BE FM-25T Fits the Bill
     

WATERTOWN, N.Y. — Over the past three years, we knew WFRY(FM)’s main transmitter was on its last legs and would need replacement. Last spring that moment occurred.

WFRY requires a TPO of 24.5 kW and we had reviewed several transmitters of several manufacturers, both tube and solid-state.

WFRY does not operate HD Radio, and it is not being considered for the foreseeable future, even though this was an option with most units. Watertown, N.Y, is a modest market and even though WFRY is the top-ranked station, budgetary considerations were the primary concern.

Design

Solid-state FM transmitters were substantially more expensive and there are questions about future semiconductor parts availability.

Broadcast Electronics’ quote for an FM-25T tube transmitter was competitive. WFRY’s sister station WCIZ(FM) has operated since 1986 with a Broadcast Electronics FM-3.5A transmitter that has been reliable. This gave us confidence that the cost of ownership of the BE FM-25T would be reasonable too.

Another plus was that the power supply cabinet could be separated from the control/IPA and final PA cabinets. Our building dimensions required this capability. The FM25T uses a 4CX20000A final PA tube with a modular solid-state IPA driver. Interestingly, the FM-25T is basically the same transmitter as BE’s larger FM-30T and FM-35T models. It was reassuring to know that our transmitter would be running with a comfortable design margin.

Our FM-25T was delivered within 30 days of our order. BE specs each of the two cabinet assemblies at approximately 1,800 pounds. There were several pallets. A forklift enabled delivery just inside our building and then into place. The externally-mounted low-pass filter and several other parts were packed separately. The cabinets are all 31.5 inches deep and 70 inches tall. The PA/driver/control cabinet is approximately 57 inches wide, while the power supply comes in at 34.5 inches wide.

We realized that the output network of the BE design requires a frequency determined length of vertical line at the transmitter output. And we made sure there was enough ceiling clearance!

The transmitter assembly and hookup were uneventful. All interconnecting wiring was well-tagged and the manual and installation instructions clear. The power supply to PA cabinet connection required a 1-inch metallic conduit. We hired a local electrician to do the AC hookup and install the conduit for us.

The 4CX20000, driver module installation and interconnection hookup were easy and straightforward. The remote interface connections are all conveniently located and should work well with most remote control units. When powered on, the transmitter tuned up easily to the required TPO.

The FM-25T has automatic power control and auto-restart on power failure features that save remote control programming. Status lights are provided for major items and metering is adequate.

The power supply cabinet is passively ventilated. Both the PA and IPA cabinets have blowers with high-quality air filters. The only “problem” we had with the transmitter was due to our relatively small building and high-capacity air conditioning system. The air-flow sensor in the transmitter is extremely sensitive, using a set of air hoses and a diaphragm switch to insure proper cabinet pressures. Our building pressure changes caused intermittent air-interlock trips. BE helped us diagnose this and sent us a new pressure switch. The air filters must be kept very clean, which is good maintenance practice anyway.

Overall, we have been very happy with our new Broadcast Electronics FM-25T.

Michael F. Ring, CE is chief engineer with Stephens Media Group station WFRY(FM), WCIZ(FM), WTNY(AM) and WNER(AM).

For information, contact Tim Bealor at Broadcast Electronics in Illinois at (217) 224-9600 or visit www.bdcast.com.


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