There are multiple online T-Network and L-Network calculators online and elsewhere, but one thing that I've always found to be a limitation is that they only show a result for one frequency. In an actual application, we might calculate a fixed network for a particular frequency but we wouldn't readily know what it does at other frequencies. To address that, I have created a browser-based application that allows you to include multiple different frequencies and see the effect on various parameters (SWR, element voltages, element currents, and element power dissipation, etc) at those other frequencies when you build a matching network for just one of those frequencies.
Here are the basics for using it:
1. The topology assumes a series-shunt-series T-network configuration with any of the elements being either a capacitor or an inductor, but it provides the option to declare one of the series elements to be a Short in order to turn it into an L-Network. You can change the type of element by clicking on its type label. In the case of an L-Network, there is no need to specify a Q and whatever you enter there will be ignored.
2. The application assumes that you can use a network analyzer like a NanoVNA or other unit to determine the complex impedance of your actual load at various frequencies. The data for each frequency is considered to be a "Case", and while the default when you start the web page is only three cases you can add as many as you'd like (and later delete them if you want). The only real limit to the number of cases is how much left-right scrolling you're willing to do. The "Add Case" button is at the far right of the page.
3. Case 1 is special in that it represents the frequency and load impedance used for the calculation of values for the Network. All other cases will use those network values to calculate their results.
4. There are two calculation modes. A T-Network is basically two L-Networks connected back to back, and as such if left open ended there are multiple possible solutions. The way to address that is to specify a network Q, which basically determines the midpoint impedance that each L-Network transforms to. So one calculation mode involves specifying a network Q and the app tries to satisfy that condition, but I also added the option to sweep through multiple possible Q values to find the one that results in the lowest currents and voltages for the network elements. That provides the lowest component stress and lowest power dissipation, but it can sometimes result in very large or very small component values. It's worth trying both modes, as well as different Q values for the fixed Q mode.
5. You can restrict the range of values for each element in the network, and you can independently specify their Q. The calculation will honor the boundaries you specify. You can even specify a min and max value very close to each other in the situation where you might want to build part of the network using a particular component you might have on hand. The application will do its best to satisfy whatever limits you give it.
6. Although the application provides for automatic calculation of the network values for Case 1, you can manually change any of the network component values and the results below will change accordingly. The "Auto-Solve from Case 1" button will flash and try to get you to recalculate, but you don't have to do that for the output results to be valid.
7. The default input values when you start the page are garbage ... purposely so. Be sure to change:
a. The available source power at the top
b. The element types, min/max range, and Q
c. The frequency and complex load impedance for each case you are interested in. The network values will be based upon Case 1.
8. There are loads, conditions, and network configurations that mathematically cannot provide a solution. You will get an error message for those situations.
