On 8/23/20 1:42 PM, ea3iji@... wrote:
Hey,
I've just received my nanovna this week, and started to optimise the length of my half wavelength dipole wire, it's just two 5 meters wires connected with a 1:1 balun and attached to the facade of my balcony to work at in the 20meter band.
I start cutting the cable until I reached the minimum SWR measured in the Nanovna. but to my surprised I ended up with 4,25m, far from the theoretical 5 meters, Have I done something wrong????
Sorry if the it is a stupid question, I'm just a newbie.
Thank you!!!!
Not a stupid question..
Lower than expected isn't unusual - all manner of things around the antenna "loading it down" will tend to reduce the resonant frequency.
What I do is fold or crumple the excess length (because if you go too short, or move the antenna, and you need it longer, you can just uncrumple some).
If you're hanging it off a balcony, I wouldn't be surprised if it tunes low. Brick, Stucco, Wood, etc, all have an epsilon lower than free space.
Crumple til it's resonating in band, be happy, and move on.
Be glad you've got something like NanoVNA to see it.
