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By Paul Thurst, on January 30th, 2012
I sometimes get the distinct impression that the corner office doesn’t understand what it takes to keep a radio station on the air and in good repair. It is most often the problems or “issues” that tend to get the most attention. The things that are working well tend to get ignored. After all, how often do you hear a news report about the airliner that landed safely.
 Lightning strike, TV tower When lightning strikes the tower and knocks the transmitter off the air causing major damage and expensive repairs, that is a problem. When lightning strikes the tower and nothing happens, no problem. What is the difference between those two situations?
 Grounding strap, FM transmitter site If the generator starts and runs during every power outage and has done so for the last five years straight, it is obviously a reliable unit, does it need all that maintenance?
 Caterpillar 75 KW diesel GENSET Money spent on preventing undesirable outcomes can be difficult to quantify as disasters and events that do not happen are ill defined. It is difficult to quantify the “amount saved” on something that didn’t or won’t occur. Using past situations is good start, but that only covers a fraction of possible outcomes. In order to invest money wisely, one has to look at the probabilities. If there is an unlimited budget, then the probability exercise should be minimal, however, there is very seldom an unlimited budget.
For example, how much does a back up STL system cost vs the risk of being off the air while the main STL system is being repaired? How often do failures occur, when are they likely to occur and for how long are all good questions. Is there an alternative to a full back up like an IP CODEC? Such a solution would cover all aspects of the STL system including antennas, transmission line, transmitters and receivers.
There are certain FM stations north of here that have neither RADOMES or antenna heaters. Once every two years or so, the antenna ices up and the transmitter folds back due to VSWR. How much of an impact to listeners notice when this happens? If it happened more often, say two to three times a year, would it be wise to invest in some type of deicing equipment?
What is the ownership and management opinion on off air conditions? I have often heard tell “Oh, its only the AM, we don’t mind if it goes off the air.” That is, until it actually goes off the air, then it is a big problem.
Based on my and others experiences, these are the things that will happen at an average transmitter site:
- The electric will go off at least once per year for several hours.
- The main transmitter will fail at least once every two years.
- Lightning will strike the tower at least once per year.
- The STL system will fail, at unknown intervals.
At studio sites, these things will occur:
- The file server will crash depending on the operating system
- The telephone lines and or T-1 service, internet service, ISDN etc will go out
- The electric power will go out for several hours
- The satellite dish will fail once every two to three years
- If there is a tower, it will get struck by lightning
Other site specific things can occur like floods, blizzards, earthquakes, fire, etc.
Money spent on backup systems for those items is good insurance. Not only will the station stay on the air, the on call engineer’s phone will ring less often, which, if you are the on call engineer, should make you happy.
If a full backup is not available, a second transmitter for example, having a good stock of spare parts on hand can mean the difference between an early evening and an all nighter. Keeping good maintenance logs and well documented repair records can point out trends and give a good basis for ordering spare parts.
Repair trends are important. If the same part seems to be going bad over and over, it is time to dig deeper and find the cause of failure.
The old adage “An once of prevention is worth a pound of cure,” still holds true.
By Paul Thurst, on December 14th, 2011
Blogging has been light due to work load being heavy, at the moment. We are engaged in moving transmitters out of this old house:
 WINE 940 WRKI 95.1 former studio and transmitter site Into this new transmitter building:
 WINE WRKI transmitter building at base of tower The former building was the original studio for WRKI, 95.1 MHz, which signed on in 1957. The co-located AM station, WINE 940 KHz, did not sign on until 1963. As such, the building is a little worn around the edges, so to speak. The FM transmitter has an auxiliary cooling device, for those hot summer days as the building itself is un airconditioned:
 WRKI Harris FM25K transmitter, circa 1986 The rest of the building is in similar condition. Ceiling tiles are falling off the ceiling and getting ground into the floor, junk is pile up in almost every corner, rodent feces, and the basement, don’t even get me started on the basement.
