Tales of disaster – Page 4 – Engineering Radio

Transmitter repair

Sometimes it is obvious and relatively easy, other times not so much. This summer we have had wave after wave of afternoon thunderstorms. It is almost like living in Florida; almost, but not quite. Anyway, with the storms occasionally comes some lightning damage. At most of the transmitter sites we service, every step has been taken to ensure good grounding and adequate surge suppression. This is especially true of sites that have been under our care for a few years. Even so, occasionally, something gets through. After all, those five-hundred-foot steel towers do attract lightning.

Broadcast Electronics AM5E output tuning section

This is the output section of the BE AM5E transmitter at WROW. The transmitter got pretty trashed; a bad PA module and power supply and this capacitor in the output section. This particular transmitter is 14 years old and this is the first major repair work we’ve had to do it.

Broadcast Electronics AM5E output tuning capacitor

The capacitor was fairly easy to change out. As a general precaution, both capacitors were changed. There was a spare PA module and power supply on the shelf, thus the transmitter was returned to full power relatively quickly.

Broadcast Electronics AM5E output forward and reflected power meters

The rest of the antenna system and phasor were inspected for damage, a set of common point impedance measurements taken, which showed that no other damage was sustained.

Next, the 30 year old Harris SX2.5 A transmitter at WSBS. This failure was slightly more exotic; the transmitter started randomly turning itself off. The culprit, in that case, was this:

Harris SX2.5 remote control interface bypass capacitor

Literally, a two cent part. The transmitter remote control uses optoisolators. The inputs to these opto-isolators are RF bypassed to ground on the back of the “customer interface board.” After determining that the remote control was not malfunctioning, it was down to either a bad opto-isolator or something really silly like a bypass capacitor. This capacitor was on the ground side of the remote off terminal. It shows short on the capacitance meter and 4.1 K on the ohm meter, just enough to randomly turn the opto-isolator on and shut down the transmitter. Being a Harris transmitter, removing and replacing the “customer interface board” was no easy matter. Overall, it took about three hours to find and repair this problem.

North Adams tower update

As promised in an earlier post, here is an update on the progress at the North Adams tower site for the restoration work on WUPE-FM and WNNI. For those unfamiliar, refer to this post: North Adams Tower Collapse.

A contractor installed a 70-foot wooden utility pole last week. We ordered new Shively Versa2une FM antennas as replacements for the antennas destroyed when the tower fell last March. These new antennas are field tunable, which is a nice feature. The idea is that this pole will be used until the replacement tower is constructed, which is many months away. After the new tower is up, I would like to keep the pole in place as a backup facility for both stations.

The bucket truck arrived but the driver had a bit of bad news; there is room for only one person in the bucket. The boss pipes up and says “Oh, that’s okay, Paul can go up and run the bucket”

WAT!

So anyway, it turns out running a bucket truck is not a huge deal; there is a joy stick of sorts that moves the booms around, up down, sideways, etc. Once you get the feel for it, it is pretty easy and three dimensional movement becomes second nature. That being said, at 70 feet in the air, everything gets a little wobbly, so it is best not to jerk the controls around.

The antennas were mounted on a 2 inch pipe which was attached to the pole with 1/2 inch threaded rod. We left a little bit of pipe sticking up above the top of the pole to get the FM antennas as high as possible.

Some dude in a hang glider checking out the work

Getting photobombed by some guy in a hang glider is a new experience. No day is exactly like another in this line of work.

WUPE and WNNI temporary antennas — WUPE-FM and WNNI temporary antennas

The antennas were tuned up once they were up on the pole. We did this with the network analyzer, which made the job very easy. WUPE-FM (top antenna) started using this antenna on Wednesday afternoon (5/7) with greatly increased power output. This gets the station almost the same coverage area as they had before the tower collapse. We tested WNNI (bottom antenna) and it all looked good. WNNI is still waiting for a temporary wireless internet feed for program delivery. Once that is established, we will have to do the intermod measurements one more time before they can go on the air.

Here are some pictures of the cleaned-up site:

The temporary monopole being used by the cell providers:

Basically the pole is ballasted in place by those huge concrete blocks.

North Adams Tower Collapse

High winds seem to be the culprit in the collapse of two towers in North Adams. According to the Motorola system technicians, it happened at about 12:30 am Sunday morning, which is when all their link loss alarms started going off. The larger, self-supporting tower broke from its mounting plate and tipped over into the smaller guyed tower next to it. Effected are WUPE-FM and W226AW (WFCR New England Public Radio) as well as NEPR’s new station WNNI which has not officially signed on.

Cellular service for ATT, Verizon, and Sprint/NEXTEL were all knocked offline as well as internet services and E911 dispatch. Those services are coming back online, with temporary modular cell units en route. N

Here are some pictures:

WUPE-FM WNNI and W266AW transmitter building — WUPE-FM, WNNI, and W266AW transmitter building

Tower base mounting plate, apparent failure point

For pictures of the towers during happier times, refer to this post: Filtering for co-located FM transmitters.

Restoration work is underway with WUPE-FM expected to return to the air at low power by Monday afternoon.

Update:

WUPE-FM was returned to air at low power by about 1pm on Monday 3/31. We took an unused Shively 6812 antenna that was tuned to 94.1 MHz and retuned it to 100.1 by cutting 1/4 inch pieces from the end of the elements until it was on frequency. It took a bit of doing, but with a network analyzer, we were able to get it to 1.2:1 SWR with symmetrical sidebands. Running 600 watts, it covers the city of license and then some.

The STL antenna is a survey antenna mounted on the side of the building. In this configuration, with the leaves off of the trees, we are getting about 250 uV signal, which is pretty good.

The site is now crawling with insurance investigators, cell site technicians, North Adams fire department, Berkshire County Sheriff’s officers, tower workers, etc. After we finished this work, we cleared out to make more room for everybody else. Estimated restore time for W266AW is Wednesday 4/2.

Planning for the replacement tower is already in progress, I’d expect it to happen fairly quickly. The next step for the broadcasters is to put up a 70-foot utility pole and get a full-powered antenna for WUPE. This should happen in the next two weeks or so. That will serve as the temporary facility until the new tower is constructed.

The roof is on FIRE!

We don’t need no water, let the… oh, wait… The actual roof is actually on fire you say?

YES: Ahh! Time to run around like crazy people!

This happened over the weekend at one of our clients in NY. The back story is this; over the last two weeks, the area has received almost three feet of snow. This roof is pitched slightly toward the back of the building. The roofing material is some type of PVC, which is very slippery when wet. Thus, at some point the snow/ice pack shifted towards the back of the building, and it broke the natural gas pipe off where it entered the unit:

The next time the HVAC unit cycled on, there was a giant torch on the roof with flames reportedly eight feet high. A local firefighter just happened to be driving down the road and spotted the fire, thus likely saving the building from major damage. The fire department came and cut off the gas and electricity. The building was evacuated for about 20 minutes while they overhauled and checked for internal fires.

A second unit suffered the same fate, only with less damage:

The fire in this unit was contained in the controller area. Same situation with the gas pipe, only it looks like the pipe was not broken all the way off:

The other two units are shut off while the gas pipes are dug out of the snowpack and checked for damage. At some point, they will be turned back on so that the heat can be restored to the second-floor sales bullpen. Meanwhile, the salespeople; are complaining.

We threw a tarp over the unit with the cover ripped off because more snow is on the way: