Wanting to use my new nano VNA for something practical, I wanted to try building a small dipole antenna to have a look at SWR and complex impedance. I’m really debating building a much larger antenna for a radio telescope to measure the galactic hydrogen line at 1.42GHz, so a smaller dipole like this would be a great way to start with using the VNA to tune/test antennas.

I went with cannibalizing a right-angle SMA connector and soldering on some 14AWG solid copper wire to both the center terminal and shield. It came out pretty nice but what I quickly noticed is that despite cutting sections of copper with length λ/4 (quarter wavelength), the antenna was at a fairly lower frequency than was expected. After quickly researching on veloctiy factor, I figured out the issue and cut the antenna smaller and smaller in little increments till it matched the cetner freq of 1420MHz.

dipole antenna dipole antenna