This is the first one of these transmitters that I have installed. This particular unit is analog only, but there is lots of room left over for an HD exciter if need be.
GatesAir Flexiva FAX-10, 10.000-watt FM transmitter
The size of a 10 KW FM transmitter these days is pretty small, basically taking up the equivalent of one rack. This is a relatively small transmitter room, the old tube transmitter basically took up the entire room. With this unit, there is room to install a full power spare, if that was desired.
GatesAir Flexiva series RF modules.
RF modules use LDMOSFET devices, each module has a power output of approximately 1,600 watts.
GatesAir Flexiva FAX10 power amp section
There are eight power amp modules and seven switching power supplies.
GatesAir FAX10 transmitter on the airGatesAir FAX10, licensed transmitter power output
One issue at this site, there is no reliable three-phase power available. There was a three-phase open delta, but man, that thing scares me a little bit. Since this is a single-phase setup, I was curious to know what the current draw on each leg was at full power. I measured with my clamp-on ammeter; 54.3 Amps at 120 volts, or 6516 watts per leg. Overall power draws 13,032 making the AC to RF efficiency 65.2%. VSWR calculates out to 1.21, which is not great. I think the antenna could use a little bit of tuning love.
On the subject of project management; oftentimes, we need to keep track of the small details that can derail a project, blow the budget, and upset schedules. A quick checklist can help to identify things that might not have been planned for. I developed a checklist mentality in the military. There, we had checklists for everything. Simple day-to-day things like disposing of garbage over the side, or pumping the CHT (sewage) tank to complex evolutions like entering or leaving port all had a checklist. On the aforementioned CHT tank; the Coast Guard cutter I was on had a vacuum flush system to conserve water. Emptying the CHT tank involved a complex set of valve openings and closings to route compressed air into the vacuum tank and literally blow the sewage overboard. Anyone can see the danger in such a design. Failure to follow the exact procedure resulted in raw sewage blowing out of the nearest toilets, which were unfortunately (or perhaps humorously) in the lower-level officer’s staterooms.
But I digress.
I have made a series of outlines for different project types. These can be used as general guidelines for project planning and management. Of course, each project is different, but these are flexible enough that they can be adapted on a project-by-project basis.
We have been poking away at this one for the last year or so. It seems that the previous owners of Berkshire Broadcasting had filed for a translator to rebroadcast WNMB, (100.1 WUPE-FM) North Adams in downtown Pittsfield, during the great translator rush of 2003. When the CP showed up in the mail last March, the current owners were quite surprised.
After looking at the Construction Permit, we made some modifications;
Moved the transmitter location from 100 North Street to 1 West Street (Crowne Plaza Hotel) which is the tallest building in Pittsfield. Antenna AGL is 44 meters (145 feet).
Changed the rebroadcasting station from WUPE-FM, North Adams to WUPE-AM Pittsfield
Changed the antenna to non-directional
Changed the ERP from 48 watts to 100 watts
We were able to make those antenna and power changes because we changed the parent station to the local AM station, WUPE, 1,110 KHz. The previous power/pattern was submitted to keep the translator signal within the 60 dBu contour of the FM station in North Adams.
This, I feel, is the best use for an AM to FM translator. WUPE-AM is a class D station with no nighttime service. Adding a nighttime service greatly increases the station’s value to the community. While the 100 Watt translator does not cover nearly as much as the 5,000-watt AM station, the transmitter location is right in the center of Pittsfield, so coverage of the population center is excellent.
The view from the top of the Crowne Plaza is quite spectacular. I am pretty sure I will have a lot of transmitter maintenance to do right about the middle of October.
W277CJ 60 dBu contour
The installation is fairly straightforward:
W277CJ installation, roof of Crowne Plaza, Pittsfield, MAW277CJ transmitter in an outdoor enclosure
The outdoor enclosure is a DDB POD-16DXC which is rather nice, it comes with rack rails and a thermostatically controlled fan.
W277CJ Shively 6812B antenna
The antenna is a Shively 6812B with RADOMES. The transmitter is a BW Broadcast TX600v2. I really like these transmitters, they are well-designed and rugged. We have yet to have a single failure of one of these units in the field.
The station ERP is 100 watts, so a small bit of calculating is required to arrive at the proper station TPO. I find it easier to make all these calculations in the decibels per milliwatt (dBm) unit domain, then convert them back to watts. Thus, the ERP is 100 watts or 50 dBm. The antenna has a gain of -3.4 dBm. We used 25 feet of LMR-400, which at 103.3 MHz, has a loss of -0.26 dBm. The total losses are -3.66 dBm, making the necessary TPO 53.66 dBm, 232.27 watts, or rounding down to 232 watts.
One of the reasons for the recent lack of posts; I have been busy rehabilitating several transmitter sites for various broadcasting companies. These are mostly FM transmitter sites and vary in power from one kilowatt to twenty-six kilowatts ERP. I enjoy project work, but I have been driving hither and yon, racking up 27,000 miles on my new car since last August.
Subaru Crosstrek XV at remote transmitter site, somewhere in rural New York
So, here is one transmitter site that I just finished; WFLY, Albany, New York. Removed Collins 831F2 transmitter which was functioning as a backup and installed new Broadcast Electronics FM20S. The Continental 816R2 is becoming a little bit long in the tooth for a main transmitter, being new in 1986. Thus, it was time to install a new unit, and I like the Broadcast Electronics solid state and tube designs. With the BE AM and FM solid-state units, their simplicity is their beauty. We service many BE transmitters, some are thirty years old and are still supported by the manufacturer.
WFLY transmitter building, New Scotland, NY
The BE FM20S transmitter is actually two FM10S cabinets combined with one controller. Each cabinet requires a 100 amp three-phase mains connection. This station’s TPO is 11.5 KW, so there is plenty of headroom in case the owners ever want to install HD Radio or replace the three-bay antenna with a two-bay unit.
WFLY main transmitter, Broadcast Electronics FM20S
In transmitter cabinet two, above the exciter is room for HD equipment.
BE FM20S exciter housing
I also reworked the coax switches to provide an easier implementation of the backup transmitter. Basically, the main transmitter is on the main antenna, and the backup transmitter is on the backup antenna. We can move the second coax switch to test the backup into the dummy load. We can move the first coax switch to change antenna feeds.
WFLY backup and main transmitters
Pretty standard setup.
WFLY RF path diagram
We moved the Collins 831F2 from Albany to here to replace another, dead Collins unit at WKXZ in Norwich, New York. This transmitter is forty years old but still runs reliably. Of course, doing this work in the dead of winter added a degree of difficulty to the job, as the roads to both the WFLY and the WKXZ transmitter sites needed work to make them passable for a moving truck. In the end, we used a skid steer with forks on it to get the transmitter up the final hill and into the small WKXZ transmitter building.
