Ham Challenge HC34 - Match an Impedance

HC34: Match an impedance!
You've got an antenna that has a feed point impedance of 36 Ohms at 7 MHz. How can you match it to 50 Ohms? Try using an online Smith Chart tool to create a matching circuit!

There are many different impedance matching tools available on the internet to simplify and solve this challenge. One RF impedance matching example is at Analog.com.

https://www.analog.com/en/resources/interactive-design-tools/rf-impedance-matching-calculator.html

Entering in the provided parameters (frequency, source impedance, load impedance) provides two solutions. For those familiar with Smith Charts, two different paths will be followed to move from the 36 ohm load impedance to the desired 50 ohm feed point. See the Smith Charts below for these two paths.

The Ham Challenge provides us a link to an add-a-component matching circuits web page: https://www.will-kelsey.com/smith_chart/

Again, there are many examples of this type of web pages that allow adding a component and then calculating how the impedance was changed.

Solution 1: Shunt C & Series L (using L1 & C1 above)

Solution #1 looks good! We've sucessfully matched between 50 ohms and 36 ohms at 7 MHz.

Solution 2: Shunt L & Series C (using L2 & C2 above)

Solution #2 also looks good! We've sucessfully matched between 50 ohms and 36 ohms at 7 MHz.

Which is the better solution? That depends upon a number of factors, including whether a low-pass or high-pass match is preferential, component values and availability (on-hand or purchased), and ease of construction if winding inductors. Largely depends upon your needs and abilities if creating DIY...

There are lots of details and fun things to learn about matching impedances.

See https://hamchallenge.org/ for more ham challenges in 2025!