March 2019
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Time to consult the transmitter wall

I saw this at the WIZN transmitter site in Charlotte, VT:

WIZN FM25K  transmitter log

WIZN FM25K transmitter log

Somebody went through quite a bit of trouble to chart the transmitter readings from April of 1987 through about February of 1992.

A closer view:

WIZN transmitter log

WIZN transmitter log

I have not seen this at any other transmitter site, so I though it was an interesting way to keep a transmitter log.  It also seems to be time consuming and a bit obsessive.  Over the years, I have found my fellow broadcast engineers to be a somewhat strange group sometimes.

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.

The NASH: WNSH, Newark, NJ

Lately, I have been working at a site in West Orange, NJ connecting various parts and pieces and thought that this was interesting:

WNSH 94.7 MHz, Newark, NJ main antenna (top)

WNSH 94.7 MHz, Newark, NJ main antenna (top)

That is the main antenna for WNSH, 94.7 MHz Newark, NJ, aka “Nash-FM.”  Below that is the backup antenna for WEPN-FM (98.7 MHz), WQHT (97.1 MHz) and WFAN-FM (101.9 MHz).  More on those stations later.

WFME studio building

WFME studio building

This is the WFME studios, located off of NJ Route 10.  It is kind of hard to see the call letters behind all those trees and whatnot.  There is an older picture from 1999 floating around, which shows the studio building in better condition.  This is a better angle:

WFME studio

WFME studio

I believe WFME is still originating its programming here, now being broadcast on WFME 106.3 MHz, Mount Kisco.  I had to use the facilities there, the interior is like a way back 80’s time machine, which is kind of cool.  If I owned a radio station, I would go for the 70’s office decor; dark wood paneling, shag carpets, bright blue bathroom tile and avocado green appliances, but hey, that’s just me.

WNSH backup antenna, WFME-TV antenna

WNSH backup antenna, WFME-TV antenna

This is the WNSH backup antenna, mounted on top of a UHF slot antenna for WFME-TV.  There is an LP TV antenna mounted there also, but I don’ t know who it belongs to.  Overall, it is an interesting transmitter site on “First Mountain” in West Orange, NJ.  Also located here, WFMU-FM, an old ATT microwave site, now owned by American Tower and several cell carriers.   In other words, it is just like most other mountain top transmitter sites, except there is a shopping plaza across the street.

I gave a listen to the NASH while driving there.  For where it is, it seems to have a pretty good coverage area.  As for the music, well, I am not sure how a Manhattenite will relate to Tracy Byrd’s “I’m from the Country” wherein:

Everybody knows everybody, everybody calls you friend
You don’t need an invitation, kick off your shoes come on in
Yeah, we know how to work and we know how to play
We’re from the country and we like it that way

Being from upstate NY, I get it.  Perhaps the Manhattan salary man will too.  There are no DJ’s on air quite yet, just music, some commercials and a few “Nash-FM” liners that sound slightly distorted.

FM transmitter site tour, Bavaria, Germany

Short, but interesting video tour of an FM transmitter site in Germany. The analog transmitters are 10 KW Telefunken solid state units, 5 main transmitters and two reserve units into an antenna combiner. At approximately the 35 second mark, the video shows a Rhode & Schartz DAB transmitter. Germany uses DAB+ in band III (174-240 MHz).

It is always interesting to see how others are broadcasting.

Do radio transmitters have the capability of electrocuting copper thieves?

I found that question while perusing my search engine statistics today.  The short answer in theory is yes.  If you are a copper thief, it will most likely look like this:

That being the case, however, it is much more likely that an RF burn will result if one comes in contact with an energized antenna or transmission line.  Even small RF burns are painful, large ones can be nasty things.  RF burns occur because of the skin effect, that is to say, the higher the frequency of the AC waveform, the closer to the surface of any given conductor the current will flow.  It is the reason why five watt STL transmitters on 950 MHz use 7/8 or 1 5/8 inch cable to reduce losses.

When a human body part comes in contact with an energized RF antenna, the body part becomes part of the circuit, thus it follows the same principals.  The extremity that is making contact will have its skin burned off.  It also smells bad.

Getting an RF burn is a painful lesson on what not to come in contact with around a transmitter site.  But, that is not all.  Simply being in close proximity to radiating elements of antennas will induce body tissue heating, just like a microwave oven.  This can lead to all sorts of short term and long term damage to organs and other problems.

Therefore, the best thing is to avoid radio and cellular towers if you do not know what you are doing.   Stay out of fenced in areas around tower bases.  No matter how tempting that copper may look, you could be seriously injured or killed if you cut the wrong thing.

