Introduction
Recently I discovered the NanoVNA vector network analyzer. I had seen articles in QST magazine over the last several years and was intrigued (Ref.1/2). My first experiment was with my HF vertical antenna. I calibrated the unit for the HF band from 1MHz – 30MHz and tested the SWR (Ref.3). The results were exactly what I was expecting showing the resonance at the tap point on the matching load inductor. In this post I will examine the results of testing my Marine VHF antenna. Since the last test, I was able to get the NanoVNA software to interface with my laptop so all the results can be easily displayed.
Initial Setup
Figure 1 shows the NanoVNA Port 1 connected to the VHF antenna RG-58 coaxial cable through a PL259/sma adapter. The first step is to calibrate the unit over the frequency range of interest. You can work directly with the unit, or use the pc software to access the unit which I did (see YouTube video). I entered the frequency range of interest which is 150MHz – 180MHz. Then I placed an Open on Port 1, followed by a Short, and finally a 50 termination.
Test Results
Figure 2 shows the SWR of the VHF antenna plus transmission mounted on my lab bench. Figure 3 shows the antenna mounted on a steel balcony beam outside. For most transmitters, an SWR <1:5:1 is acceptable so the performance is very good. An ideal mount would be on a mast high above the blue ocean.
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References
#1. – “NanoVNA V2 Plus4 50KHz – 4GHz Two-port Vector Network Analyzer”, P.Salas AD5X, QST Magazine April 2022
#2. – “NanoVNA Vector Network Analyzer”, P.Salas AD5X, QST Magazine May 2020
#3. – “HF Antenna Testing with NanoVNA”
https://jeremyclark.ca/wp/telecom/hf-antenna-testing-with-nanovna