The basic floor plan for the new building is simple:
 WRKI WINE transmitter room floor plan Right now, the preliminaries are being done, mounting the coax switch, running conduit, pulling wires, etc.
A few design notes:
- This building is much closer to the tower, which is sited on a high hill (715 feet, 218 Meters) and sticks up 500 feet (152.1 Meters) above that. Basically it is the area lightning rod, thus special attention will need to be paid to grounding and bonding. I decided to isolate the electrical ground in favor of the RF ground for lightning protection. This involves putting toroids on the electrical ground conductors.
- The building itself is shielded with continuous steel plating, but that has been cut in a few areas to install air conditioners. Those areas will have to be repaired and the AC units bonded to the steel plate.
- Back up cooling will be in the form of a large exhaust fan and intake louver.
- The tower itself is AM radiator for WINE. It is 170 degrees tall, which means high RF fields at the base, therefore good RF bypassing is needed.
- The transmitter room itself is fairly small for what needs to go in there. careful design and placement is required.
Here are some in progress pictures:
 WRKI backup transmitter, Harris FM3.5K, coax switch in the background The first order of business was retuning a Harris FM3.5K transmitter to function as the backup. The current backup transmitter is an RCA FM20E, which no longer runs. After the move is completed, that transmitter will likely be scrapped.
I attached super strut to the ceiling at four foot intervals. I used this strut to support the 4 port coax switch. All coax in the transmitter room is 3 1/8 inch hardline, which has a power rating of 40 KW. Since the transmitter power output is 20 KW, this leaves a lot of head room for problems. When working with 3 1/8 inch coax, it is important to remember to cut the inner conductor 1 1/2 to 1 3/4 inches sorter than the outer conductor, otherwise the stuff doesn’t go together right.
The 30 KW air cooled dummy load was moved up from the other building and connected to the coax switch. This allowed the backup transmitter to be tested.
 WRKI backup transmitter and dummy load Three inch ground strap connects all the transmitters, racks, and dummy load to the station ground.
 WRKI ground strap, new transmitter building Electrical requirements are being met by a 400 Amp service backed up by a 120 KW generator. Once the conduit work is finished and all the wires pulled, the coax to the old building can be cut and brought into the new building, then the station can go on the air with the “new” backup transmitter.
By Paul Thurst, on December 2nd, 2011
This is the main transmitter for WYJB in Albany, NY. The backup is the Harris FM20H3 on the right. I haven’t turned that unit on lately, but it normally makes quite a fuss the first time the Plate On button is pushed. The FM 20T on the other hand, is mellow and even tempered.
 WYJB 95.5 Mhz, class B, transmitter Albany, NY One other thing of note; The FM20T is still on its original tube. I looked up the maintenance records for this transmitter, it was installed in December of 2000. Eleven years later, the 4CX15000A is still cranking out 15 KW TPO, which is impressive. I found that high power ceramic vacuum tubes actually seem to last longer when run closer to their limits than those that are running at half power.
Judicious management of filament voltage is required to achieve this type of longevity. There is a set procedure for installing a large ceramic vacuum tube:
- After the tube is in the transmitter, run it a full filament voltage for at least an hour or so before turning on the plate voltage. This allows the getter to absorb any stray gases in the tube.
- Once the plate voltage is applied, proper tuning should be completed a quickly as possible. Tuning procedures vary from transmitter to transmitter, however, the general idea is to obtain the maximum power output for the least amount of plate current while keeping the PA bandwidth within acceptable limits. Some transmitters can get narrow banded at high efficiencies, which manifests itself as higher AM noise.
- After the tube has been in use for 90-100 hours, the filament voltage should be reduced gradually until a drop in the transmitter output power is noticed, then increased by 0.1 volts.
This maximizes the filament life for that particular transmitter and power output. Once the filament can no longer boil off enough electrons, the tube power output drops and it is time to replace it.
