PIROD tower company has been around for a while, thus there are likely many of these tower light controllers out in the field. They perform a vital service in controlling and monitoring tower lights at remote transmitter sites maintaining a safe operating environment for aircraft and compliance with FCC rules.
PIROD was sold to Valmont in 2004, Valmont no longer manufactures or supports the product. All is not lost, however, as XCEL Tower Controls does support it and parts are still available through them.
These units were fairly rugged, had good surge suppression on the incoming AC lines and are designed for easy access to service parts.
This particular controller is being installed at WRKI in Brookfield, CT. We are adding toroid cores to the tower lighting circuits coming off of the tower because the last controller has been mostly destroyed by lightning. It is a tall tower, on top of a tall hill, thus it gets struck by lightning many times over the course of a year.
WRKI tower, Brookfield, CT
The block diagram looks like this:
PIROD PRLCA block diagram
Click for higher resolution.
The basic schematic looks like this:
PRCLA tower light controller schematic
Click for higher resolution.
The entire manual can be found here, (medium sized .pdf) courtesy of John Brickley of EXEL tower controllers.
Good troubleshooters are becoming rare these days. To some, the idea of working through a problem, finding and then fixing an issue seems like a time-consuming, wasteful evolution. More often than not, it is easier to replace the entire assembly with a new one, throwing the old one away. This is especially true with computer components. The other option is to send a module or assembly back to the factory for repair. Truth be told, often that is a good course of action when a fully equipped repair bench is not available. Surface mount technology can be difficult to repair in the field, as can many RF components.
Being able to troubleshoot components and assemblies is still a valuable skill. Finding and identifying trouble is a good skill no matter what it is used for. I find analytical troubleshooting skills to be good life skills to have. I think my in-laws are occasionally amazed when I walk into a situation and point to something and say: There it is, fix that.
Coil burned out on 40 amp RF contactor
Many times, however, there is no smoking gun. Those situations require a bit of investigative work. The first step in troubleshooting is developing a history:
Has this failed before
Is there a history of failures
Has it been worked on recently
Is it new
Has it been installed properly
It is old
Has it been affected by some outside force like lightning or a power surge
This is where good maintenance records or maintenance logs come in handy. Recently, I have found many places that lack any type of maintenance documents, which means the repair history is unknown. This makes it difficult to find a good starting point and can greatly increase the amount of time required to troubleshoot a problem.
Once the pertinent history is gathered, it can be organized and analyzed for clues. For example, if something has been worked on recently, that is a good place to start. If something has a past history of failures, that is a good place to start. Newly installed equipment is subject to early failures under warranty due to component failures. Old equipment may just be plumb-worn out. Improperly installed equipment can exhibit all kinds of bizarre failure modes. That information coupled with known symptoms would indicate a good starting point for troubleshooting the problem.
If no good starting point can be discerned, then the next step is to recreate the failure. This usually means turning the thing back on to see what it does. Chances are good that whatever the problem is, it will still be there. Once a good set of symptoms have been identified, then it is time to start working at one end of the problem unit once the failed component is isolated.
Oftentimes, equipment manuals will have troubleshooting guides. These can greatly speed up the process for large, complicated things like transmitters, generators, and so on. There is also the tried and true troubleshooting chart:
Generic transmitter power supply trouble shooting chart
This is an example of a troubleshooting chart for a transmitter power supply. Many equipment manuals will have this type of information in the maintenance sections.
It is also important to note that when working on high-voltage systems, it is necessary to have two persons on-site at all times.
Good troubleshooting skills have many applications.
So sent wireless operator John “Jack” Phillips on the night of April 14th, 1912, and likely sealed the fate of some 1,514 passengers and crew of the RMS Titanic, radio call sign MGY. That message was sent in response to the radio operator on the SS Californian/MWL, who was attempting to report icebergs nearby.
RMS Titanic side view
Of course, it would be a gross error to blame the sinking of the Titanic on the radio operator, he was but one small link in a long chain of events that unwound that fateful night one hundred years ago. Beginning with the ship’s design and ending with the Captain of the Titanic, Edward Smith, many seemingly unconnected decisions lead up to the ultimate disaster that befell the Titanic.
After about four days at sea, during the late morning/early afternoon of April 14th, the Titanic began receiving wireless messages indicating “growlers, bergs, and ice fields” were in the area. The Captain decided to alter the ship’s course to the south, out of the supposed ice fields.
