During a routine tower inspection, a bay in a large FM antenna array was found with
a damaged feed point. Photos to confirm this damage were taken and reviewed. The tower was than rigged for repairs and a section of the array with 2 FM bays and their matching sections were removed. They are shown below.
On closer inspection, damage is found to one of the bays’ two the feed point shunts. This type of damage may not obvious or even show up as reflected power presented to the transmitter. In this particular case, this bay was one from of a total of eight bays with only one of its two shunts working. Negative effects were not readily apparent due to the mutual coupling and loading of the other seven bays along with the generally broadband characteristics of this array. However, a problem was suspected when the wind would blow a certain direction and occasional transients were noticed on the loading presented to the transmitter. This in turn, would cause a less occasional high voltage plate fault.
This is a reminder that damage to any bay can effect an entire FM array. This in turn, will cause coverage issues in the fringe listening areas!