This site also has two other radio stations, WZMR, 104.9 and WAJZ 96.3 , both class A using solid state transmitters of less than 1,000 watts:
 WAJZ and WZMR Energy Onix solid state transmitters Not the prettiest sight in the world, but it does stay on the air. There is no money to go back and neaten up this work, unfortunately.
The tower supports all three antennas. There was some discussion of a common antenna for all three stations, however, WZMR is a directional station, thus it would require it’s own antenna. Doing a common antenna for the other two stations was cost prohibitive, so the tower supports three two bay antennas.
 WYJB, WZMR, WAJZ FM antennas, New Scotland, NY The stations are all located in the New Scotland, NY tower farm. WYJB is licensed to Albany, WZMR is licensed to Altamont and WAJZ is licensed to Voorheesville.
By Paul Thurst, on October 20th, 2011
This is a situation that is and will be playing out over and over throughout the country as the decay advances. W*** signed on the air in March 1963. I believe this is the original tower:
 W*** tower As you can clearly see from this picture, this tower has several problems. Aside from the loose guy wires, the rust and general structural decay, it is bent in several places. Currently, the forces are in equilibrium, but for how long, no one knows. It is certainly not safe to climb. At 144 feet, it is no longer required to be marked or lit, thus, over the years, the paint peeled, the weep holes filed up, the guy wires rusted and loosened, which leaves us with the situation today.
At the transmitter building, there are other issues with the basement flooding, mold, etc. Truth be told, this station makes no money on it’s own. It would cost several tens of thousands of dollars to fix all these issues, and for what; a high end of the broadcast band class D AM station which has not shown up in the ratings for fifteen years. Once upon a time, it was a surviving, perhaps not thriving, local radio station. Those times have long since past.
The question is; what to do with it. Sign it off and surrender the license? Fix all the problems and continue to broadcast? Donate it? If so, who would take it? Or, more likely, wait until the tower collapses and deal with it then.
I’d imagine that there are many others just like it dotting the country. On the whole, the AM broadcasters that are viable would be better off if this dead wood was cut away and discarded.
By Paul Thurst, on October 3rd, 2011
Back last February, it was reported that FEMA/Department of Homeland Security was mysteriously constructing prepackaged AM transmitter buildings at various PEP (Primary Entry Point) transmitter sites across the country as something call “Primary Entry Point Expansion.” These buildings contain a 5 KW Nautel AM transmitter, EAS gear, satellite equipment (the exact equipment list is undisclosed) and a backup generator all in a shielded (Faraday Cage), prefabricated building placed inside of a fenced in compound at the station’s transmitter site. The buildings are being put in place, but not connected to anything in the outside world. They are planning to have about 80 (the number keeps increasing) of these structures in place when the project is completed by mid 2013.
 FEMA/DHS IPAWS PEP expansion project Why, inquiring minds want to know, would they do that?
The new buildings and equipment are, of course, not provided to the government for free. I would estimate each unit costs at least $200,000 based on the following:
- A new solid state 5 KW AM transmitter costs $50-55K
- A new 35 KW generator costs $23K
- A new, shielded communications structure costs $70-85K
- Misc racks, equipment, wiring, shipping, installation costs, fuel tanks, fencing, etc $40K
Those prices are roughly what a private company might pay, the government procurement costs would be higher. Multiply by 80 and it equals at least $16M, perhaps double that when project administration is considered. In the distant past, through something called the Broadcast Station Protection Program (BSPP), FEMA did provide generators, fuel tanks, transfer switches and occasionally a bomb shelter to key EBS stations throughout the country. In the recent past, FEMA and the government in general has been reluctant to fund even mandated changes in the EAS system, first in 1997 when EAS was first implemented and again in 2011 when the CAP modifications were mandated. Why are they now spending at least $16M to provide EMP hardened facilities for AM radio stations?
The rational for this current wave of government generosity, as reported in several industry periodicals, is simply a matter of supplying in depth backup facilities in accordance with Executive Order 13407. The design of the structure and manner of installation seems to indicate the main concern of FEMA is some type of Electromagnetic Pulse (EMP). If an EMP were to happen and it took out the station’s main transmitters, these could be connected to the existing antenna system and switched on. They would provide emergency programming and interface directly with FEMA’s IPAWS (Integrated Public Alert and Warning System). No mention at all of the station licensee’s ability to use these facilities, only FEMA. It would seem that the licensee would be excluded from using their own frequency if these “backup” transmitters were put into use.
The interesting thing about this is that there is a coincidence with the upswing of solar cycle 24. Back in 2008, likely when this project was likely first dreamed up, the predictions were for a great number of sun spots in this cycle. That has not happened and in fact, this cycle in now predicted to be the weakest solar cycle since 1823. Even weak sun spots cycles can create problems, but does that warrant supplying 80 backup transmitters, generators, fuel tanks and buildings to various AM broadcasting stations throughout the country? Further, solar flares and Coronal Mass Ejections (CME) are fairly slow moving events, the sun is well monitored; alerts would be issued and precautions taken.
The story doesn’t add up, but it is difficult to say exactly why.
One other thing to consider: HEMP (High altitude Electromagnetic Pulse from a nuclear air burst). AM transmitters are more robust when it comes to HEMP than FM transmitters are. This is because of their modulation type and frequency of operation. A 5 KW AM transmitter can withstand RF voltages six or eight times it’s name plate carrier rating. Tube type transmitters are even more robust than solid state. The FM broadcast band falls right in the middle of the HEMP fast pulse frequency (72-225 MHz), which will likely resonate in the tuning circuits of the transmitter exposed to it and destroy all of the active devices. Not so with AM transmitters.
A HEMP event would cause catastrophic damage to the electrical grid across wide areas of the continent (see also; Starfish Prime). The voltages instantaneously induced on computer circuit boards and power supplies would be so high, they would likely burst into flames if they were close enough to the detonation. The same for almost all other electronic devices with circuit boards. It would set the country back one hundred or more years, technologically, causing massive disruptions in the food supply chain. Such an act would surely be met with massive nuclear retaliation by the US. The military has not only hardened all of it’s communications and command facilities, they have undergone rigorous EMP testing, finding and fixing design flaws. Thus, the US military’s capacity to wage war would continue undiminished after a HEMP event, a fact that all other members of the nuclear club are surely aware of.
Who, in their right mind would launch such an attack? Nobody.
In the light of current government trends where the FBI engages in a one year sting operation on a Amish farmer selling raw milk, the Bureau of Alcohol Tobacco and Firearms is running guns to Mexican drug cartels, The US Department of Education employing its own SWAT team to serve warrants for delinquent student loans (they say no but offer no other explanation), Gibson Guitars being repeatedly raided for improperly labeled wood products, and so forth, makes me wonder what the government is doing.
Ponder this:
“Take care, sir,” cried Sancho. “Those over there are not giants but windmills.”
Or are they. We need to start asking more questions.
By Paul Thurst, on June 1st, 2011
I have been to many, many transmitter sites. They range from mountain top sites in NY and VT to flat fields with tall towers in Florida to coastal or wetlands AM sites. One site in Massachusetts was located in a state part near Westover AFB. It was formerly the microwave relay site for the Northeast Command and Control bunker, now reused as an FM site for WRNX, Amherst. Access to that site required walking about a mile and a half on a hiking trail, often carrying things like a shop vac, garbage bags or other stuff. Walking in the woods carrying a shop vac will get you some funny looks by fellow hikers.
Yesterday was my Bridgeport, CT day and I took the time to head out to the WICC transmitter site. There are two ways to get there, one can call the Bridgeport harbor master or harbor police and catch a ride via boat, which is fun. Or one can walk down the beach from the long beach parking lot. If it is not an emergency or a night time access, I like to walk down the beach. It is about one mile either way. I normally bring my back pack with some basic tools, water and a sandwich.
 WICC towers in the distance I have been working with another engineer who complains about this.
