There appears to be some issue with my version of WordPress, the server in use, and the version of PHP. The ISP recently upgraded my server and migrated my site over to a new unit, which was supposed to be transparent. Right. I am working with the ISP to resolve these issues as quickly as possible and return to my regular blogging.
In the meantime:
Update: All fixed, for now anyway. Something about a mismatched password in the backend. To all those that tried to comment, my apologies. It should all be working correctly now.
Tower light outages are fairly typical in this business and I have spent a fair amount of time at various tower bases poking around in the junction boxes looking for trouble. Over the years, I have replaced several old mechanical tower light flashers with these SSAC solid-state units. The SSAC units are nice, in that they have a zero voltage turn-on, which tends to extend the service life of incandescent bulbs.
This unit appears to have taken the brunt of a lightning strike:
SSAC BKON FS155-30T tower light flasher
I would hazard a guess that lightning struck the top part of the beacon housing where the bulb socket is located, then traveled down the AC line to this device. Luckily, it appears the wire insulation inside the conduit to the beacon fixture is still intact. Sometimes, under high stress, wire insulation can fail, as it is most often rated for 600 volts maximum. I have also seen that happen on more than one tower, especially if water has made its way into the conduit.
SSAC BKON tower light flasher
Side view, this was mounted on a hot AM tower, but was not the unit designed for high RF environments. Those units are denoted with an “RF” suffix. The difference between the two, the RF models have bypass capacitors installed internally.
SSAC FS155-30T destroyed by lightning
Lightning path to ground, through the bottom of the case.
This is a universal truism that can also be expressed as “Murphy’s Law.” I don’t rightly know how Murphy received credit for this, however, I chalk it up to either the luck of the Irish or the gift of self-promotion. Either way, that principle was demonstrated again with a 950 MHz STL link between Mt. Beacon and Peekskill, NY for WHUD.
I noticed, while doing some transmitter maintenance, the receive signal strength of the STL had dropped from 300 µV to 30 µV. That is an alarming development. Therefore, we scheduled a tower crew for the next day, not wanting to go off the air over the coming holiday, which would be a sure bet otherwise. Upon arrival, the tower crew noticed a strange thing in the STL transmission line at the base of the tower, which looked like some type of a splice. Truth be told, I have been associated with this station since 1999 and had never noticed the splice before. This STL system was installed in 1998 when the station’s studio moved from Peekskill to Beacon. I can say, of all the things that have gone wrong over the years, this STL system was always very reliable. Regardless of that, I quick check with a spectrum analyzer showed a 3 dB return loss at 137 feet (41.75 m), exactly the distance from the transmitter room to the base of the tower.
3 dB return loss, distance to fault 137 feet
A 3 dB return loss coincides exactly with the drop in received signal strength at the other end of the path. Thus, the tower crew took apart the splice and water poured out of it. I would estimate at least 4-6 ounces of water (180 ml), perhaps more.
7/8 coax cable splice connector, opened up
We then began to take in the details:
The 7/8 coax coming out of the building was Cablewave FLC78-50J
The 7/8 coax going up the tower was Andrew LDF4-50A
The splice connector was Andrew L45Z
The center conductor threaded connector did not fit properly into the Cablewave cable, it was too loose.
The cable was chaffing on a tower leg, about 50 feet above the splice because it was not properly secured to the tower
The 7/8 splice connector was missing an O ring on the backnut of the Cablewave cable
Thus, water ingress causes the high return loss. Problems with this system began immediately after Hurricane Irene, at the end of last August. We were able to make a temporary fix using two type N connectors of the proper manufacturer for each type of cable. The radio station returned to air just before noon, about 45 minutes after turn off. After the repair, the return loss dropped to about 20 dB, which is good.
The permanent fix is for the entire run of cable from the transmitter room to the STL antenna to be replaced. That type of line splice should have never been used on a 950 MHz STL, and it was certainly wrong to mix cable types with an Andrew connector. Those little details will always manifest themselves eventually.
