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The GatesAir FLX-40 transmitter

The GatesAir FLX-40 transmitter is my first liquid cooled transmitter installation.  Previously, I have installed an air cooled Nautel NV-40, a V-40 and a couple of BE FM-35T/20T units.  The WEBE transmitter site in Bridgeport, Connecticut is an interesting facility.

Smoke Stack, Bridgeport Energy, Bridgeport, CT

Smoke Stack, Bridgeport Energy, Bridgeport, CT

This coal fired power plant smoke stack which currently holds up the six bay, half wave spaced Shively antenna.  The old BE FM35A transmitters are getting little bit long in the tooth.  Thus, we picked one to scrap, the other will be kept for backup service.

Scraping 34 year old BE FM30A transmitter

We saved a whole bunch of parts to keep the other FM35A on the air in backup service.

BE FM30A power supply cabinet

The power supply cabinet with that 500 pound plate transformer was the last to go.

On second thought, that plate supply transformer is a good spare to have

On second thought, that plate supply transformer is a good spare to have

The FLX-40 came on a large truck.  Fortunately, we were able to open the side gate at the power plant and get the truck to the front door of the transmitter building easily.  The transmitter consists of two large cabinets, each with two 10 kilowatt power blocks.  There is also a pump station and an outdoor heat exchanger.

FLX-40 cabinet two off the truck

FLX-40 cabinet two off the truck

FLX-40 cabinet one

FLX-40 cabinet one

FLX-40 in place, cabinets bolted together

FLX-40 in place, cabinets bolted together

This transmitter design is based on the Harris digital TV transmitters.

FLX-40 pump station

FLX-40 pump station

The pump station and heat exchanger are the same systems used for TV transmitters.  Liquid cooled units require a bit more planning on the installation end.  The coolant piping should have a high spot from which everything else slopes down hill.

Send and return coolant lines

Send and return coolant lines

I put a 1/4 to 12 inch pitch on everything.  Of course, there are several low points, the heat exchanger, pump station and bottom power blocks.

Holding steady at 18 PSI for 24 hours

Holding steady at 16 PSI for 24 hours

After assembling the cooling system, we pressure tested it for 24 hours.

Installation debris in the coolant line strainer

Installation debris in the coolant line strainer

Following that, we flushed the system with distilled water for several hours before we filled it with 40/60 glycol/water mix. Record low temperature in Bridgeport is -7 F (-22 C), thus a 40/60 mix will give protection down to -15 F (-26 C). The more water in the coolant, the better heat transfer capacity it has.

At the highest point in the system, there is a sight glass and an air purge valve

At the highest point in the system, there is a sight glass and an air purge valve

The pump station is controlled by the transmitter, which speeds up the pumps according to how much heat needs to be moved. In turn, the pump station control the fan speed on the heat exchanger outside.

FLX-40 pump station on line

FLX-40 pump station on line

The pump station runs with one motor most of the time. The other pump motor will run in the event of failure or if there is not enough flow through the power blocks. Each of the four power blocks has a flow rate meter on the return line.

Heat Exchanger Fan motor controllers, Variable Frequency Drive modules

Heat Exchanger Fan motor controllers, Variable Frequency Drive modules

Variable Frequency Drive (VFD) fan motor controllers show them running at half speed.

50 KW heat exhanger

50 KW heat exhanger

GatesAir 50 KW heat exchanger mounted on concrete pad behind the building. Air flows out from the motor side.

One of several shipping containers with modules and other parts for the FLX-40

One of several shipping containers with modules and other parts for the FLX-40

As with most things, some assembly required.  The RF modules needed to be placed in the power blocks according to their serial numbers on the test data sheet.  This insures that the information on the test data sheet matches the installed transmitter configuration.  The power combiner between the two cabinets as well as the reject load and directional coupler all need to be installed.

RF modules with large aluminium heat spreaders.   Coolant flows through each module.

FLX-40 power amp module

FLX-40 power amp module

WEBE, Bridgeport, CT GatesAir FLX-40 on the air for the first time

WEBE, Bridgeport, CT GatesAir FLX-40 on the air for the first time

On the air!

FLX-40 into the antenna

FLX-40 into the antenna

We ran the transmitter for several hours into the antenna yesterday afternoon. The coolant system is still purging air, so we periodically needed to add water/antifreeze to the pump station to keep the pressure between 12-18 PSI. Eventually, the TPO will be 34 KW with the HD carrier(s).

All in all, I would say that this was a fun project. The liquid cooled transmitter had a few extra steps during the installation process, but not too difficult.

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