Some broadcast engineering tasks are a bit too daunting for me to consider. Climbing the massive towers that power radio and TV stations is one of them!
Recently, local engineer Aaron Cox had the perfect set of conditions for a drone flight to capture some of that risk, as the weather and timing of an antenna inspection lined up perfectly with his schedule.
Video
I'll summarize a bit of what we talked about in today's Geerling Engineering video, but if you want to watch that directly, it's embedded below:
Safety first
Since every time drone footage is posted, there's a subset of comments about drone safety, I'll summarize what Aaron said in the video: he's a certified remote pilot, he did not have to file a flight plan as the location is registered and not in a restricted airspace, and he worked directly with the tower climbers (and was in communication with them) while flying.
Just like drone pilots have to take responsibility for the dangers inherent to piloting a remote aircraft, tower climbers take a lot of responsibility too. They move with spider-like, intentional action, adjusting their three points of contact during the entire inspection... and that's after lugging 50 lbs of climbing gear vertically, 1115 ft (340 m)!
As noted in the video, the climbers also have trust in the antenna designers to build the system with enough safety factor they can clip on to a single antenna reflector panel and not worry about a fall!
And both tower climbers from ERI are professionals, the best at what they do. Not just physically fit, they know what to look for when inspecting a complex antenna system, and know a lot more about broadcast radio and RF than most.
Antenna inspections
That doesn't explain why they went up and inspected the antenna system, though. But even before that, why not just send up the drone? With the antennas powered down, a drone could capture crisp detail...
Well, some antenna inspections are done with drones. But when you're talking about a multi-million-dollar antenna system with as much complexity as the 'super tower', you need eyes (and sometimes hands) on the small detailed parts. If one of the dozens of hardline coax elbows fails, or if one of the dozens of flex joints develops a leak large enough the pressurized nitrogen gas can't keep out moisture, the entire system could be down for days (at least).
Preventative maintenance means this antenna—installed in 2006—should provide FM and HD radio service to the entire St. Louis metro area for all 10 Class C0 and C1 stations broadcasting on the tower.
A 'super' tower
The tower is technically called the Crestwood Master FM Tower, or the "MacKenzie Road" tower, but I like the nickname some of the local engineers use, supertower.
And one look at the combiner hall, or the final feed line (pictured above, with Aaron standing below it), and you'll see why:
There are 10 stations in this facility, and each of these giant boxes takes a 3" coax hard line output from a transmitter (outputting between 25-35 kW of RF), and combines it into one massive pipe, which is then split up to head up all 1000+ ft to the antenna system mounted on top of the tower.
Watch the whole video for the full story. If you're interested in this kind of thing, check out our Tower Tours playlist.