There are so many things wrong with my up-link feed:
- RG-6 75 Ohms feed line from a 50 Ohms PA
- the base of the helix is embedded in hot-glue
- the material is Zn-plated Cu-wire (Zn corroding)
- the spacing of the helix is off and narrows towards the end
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| 2.4 GHz up-link helix feed |
You are seeing the result of ignorance and tweaking, which resulted in the feature of point 4).
I hooked a nanoVNA2 up to the PA side of the RG-6, then pushed and pulled on various parts of the helix to minimize the SWR. This procedure included the 75 Ohms transmission line of course. Thereby, I improving the SWR from 4.6:1 to 2.4:1.
Next step you probably be to play with a wire-cutter again. As you can see, the helix has 3+3/4 turns, so, there might be room for improvement still.
For the time being, I am pretty happy with my up-link signal anyway.
