FM transmitters – Page 2 – Engineering Radio

Fixing the switching power supply

This particular power supply is used in Broadcast Electronics AM1A, AM2.5E, AM5E, AM6A, AM10A, FM1C, FM10T, FM20T, FM30T and FM35T transmitters. It is a Computer Products NFN 40-7610, 40 Watt, +5 VDC, +/- 15 VDC BE part number 540-0006.

BE AM1A ECU power supply, C-15 marked with pen for replacement

Generally, one component fails over time on this unit, C-15 which is a 680 uF 35 V electrolytic capacitor. When that capacitor dries out, the power supply will fail to start, do odd things like start and fail after a second or two, or cycle on and off. This will happen after the transmitter has been off for a few minutes. Replacing C-15 with a 1000 uF 50 V capacitor will fix the problem. There is enough room for the larger capacitor if the leads are left a little bit long.

BE AM1A repaired ECU power supply re-installed

We have several of these repaired units on various shelves at various transmitter sites.

As always, when replacing electrolytic capacitors, pay attention to the polarity otherwise this will happen:

Blown Electrolytic Capacitor installed backward

I suppose somebody was in a hurry to get home that day. After I installed this repaired unit, it ran for about 15 seconds and then there was a pop. I opened the door on the ECU and white smoke was wafting out from under the power supply cover. Since the Pope is still The Pope, I knew it was the electrolytic capacitor.

Our beloved BE AM1A is back in service. This transmitter is 22 years old and we can keep it going for as long as parts are available.

Continental 816R2 still chugging along

Had to do some work at a transmitter site today and had to put the backup transmitter on the air for a few minutes.

These were good units in their day and many continue on. This transmitter was new in 1986 and served as the main transmitter until 2015 or so. This unit still has the tube driver (4CX250B) which tended to use a set of tubes every year or so. The PA tube normally lasted 4 years or so.

I miss the analog meters sometimes. There is something satisfying watching all the meters come up together when the plate on button is pushed.

FLX20KFAX50K+HD

Greetings from the Roxborough tower farm, a place with roots. It is slightly northwest of Philadelphia, PA, and is home to many TV and FM stations. The public road that cuts through the tower farm is called Domino Lane because if one tower falls, they all fall. A comforting thought to those that live in the vicinity I am sure.

View from the residential neighborhood next to the site

The reason for the visit; this rather nice GatesAir FLX20 transmitter:

Newly installed FLX20+HD, WRNB Philadelphia, PA

I must admit, I am growing rather fond of these transmitters. This unit is being installed because the station had to move from its old site, just down the hill. The tower owner is taking down the tower and building due to the age of the tower. Thus, it was moved into the KYW-TV building. If Wikipedia is to be believed, KYW-TV is the oldest TV station in Philadelphia, signing on in 1932.

The site is still being built as we were installing this transmitter. These days, the electricians are having supply chain problems like everyone else. There were delays getting the large electrical panel board and other necessary things for the build-out.

Cooling system high point, sight glass, and air purge valve

Overall, the installation went well. This system is using flexible hoses for the coolant loop. We have installed two of these liquid-cooled transmitters with 1 1/2 copper pipe. These days, copper pipe is expensive, so most are opting for flexible hose installation.

Topping off the pump station after 50/50 fillup. After the initial system fillup, it takes a while for all of the dissolved air to come out of the Heat Transfer Fluid (HTF). The extra steps with a liquid-cooled system are worth it, especially if the station is running HD. With the HD carrier on, the transmitter efficiency is 54% AC to RF. With a TPO of around 15 KW, that is a whole lot of heat that needs to be dissipated during operation. It is much cheaper to pipe the heat outside to a heat exchanger than to use several tons of AC to remove it from the room.

Overall, this was a fun project.

A nice pair

I am reminded of a Pink Floyd compilation album from the very early 70s. The music dates back to the late 60s and Syd Barrett. Poor Syd; shine on you crazy diamond!

I recently finished installing these rather nice GatesAir FLX-40 transmitters:

WXBK-FM New York, GatesAir FLX-40 x 2 installation

Audacy New York decided to move 94.7 from the East Orange, NJ location down to the WOR transmitter site in Rutherford, NJ. Acting as contractors for GatesAir, we installed these two transmitters. I can say, I like the liquid-cooled transmitters for several reasons. First, once installed, they seem to be very stable. I believe that the cooling scheme helps prolong the life of the RF devices by keeping the junctions at a constant temperature. Those semi-conductor junctions are tiny for the amount of current that they need to handle. Second, they cost less in the long run to operate. Anytime a refrigerant cycle can be skipped, that reduces or greatly reduces the electrical use. The Heat Exchangers in this system use VFD’s for fan motor control. That means more constant control over the HTF temperature and reduced electrical use on the fan motors themselves.

The pump stations have backup pumps as well. In the newer transmitter firmware, the pump control needs to be set up to automatically failover to the standby unit. It is a couple of clicks in the GUI to do this.

We didn’t have anything to do with the antenna installation, however, it is a good-looking antenna! ERI 4 bay 3 around mounted on one of the WOR towers.

Overall, this was a good project. Lots of moving parts during the installation, but we were flexible working with the client and other contractors and sub-contractors on site.