 Pleasure beach former cottage area Now that the cottages are gone, it is a very pleasant walk.
 Osprey on WICC north tower This Osprey apparently didn’t get the memo: Radio towers are the arch enemy of birds, actually sitting on one and using it as a good place to scout for lunch is akin to sleeping with the enemy.
 United Illuminating pole mounted circuit breaker Circuit breakers on new three phase power circuit installed by United Illuminating last fall.
I wouldn’t want to hike down this strand of beach at night or in a thunderstorm, but on a nice day, it is a pleasant stroll. There are far worse transmitter site access problems. It is a pain if any equipment needs to be taken in or out, that requires some special equipment.
By Paul Thurst, on April 27th, 2011
When confronted with something like this:
 Transmitter Remote Control Wiring It is often faster to cut all the old wiring away and start over. This is a transmitter remote control system which was initially installed in the early 70′s. Over the years, it was added to, subtracted from, divided, multiplied, sliced, diced, etc. In the end, the existing wiring documentation did not match most of what was there. Additional to that, several of those terminals have 120 volts and I found at least one instance of 208 volts.
Therefore, we began by removing all of the wiring from the backup transmitter, running a temporary audio wire and switching to the backup. Then, with all the breakers turned off, all the wiring was removed from the main transmitter, phasor and remote control interface and we started over:
 Transmitter site remote control interfaces Once upon a time, some engineer built these remote control interfaces, which are quite nice. We decided to re-use them where 120 volt control is required. When completed, I will tape over the terminal and label them accordingly. The main transmitter uses open collector control, therefore, it can be wired directly to the Burk ARC-16 IP-8 panel.
 Burk IP-8 Remote Control interface panels The Burk unit, as wired with the main transmitter, common point, tower lights, phasor and antenna monitor. The project has not been without some small off air incidents, once while we removed a metal name plate that had fallen into an inductor in the phasor. All in all, progress is being made.
By Paul Thurst, on March 21st, 2011
I received this link in the comments of a previous post and found it interesting. The BBC will be closing down 648 KHz, Ordfordness England at the end of March, no doubt due to budget cuts. The site has been in use since 1972. Prior to this, site was formerly an OTH array, COBRA MIST, which was then adopted for MW broadcasting. The video is 17 minutes long, but, if you are interested in radio history, technical aspects of AM broadcasting and the like, it is interesting.
Tribute to BBC 648 kHz Orfordness – The Enthusiast’s Version from Jonathan Marks on Vimeo.
These are 600 KW transmitters. As Andy Matheson, transmitter engineer, explains, with a wry smile “I find them (transmitters) very satisfying, I enjoy either day work or shift work, just really working with transmitters has always been very satisfying…” I couldn’t have said it better myself.
By Paul Thurst, on March 11th, 2011
We have received somewhere between 5-6 inches of rain in the last four days. That, coupled with the deep snow pack and the still frozen ground has lead to some flooding. The WLNA antenna array is located along the Peekskill Hollow Creek in northern Westchester County, NY. Back in 1980, it might have seemed like a good idea to locate an AM station in a tidal swamp along the Hudson river. I am sure the land was not that expensive and from an engineering standpoint, having a continually wet, partially brackish ground system may have seemed like a slam dunk.
Unfortunately, the idea never really panned out in application. First of all, the neighbors had other ideas, fighting the radio station owners all the way to the NY State Supreme court. Secondly, technically, it never lived up to expectations. The original non-directional antenna on 1430 was a 1/2 wave tower which by all accounts, worked very well. It did not, however, allow for night time service, which is why the new sight and array was sought. By the time the system was built, AM was already in steep decline and I doubt the owners ever recouped their investment.
Fast forward to today. All five base insulators are under water and the transmitter is off the air. These are pictures from last Wednesday after the first flood waters receded from the Monday/Tuesday storm. I imagine it looks worse this morning, although I don’t own a boat and won’t be wading out there to look.
