Field notes · all posts · DRAFT: Keanan's edit pending

Three airports in one day (KPWK, KORD, KMDW)

I used to work with lofiatc.com open in a tab most days, so when it went dark in 2024 I was sadder about it than I expected to be. Then I had a thought: what if I recorded the transmissions myself and turned each airport into an album?

It took a minute to get there, but this is how the first iteration of that came together. It involves three Chicago airports, a twelve hour day, one rented Fiat 500 Abarth and a whole bunch of radio equipment daisy-chained into my laptop. The end result is something I'm really proud of and I can't wait for you to hear it. If you're looking for the behind-the-scenes story, read on.

The part where I learned what an antenna is

I'm generally not a hardware nerd or a radio person and my first attempt at a test run of this project was using a handheld ham antenna propped on the trunk lid. I really struggled to get any consistent signal and it was mostly just noise.

After doing some research (with the help of Claude) the fix ended up being a $21 antenna with a magnetic-mount (and one more adapter). Between the antenna and the software-defined radio (SDR) sits a filter that keeps all the non-airport radio frequencies) from drowning everything out. For anyone who wants to build the chain the whole setup was: antenna in the middle of the roof, coax, adapter, airband filter, RTL-SDR, USB hub, and a MacBook Air running SDR++.

The night before, I tested it from the roof of my building, fourteenish miles from O'Hare and I was able to get a signal! That's when I started to get excited.

9:45 a.m.: Chicago Executive (KPWK)

I picked the car up on Ashland at nine, took the Edens north, and started at the smallest of the three on purpose, as a warm-up. Chicago Executive is a business-jet field in Wheeling with a proper viewing area on Palatine Frontage Road: a parking lot, a fence, a sign informing you that the airport does not consent to drones within five miles, and the runway right there in front of you. Seventy-one degrees and dead calm at nine. Tower on 119.9.

First problem: no audio. I spent ten minutes checking cables before finding that SDR++ was politely sending the sound to a speaker that no longer existed. Second problem, which I discovered while fixing the first: I had put a car charger on the packing list and never bought one. The laptop was at full charge and draining, and everything I'd planned for the day was on that laptop.

I had expected a sleepy field. What I got was everything: business jets, Cessnas, and a parade of prop planes I couldn't name, one after another off the same runway, with the tower working all of it in one unhurried voice. And I wasn't alone. The lot was full of people eating lunch out of the trunk and watching with their kids and grandkids. The viewing area is a real place that real families go on a Monday, which I hadn't known and now can't stop thinking about.

I decided to record until it got interesting to stop, and it never did. The warm-up ran until noon (seventy-nine minutes of tape), and when I analysed the audio later, Executive's tower turned out to be the cleanest channel of the whole day. The smallest airport, the one I'd budgeted an hour for, gave me the best recording.

3:30 p.m.: Lincolnshire, and the Target on Mannheim

By mid-afternoon the battery had turned the day into a countdown, so I sat in Lincolnshire and re-planned it: O'Hare from a quarter past four to a quarter past six, Midway from seven until ten to eight, hard stops, car back by nine. Plus a detour to the Target in Rosemont, which is on Mannheim Road and therefore on the way, for the only charger they had that would do the job: a 35-watt Anker that could hold the laptop level while recording and actually charge it while I drove between airports with the lid closed. Never close the lid while the recorders are running. I learned that one too.

4:50 p.m.: O'Hare (KORD)

The plan had said Scott Street, a dead end off Mannheim where you can watch the arrivals come over the fence on a normal day, when O'Hare lands to the west. At 4:09 the recorded weather broadcast said otherwise. The wind had swung around to the east, eight knots, straight down the runways the other way, and O'Hare had flipped the whole airport around to land on the nines. On an east-flow day, Scott Street is the wrong side of the field. So I went to the backup on my day sheet: the cell phone lot on Bessie Coleman Drive. It's free, nobody minds you sitting there, and on an east-flow day the arrivals to 9 Left come over the lot low enough to read the airline.

Eighty-one degrees, hazy, scattered clouds. I had both recorders rolling by ten to five, one capturing the raw slice of spectrum and one capturing what I was listening to. Tower North on 126.9 and 128.15, ground on 124.125, departures on 126.625, and the metering frequency, 121.675, the one I'd never thought about: pushed-back jets waiting their turn, with a controller handing out sequence numbers like a deli counter. It is the calmest sound at the busiest airport in the world.

Late afternoon is when the world arrives at O'Hare. The transatlantic and transpacific heavies come in on a bank, and on an east-flow day they come in over the cell phone lot, one tail after another from airlines I'd only ever seen at the gate, each one calling the tower in a slightly different accent as it crossed the fence. East flow is rare at O'Hare, which means this album is the airport running backwards with the whole world landing on it. The poster art matches the tape.

6:55 p.m.: Midway (KMDW), golden hour

Down the Tri-State to the South Side and up to the top floor of the terminal garage on Cicero, which has about three-quarters of the field in view, costs a couple of bucks, and has no sign saying you can't. Nobody came to ask. Ten knots out of the east, seventy-five degrees and falling, the sun going down at 8:08. Tower on 135.2. Midway is Southwest's house: shorter runways, tighter patterns, and 737s wheeling around in the last light while the city turned orange behind them. It was the calmest hour of the day, and the best photos I've ever taken of an airport cost two dollars in parking.

I second-guessed the tower frequency halfway through and retuned to check another one. It was 135.2 all along, but the detour caught forty-five minutes of the airport's automated weather broadcast, that steady synthetic voice reading wind and runways on a loop, which turned out to be exactly the kind of thing this project is for.

What came home

Three raw spectrum recordings, three audio recordings, and a laptop under twenty percent, charger and all. There was some battery management. Analysed afterwards: 4,740 individual transmissions, about five and a half hours of voices across forty channels, and not one clipped sample. Every airport becomes an album, real transmissions from that day cut into lo-fi tracks by hand, with the frequencies as the titles. O'Hare comes out first, September 29, on Bandcamp and everywhere else you stream. Then Midway. Then Chicago Executive. The raw recordings (just the tower, no music) are on Bandcamp too, for anyone who wants them for their own projects. And there's a free player at finalapproach.fm with the two sliders that made the original worth loving.

I'm calling it Final Approach Radio. It's back, it's legal, and it was recorded from a parking lot by a guy who had to go to Target for a charger.

San Francisco is next, and soon. After that, New York. If you want your home airport on the list, tell me. I'll need to know where to park.