Purpose - This calculator applies to radio receiving systems operating at frequencies above about 100 MHz. The concept is that the Sun, Earth and "quiet sky" are noise sources of (approximately) known levels. Relative measurements of the total receiver input power for all three allows estimation of the receiver noise contribution and of the antenna gain. The theory behind these measurements, along with ways to apply this information are contained in a 2003 Microwave Update Paper. The calculator below uses the same equations the paper. The initial values for this calculator are for the example case in the paper. Those "Data Input" values should be replaced by the applicable values for your station. To calculate the receiver noise and antenna gain, click on the "Calculate button. The "Clear" button clears all data and the "Reset" button brings back the sample data.
Current Solar Intensity - The information on the noise output from the Sun can be set by either of two different methods. Most internet data sources show Solar Flux Units (SFU) corresponding to particular RF frequencies. This data can be interpolated to find the SFU corresponding to the frequency of interest. For the following two buttons, choose "Solar SFU and Frequency" for this type of input. Solar intensity, i, will be calculated from this SFU and frequency.
Alternatively, if you have already calculated the Solar Intensity, i, this can be entered directly by checking the button, "Solar Intensity."