How much is prevention worth?

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

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

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

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.

FM transmitter site design

We are currently working with one of our clients who needs to rebuild an FM transmitter site.   The site is an old house which used to function as a studio.  The transmitters are wedged in to various places and the whole place looks like a fire trap.  We are working on moving the transmitters to a new building at the base of the tower and installing all ancillary equipment according to good engineering standards.

Transmitter site design has changed somewhat over the years.  What may have been good engineering standards in the past have changed with newer transmitter designs and needs.  Up until about 1990 or so, most transmitter sites were cooled with outside air.  As such, there was often a “filter room” or “air mixing room” with associated blowers and fans for moving air through the building.  Older sites often had these features built in as part of the transmitter installation.  WPTR’s GE BTA-25 was a good example of this.

Modern solid state transmitters are a little more delicate than there older tube type brethren.  Tubes were designed to run hot and had no troubles with temperatures up to 110 to 120 degrees or so.  Continental transmitters were famous for this.  As Fred Reilly once told me “We’re Dallas and it gets hot here.  The manufacturing floor is not conditioned.  It don’t matter, 100 degrees, 105 degrees, they just keep on working.”  I think he was talking about the assemblers as well as the transmitters.

Solid state transmitter switching power supplies are also somewhat finicky.

A good transmitter site design will incorporate the following:

  1. Good air conditioning.  Calculating the AC load for the transmitter waste heat, other installed equipment, as well as the building solar gain.  Waste heat is a function of AC/RF transmitter efficiency, which is found in the owner’s manual.  If unknown, 50% is a good design standard, in other words, waste heat equals TPO.
  2. Good grounding.  A good grounding system is a must for all transmitter sites.  This includes lightning and RF grounds.  Low impedance paths to a single point ground is a must.
  3. Good power conditioning.  Mountain top transmitter sites are susceptible  to all sorts of utility company irregularities.  Surge protection is a must.  Series type are better than parallel.
  4. Good lighting.  Nothing is worst than fumbling around in a half lit transmitter room trying to make repairs.
  5. Adequate work spaces and clearances.  Electric panels require three feet of clearance from the front.  Cabinet doors should be able to swing fully open.  All access panels should be, well, accessible.
  6. Adequate electrical system.  Pole transformers and service entrance properly sized for load.  Backup power.  Plenty of work outlets around the room.

Some of these may seem like no-brainers, however, one would be surprised at how transmitter sites have grown over the years.  An FM site that may have started with one 5 KW transmitter in 1950 will have been greatly upgraded over the years.  Today, that same site may not employ a 30 KW transmitter, full air conditioning, have several tower tenants, etc.

WHUD transmitter site diagram

WHUD transmitter site diagram

This is a transmitter site that we redesigned about four years ago.  The original site was built in 1958 and had a Gates FM5B as the main transmitter.  The electrical service consisted of two 200 amp panels which had been greatly altered over the years.  It had an old Onan 65 KW propane generator inside the building.  Grounding, Air Conditioning, lighting and work space were all substandard.

The first thing we did was replace the generator with an outdoor unit.  That allowed us to remove an interior partition, freeing up a good deal of floor space.  Next thing we did was upgrade the electrical service and replace the generator transfer switch.  Much of the interior wiring had been altered or added to in non-code compliant ways.  All of those modifications were removed or bought up to current electrical code.

A safety grounding ring was installed around the outside of the building and all grounding points were bonded together.  Nautel has an excellent guide for transmitter sites which includes lightning grounding and protection for AM and FM transmitter sites.  Recommendations for Transmitter Site Preparation (.pdf) and Lightning Protection for Radio Transmitter Stations (.pdf) are available for download from their site.  All RF cable outer jackets are bonded to the ground at the base of the tower and the entrance to the building.  All the interior equipment is bonded together.  Ferrite toriods are placed on all cables going into and coming out of the transmitter cabinets.

With the electrical service upgrade, we added the series LEA surge protector.

LEA series surge protector

Inside view of LEA surge supressor

This site as at the very end of the utility company line and has always suffered from power issues.  This unit greatly smooths out the various nasties that get sent our way.

I decided that it was easier to use compact florescent lights (CFL) rather than the long tubes.  This site is as the top of a rough mountain road and it is simply easier to carry several small boxes in the cab of the truck than four foot or eight foot florescent light tubes.  There is a total of ten 28 watt fixtures in the main transmitter room which light up every nook and cranny.

WHUD transmitter

WHUD transmitter

All of the transmitters and electrical panels were laid out to give working room around them.

