FCC rejects petitioner’s reliance on 1984 public notice

The Ghost of Public Notices Past dropped by the FCC recently, rattling its creaky 24-year-old regulatory chains. While the Audio Division staff had little difficulty shooing the problem away, this kind of ghost is hard to exorcise entirely. Broadcasters (and particularly FM stations) with plans to change their antennas in the near term may wish to take note.

The public notice in question is a four-paragraph item, released in September, 1984, entitled “Criteria for Licensing of FM Broadcast Antenna Systems”. According to the notice, the Commission assumes that omnidirectional FM antennas have “perfectly circular horizontal radiation patterns”. The notice then warns ominously that the “use of any technique or means (including side mounting) which intentionally distorts the radiation pattern of what is nominally a non-directional antenna makes that antenna directional and it must be licensed as such.” Of course, the licensing process tends to be considerably more complicated and expensive for a directional than for an omni, so it would normally be an unpleasant surprise if you planned on installing an omni only to find that the FCC will be treating it as a directional.

As far as we can tell, the 1984 notice has been cited by the FCC only twice in the last 24 years, and not at all since 1992. The Commission does not appear ever to have even suggested, much less formally held, that the public notice could or should be invoked with respect to your average, garden-variety omni installation, whether that antenna be top-mounted or side-mounted. Despite the fact that hundreds – or, more likely, thousands – of omni antennas have been proposed, installed and licensed since 1984, none of them has been declared a de facto directional under the public notice.

But that didn’t stop a petitioner who recently tried to block a proposed station modification by claiming (among other things) that the omnidirectional antenna proposed should be treated as a directional.

The petitioner was relying largely on claims by the antenna manufacturer that suggested that its specially-designed-and-mounted “lambda” design would effectively “directionalize” the station’s pattern.  The manufacturer in this case was ERI, a highly-experienced, highly-respected company. According to its website, the performance of most omni antennas is determined by “free space evaluation”, meaning that the evaluation is made as though the antenna were magically suspended in space, far away from any nearby structure (like, say, a supporting tower) that might otherwise distort the antenna’s pattern. But since, as a matter of physics, close proximity to a large metal object (like, say, a supporting tower) will invariably alter the antenna’s performance in various ways, the theoretical omni pattern will be subject to distortion as soon as it gets mounted in the real world. Accordingly, ERI devised the “lambda” system to take into account the distortive effects of the tower and mounting hardware (and other factors) and produce a more accurately predictable signal.

So yes, the “lambda” system “intentionally” affects an omni signal in some sense, but only for the purpose of counteracting the unintended distortion which naturally occurs when you bolt the antenna onto a tower. If the goal is to correct unintended-but-unavoidable natural distortion, can that really be said to be “intentional distortion”? That seems quite a stretch.

The Commission’s staff accepted the applicant’s (and ERI’s) explanation, which ideally will send the 1984 public notice back into the dusty books for good. After all, the mere mounting of an omni on a piece of hardware will cause some distortion – that’s just the way these things go. Does that mean that the staff should re-visit each and every omni that has been installed since 1984 to check on distortion levels? And so what if some intentional counter-distortion is engineered into the installation for the purpose of insuring that the signal goes where it’s predicted to go – does it make sense to penalize such efforts?

Still, at least one petitioner thought it was a good idea to conjure up the 1984 public notice. Perhaps it’s time for the Commission to dispatch that notice to the ever-after for good, so that it can’t haunt the FCC’s halls anymore. At a minimum, if the public notice is going to linger on, the FCC might want to provide broadcasters, equipment manufacturers and tower riggers some clear guidance as to just what the notice means, so that all concerned can avoid any unexpected surprises.