A recent FCC action has established a new level of fear for those stations that are in a multiple facility location. This includes any site that is shared by several stations, including mountains and buildings. The action involved stations on Mt. Wilson in the Los Angeles market.
This view of Mt. Wilson antenna farm in Los Angeles was taken from the observatory visitor parking area in the spring of 2003. The far left tower is KCAL(TV) and the tower on the far right is KCET(TV). Photo courtesy Don Mussell.
Anyone who has had the opportunity to visit Mt. Wilson will remember the unbelievable number of antennas of every type and description to be found spread along the mountaintop. With all of those stations happily pumping out RF, it probably shouldn't come as a big surprise to find one or more locations where the total RF level exceeds the applicable standard. The FCC recently did an inspection of the mountain-top and found a location where the total RF level did exceed the applicable standard. It was said to be approximately 100 feet from a United States Post Office. A news release discussing this matter can be found at www.fcc.gov/Daily_Releases/Daily_Digest/2003/dd031022.html or simply by going to www.fcc.gov, the Daily Releases, Browse Past Issues and checking October 22, 2003.
The rules are specific in this matter. If a location is found where the standard is exceeded, all of the stations whose transmitters produce power density levels exceeding 5 percent of the power density exposure limit applicable to their particular transmitter share responsibility for reducing the RFR to permissible levels. In this case, four stations were found to each be contributing more than 5 percent of the limit. They were then found to have not taken adequate steps to keep the public out of that area. The result was a fine of $10,000 each for the four stations. That would no doubt bring strange cries from the front office of your station, including loud shouts starting with “Why didn't you _____?” You can fill in the blank with whichever part of the problem you will be charged with.
The Resonant Results’ Tower Watcher TW-100 model has power supply, remote control interface, and a sensor as one unit. It separates the electronics and the detector with the detector outdoors and the electronics indoors.
So, what to do? To start, a site survey should be done with a non-ionizing radiation meter. This column has long argued that the point should be to find any location where the standard is exceeded without any consideration of time averaging. The standard is concerned with the average exposure over a 6-minute period. In addition, the standard concerns levels averaged over the whole body. Both of these little phrases open the door for mistakes, mis-evaluation, lawsuits, damages and fines. Don't go there at all. If the standard is exceeded at any location, without regard to any averaging, take steps to either eliminate the RF or block access to the location.
Remember, you don't have to be at the tower base for this to be a problem. In the Mt. Wilson incident, the problem location was well away from the towers in an area where public occupancy should have been expected. So, don't just walk around the tower base and then head back to the coffee pot. It is necessary to cover the whole area where anyone might go. This opens a whole new set of questions — How far down the mountain side should you go? Do you worry about such folk as rock climbers and where they might be? It would seem feasible to assume that only those locations where someone might reasonably be expected to go should be of concern. You simply have to use your own judgment in that matter.
One of the manufacturers of non-ionizing radiation meters recently announced a new model that will make it possible to determine who the contributors might be to the overall radiation level. In the past, meters have read total radiation. The individual contributors were then determined by using a spectrum analyzer with an antenna or by turning off stations while monitoring the radiation level. The new meter should make that situation easier.
A technician once advised a station owner that his AM towers had to be surrounded by a chain link fence at least 8-feet high with razor wire around the top. While that might seem like a wonderful idea in order to keep everyone off of the tower, it not only isn't necessary, but also might lead to more trouble than it's worth.
First, the rules only require a fence around AM towers without really nailing down exactly how that fence should be constructed other than saying that it must provide access for maintenance. It isn't necessary to fence each individual tower, if there is a fence around the entire site. There is a requirement that the federal registration number be posted at the site along with the name of the tower owner and contact information. There also should be a no trespassing sign posted along with a sign advising of a danger from radiation and high voltage. There isn't a requirement for FM and TV tower fencing in the rules other than that the public must be restricted from access to high-radiation areas.
On the other hand, there are numerous laws and statutes concerning attractive nuisances, liability, etc. To this regard, you should determine just what your responsibilities are by discussing the matter with the station's local attorney. In this case, the local attorney probably is a logical choice due to his familiarity with state and local regulations. They do vary considerably from state to state. You also should discuss this matter with your insurance representative to insure that your protection meets their requirements and preferences.
You may be advised by the attorney not to use such devices as razor wire. It is not unheard of to be sued for damages by an idiot who slices himself up on such wire when illegally trying to get over the fence. One of this author's clients was recently advised not to use either an unusually tall fence or razor wire. The opinion was that a reasonable fence, in this case consisting of six-foot tall chain link construction without barbed wire or razor wire, met the criteria of removing the tower from the attractive nuisance category without adding the risk of lawsuits. The general feeling was to comply with the law in a manner that would eliminate liability as much as possible. If the nuisance problem was eliminated and the public was suitably warned, they were on their own if they got hurt. Again, discuss this with the station's attorney and insurance company to make sure that they are ready for the results of their decision, not your decision as chief engineer; even better, try to get this approval in writing for your files.
There is a new item that can be of some help in keeping people off your tower. Richard Wood of Resonant Results recently introduced the Tower Watcher at the Madison Broadcasting Clinic. It contains a dual passive infrared detector (PIR). This detector is used to prevent false alarms from small objects and senses the movement of someone climbing on the tower. Multiple motion sensors are oriented so that they will sense someone on the tower itself without being set off by someone walking around the base. This device then gives a fault indication that can be wired into the transmitter remote control system.
It is unfortunate that unauthorized persons seem to consider climbing a tower to be some rite of passage. High school boys as well as drunken college students seem to believe that such action demonstrates some testosterone-laden bravery. In reality, it is just as stupid as trying to demonstrate one's ability to perform great driving feats in one's pickup truck without spilling a beer. The best a station technician can do is make it reasonably difficult to get access to the tower and to post signs advising of the danger and warning against trespassing. If fools ignore the warnings, climb the fences and get on the tower, they simply are taking their own chance at joining that great club made up of those whose last words were, “Hey, watch this.”
Don Markley is president of D.L. Markley and Associates, Peoria, IL.
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