Is hiring the farmer down the road to come and mow the AM field a smart thing to do? It depends, I suppose, on whether or not your towers will be standing afterward. Hopefully, the guy had some insurance, if not then the station is basically screwed. The article did not mention that, although it did state that “The station is weighing its options,” Which does not sound good.
The good news is at least they were doing the maintenance. Most AM stations these days don’t even bother to mow the fields. Look at this picture:
Tall grass at an AM transmitter site. Owner says don’t cut it.
It is not that I don’t want the grass cut, I do. However, I am not going to pay for it out of my own pocket, that is ridiculous. So, it grows.
Most (if not all) radio engineers cringe when they hear a clap of thunder. Then the waiting begins. What are we waiting for? The cellphone to start ringing, of course. Over the twenty or so years I have been doing this, I have learned a few things. One of them is you cannot overground something.
That being said, you can, of course, ground something improperly.
The worst areas we have for lightning damage are the Gainesville/Pensacola markets. Those places are in the lightning capital of the US. Time was our class C FM station was getting knocked off a couple of times a month.
US Thunderstorm Days map
There is hope. When we upgraded the stations and installed new transmitters in 2004 I insisted that the tower and building be properly grounded. I even got into an argument with the CFO about the “mission creep” as he put it. Never mind that I put $20K in the initial work specification for grounding.
There are a couple of strategies to use when dealing with lightning at transmitter sites:
Grounding: First, foremost, and always. Grounding should consist of multiple ground rods driven as deeply into the earth as possible. At the Trenton Florida transmitter site, we used 20-foot-long ground rods driven in 20 feet apart all the way around the building and in five 60-foot spokes around the tower. All of these ground rods and tower bases were bonded with #2 solid copper wire CAD (exothermically) welded to the ground rods. All turns were kept to a large diameter radius to keep inductance down. When lightning strikes the tower, this creates a large electron sink to dissipate the strike energy into.
Bonding: All equipment cabinets, racks, and everything metal is bonded together and to the same ground point presented by the grounding system. When lightning strikes, often the ground cannot dissipate the energy fast enough. When this happens, the entire ground area around the tower gets charged up. Current will only flow down a less resistive path. If everything is bonded together, the potential between any piece of equipment or component is the same, even if that potential is +10,000 volts. No flow of current means no damage.
The transmitter building is located away from the tower. At almost every FM and TV transmitter site I have visited, the building is right smack at the tower base. By moving the building away about 100 feet or so, the EMP from the tower strike has dissipated (log function) significantly before it passes through the transmitter building. It is a little more expensive to install due to the added transmission line lengths and losses, however, it works.
I have been at the Trenton Florida transmitter site when lightning struck the tower. The result, not even a transmitter overload. Nothing was noticed on the air, no damage was sustained by any equipment. For the last five years, there has been no off-air time due to lightning damage at this site.
Studio building with lightning rod, Gainesville, Florida
The studio site has a similar story. We built a new studio building in 2005, there is a 100-foot monopole that holds the STL antennas. You know that it gets hit during a storm. I remember the manager and IT guy from Pensacola commenting about how nice the new SAS Rubicon consoles were. Both of them also said that they wouldn’t last through the first summer because of lightning damage. Four years later, not a single incident of damage to the consoles, computers, or anything else in the building because we grounded everything as I described above.
Radio is not what it used to be. Sure, the roaring nineties and zero zeros (or whatever you call this decade) were great for the owners. They sold, bought, consolidated, laid off, installed automation, made redundant, and so on. Those that got out before the summer of 2008 made a lot of cash.
They also left the industry hurting. Our competition is keen on eroding whatever revenue is still left in radio, and that competition is large and multiple. New technologies like ipods, iphones, PCS phones, and whatever other wireless mobile device they thought up to 5 minutes ago, is trying to gain our listeners. Satellite radio, which is more like meh, who cares, is making small inroads. But worse than all of that, we have ourselves.
The rot is increasing and it is from the inside out. Everyone is looking to cut expenses. The easiest way to do that is automation. Those stations that have not already automated are likely to, which will further exacerbate the radio losing listeners problem. I mean really, how many more crappy bland “mix” formats, or satellite-syndicated talk radio formats do we need. We are already swimming in a sea of mediocrity. And who gets to take care of all these high-tech gizmos that keep the stations on the air? Usually the Engineering Department. So, we get more work, for the same, or less (by the time inflation is calculated in) money.
That trend has to stop.
It is not irreversible (yet). The station that stands out, can win, and win big. That is all for now, I look forward to writing about radio engineering.
