antennaicon Antenna Virtual Slide Rule Calculators    
Download a PDF guideA PDF primer explaining basic parabolic antenna parameters
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This page contains several virtual slide rules useful for estimating parabolic antenna parameters, signal losses and several other important radio frequency link attributes. Click and drag the hand symbol   hand  or the dashed line below the slide rule to move the scales. This page does not work on mobile browsers. Press "F5" or refresh your browser if you resize the window to reset things.

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Beamwidth/GainBeamwidths, nulls and gain
Free Space Loss/Far FieldSpace loss and distance to far field
VSWR/Angle/EIRPVSWR, subtended angle and power
G/TGain over temperature
Effective NoiseNoise considering system bandwidth
Wind ForceForce due to wind
Fig of Merit/Off Axis EIRPFigure of merit considering temperatur and EIRP on/off axis
Illumination LevelSignal level at another satellite
Classic SliderulePickett N600 ES Slide Rule
   
Beamwidth and Gain Beamwidth is also known as half-power beamwidth. Beamwidth is the angular measurement between peak power and the point where the power drops 50% (3 dB). Gain is a property dealing with an antenna's ability to direct its radiated power in a desired direction.
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Free Space Loss and Far Field Free-space path loss is the loss in signal strength of an electromagnetic wave resulting from a line-of-sight path through free space with no obstacles to cause reflection or diffraction. Far field is the point at which the energy radiated becomes predictable.
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VSWR, Subtended Angle and EIRP The Voltage Standing Wave Ratio (VSWR) is the ratio between the impedances of the feed lines and the load. A reflector with a long focal length has a relatively flat surface and a narrower subtended angle requiring relatively large feed horns and consequently higher aperture blockages. The Effective Isotropic Radiated Power (EIRP) is the apparent power transmitted towards a receiver assuming that the signal is radiated equally in all directions. The EIRP is a function of the gain and transmitter power.
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Gain Over Temperature (G/T) G/T is the gain referenced to the system temperature.
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Effective Noise Effective noise is a measure of the noise in the system considering the bandwidth of interest.
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Wind Force Computes the overturning force on the antenna.
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Figure of Merit / On-Off Axis Effective Isotropic Radiated Power (EIRP) Computes the Figure of Merit and EIRP on and off-axis.
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Illumination Level Computes the signal strength at another satellite.
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Classic Slide Rule A beautiful virtual implementation of the Pickett NS-600ES by Derek Ross. This is the model that was aboard the Apollo 11 mission and taken to the moon by Buzz Aldrin. Click the image to go to Derek's page to see it in action.
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