Tower Safety Equipment

The tower climbing video that has gone near viral pointed out a few things.  Climbing towers is dangerous business, best left to those who are trained for it and have the insurance.

It is true that tower climbing contractors have the responsibility to protect their own workers while working on a clients tower.  That does not completely absolve the tower owner from liability.  The it is incumbent on the tower owner to provide a safe structure to climb.  This can mean the mechanical integrity of the tower, reduction of transmitter power while workers are in high RF energy fields, and providing the proper permanently attached safety equipment on the tower itself;  Climbing ladders, ladder safety cages, rungs, elevators, and fall arresting gear.

In that tower video post, I mentioned something called a safety climb.  That is a cable, usually 3/8 inch stainless steel aircraft cable, attached, about eight inches from the climbing surface like this:

Western Electric 200 foot tower with retro fitted safety climb[
Western Electric 200 foot tower with retro fitted safety climb
The tower itself was built in 1959 and did not have this equipment when new.  This was a retro fit kit, installed in 2003, I believe.

The tower climber wears a harness with a special karabiner attached to the front and waist level.  When climbing this ladder, the karabiner slides up the cable.  If he were to fall, the karabiner has an auto locking or braking mechanism that would stop his fall.

Tower safety climb
Tower safety climb, attached to climbing ladder

Many tower climbers, especially those that have been in the business for a while, do not like these things.  When climbing, especially if one has long legs, the tendency is to bump your knees on the bottom of the next ladder rung.  This is because the belt holds the climber’s waist in making it difficult to get the rear end out, away from the ladder the way most people like to climb.  The alternative is to climb with the knees spread apart, like a frog, which is hard on the hamstrings and quite literally, a pain in the ass.  However, if a tower is so equipped, it must be used.

I have, wherever possible, retro fitted towers with these devices.  Of course, all new towers come equipped with them. In some situations, it is not possible to retro fit towers with safety climbs, either because there is no attachment point at the top of the tower that meets the OHSA spec, there is not a climbing ladder, or it would affect the tower tuning, as in an AM tower or near a TV or FM antenna.

Hundreds of gallons of ink have been spilled by Los Federals in OHSA regulations 29 CFR 1926 and 29 CFR 1910.268(g) regarding fall protection and fall protection equipment for telecommunications workers.  In this litigious world we live in, tower owners and or their on site representatives should know these rules and make sure they are followed.

The Problem with the Phone Company

It they don’t care all that much about traditional phone service anymore.  Through attrition, they have reduced their tech work force to about half what it was 15 years ago.  All of the infrastructure; over head cables, buried cables, office frames, switching equipment, is getting old.  Some of the cabling around here, both buried and overhead,  is the original stuff, installed 100 years ago.  Because it is expensive to replace, they don’t want to change it out, opting to simply limp along, swapping out pairs when a line or circuit goes dead.

I will be surprised if the traditional wired telephone network still exists in ten years.  Think about it, ten years ago were were just heaving a collective sign of relief that Y2K turned out to be nothing, remember that?

For the local phone giant, offering 3 in one (telephone service, internet service and cable TV) is more appealing than servicing their existing accounts, including HICAP (high capacity) data circuits like T-1, BRI&PRI ISDN, etc.  Much less so for a POTS line, which, good luck if you really need it fixed right away, we’ll be over when we get to it, just keep your paints on mister.

I’ve written about this before. A particular station for my former employer uses a T-1 circuit to relay the program from the studio to the transmitter site.  This is fairly common in larger metropolitan areas where 950 Mhz STL frequencies are not available, nor is line of site between the studio and transmitter site obtainable.

Back in 2002, when the company was in the process of aquiring said station, I recommended a 950 Mhz STL.  There was an existing STL license, fully coordinated, that came with the main station license.  Only the equipment was needed.  No, I was told by the CFO, we will do a T-1, thank you very much.  I argued my point, saying that putting our radio station exclusively in the hands of the phone company was a bad idea.  We would have problems with outages and service.  No, said the CFO, this is New York, all the radio stations do that.  Not exactly, New York is about 15 miles SOUTH of here, this is Westchester, the cables are old, a lot of them are overhead, which exposes them to lightning, vehicle damage, water, etc.  There will be service issues if we rely solely on a T-1.

No, he said, “We are using a T-1 and that is final.”  I hate to say I told you so, but… Let us examine the history between then and now:

Date of outage Date of restoration Total days
April 5, 2004 April 9, 2004 4
September 8, 2006 September 10, 2006 2
May 2, 2007 May 5, 2007 3
August 27, 2009 September 4, 2009 10
September 5, 2010 September 15, 2010 10

Fortunately, I wrote all this down in the transmitter site log.  I was able to check it yesterday, when I went to restore the station to normal operation after the latest T-1 failure.

During those periods, we have used BRI-ISDN, which is okay but it was carried the same phone cable.  It is likely to go down if there is a major cable interruption.  We have installed a second T-1 circuit, which fails when the other T-1 circuit fails.  We have used 3G wireless sprint card and streamed audio from the internet.  That didn’t sound great, but we did clear inventory.  We have moved one of the AudioVault servers to the transmitter site, and updated it once a day via shoe leather network, that sounded great, but it was difficult to do.  We have borrowed an ethernet connection from another tower site tenant onsite and streamed internet audio via wired connection, which sounds pretty good.

Still, the best thing to do would be to establish our own STL path to the transmitter and get rid of the T-1 lines.

