Ref Length 501/F_MHz (152.7/F_MHz)	Element Spacing 140/F_MHz (42.7/F_MHz)	1.75:1 SWR Bandwidth	Element Diameter
8.0 to 8.5 dB	25 dB	20 Ω						840 KHz	1"

3-Element 20 Meter Antenna

The diagram below contains all the information you would need to build a 3-Element 20 Meter antenna. A General Coverage frequency (14.2 MHz) is selected as this provides the best coverage of the 20 Meter band. The SWR chart on the right show the General Coverage antenna's SWR performance, within the 20 Meter band. If you wish to use a center frequency above or below the General Coverage frequency, the Element Length .vs. Frequency chart can be used to determine new element lengths. The chart only lists the length of the driven and director elements. The Element Spacing can be kept the same, as there is very little change (3 inches) across the 20 Meter band. The spacing listed on the diagram is a good mean value.

Gain	F/B Ratio	Rad. Res.	Frequency	DE Length 473/F_MHz (144.2/F_MHz)	Dir Length 445/F_MHz (135.6/F_MHz)	Ref Length 501/F_MHz (152.7/F_MHz)	Element Spacing 140/F_MHz (42.7/F_MHz)	1.75:1 SWR Bandwidth	Element Diameter
8.0 to 8.5 dB	25 dB	20 Ω						450 KHz	1-1/2"