 Base insulator, tower 2 WLNA array, Peekskill, NY This is tower two of the daytime antenna array. Clearly, it spent some time underwater. We cleaned off all the debris from all the tower bases. A far worse prospect are the ATU’s:
 WLNA tower 1 ATU, Peekskill, NY This is the Antenna Tuning Unit for tower 1, which is the reference tower for both the day and night arrays. The E.F. Johnson contactor in the bottom of the cabinet was fully submerged for an undetermined amount of time. The bottom of the unit is covered in fine silt. The high water mark is visible on the right side of the aluminum cabinet.
The contactor is going to need to be replaced, or at least rebuilt. The ATU cabinet will need to be washed out. There are two other ATUs that suffered the same fate.
 WLNA antenna array, towers 3 and 5 This is the end of the catwalk next to the Peekskill Hollow Creek looking west towards the Hudson River. The water level reached the bottom of the catwalks and had receded about 4 feet when this picture was taken.
 WLNA antenna array, tower 5, Peekskill, NY Lookup east, upstream at tower 5.
 WLNA antenna array looking north, Peekskill, NY This is the antenna array looking north, with my back facing the creek. Tower one is the center tower, tower two is on the right and tower four is on the left. The daytime array consists of towers 1, 2, and 3 bearing 300 degrees. The night time array consists of towers 1, 4, and 5 bearing 335 degrees, so the array makes a big X in the swamp. More from the FCC database.
It is going to take a lot of work to clean out all these ATUs and repair the damage. Clean water is at least 1000 feet away. My question is; why bother? Once upon a time, this station was viable, well thought of in the community, etc. Now, I doubt anyone knows it is off the air. The current ownership over the last thirteen years did, what I’d like to call, a controlled flight into the ground. Axing staff, cutting maintenance and generally neglecting the station. Why not take it dark for a while and figure out what to do with it. Likely somebody would buy it, even if for the land it sits on. Anyway, the grind continues…
By Paul Thurst, on February 23rd, 2011
WISN 1130 AM has been on the air since 1922, although not always with those call letters. In an interesting twist, the license was granted to the local newspaper, the Wisconsin News and the Milwaukee School of Engineering. Initially, both entities were programming the station, however, by about 1925, the newspaper was responsible for programming and the engineering school was responsible for technical operations.
In 1941, the station increased power from 1,000 watts to 5,000 watts and added night time service. This is a series of pictures from that time period.
 WISN night time allocation study Back in 1941, night time interference was taken seriously. The night time allocation study (on 1150 KHz, WISN’s former frequency) includes co-channel stations in the US, Canada, Cuba and Mexico.
 WISN night time allocation ma The array consisted of four Blaw-Knox self supporting towers in a rectangle. Notice the lack of fencing, warning signs and the like around the towers.
 WISN antenna array From the front of the transmitter building
 WISN transmitter site, 1941 The site looks well designed, no doubt manned during operation, which at the time would likely be 6 am to midnight except under special circumstances. Most of these old transmitter sites had full kitchens, bathrooms, and occasionally a bunk room. The transmitter operators where required to have 1st telephone licenses from the FCC. There is only one manned transmitter site in the US that I know about; Mount Mansfield, VT. There, WCAX, WPTZ, WETK, and VPR have their transmitters.
 WISN RCA BT-5E transmitter, 1941 The WISN RCA BT5E transmitter looks huge for that power level. Back in the day when AM was king, these units were designed to stay on the air, no matter what. I don’t know too much about this model transmitter, but if it is like other RCA/GE models from the same era, it has redundant everything.
 RCA AM antenna monitor Old school antenna monitor. I have never seen one of these in operation, however, as I understand it, the scope was used to compare the phase relationship of each tower against the reference tower.
These pictures are of the WISN 1150 array was it was in 1941. Since then, the station has changed frequencies to 1130 KHz and increased power to 50,000 watts daytime/10,000 watts night time. The daytime array consists of six towers and the night time array has nine towers, all of which are 90 degrees.
Special thanks to John A. for sending these pictures along.
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