Monday, March 27, 2023

RF Chokes and my NanoVNA

Spent some time last week working with my NanoVNA. I've had the VNA for a couple of years now  but used it mostly for checking SWR on my antennas. It's the 4-inch screen model, which is easier on the eyes but still small enough to throw in my go-bag. 

I've had a few issues with RF in the shack causing some interference. I use a multi-band vertical and an 80-meter dipole as my primary antennas. The vertical is prone to producing some RF on the coax so I built a couple of chokes to help eliminate the problem. After watching some YouTube videos on using the NanoVNA properly (I really like Barry's videos - , I was thrilled to be able to measure the signal loss on each choke.

I started by building a testing jig which allowed me to use the "Through" function of the VNA with a choke inline. I cut a set of alligator clips to use with it and wrapped it all in heavy-duty shrink wrap to protect it. My "Ugly Balun" choke was fair. Probably enough to be ok at the lowest frequencies, but not efficient higher up the dial. I then built a choke with RG-316 coax and a 140-43 toroid. This one was much better across the band. I took the opportunity to also install my grounding box with lightening arrestors at the same time.