The Antenna Tools feature has a couple of calculators to help with antenna design and tuning.
* A dipole calculator, for calculating the length of a half wave dipole for a given frequency.
* A parabolic dish calculator, for calculating focal length for a dish with a given diameter and depth, as well as corresponding gain and beamwidth for a given frequency.
Each calculator is contained within an individual tab. Settings in one tab do not effect calculations in other tabs.
This field selects the units lengths are entered and displayed in. This can be:
* cm - centimetres.
* m - metres.
* feet - feet.
<h3>5: Dipole Element Length</h3>
This field displays the element length of each dipole for a half wave dipole corresponding to the frequency entered in (1) or total length (3).
When a length is entered in this field, the calculator will calculate the corresponding frequency (1) and total length (3).
<h3>6: End Effect Factor</h3>
A half wave dipole in free space with total length being half the wavelength of operation has a reactance of 43 Ohms.
To eliminate this reactance, the dipole should be shortened. The amount it needs to be shortened by depends upon the ratio of the diameter of the dipole to wavelength,
with factors ranging from 0.98 for a thin dipole (0.00001 wavelengths) to 0.94 (thickness of 0.008 wavelengths) with a commonly used value of 0.95.
The calculator doesn't use an analytical formula for this, as the reactance also depends on the environment (such as distance to ground), so some experimentation
When entering a frequency in MHz in this field, the calculator will calculate the beamwidth (15) and gain (16) for a dish of the given dimensions (10 & 11) at the entered frequency.
Specifies the efficiency of the dish in %. When entered, the calculator will calculate the gain (16), according to the entered frequency (7) and dimensions (10 & 11).
