Balcony Into the Sky

Getting more brazen with my antenna projects at my apartment.

Used a reshaped coat hanger with a pulley and a lead weight to hook over a tree limb over my balcony. Now I have an anchor point to hang my 10m vertical dipole (or any other antenna that’ll fit). The anchor is below the peak of my apartment roof, so it’s deaf to the East for groundwave, but at least I can get out to anybody locally with decent towers at their QTH. Can’t wait for sunspots to kick up again for 10m to open up for DX, but that might be a while yet.

I also built this crazy, screwy-looking antenna.

Slinky Dipole, mounted and ready. Just add feedline. Radio not included.

It’s a Slinky Dipole, made from a pair of Slinky™ metal spring toys attached to a custom PVC center insulator and suspended with clothesline rope. I have it slung under the eve of my balcony for protection from rain since it’s not galvanized.

I used the length = 2πr * turns formula to calculate the actual uncoiled length and determined that it would resonate somewhere around 12.8MHz if completely straight. What I got was somewhere around 9.5MHz due to the induction of the coils lowering the resonance, as well as its proximity to the metal rain gutter and balcony railing. It’s electrically too short to resonate on 40m, so I tuned the antenna to 20m by clamping turns of the spring together with twist-ties to short them out. That got me close enough. I could probably dangle some wires from the ends or add another pair of springs to lower the resonance, but that’s another battle for another day.

Slinky Dipole, from the end, showing rope and mounts

Anyway, it’s a crappy antenna. It’s kinda deaf to real signals and picks up a ton of nearby noise, but it’s better than not having an antenna at all. I was kinda let down by how badly it performs, considering all the work I put into it, but heck, I did it and now I know.

The Slinky Dipole after completed construction.

I do have some improvement ideas, though. Maybe if I built a swing-arm assembly to move it out over the yard and away from the building. I could also try using a 1:1 balun to kill some of the common-mode interference, or just connect a 300Ω twinlead or 450Ω window line with a 4:1 balun to make it more broadband so that it almost always resonates with lower feedline losses. Speaking of, with my antenna tuner, I can get a resonant match on 40m, 20m, 30m, 10m, and sometimes 15m with 1.5:1 SWR or better. I’m surprised, even. However, 17m is 2.5:1 SWR, 80m is unmatchable, and 160m is almost dead silent.

Slinky Dipole, close-up feature of center insulator, bracket, and feedline attachment.

I’m going through the ARRL Antenna Book for inspiration. I wonder if I should make an inverted V and hang it from the tree hook, or if I should attempt something more grandiose like a triangle loop antenna from the hook or some kind of antenna-and-pulley system to ascend the arch of my roof. Who knows? I certainly don’t.

And I certainly don’t want to hear my landlord complain about it, that’s for sure. I haven’t paid an antenna deposit yet. Don’t want to hear it from my neighbors, either. But so far in the past week of operations, I haven’t heard a single knock on my door, but that’s not to say the neighbors aren’t getting interference. I have a desk lamp that gets brighter when it’s touched; when I key down and speak while pushing more than 40W, every voice peak causes the lamp to change state. So it’s a reminder to be kind.

BTW, I almost had a successful QSO with a station in Cuba on 40m the other night, running at 50W with FT-8 mode while using my Slinky dipole. Would’ve worked if my timing on FT-8 was right. Amazing, considering my balcony faces East and Cuba is due West-Southwest. Radio is funny sometimes.

Here’s hoping I can figure it all out, or at least enjoy the bumbling.