kopia lustrzana https://github.com/f4exb/sdrangel
133 wiersze
4.7 KiB
Markdown
133 wiersze
4.7 KiB
Markdown
<h1>Antenna Tools Feature Plugin</h1>
|
|
|
|
<h2>Introduction</h2>
|
|
|
|
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.
|
|
|
|
<h2>Half Wave Dipole Calculator</h2>
|
|
|
|
|
|
|
|
<h3>1: Frequency</h3>
|
|
|
|
When entering a frequency in MHz in this field, the calculator will calculate the total and element length for a half wave dipole at this frequency.
|
|
|
|
When a length is entered in (3) or (5), this field will display the corresponding resonant frequency.
|
|
|
|
<h3>2: Frequency Select</h3>
|
|
|
|
Select how the frequency is chosen:
|
|
|
|
* MHz - A frequency can be manually entered in (1) in MHz.
|
|
* Device set N - The frequency automatically tracks the centre frequency of Device Set N.
|
|
|
|
<h3>3: Dipole Total Length</h3>
|
|
|
|
This field displays the total length of a half wave dipole corresponding to the frequency entered in (1) or element length (5).
|
|
|
|
When a length is entered in this field, the calculator will calculate the corresponding frequency (1) and element length (5).
|
|
|
|
The dipole length is calculated as: l=0.5\*k\*c/f
|
|
|
|
<h3>4: Dipole Length Units</h3>
|
|
|
|
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
|
|
is needed in finding the true value.
|
|
|
|
<h2>Parabolic Dish Calculator</h2>
|
|
|
|
|
|
|
|
<h3>7: Frequency</h3>
|
|
|
|
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.
|
|
|
|
<h3>8: Frequency Select</h3>
|
|
|
|
Select how the frequency is chosen:
|
|
|
|
* MHz - A frequency can be manually entered in (7) in MHz.
|
|
* Device set N - The frequency automatically tracks the centre frequency of Device Set N.
|
|
|
|
<h3>9: Efficiency</h3>
|
|
|
|
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).
|
|
|
|
This value should include losses for things like spillover, illumination loss, feed and support blockage, focus errors.
|
|
|
|
<h3>10: Surface Error</h3>
|
|
|
|
Specifies the RMS surface error of the dish in length units (as determined by (12)).
|
|
|
|
<h3>11: Diameter</h3>
|
|
|
|
When entering the diameter of the dish, the calculator will calculate the focal length (14), f/D ratio (15), beamwidth (16) and gain (17).
|
|
|
|
<h3>12: Dish Length Units</h3>
|
|
|
|
This field selects the units lengths are entered and displayed in. This can be:
|
|
|
|
* cm - centimetres.
|
|
* m - metres.
|
|
* feet - feet.
|
|
|
|
<h3>13: Depth</h3>
|
|
|
|
When entering the depth of the dish, the calculator will calculate the focal length (14) and f/D ratio (15).
|
|
|
|
<h3>14: Focal length</h3>
|
|
|
|
Displays the calculated focal length.
|
|
|
|
Focal length is calculated as: f=d^2/(16*D)
|
|
|
|
<h3>15: f/D Ratio</h3>
|
|
|
|
Displays the calculated focal length to diameter ratio.
|
|
|
|
<h3>16: Beamwidth</h3>
|
|
|
|
Displays the halfpower (-3dB) beamwidth in degrees.
|
|
|
|
Beamwidth is calculated as: pi/180*1.15*lambda/D.
|
|
|
|
Note that the constant 1.15 is dependent upon illumination tapering, which is determined by the feed.
|
|
|
|
<h3>17: Gain</h3>
|
|
|
|
Displays the calculated gain in dB.
|
|
|
|
The nominal gain is calculated as: g0=10\*log10(eff/100.0\*(pi*D/lambda)^2)
|
|
|
|
The gain is then adjusted for surface error with Ruze's equation: g=g0-685.81*(e/lambda)^2
|
|
|
|
<h3>18: Effective area</h3>
|
|
|
|
Displays the effective area in m^2.
|
|
|
|
Aeff is calculated as: g*lambda^2/(4*pi)
|