In spite of numerous reports of nearby ice, the Captain did not order the ship to reduce speed. It continued on at 22 knots (41 kp/h) up until the time it struck the berg. Lookouts were posted in the crow’s nest, near the bow, to spot icebergs. This was considered normal operating procedure at the time but is the most significant factor in the collision. A number of nearby ships had spotted ice and had greatly reduced speed or stopped for the night. Further exacerbating the situation, the lookouts on the Titanic did not have binoculars, which was due to a mix-up before they sailed from England.
Some of the ice reports received later in the day and evening did not make it to the bridge. Wireless operator Jack Phillips was either repairing a malfunctioning spark gap transmitter or was sending messages from passengers to Cape Race Radio/MCE, Newfoundland. At the time, the (wireless) radio operators were not a part of ship’s company but rather were employed by the Marconi Company for the purpose of sending messages for profit. Any notion of safety or distress communication was an afterthought.
The SS Californian, the closest ship to the Titanic at the time it sunk, was attempting to broadcast another ice warning to all ships in the area at about 10:30 pm. The message was broken off by Phillips with a terse: “SHUT UP! SHUT UP! I AM WORKING CAPE RACE” At about 11:30 pm, Cyril Evans, the Californian radio operator closed the station and went to bed. Ten minutes later, the Titanic struck the iceberg.
5 KW synchronous rotary spark gap transmitter
The Titanic used a 5 KW synchronous rotary spark gap transmitter, which was state of the art at the time. The power is measured at the input of the DC motor. Considering the efficiencies of the motor and generator, the ability of the spark gap to generate RF, and the efficiency of the tuning circuits and antenna, the actual power radiated by the transmitting antenna would have been significantly less, on the order of a couple of hundred watts. The above schematic is not exactly the same as the unit installed on the Titanic, as the meters and additional controls for motor speed and generator voltage have been omitted. Additionally, some sources report the transmitter as a 1.5 KW non-synchronous unit. The difference between the two would be very apparent in the sound of the received signal; a synchronous transmitter had a tonal quality to it versus a non-synchronous or simple spark gap, which sounded like hissing. Wireless operators from shore stations and other ships who worked the Titanic reported that they were using a synchronous unit.
The transmitter used two frequencies; 600 meters, or 500 KHz, and 300 meters, or 1,000 KHz. Because of these frequencies, the maximum range during daylight hours was about 200-400 miles (322-644 km). At night, the ranges were considerably more, 1,000-2,000 miles (1600-3200 km), which is typical for medium frequencies, including the AM or standard broadcast band in use today. Thus the effort by the Titanic radio operators to clear the backlog of message traffic during darkness, when Cape Race was about 374 miles (602 km) away.
Another part of the problem was with the transmitting and receiving apparatus itself. The transmitters were crude and generated broad harsh signals. The receivers were also very broad, and nearby transmitting stations could easily wipe out all frequencies on early receivers. That is what likely prompted Phillips’ outburst, something termed today as blanketing interference. Vacuum tubes (aka valves) had yet to be accepted for widespread use as amplifiers and most receivers were simple tuned circuits connected to a detector of some type. As such, receivers were far less sensitive and selective than they are today.
Interestingly, the Titanic had both types of receivers on board. The main receiver was a tuned circuit with a Marconi Magnetic detector (aka “Maggie”) and a valve receiver as a backup. The valve or vacuum tube was likely a simple diode detector connected to a tuned circuit.
After the collision, Jack Phillips stayed at his post sending out distress messages and communicating with other ships en route to assist. Long after the Captain told the radio operators they were dismissed, Phillips persisted until power was lost and the radio room began flooding. He perished shortly after in the 28° F (-2°C) water, however, assistant operator, Harold Bride, survived.
There is also some bit of discussion about the rudder commands given after the iceberg was sighted. Most accounts say, First Officer, William Murdoch, gave the command “Hard over starboard” which would be the equivalent of the right full rudder, effectively pushing the back of the ship to the left.
As rudders work, the amount of water flowing over the rudder determines its effectiveness or loading (resistance to water flow). With the center screw turning at full speed, the rudder would have quickly loaded and pushed the rear of the ship away from the center line by re-vectoring the water coming from the propellers. There is no way to know if this would have changed the outcome as not enough is known about the maneuverability of the Titanic. Her sea trials consisted of about seven hours of sailing time before passengers were embarked.
