Last week I did some repair work at WDDY in Albany NY. It seems the sample line on one of the towers was melted in half by a lightning strike. This station uses sample loops up on the tower for their directional antenna monitoring system.
As it happened, the sample line in question was on the reference tower, which makes everything else meaningless. Before the meltdown, there were several years worth of maintenance logs which showed the previous values for current ratio and phase relationship.
With the transmitter turned off and locked out, I removed the damaged section of line from the base of the tower to the RF choke coil in the tuning house. Where the sample line came off of the base of the tower, there was a UHF type connector which had been improperly applied. Using spare parts, I fixed that connector, then spliced the line into place. Upon power up, the transmitter and antenna readings returned to there previous values, which were slightly out of tolerance.
Thus, some phasor tuning was needed. There are not too many people left that can properly tune an AM phasor. All of the control interact with each other; moving the power or phase to one tower will likely effect all of the other towers and possibly the reflected power on the transmitter. This phasor was made in the 1970’s by Multronics with what looks like all RCA parts. Multronics, I think, was John Mullaney who is more known for the folded unipole antenna. In anycase, after a good few hours of careful hand cranking and a run out to the reference tower to move a coil tap, here are the results:
Not bad for a day’s work.