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G4URH - Calculations to Design Your Own Antennas
Ground Planes
Halfwave Verticals
Quad Antennas
5/8th Wave Vertical
Dipoles and Inverted Vees
Ground Planes
The standard ground plane antenna consists of a vertical radiator which is insulated and centered between 4 horizontal surrounding radials which extend out from the base of the antenna. Each radial is evenly spaced 90 degrees or so from each other around the vertical element.
Enter the formula for the antenna calculation (normally 234/f):
divided by
Freq. MHZ
The vertical length is
feet.
The 4 radials are each
feet.
Halfwave Verticals
The halfwave vertical antenna consists of a vertical radiator which is fed from the bottom of the antenna. A matching device should be added between the antenna and the feedline if you wish to use coax.
Enter the formula for the antenna calculation (normally 468/f):
Switch to:
divided by
Freq. MHZ
Your halfwave antenna's vertical length is
Quad Antenna
The cubical quad antenna is a four sided antenna, with each side a quarter wave length long. Several factors influence the performance of the antenna, such as :
The antenna height above the ground
The diameter of the wire used
Nearby structures to where the antenna is mounted
Effects of other antennas or metal objects in the area
The conductivity of the soil
Enter the formula for the antenna (normally 1005/f):
divided by
Freq. MHZ
Your quad's total length is
feet
Each of the 4 sides are
feet.
5/8th Wave Vertical Antenna
The 5/8 wave antenna consists of a vertical radiator fed at the bottom of the antenna. A matching device should be used if you feed it with coax.
Enter the formula for the antenna (normally 585/f or 178.308/f for metric):
Switch to:
divided by
Freq. MHZ
Your 5/8 wave antenna's Vertical element is:
Dipole and Inverted Vee Antennas
Most familiar are the centerfed, halfwave dipoles and inverted vees that are so popular.
A basic formula for these types of antennas is below. For center fed, wire dipole antennas, the formula is 468/freq(mhz).
Enter the formula for the antenna:
divided by
Freq. MHZ
Percent smaller for an Inverted Vee.
Your dipole's total length is
feet. Each leg of the dipole is
feet.
Your Inverted Vee's total length is
feet. Each leg of the Inverted Vee is
feet.
>-Send me an email at:
jon@g4urh.co.uk
with any comments.
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This page was last modified on Fri, 29 May 2015