Sun sets over large communication towers

The winter sun sets behind the Ermingen communications tower near Ulm

The other day I had to check on some antennas on a large communication tower near Ulm – part of my responsibilities for the analog communication system linking the county’s emergency medical service ambulances to their dispatch center in Ulm.

Not having been at the site for over a year, I was struck by how empty the installation was. When I first took on this (volunteer) job, there were still two engineers working at the installation, taking care of the various microwave links owned by Deutsche Telekom, as well as the radio and TV transmitters which share the site. Now, the tower is operated by Deutsche Funkturm GmbH, who used to have at least an office downtown where we could get the keys – not anymore. Gladly, the police communication specialists have a set of keys which they are willing to share.

No technicians on site, most of the microwave links given up in favor of fiberoptic links, the large analog TV transmitters replaced by much smaller DVB-T racks. The big bundles of coax and waveguides heading up the tower are still there, but mostly they lead into neverland. A private mobile phone operator, at least, discovered the site as a hub for his millimeter-wave links.

Were it not for the public safety agencies still using the tower for their analog 4m VHF networks, the once-cramped basement housing the electronics would be almost deserted. Once the nationwide inter-agency 380 MHz TETRA network becomes operational, they, too, will be gone.

Once these tall towers were widely visible beacons of high technology, hubs for streams of phone calls and Fax messages, carrying radio and television signals to rural areas, providing entertainment and the information fueling democracy. The trunking traffic has gone to fiberoptic cables running invisibly (and reliably) underground. TV satellites and broadband cable marginalized terrestrial TV broadcasting – already in 2002, only 8% of German households relied on this original form of distribution. To expand network capacity and to offer high-speed data services, mobile phone operators move to smaller and smaller cell sizes, no longer requiring the towering behemoths, far over 100m tall, exposed on hills and mountaintops.

So what is wrong about this? In principle, nothing – the towers were seen by many as eyesores, and are already replaced in this capacity by the wind power generators springing up all over Germany, sometimes rivaling the communication towers in height.

But the fact that wireless technology loses another one of its symbols is also closely linked to the observation that fewer and fewer students take up engineering as a career. It has been claimed that we become victims of our own success. Telecommunications has become ubiquitous to the point that a new generation encounters it only in the form of “media”, not spending a single thought on how the content arrives here from continents away in the fraction of a second. The mystique of radio, for my generation still fueled by the glow of electron tubes in our parents’ radio sets, and also symbolized by the large towers, is rapidly disappearing. Wireless is everywhere, and therefore unattractive.

Yet radio frequency engineers are in higher demand than ever. The demands on the analog portions of wireless communications systems increase dramatically. New modulation formats require high linearity, we move up in frequency to accommodate new services and users, and the congestion at lower frequencies is a nightmare on its own. I know, it is called digital communications … don’t believe it, the crucial parts are still analog, and always will be.

Two element Yagi antenna on the Ermingen communication tower, providing 4m FM links for county emergency medical services.

The Ermingen communications tower near Ulm is a dinosaur in its own right. It is one of the few structures of this size without an elevator. Our antennas are on a platform 109m above the ground, reachable via a very narrow spiral staircase made of steel, seemingly endlessly climbing the inside the conical concrete tower structure. At the top, it gets almost claustrophic, before you open the door and step onto the gridiron platform which provides a clear view, between your feet, of the vehicle which brought you to the hilltop. Not for the faint of heart, and a good motivation to stay in shape.

For me, this tower epitomizes everything which fascinated me with radio when I was a child, everything which brought me into this profession. To paraphrase CNN’s Anderson Cooper – “you can’t sit behind your desk all the time, you have to get out and see for yourself”. Forget about Matlab, folks, real life means coax, solder, and steel.