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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

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

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

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

Harris SX2.5 remote control interface bypass capacitor

Literally, a two cent part.  The transmitter remote control uses opto-isolators.  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.

North Adams restoration work

North Adams restoration work

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!

Are you sure this is a good idea?

Are you sure this is a good idea?

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 a possible.

Mounting pole to tower

Mounting pole to tower

Mounting pole to tower

Mounting pole to tower

Some dude in a hang glider checking out the work

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:

North Adams, fallen tower removed

North Adams, fallen tower removed

North Adams, fallen tower removed

North Adams, fallen tower removed

The temporary monopole being used by the cell providers:

North Adams temporary cell tower

North Adams temporary cell tower

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 it’s 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 new station WNNI which has not officially signed on.

Cellular service for ATT, Verizon and Sprint/NEXTEL were all knocked off line as well internet services and E911 dispatch.  Those services are coming back on line, with temporary modular cell units en route. News report from WWLP channel 22, Springfield, MA:

Here are some pictures:

North Adams Cell Tower

North Adams Cell Tower

WUPE-FM antenna on the ground

WUPE-FM antenna on the ground

WUPE-FM antenna

WUPE-FM antenna

WUPE-FM STL dish

WUPE-FM STL dish

Base of WUPE-FM (formerly WMNB) tower

Base of WUPE-FM (formerly WMNB) tower

WNNI antenna

WNNI antenna

WUPE-FM WNNI and W266AW transmitter building

WUPE-FM, WNNI, and W266AW transmitter building

North Adams Cell Tower

North Adams Cell Tower

North Adams Cell Tower

North Adams Cell Tower

North Adams Cell Tower

North Adams Cell Tower

North Adams Cell Tower

North Adams Cell Tower

Tower base mounting plate, apparent failure point

Tower base mounting plate, apparent failure point

Tower base mounting plate

Tower base mounting plate

Tower Base Mounting Plate

Tower Base Mounting Plate

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 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.

WUPE-FM temporary antenna

WUPE-FM temporary antenna, Shively 6812

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.

WUPE-FM temporary STL antenna

WUPE-FM temporary STL antenna

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!

Carrier HVAC unit damaged by fire

Carrier HVAC unit damaged by fire

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, it broke the natural gas pipe off where it entered the unit:

Broken gas pipe, HVAC unit 1

Broken gas pipe, HVAC unit 1

The next time the HVAC unit cycled on, there was giant torch on the roof with flames reportedly eight feet high.  A local fire fighter 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 electric.  The building was evacuated for about 20 minutes while they overhauled and checked for internal fires.

Carrier HVAC unit damaged by fire

Carrier HVAC unit damaged by fire

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

Carrier HVAC unit damaged by fire

Carrier HVAC unit damaged by fire

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

HVAC unit broken gas pipe

HVAC unit broken gas pipe

The other two units are shut off while the gas pipes are dug out of the snow pack 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 sales people; they are complaining.

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

Carrier HVAC unit tarped

Carrier HVAC unit tarped

Man electrocuted putting up a pirate radio antenna

A south Florida man was electrocuted when the antenna he was putting up struck a power line. Police say 42 year old Jean Adelphonse was working in the dark Monday night when part of an antenna to be used for an unlicensed radio station collapsed and struck a power line.  The Fort Lauderdale Sun Sentinel reported that he was working on the roof of an office building where his other businesses were located.

That is rather unfortunate and completely preventable.  The first red flag here is working in the dark.  The second would be working alone.  Safety is always paramount; whether it is working on a transmitter, putting up an antenna, working on a ladder, environmental conditions such as heat, weather, etc.  In my younger days, I had gotten away with a few careless moments mainly due to blind luck.  I cringe thinking about it today.  Nothing in radio is worth killing yourself or anyone else over.

This type of thing used to happen more often when almost every house had an outside TV antenna.

Let’s be careful out there.

It lives! The PRE BMX III

I have just finished putting back together this PRE BMX III console.

PRE BMXIII analog audio console, reassembled

PRE BMXIII analog audio console, reassembled

We basically ripped the guts out of this unit and in doing so, I was reminded of how well these things are built.  The PRE BMX series consoles were truly wonders of audio engineering.  It is a testament to their ruggedness and serviceability that so many of these units are still in use twenty to thirty years after they were manufactured.

This console suffered some pretty bad water damage to the backplane:

PRE BMXIII module backplane

PRE BMXIII module backplane

Which was replace, along with many switches and buttons.  The Mic2, Mic3 and CD1 modules seemed to have taken most of the damage, there were several logic ICs and IC sockets that needed to be replaced on those modules.  Of course, this was not inexpensive; the parts were somewhere north of $3K plus about 40 man hours of labor… that adds up fast.

The good news, I think that the studio was back in service last night.

Message from the General Manager

Or whatever those guys are called these days:

lumbergh

Especially when that sink is located on the second floor, above the studio on the first floor.  ‘Tis but a small thing really, one of those little details, but in light of the sink also being clogged, it becomes very significant.  That, coupled with the fact that the building is uninhabited at night and disaster is afoot.