The Problem with the Phone Company is they are not all that interested in simple copper circuits anymore.  Now, there is something called FiOS, which, it would appear is a much better profit center than ordinary copper circuits.

Rebuilt tubes

As broadcasters, we don’t really hear that much about ceramic power vacuum tubes these days, as more and more broadcast transmitters migrate to solid state devices.  Once upon a time, however, power tubes where the engine that drove the entire operation.  Tubes had to be budgeted for, stocked, rotated and replaced on a regular schedule.  Some of those dern things were expensive too.

Take the 4CX35,000A which was used in the Harris MW50 transmitters.  The transmitter used two of these tubes, one in the RF section and one it the modulator.  As I recall, new tubes cost somewhere north of $8,000.00 each from EIMAC.  Plus, in the A models there were two 4CX1500A driver tubes.  All of which could add up to an expensive maintenance cost every two years or so.

The next best option was to buy rebuilt tubes.  Rebuilt tubes were about half the cost of brand new ones.  Some people complain that rebuilds don’t last as long, or only last half as long as the new tubes.  I never found that to be the case.  I often found other factors effected tube life far greater, such as filament voltage management, cooling and by extension, cleanliness.

I can say I never had a warranty issue with ECONCO tubes.  I cannot say that about EIMAC, as during the late 90’s and early 00’s (or whatever you call that decade) I had several brand new 4CX3500 tubes that were bad right out of the box.  These days, ECONCO and EIMAC are both owned by CPI.

I spoke with John Canevari from ECONCO who had a lot of information.  For example, as the tube ages, the filament gets more flexible, not less.  Most ceramic power tubes use a carbonized tungsten filament containing some small amount of thorium.  As the tube ages, the filament can no longer boil off enough electrons and the emission begins to drop off.  That is the normal end of life for a power tube.  Occasionally, some catastrophic failure will occur.

There are many steps in the rebuilding process:

  1. Dud is received from the field, the serial number is recorded and the tube is tested in.
  2. The tube is prepped by sand blasting the sealing rings
  3. It is opened
  4. Filament is replaced.  In 60-70% of the cases, the grid is replaced.  In those tubes that have a screen assembly, 20-60% of those will be replaced.
  5. Interior of the tube is cleaned
  6. Tube is resealed and tested for leaks with a gas spectrometer
  7. Tube is placed on the vacuum machine.  Tubes are evacuated hot, smaller tubes take 12 to 24 hours, very large tubes can take up to one week.
  8. The tube is nipped off of the vacuum while still hot.  When the tube is fully cooled the vacuum scale is normally around 10-12
  9. Exterior of tube is cleaned and replated.  Silver for tubes that are socketed and Nickel for tubes that have leads.
  10. Tube is retested to manufacture’s original specification or greater.

After that, the tube is sent back to its owner or returned to stock.  John mentioned that they are very proud of there vacuum tube processing machines, so I asked if he could send along a picture.  They certainly look impressive to me, too:

vacuum tube processing machine
Vacuum tube processing machine, photo courtesy of ECONCO

Not exactly sure which tube type these are, but they sure to look like 4CX15,000:

vacuum pump on rebuilt ceramic power tubes
Vacuum pump working on rebuilt ceramic power tubes, photo courtesy ECONCO

Econco has been in business since 1968 and rebuilds about 600-1,000 tubes per month.  In the past, broadcasters used most of the larger tube types.  However, with the majority of broadcast transmitters shifting to solid state, other markets have opened up such as industrial heating, military, research and medical equipment.

Copper theft and how to avoid it

One of the unfortunate signs of the times is increased theft of valuable materials. Copper, while not as expensive as it once was, still fetches a fair amount at the scrap dealer. One local telephone company has been having a difficult time keeping their aerial cables intact in certain areas. For radio stations, the situation is compounded by remote transmitter sites with lots of copper transmission lines and buried ground radials around AM towers.  Reduced staffing levels also means that the weekly trip to the transmitter site is now every two weeks or perhaps once a month or even less.

Site that are not visited or monitored very often are prime targets for copper theft.  Forget asking the local constabulary to patrol more often, the few times I tried that I was met with a blank stare.

A few common sense type things that I have learned over the years may keep your site intact:

  1. Keep  up appearances.  A neglected transmitter site is more likely to attract the wrong type of attention from the wrong type of people.  Clean up any rubbish, dead equipment, keep the weeds and trees cut down, etc.  If a site looks well tended and often visited, a thief may think twice about lifting valuable metals.
  2. Along with #1, keep things buttoned up.  Secure all transmission lines to ice bridges, remove any dead lines, etc.  If there are ground radials poking out bury them, same with ground screens, copper strap, etc.  Out of sight, out of mind, leaving this stuff exposed is asking for somebody to come along and give a tug.
  3. Fences and locks.  Towers are required to be fenced and locked to prevent electric shock hazard.  It is also a good idea to fence the building, generator and fuel tank if possible.
  4. Post all sorts of warning signs, RF warning, high voltage, no trespassing, under video surveillance, pretty much anything to deter trespassing and vandalism.
  5. Add video cameras with a video recording device since most theft occurs during non-working hours.  Last year, the company I used to work for traded a video surveillance system for the studio location.
  6. Compensate a neighbor to keep an eye on the place and call you if they see any suspicious activity.  It doesn’t even have to be money, I once worked out a deal with a neighbor for some T-shirts and CD’s.   That was the best alarm system we ever had.

In the long run, keeping all the copper parts where they belong is a great way to avoid those annoying “the station is off the air” phone calls not to mention the expense of replacing damaged transmission and ground systems.