Indoor UHF Experiments

Since I was stuck doing antenna stuff indoors in September of 2025, I decided to start playing around with UHF stuff, starting with this antenna, which didn't quite work:

70cm dipole with sleeve balun

NanoVNA: SWR of 3.710 @ 400 MHz, 14.34+j12.09Ω

I then tried a toroid feed, which I now know isn't suitable for 70cm because coils tend to start resonating before even hitting that band.

1:1 current balun feed

NanoVNA: SWR of 1.406 @ 433 MHz, 51.92-j17.3Ω

I still went with it anyway, though!

70cm dipole with toroid balun feed

NanoVNA: SWR of 1.285 @ 442.8 MHz, 39.57-j4.057Ω

Since coils really aren't suitable for this band, I ended up switching to a Mix 61 bead balun instead, but the resulting impedance wasn't good, most likely because of the surroundings:

70cm dipole with a balun made of four Mix 61 beads

NanoVNA: SWR of 2.947 @ 435.9 MHz, 16.97-j64.7mΩ

And just for fun, I threw together a basic dipole using a pair of Red Bull cans with the same bead balun, which ended up faring about the same

Red Bull dipole

NanoVNA: SWR of 2.235 @ 435.6 MHz, 22.38-j962mΩ

Even though none of those worked well enough for my taste, I didn't give up there! Tune in next time for more UHF shenanigans.

#AmateurRadio #HamRadio