The air conditioners were also greatly upgraded and added to the generator load.  Prior to this, when the power went out, which was often. the air conditioners did not run and the transmitter room would overheat unless the door was left open.  What we previously the filter room became space for tenant equipment.  There are a few two way and paging companies still at this site.

Of course, all this work was done while keeping the station on the air as much as possible.  There were a few instances of having to turn off to move transmission lines and so on.

The result of all this work is greatly improved site reliability.

All is not well in paradise

If one considers paradise an FM35A. Going through another iteration of blown transmitter fuses for WEBE, Bridgeport, CT. Yesterday, I spent the afternoon examining the transmitter and found several interesting things:

  1. Fresh arc tracks on the PA cavity and PA loading capacitor
  2. The shoes and bars in the high voltage contactor were severely pitted
  3. One of the mains phases (middle) in the high voltage supply appears to be heating up, likely due to a loose connection.
Discolored wire on buss bar

Discolored wire on buss bar

I checked and re-tightened all of the mains connections.  Apparently, this is an old problem, as the Allen screw was tight.  Interestingly, the fuse that was blown was on the red phase, which is different from what it was last time.

I spent the afternoon filing and sanding off the arc track marks in the PA cavity.  It is very important to file flat all sharp points that where the result of arcing.  Any sharp points will induce corona.  I also filed down all of the contacts in high voltage contactor, which took a fair amount of time. These are soft copper shoes and bars which had so much pitting and carbon I wonder how they didn’t catch on fire.  I filed them flat.  We were back on the 35A transmitter at full power by 4:30pm.

If this happens again, I will bring my megger out and check the insulation on the wire between the disconnect switch and the HV power supply.

When I left the site at 5:30, I felt like we did some good work.

WSPK antenna replacement, part I

WSPK is located on North Mt. Beacon, which is the highest point for miles around. It has a fantastic signal. The site is a little difficult to get to, however, especially in the winter.  In previous years, the road has been impassable four months out of the year.  Some engineers have hired a helicopter to get up there when the snow is deep.  For that reason, it is important to keep the equipment in good shape.

WSPK Shively 6810 antenna with damaged top radome

WSPK Shively 6810 antenna with damaged top radome

After last February’s snow/rain/ice storm, it was noted that the top antenna radome was missing it’s top.  A tower climber was sent up to look at it and it was also discovered that the top bay was bent down and the element was almost cracked in half.  A result of falling ice, likely from the big periscope microwave reflector (passive reflector) mounted above it.

WSPK tower

WSPK tower

The periscope reflectors went out of service in 2007, but the tower owner did not want to pay to take them down, thus a problem was not being solved.   It was decided to replace the 25 year old Shively 6810 antenna with a new one, during which work, the radio station would pay to remove the reflectors from the tower.  In exchange for that work, the radio station would then be able to repair and remount the old Shively antenna below the new one, thus having a backup antenna.  Problem solved, except for, you know:  The actual work.

The tower and the periscope microwave system was installed in 1966, operated on 12 GHz and was used by the Archdiocese of New York to relay their educational television programming from their Yonkers headquarters to the various schools in the Hudson Valley.  Sometime around 1975 or so, the FCC mandated that periscope microwave systems could no longer be used due to all the side lobes and interference issues they caused.  They were to be taken out of service as soon as possible.  The Catholic Church, being a multi millennial organization figured “as soon as possible” meant within the next fifty years or so.  Anyway, somebody else needed that frequency, therefore in 2007, they bought the Archdiocese a new digital microwave system.

The problem with the reflectors; they are big.  They are also heavy, and present a huge wind area.  They are also 300 feet up in the air.

WSPK tower periscope reflectors seen from ground level

WSPK tower periscope reflectors seen from ground level

Finding a day with lite winds on top of Mount Beacon can be a problem.  Luckily, the weather was with us.  Still, it took a while to get this work moving along.  The other consideration is RFR and tower climber’s safety.  There are two digital TV stations, WSPK, several cell carriers, something called “Media Flow,” and a bunch of two way radio repeaters.  The main concern was WSPK, the DTV’s and Media Flow since the top of this tower is right in the aperture of those antennas.  All either went way down in power or off the air while this work was on going.

Rigging a gin pole and getting it to the top of the tower was a chore.  The gin pole needed to be threaded through those torque arms like a needle.

Gin Pole

Gin pole

The tower riggers truck had two winches, one a basic 120 volt capstan, the other a hydraulic winch in the bed of the truck with 1/2 inch steel cable.

Tower rigger's truck

Tower rigger's truck

The bolts holding the reflectors in place had to be cut with a saw, you can see the tower climber working on the left hand reflector, gives you an idea of size.  If this reflector were to fall off the tower, chances are good the major damage and or injuries would result on the ground.  Proceed with extreme caution.