The next commands issued were “full astern,” on the engine room telegraph. Because of the design of the ship, it took about thirty seconds to engage the rudder and backing engines. The ship continued straight ahead at 22 knots (11 meters per second), traveling 372 yards (340 meters) before beginning to turn. The center screw had no reverse, so it was simply stopped. Once the engines were reversed, the rudder lost much of its effectiveness due to turbulent flow and stalling. The ship could not maneuver around the iceberg, striking it in a glancing blow springing the hull plating in five forward compartments on the starboard side.
As it was the Titanic’s maiden voyage, the first officer did not have much deck time and was likely less familiar with the maneuvering characteristics of the ship versus other ships he had conned. On most other ships of the time, including the SS Californian, which had just completed the identical maneuver, that combination of rudder and engine room telegraph commands would have been appropriate to stop and swing the ship around the berg.
The SS Californian was within sight of the Titanic as it sunk, observing several “rockets” (as many as eight) being fired. When informed of the rockets, the Captain of the Californian asked for their color but did not move to investigate or wake the wireless operator. According to some of the Californian bridge crew, the Titanic looked strange in the water, like something was wrong. The Californian attempted to signal the Titanic with a blinking light, which was not acknowledged. Inexplicably, the Californian never attempted to investigate further until 5:30 am the next morning when wireless operator Evans was back on duty and reported the sinking to the bridge.
Therefore, the entire chain of events that led up to the disaster includes:
Too few lifeboats for passengers and crew
Not enough training in the deployment of lifeboats
Very short sea trial period for the ship’s crew before passengers were embarked
Overconfidence in the water-tight door system in keeping the ship afloat
Binoculars for lookouts were not procured in time for sailing
The ship’s rate of speed is too fast for the conditions, with numerous reports of ice in the area
The ship’s radio operator dismissed ice report from the nearest ship (almost within view at the time) so he could continue to send paid message traffic
The combination of helm and engine room telegraph commands did not produce optimum maneuvering
Failure of the nearest ship to recognize distress flares (or rockets) as such and render assistance
Change any one of those nine things and the outcome might be entirely different. Something to ponder.
The result of this disaster was the formal codification of shipboard safety requirements known as SOLAS or Safety Of Life At Sea. Those standards include the transmission of distress signals, distress communications, numbers of lifeboats, radio watches, fire suppression systems, and training for passengers and crew. Currently, the distress communication system is known as the Global Maritime Distress Safety System or GMDSS.
Troubles at the AM tower; I don’t know why, it won’t switch power. Over the phone I can tell, the program director’s day is not going very well. Press the “day” button but there is no kerchunk, the directional coupler shows the load is junk. Out into the big field, I go to find the problem quickly and fix it just so. The wind is cold, the snow is deep, I think of the contract terms I must keep. Reaching the tuning house, take out the keys, lock, do not be frozen, please. Once inside, there I find, no big surprise, the mice have been a working this pre-sunrise. A nest they have build in a most inconvenient place, in the back of the phasor wiring chase. Oh, the wires they have chewed, the circuit’s destroyed, all for the lack of mousetraps deployed. As I reach in to clean out the mess, the smell of mouse makes me gag, I confess. The fuses are blown, the contactor is jammed, perhaps, if I am lucky, I can move it by hand. A large screwdriver strategically employed, I pry up slowly, further damage to avoid. The bar thunks up, the contacts engage, the transmitter is ready to apply amperage. Call on the cell phone, tell them it’s fixed, stand back and watch the base current meter, transfixed. Then; Up it goes! Wonderful radio frequency current flows! I clean up, lock the door, lock the gate, carrying bad news the owner will hate. The damage is grave, the repair bill is steep, if a good relationship with the FCC you desire to keep. Business is off, the accounts are low, is this really necessary, he wants to know. The terms of the license are your obligation to keep, getting caught out of tolerance will not be cheap. Looking forlorn, the owner says in disgust, it is only the AM, but fix it if you must. Happy as a lark, with a song in my heart, I dig though the manual and order the part. Time to go home, eat breakfast, brush teeth, take a shower. I have another client to see before the noon hour.
40 amp RF contactor
Dedicated to all those who have been there, done that and the breed of RF men and broadcast engineers who are slowly fading away.