August 2010
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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

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4 comments to FM antenna mounted on the side of a smokestack

  • J. Aegerter

    I assume the fuse was inside the disconnect switch feeding the transmitter. Never heard of “Brush”, but it says “time delay” so it must be a High Interrupting Capacity unit. Circuit breakers occasionally trip with transients, but when fuses blow, this is usually a bad sign. I would carefully cut open the fuse to see if actually opened do to an overload or a “old age” break. Personally I like Shawmut fuses, and would replace with these. Buss is good also, but a little higher price (at least around here). If it continues to blow, check wiring to the transmitter for scafed insulation, run a hi-pot test on power supply components and/or HV circuits in and around the PA, then a look at your utility power coming in the building. As for the smokestack, I would never have built a station there.

  • admin

    Actually, I know why these transmitters blow fuses/trip circuit breakers. BE provided something called a “Surge Protector” with the transmitter when it was new. The stated reason was to protect the plate transformer, which I believe. The surge protector is nothing more than some large heavy duty MOV’s across all three phases at the transmitter disconnect switch. That is what blows the fuse. I went through this before.

    I will bring my megger next time we go there and check the wire insulation in the conduit though, that is a good idea, I don’t want any fires.

  • J. Aegerter

    It would seem to me that with a “NON” type fuse you might pop one do to an MOV breakdown; however a “FRN” time delay type (as illustrated) would have to have a sustained overload to actually blow. Most of these time-delay or motor-starting fuses have interrupting capacities in excess of 100,000 amperes. I would examine the fuses by carefully taking them apart, and if overload condition (rather than old-age condition) appears, then look at the MOVs to see if they are not cumulatively failing.

  • Pete Tauriello

    That site puts out one tremendous signal even here in Essex County NJ. I have always been a proponent of more watts closer to the ground.

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