Cutting bracket mounting bolt on periscope reflector

Cutting bracket mounting bolt on periscope reflector

Carefully lowering reflector past Shively 6810 FM antenna and Scala PR-950U microwave antenna.  During this phase, the tower climbers had to push the reflector out away from those obstacles with their legs.  You can see the gin pole at the top of the tower.

lowering periscope reflector

Lowering Periscope reflector

Another view:

Lowering reflector

Lowering reflector

Another view:

Lowering reflector

Lowering reflector

Almost down to the ground.  This measured 15 by 10 feet and ended up weighing 830 pounds.

Reflector almost to the ground

Reflector almost to the ground

One down, one to go.  I can’t believe those gigantic things were at the top of this tower, on the top of this mountain for 43 years and the tower is still standing.  This is going to change the appearance of the mountain top from down below.  For years, it looked like a pair of mickey mouse ears, now it will only look like a tower.  I wonder what the environmentalists will think.

I will make a second post with the antenna pictures as this one is getting a little long.

FM antenna mounted on the side of a smokestack

If a person were to drive south down I-95 through Bridgeport, CT and look off to the left, they would see a 500 foot smokestack for a coal fired power plant.  Side mounted on that smokestack is a 6 bay Shively FM antenna.  The antenna is more visible when driving south.  That would be the antenna for WEBE 107.9 Mhz.  This is right down town, therefore, I would imagine this station has no problems with reception.

Bridgeport Power Plant smokestack, viewed from the west

Bridgeport Power Plant smokestack, viewed from the west

WEBE is a class B FM with a full 50 KW ERP.  Most FM’s around here take advantage of a nearby mountain to gain some altitude and thus reduce the TPO a bit.  There are several class B stations that run less than 5 KW into a relatively small antenna, but they are way up in the 900 to 1000 foot HAAT range.  In this case,  the power plant is located right on the Pequonnock River bay, so the AMSL at the base of the smokestack is only 10 feet.  This means lots of watts out and a fairly large antenna.

They are using Broadcast Electronics FM35A for the main and backup transmitters.  They were installed in late 1986 and are a little long in the tooth.

Broadcast Electronics FM35A transmitter

Broadcast Electronics FM35A transmitter

They run near 12 KV plate supply, about 3.8 amps making 34 KW TPO.  That goes into a six bay Shively 6 bay 6813 antenna centered at 475 feet, which makes the HAAT 117 meters.

One of the problems encountered with at site is the smokestack emissions.  It seems that a fair amount of mercury comes out to the top of that thing.  In the past, this has caused major problems with the antenna shorting itself out and burning up transmission line.  Because of this, the entire antenna system, radomes, and transmission line is supplied with Nitrogen from this liquid nitrogen tank:

Liquid Nitrogen Tank

Liquid Nitrogen Tank

The antenna then intentionally bleeds N2 into the radomes continuously, overpressurizing them,  to keep the smokestack emissions out.  This type of tank is needed because a conventional N2 tank would last about a day, whereas the liquid tank lasts about 20 days.

The BE FM35A decided to blow a 200 Amp fuse on Friday afternoon:

Blown 200 Amp fuse

I had a BE FM30A that would randomly trip the 200 amp main breaker every once in a while.  I could never find anything wrong with the transmitter, it would just come back on and run normally again after the breaker was reset.  I even replaced the breaker thinking breaker fatigue.  Still happened.  In the end, we replaced that transmitter.  In this case, I don’t see that happening anytime soon.

BE FM35A heavy iron:

Broadcast Electronics FM35A plate transformer

Broadcast Electronics FM35A plate transformer

I would not want to replace this thing, it must easily weight 1,000 pounds.

And rectifier stacks:

Broadcast Electronics FM35A rectifier stacks

Broadcast Electronics FM35A rectifier stacks

12,000 volts DC.  That will light up any dirt, dust, piece of fuzz, etc. in the transmitter.

It is one of the more unique FM transmitter sites I’ve ever been to.  Every time I see it, I am reminded of that song, Smokestack Lightning. My favorite version of that song is the live recording by the Yardbirds


A pessimist sees the glass as half empty. An optimist sees the glass as half full. The engineer sees the glass as twice the size it needs to be.

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~1st amendment to the United States Constitution

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~Benjamin Franklin

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~Rudyard Kipling

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~Universal Declaration Of Human Rights, Article 19 was discovered, and not invented, and that these frequencies and principles were always in existence long before man was aware of them. Therefore, no one owns them. They are there as free as sunlight, which is a higher frequency form of the same energy.
~Alan Weiner

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