Clogged sink

Clogged sink

The water was running slowly all night…

Wet ceiling tiles

Wet ceiling tiles

It filled up the sink.  It ran across the floor.  It soaked the carpet. It seeped into the sub floor and out of the ceiling on the first floor and then into this nice Pacific Recorders BMX III console.

Pacific Recorders BMX III console, draining

Pacific Recorders BMX III console, draining

Pacific Recorders BMX III console, draining/drying

Pacific Recorders BMX III console, draining/drying

You know that burning electronic/plastic smell?  Yeah, that’s it, mixed with stale funky water, wet wood and a nondescript mildewy odor; that is what the room smells like.  Very pleasing.  The furniture below the console was soaked too:

Studio furniture after water damage

Studio furniture after water damage

Some of the input module edge connectors; they didn’t fair so well:

PRE BMXIII burned edge connectors

PRE BMXIII burned edge connectors

The backplane for the power supply buss has to be replaced and these switches with the water bubbles in them, they have to go too:

Pacific Recorders BMXIII buss select switch full of water

Pacific Recorders BMXIII buss select switch full of water

We dried out the furniture with an industrial strength hair dryer.  By three PM we had unsoldered all of the bad parts and cleaned off the modules and the console back plane.

Parts for repairs are on order from Mooretronix.  I doubt this will be repaired before next Tuesday.

Somebody came in and was all “awww, this sucks bla bla bla.”  Well, maybe, but I get paid by the hour and frankly, there are much worse things that I could be doing…

Blown up surge suppressor module

This is a picture of a surge module taken from an LEA series type surge suppressor:

LEA MOV module destruction

LEA 600 volt MOV module

Looks like it took a pretty significant power hit, enough to explode several MOV’s.  This site is at the end of a long transmission line that stretches across an entire county.  Over the years, the station has made many complaints to the utility company about the quality of their power and the frequency of interruptions encountered at this transmitter site.  Occasionally, something will happen.  Often times it is the figurative shoulder shrug.

That is why we installed the surge suppressor.

Whatever can happen, will happen

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 had 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

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

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, the end of last August.  We were able to make a temporary fix using two type N connectors of the proper manufacture 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.

Of popular trees and telephone poles

This picture reminded me of something that happened early on in my radio career:

WDCD three tower array, Albany, NY

WDCD three tower array, Albany, NY

This is another view, looking across from the roof of the transmitter building before the former studio building was removed:

WFLY STL antenna

WFLY STL antenna, circa 1992

The story dates back to 1990 or so.  In the second picture, one can see two Scala PR-950U Paraflector antennas.  These are the STL and TSL antennas for WFLY.  They are on wooden utility poles because of the WPTR 1540 KHz antenna system is behind the poles, out of the picture to the left.   As you can see in the second picture, these poles were immediately behind the studio building, known as the “Gold Studio, ” the name itself being pure propaganda.

Also, in the second picture you can see behind the poles, a pair of poplar trees.  The reason for the second, taller pole was because across the street, out of the picture to the right, there was a stand of poplar trees which were growing up into the path of the WFLY STL system.

When this was noticed, then General Manager, John Kelly, tactfully approached the property owner and asked if the radio station could cut the “popular” trees down.  Of course, the property owner wanted much money to do this.  There was many telephone calls and discussions on how to kill the “popular” trees and other, not so ethical solutions to this growing problem.  Finally, it was decided that it would be simple and less expensive to install the taller utility pole.

Thus, Northeast Towers found the utility pole and came to install it.  In this area of Albany, the soil is a sandy loam, which required much hand digging and back bracing in the hole before they placed the pole in the ground.  As it is a seventy foot pole, a good 12 feet was placed in the ground and the hole was back filled with concrete.  That is why the pole still stands today.

Naturally, all of this work is taking place on the hottest day of the year.  Also, it stands to reason, the guy in the hole doing the manual labor is the oldest, most out of shape person on the crew.  After lots of grunting and swearing, our man comes out of the hole looking whiter than the driven snow and sweating profusely.  He kind of staggered into the back door of the building and collapsed on the floor just inside the back door.  At this point, he was in full cardiac arrest.  The promotions director, who’s office was closest to the door, called the ambulance.

Fortunately, the board operator on WPTR was an EMT with the local fire department.  After his pager went off, he ran out to his car, got his EMT bag and arrived on scene within seconds.  He was able to start CPR quickly.  In the mean time, a crowd had gathered out in the hallway.  John (the General Manager), hearing the commotion, storms out of his office and down the hallway.  He gets to the edge of the crowd and yells:

“WHAT ARE YOU PEOPLE DOING HERE?  DON’T YOU HAVE JOBS TO DO? AND WHAT IS THAT GUY DOING LAYING ON THE FLOOR?”

The good news is, the guy survived, thanks in no small part to the quick action of the board operator.

Anyway, tales of radio when it was fun.

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