New transmitter building for an old station

Putting the finishing touches on another transmitter site rebuild, this time in central NY. This station for many years used this rambling white residential-looking structure for both the studio and transmitter site:

Former studio and transmitter site for WDLA, Walton, NY

Unfortunately, over the years, the building has deteriorated beyond economical repair. A few years ago, the studio facility was moved to a new location in town. Now the transmitters are being moved to this repurposed cellular building:

Former NEXTEL building, now WDLA AM/FM transmitter site

This was purchased used from a local crane company, which had dozens of them on their lot after NEXTEL was absorbed by Sprint. During the permitting process with the town, they referred to it as a “Circular Use.”

They are actually nice buildings, coming prewired with a 200 amp single phase service, two working Bard HVAC units, ready-made coax entry ports, etc. My only complaint (so far), is the light switch timer. I like the idea, the lights get switched off automatically and are not left on for months at a time when nobody is at the site. However, the timer only goes up to 2 hours. Thus, when we were doing the installation work, periodically there would be an audible click, then everything would go dark. Not terrible.

Equipment racks and transmitters
Transmitters and equipment racks

There are also two other FM stations that have an STL transmitter here.

Rack placement and grounding work
STL equipment for two additional stations

All in all, an enjoyable project.

Material safety at Transmitter Sites

Recently, while working at a transmitter site built in the early 1940’s I noticed some fluorescent lights were out. Upon closer examination, I noticed that the bi-pin holder on one side of the bulb was damaged. This led to the removal of the fixture for repair, discovering these devices:

General Electric PCB Fluorescent lamp ballast

As this was made in Schenectady, NY, it is almost certainly original to the building. According to the EPA website, each one of these ballasts contains a capacitor with 3-4 ounces of PCB. There were 16 total fixtures, each with one ballast. The ballasts were removed and the fluorescent lamps were replaced with T8 120 Volt LED units. Any defective bi-pin lamp holders were replaced at the same time.

The danger posed by PCBs is minimal unless they leak or there is a fire. Partially burned PCB results in the production of dioxins, which are really bad. The old GE ballasts were properly disposed of.

The PCB capacitors and transformers were removed from the site many years ago. Other things that might have PCBs; are caulking and window glazing compounds.

That made me think; what else is around here? Several things came to mind.

Fluorescent bulbs waiting for disposal

The fluorescent bulbs themselves contain a small amount of mercury. This is not a problem unless the bulb breaks. If the bulb does break, the EPA recommends leaving the room for 15-20 minutes. Then carefully clean up the broken glass and place it in a plastic bag. Smaller particles can be cleaned up with the sticky side of masking tape or duct tape. Do not use a regular vacuum to clean up the broken glass, this will spray mercury around the room.

The fluorescent bulbs should be disposed of as hazardous waste.

Hot water pipes with lagging (insulation)

Asbestos lagging on the hot water/heating pipes. As long as the lagging is intact, there is no problem. All of the pipe lagging in this building is intact and in good shape. With asbestos, the problems start when things are disturbed. Any type of work on those pipes will require a mitigation plan. Something to keep in mind if there are any building modifications being planned.

If old-style pipe lagging like this is falling off or has been partially removed, it is best to have an asbestos survey done. Newer style lagging will be either closed cell foam, open cell foam, or fiberglass insulation with a cardboard cover.

Other things that can have asbestos are floor tiles and siding.

Halon fire supression system

The halon fire suppression system can be hazardous if one is in the building when it discharges. Of course, fire itself is also a hazard. It is something to be aware of if the alarm goes off.

Peeling paint

Since this building was constructed way before 1978, lead paint is likely on the walls. Not a huge problem unless it is chipping off and you accidentally eat the lead paint chips or inhale pulverized lead paint dust. To clean these up, use a vacuum cleaner with a HEPA filter. Alternatively, wear a HEPA filter and use a dustpan and brush. Do not use a regular vacuum cleaner.

If building modification work is being done in areas that may contain lead paint, a properly certified lead paint mitigation contractor should be hired to remove the hazardous material.

None of these situations pose a direct safety threat, however, one should be aware of these potential issues in their work environment.

Who has time to troubleshoot?

The model for Radio Engineering these days is such that one engineer is covering multiple stations in various locations. At the very least, this person has a full (if not overflowing) plate. Thus, when something breaks, the procedure very often is; to pull the suspected module or board, call the manufacturer and order a replacement. That works as long as the manufacturer supports the model in question or has parts. As we all have learned by now, replacement parts are subject to the global supply chain, which is tenuous.

Then there is the question of AM transmitters. Is it worth it to replace an AM transmitter these days? I suggest it would depend on the market and revenue. In some cases, yes. In other cases, keeping the older equipment running makes more sense.

