Yagi Beam Antenna
Wire Antenna
   
ANTENNA CALCULATORS
 
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Dipole Antenna Calculator

 
 
This calculator is designed to give the horizontal length of a particular dipole (including Tees) antenna, or one side of it, for the frequency chosen. Enter the desired frequency and select the desired calculation from the drop box. Click on Calculate and the optimum length for that combination will be displayed in feet and inches. In the case of the Tee selection, the length given is for each of the two main elements AND each of the Tees; each side of the Tee is half the length of each main side. Lengths are given in feet, inches and fractions of inches, and in meters. The center of each Tee should be joined to the end of each of the dipole main elements. To optimize the antenna for a frequency RANGE, do the calculations twice, once for the low end of the range and once for the high end; then average the two and plan to adjust the VSWR on both ends of the range as needed.
 
 
Designation
Number
Required Data Entry
Desired Frequency Mhz
Select Antenna Calculation Length
   
Calculated Results
Calculated Selected Dipole Length
 

 

 


Yagi Beam Calculator

Select number of elements:

3
Enter frequency: MHz
Press Button:

Element Feet Inches Metres
Reflector:
Driven Ele:
Director:
Spacing:

 
Note:
The driven element will need to be cut in half and connected to the feed line where it has been cut. The center wire of the feed line goes to the end of one of the halves of the driven element, and the outside of the coax feedline goes to the end of the other half of the driven element. Use an insulator for holding the ends close together.

The director will be 5% shorter than the driven element. This is not cut in half.

The reflector will be 5% longer than the driven element. This is not cut in half.

The spacing between the elements is 0.2 wavelengths.

 

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Wire Antenna Calculator

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The following program will calculate the lengths needed to construct several popular wire antennas. All you need to do is enter the desired resonant (center) frequency in the form below, then click "Calculate". The correct lengths for the various models will be displayed in the chart. (To better understand the variables be sure to read the application notes and study the drawings, following.) This calculator will accurately compute values for all HF antennas — 1.8 - 30 mHz.

 
Enter primary operating frequency in mHz.   
Inverted Vee, approximate angle from horizontal.
 
Click to       or   
 
  Standard Flat-Top Dipole   
Full Half-Wavelength Dipole For optimal performance over average ground, the half-wave dipole should be installed a minimum of 1/2 wavelength above ground.
Each Leg    
  Inverted Vee   
Full Half-Wave Inverted Vee  Over level ground, the minimum height for the apex (feedpoint) of an Inverted Vee is determined by the angle (downward slope) of the Vee legs. BE SURE to add the height above ground of the end supports. The horizontal spread of Vee will be the distance from end point to end point, plus the tie off points.
Inverted Vee, Each leg 
Minimum Vertical Height 
Minimum Horizontal Spread
 
  Quad Loop   
Full One-Wavelength Loop     Over level ground, the minimum height for the top corners of the quad loop is the length of one side plus the height of the bottom support posts. Quad loops are most frequently fed in the center of the bottom, horizontal leg.
Each Side    
Feedpoint Distance from Bottom Corner    
 
  Equilateral Delta Loop   
Full One-Wavelength Loop     Over level ground, the minimum mounting height for the apex of a Delta Loop is the altitude plus the height of the support posts. If the loop is an equilateral triangle as shown, the Minimum Horizontal Spread = the length of one side plus the distance to the tie off points (support posts).
Each Side    
Feedpoint Distance from Apex
Feedpoint Distance from Bottom Corner
Minimum Vertical Height 
 





Dipoles and Inverted Vees



Half-wave Flat Top Dipole   Half-wave Inverted Vee Dipole
     
Half-wave Dipole   Inverted Vee Dipole

The feedpoint impedance of a Dipole in free space is close to 75Ω. Dipoles can be fed directly with 50Ω or 75Ω coax, or with a 1:1 balun at the feedpoint. The slight mismatch when using 50Ω coax can be easily matched with an antenna tuner. More importantly, for symmetrical current distribution, reduced feedline radiation, and thus a cleaner pattern, a balun should always be used at the feedpoint.

Due to the proximity to ground at the end of each leg, the feedpoint impedance of an Inverted Vee is very close to 50Ω. Inverted Vees thus can be fed with 50Ω coaxial cable, with or without a 1:1 balun. (The advice regarding the use a feedpoint balun pertains to the Inverted Vee as well.)

Both Dipoles and Inverted Vees can be fed with 300Ω or 450Ω ladder or open wire feeders into a balanced Antenna Tuner. This configuration, known as a "Doublet", will work well as a multiband antenna.






Full Wave Loops

Full-wave Quad Loop   Full-wave Delta Loop
     
Quad Loop   Delta Loop


The feedpoint impedance of a full-wave loop in free space is aproximately 100-120 Ω with a gain over a dipole of 1.35 dB. In the real world, installed at practical amateur heights (physically close to ground), the range of feedpoint impedance can be from 50-240 Ω depending on configuration, orientation, and choice of feedpoint. One of the realities that comes with choosing a full-wave loop is the need for some type of feedpoint matching system.


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  Webpage designed by Andrew Buck © M6VUK - (calculators & info were sourced from various websites so I take no credit)