I almost hate to say anything, but

We have this certain transmitter which has been on the same tube since June 6, 2001.  Come to think of it, the transmitter itself has been on the air for the same amount of time without failure.  A testament to its designer…

Broadcast Electronics FM20T, WYJB, Albany, New York
Broadcast Electronics FM20T, WYJB, Albany, New York

According to my calculations, that is 151,691 hours or 17 years 3 months and 22 days.  The tube is the original EMIAC 4CX15000A that came with the transmitter.

I am a little nervous about turning it off to clean the cabinet.

EIMAC 4CX15000A tetrode
EIMAC 4CX15000A tetrode

We have a spare on the shelf for the eventual replacement of this tube, but I really want to see how long this thing will last.  This is also one of the last tube transmitters we have in main service.  There are several backup tube transmitters still around.

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.

The Gates Air FAX-10, Numero Dos

This is the second Gates Air FAX-10 that I have installed. This one is in the shipping container transmitter site from the previous post of the same name.  In this case, we dispensed with the equipment rack that came with the transmitter and installed it in a standard Middle Atlantic rack.   The Harris rack configuration wastes a lot of space and since space is at a premium, we decided to do it our own way.

Gates Air FAX-10 in Middle Atlantic rack
Gates Air FAX-10 in Middle Atlantic rack

The bottom of the rack has the transmission line dehydrator. The top of the rack has the Dielectric A60000 series 1 5/8 inch coax switch, a Tunwall TRC-1 switch controller and the Burk ARC-16 remote control.  I cut the rack panel top to accommodate the coax switch.  The racks were removed from an old studio site several years ago and were in storage since that time.

Gates Air FAX-10
Gates Air FAX-10

The Gates Air FAX-10 transmitter on the air, running a sports-talk format.

Dummy load and Broadcast Electronics FM10B transmitter
Dummy load and Broadcast Electronics FM10B transmitter

View from the other side showing the test load and BE FM10-B transmitter.  This transmitter had a problem that I have run into before with BE FM transmitters.  The jumper between the exciter and IPA had the wrong phase rotation causing reflected power.  I added a foot to it’s length and that problem disappeared.