Troubleshooting is becoming a bit of a lost art. In addition to the time it takes, we tend to be unfocused and obsessed with rapid gratification, ready for the next social media post. What is lacking is the ability to take apart the layers of a problem, accept our initial analysis may be flawed, move beyond those assumptions, and work until the issue is solved. Troubleshooting is often like a crime scene investigation. There are several logical steps;

  • Assess the current situation; take steps to ensure it is safe to proceed. Remove all power from the transmitter and don’t work on failed transmission equipment during thunderstorms
  • Gather evidence; look for fault indicators, alarms, automated log entries, burned components, abnormal meter readings, etc
  • Check external factors; power failures, lightning or storm damage, excessive heat, moisture, etc
  • Check internal factors; aged components, bad cables or connectors, improperly seated boards or components, and obvious signs of damage
  • Work from one side of the issue to the other
  • Check the maintenance logs (if there are any) to see if this problem has occurred before and what was the fix
  • Use available resources; troubleshooting guides provided in equipment manuals, factory support, and available test equipment
  • If a failed component is found, make sure that it is the problem and not a symptom of something else

Here is a good example of a recent troubleshooting evolution; I went to change over to transmitter #2 and these fault lights appeared:

DX-50 transmitter, faulted, no power output

The conversion error on the A/D converter indicates why the transmitter power output is zero.

The first step; secure the transmitter, remove all power, etc. Next, consult the book!

The Harris DX-50 manual gives good troubleshooting guidance. This transmitter was manufactured on March 22, 1990. It has been a reliable unit, to date. Section K.4 Analog to Digital Converter (A34) of the manual suggests loss of audio clock frequency sample due to the following;

  • Loose connection with the carrier frequency sample cable coming from the RF drive splitter (A15)
  • Bad or missing jumper connections on P-10, frequency divider section
  • Bad U-29 (74HC161, 4 bit binary counter, only in use if the carrier frequency is above 820 KHz, Not Applicable)
  • Bad U-12 (74HC14, Schmitt trigger)
  • Bad CR13 or 14 (1N914)

Fortunately, there was a working DX-50 about 15 feet away, so I was able to make some measurements at various places on the A/D converter board.

On the working transmitter (DX-50-1), at the RF sample input (input of R83) on the A/D converter board, I see a nice strong sine wave, on frequency:

WABC carrier from RF drive splitter to A/D converter board
WABC carrier frequency

Second, I measured the logic pulses on TP-6, as described in the manual. Those look good.

On the non-working transmitter, I made the same measurements and found a fuzzy sine wave way off frequency on the input of R83. The logic pulses on TP-6 were normal.

Definitely lost the RF sample. Since the transmitter is 32 years old, I suspected the cable (#92, RG-188 coax) between the RF drive splitter and the A/D converter had gone bad. Perhaps rubbed though on a rough metal edge or something like that. Several checks with a Fluke DVM showed that there were no shorts to ground or internal conductor shorts. End-to-end check on both the shield and inner conductor proved good. So, not the cable…

I then went on a bit of a wild goose chase suspecting the output from the oscillator to be low or the drive regulator power supply was defective. The drive level going into the PA was close to normal but slightly lower than the previous maintenance log entry. Also, drivers 8A and 8B were both on, which is not normal and made me suspect the drive regulator.

I made a call to GatesAir and spoke with a factory rep, who had me swap out the A/D converter, oscillator, driver power supply regulator board, and the buffer amp/pre-driver module between the working and non-working transmitter (while the low power aux was on the air). With the working transmitter close by, I was able to confirm that these boards or modules were not the cause.

Finally, I went back to the RF drive splitter and use my camera to take a picture:

DX-50 RF drive splitter (A15) J-17, board side

There is a 6-pin connector on the underside of the board (J-17). Pin 2 (from the right) is the center conductor and pin 1 is the shield of the cable going to the A/D converter board. Upon closer examination, the solder joint on pin 2 is suspect. I re-heated this connection with a soldering iron and viola, the transmitter started working again.

WABC DX-50-2, returned to service

The extenuating circumstances; the air conditioning at this site was slowly failing and that part of the transmitter was subjected to heat cycling several times. More recently the HVAC system was in the process of being replaced, of course, on one of the hottest days of the year. This pulled a lot of warm, humid air into the room. Also, as this is transmitter #2, it was not in regular use until recently (we began a procedure for operating on alternating transmitters for two-week periods).

All of this work took place over the course of two and a half days or so. That would be a lot of time for the module swap guys who tend to move on to the next outage quickly. On the other hand, buying a new 50 KW AM transmitter is an expensive proposition these days and there are very long lead times on some of these units. Being persistent and focused paid off in the end.

A bit of good news?

We were doing some overnight maintenance on one of the class A AM’s in New York the other night. The aged Automatic Transfer Switch on the electrical service entrance needed to be replaced, thus the power to the entire facility needed to be cut while the old switch was removed and the new switch installed.

During this period, we took the opportunity to do some maintenance on the main and aux towers. All went well. We also notified the National Radio Club that the station was going to be off the air so that their members could log some rare DX. My thought process here was that we might also find a few daytimers who were still on the air or a DA night who was operating with their daytime facilities. A quick look at MW list shows that there are several such stations on 770 KHz:

MW list, North American 770 KHz

Alas, the answer was no, nobody was on the air who should not have been. Reports from Cape Cod, Massachusetts; New Foundland, Canada; Manassas, Virginia; West Union, South Carolina; and south west, Ohio have Cuban and South American stations on the air (Radio Artemisa, Radio Rebelde, Radio Oriental) but all of the east coast daytimers are off.

The 180 degree main mast for WABC is in good shape. You can deride AM and say it is outdated. However, it still gets out and covers vast distances.