I bought my NanoVNA in large part to have a solution looking for a problem to solve. My main use for this device was the SWR sweep capability for my antennas, but I soon discovered previously unknown problems that now needed a VNA solution. How pleasantly convenient.
Having a real time Smith Chart display is absolutely invaluable for getting a good feel on impedance for one. More, I have some SDR receivers that can be overloaded by a 50KW AM broadcast station a few miles away. The solution was to build custom filters. My first one, using an online passive filter design tool, was a 500 KHz LPF. It's quite satisfying whipping up a design and then see it perform. I found that even using 10% tolerance parts and tiny axial inductors, I could still produce an effective filter. The VNA proved to me that specifying a cutoff frequency with a good gap to the required cutoff frequency meant I could get by without strict tolerances and hi-Q torroid inductors.
My latest filter design was for a 22nd order 3.5 - 30 MHz BPF. I never would have ever tried that without my NanoVNA. And it works, knocking down the BCB and giving an excellent, although not as deep [nor needed], upper cutoff. This exercise was just as much about learning how to build and test the filter as its actual use.
Testing 455 KHz IF filters made for another fun experience, especially since I had to compensate for the wildly different 2K Ohm I/O impedances.
Yes the NanoVNA for me was a solution looking for a problem to solve. Kinda like going to school and learning how to solve a problem and then look for a problem to solve, lab exercises so to speak, but with immediate real world applications. Chicken or egg? Which comes first is not important. Just pick one and work towards the other.
