Apologies for the delayed reponse. a) We were a little busy, and b) inevitably when there's a big story going on, my AVSForum notifications stop coming.
As you know, we suffered a failure in our shared antenna on Sunday evening. At the Needham site, we have a 100-foot top-mounted stick, housing two separate antennas. Channels 4, 5, 38, and 44 transmit from the upper antenna, and channel 2 from the lower. In earlier days, analog channels 38 and 44 also used the lower antenna, but since the analog shutdown in 2009 channel 2 has been the only station on it.
The failure occurred in the upper antenna and knocked off all of the stations using it. Channel 2 was unaffected. Shortly after, channel 5 switched to a low-power standby antenna. That left channels 4, 38, and 44 completely dark.
We have three 8 transmission lines running up the tower, one each for the upper and lower antennas, and one spare. We initially cut the spare line into use, in case the problem was with the top antenna's line, but that turned out not to be the case. In the meantime, an RF consultant arrived on site and took measurements with a vector network analyzer, which revealed the problem to be at the base of the upper antenna.
This afternoon we switched channel 2 into channel 5's standby antenna, which freed up the lower antenna, and we are now feeding other stations into it. Channel 2's generosity in operating at low power while permanent repairs proceed should not be underappreciated, as it is only because of that generosity that we are on the air at all.
A word here about why it takes so long to effect repairs. The transmission lines consist of copper pipes, 20 feet long and 8-3/16 in diameter, each containing an inner copper pipe, 3" in diameter, with the inner and outer separated by Teflon insulators. The sections are joined with nuts and bolts at flanges at each end. Connecting, moving, and mounting of these lines is heavy, exacting work. Now think about doing it when the pipe is vertical and you are balanced on a tower 1,100 feet in the air. It's slow. Real slow.
We expect the final repairs to take a while. Working on the antenna is especially difficult, as the panels that surround the problematic part must be removed and the part tested and brought to the ground, all while hanging from rigging almost ¼ mile up.
We do have an elevator on the tower, but it only goes up to the 850-foot level. At that point the tower reduces in width from 12 feet across to 7 feet, so tower workers have to climb the top 250 feet.
By the way, Mike Fitzpatrick is dead-on correct with his comments. We treat the over-the-air systems with as high a priority as everything else. Every transmitter engineer and his immediate superior (and I) reported to the site Easter Sunday evening as quickly as they could, and didn't leave until late that night. Yesterday I was at the site from 6:30am until 11:00pm, and then back again early this morning. In addition, representatives from all of the stations, their parent companies, and our consultants and vendors have been intensely involved and working continuously to resolve this. This was a very big deal to every station involved.
For Bill Bibeau and others interested, see these two sites for some pictures of the installation: http://www.fybush.com/sites/2004/site-040723.html
. The first site has quite a few pictures from back in the analog days; most of that stuff is gone.
I'll be happy to provide additional details for the geeks amongst us. Just ask...