As expected, the antenna did not perform as modeled on my balcony. I think my F/B ratio is not great, but I seem to have a strong beam towards CA / NM / AZ. Once I mount it above the railing, I should be able to turn it , but I’m guessing South will always be the dominant direction. I really need a drone now to map out my antenna pattern…
The impedance was much higher than expected. I don’t know why, but even without a balun (just a coax choke) it’s in range of the IC-7300 internal tuner across the whole band. I seem to have side lobes in various directions but there is a strong beam in the direction intended. So we’ll call it a qualified success.
Since the picture, I’ve added length to the reflector element. It wasn’t really doing its job. But now signals from the North and East are attenuated, and signals from the South are stronger.
I used a lot of 2″ aluminum tape. The skin effect makes tape a lot less lossy than wire, especially where low impedances are concerned. Only peeled the back off where it needed to stick. I need to buy some more PVC pipes so I can safely get it above the railing and rotate it a bit. I still use copper tape where soldering is required, but a square inch of copper tape over a square inch of aluminum tape… it might be DC blocked, but that capacitance is negligible for a 20M antenna.
The biggest hiccup was the coax cable drastically changed my impedance curve. Even with a good choke. But tuning it with the NanoVNA directly connected, but with the ground of the final coax connected to the NanoVNA ground seemed to work well.
Leave a Reply