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Here are some simple antenna calculators


 

Simple Dipole Calculator

A useful and fundamental measurement in radio antenna work is the "half wavelength". We must know how to calculate it. It gives the desired physical length of an antenna for any operating frequency. 


Enter the Desired Centre Frequency in MHz
i.e. 3.765    MHz


Total overall length of the dipole will be  Feet
|---------------||----------------|


Each leg of the dipole will be  Feet
|---------------||----------------|


The half-wave dipole is one of the most important and commonly used antennas and is very simple to construct. The length of a dipole is the main determining factor for the operating frequency.

For the dipole legs use an insulated copper wire of 14 gauge or heavier. Remember to make the legs slightly longer than the calculated length to allow for wrapping around the end insulators.

Use 50 ohm cable such as RG58, RG8X, RG8, RG213, or 75 ohm cable such as RG11, RG59, RG6 or 75 ohm twin ladder line to feed the centre of the dipole.

Be sure to solder the feed cable to each leg of the dipole for good electrical contact because the centre of the dipole is a high-current low-voltage point. It is also a good idea to provide some strain relief which can be a simple matter of wrapping the feed cable once around the centre insulator and securing it with a tie-wrap.


 

Simple Vertical Calculator

Enter the desired frequency in MHz


The total length of your vertical is:

 


 

3 element beam Calculator

 Enter desired frequency in MHz
 

 

A. Director
B.
Each leg of driven
    
Total length of driven C. Reflector
D.
Spacing
 

|----A-----------------|

|

D

|

|------B-----| -----B-----|

|

D

|

|------C--------------------|


 

Simple J Pole Calculator

Enter desired frequency in MHz

A (Long sect) length:  feet,   in,  metres

B (Short sect) length:  feet, in,  metres

C (Feed point) length:  feet, in,  metres

D (Spacing) length:      feet, in,  metres

Inside (spacing) dimensions are metal to metal measurements, NOT center to center.


 

With thanks to James E. Stewart Jr. - N3DNO for the beam and vertical calculator javascript

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