Troubleshooting an AM array

Today, there will be a quiz.

Recently, we had an AM antenna array go out of tolerance by a good margin.  This has been repaired, however, I though I’d post this information and see if anybody could identify the problem and the solution. Unfortunately, I don’t have a prizes to give away, however, you can show off your AM engineering prowess.

All of the information is pertinent:

  1. The station has two directional arrays (DA-2) using the same towers; the night time array is out of tolerance, the daytime array is not effected and is performing normally.
  2. There were no weather events connected with this event; no electrical storms, no major temperature changes, no rain events, no freezing or thawing, etc.
  3. The problem happened all at once, one day the array was performing normally, the next day it was not.
  4. Station management reports that some listeners were complaining that they could no longer hear the station.
  5. The ATU’s and phasor were inspected; all RF contactors were in the proper position, no damaged or burned finger stock, no evidence of damaged components (inductors or capacitors) was observed.  Several mouse nests were cleaned out of the ATU’s, however, this did not change the out of tolerance antenna readings.
  6. The towers are 1/4 wave (90 electrical degrees) tall.

Readings:

Tower Phase angle as licensed Current ratio as licensed Phase angle as read Current ratio as read
1 147.2 0.583 149.5 0.396
2 (reference) 0 1.00 0 1.00
3 -137 0.493 -125.8 0.798
4 107.5 0.481 92.7 0.355
5 -38.1 0.737 -60.2 0.623
6 -178.7 0.382 142.8 0.305

Licensed values for common point current is 13 amps, impedance is 50 ohms j0 and there is normally no reflected power on the transmitter.  On this day, the common point current readings were 8.9 amps, impedance 38.5 ohms +j5 the transmitter had 340 watts of reflected power.

This is the overall schematic of the phasor and ATU:

WDGJ overall RF schematic diagram
WGDJ overall RF schematic diagram, click for higher resolution

Aerial view of transmitter site, oriented north:

WGDJ aerial view showing towers as identified in schematic diagram
WGDJ aerial view showing towers as identified in schematic diagram

So, where would you begin?  Ask questions in the comments section.