Radio World Buyer’s Guide articles are intended to help readers understand why their colleagues chose particular products to solve various technical situations. This month’s articles focus on transmitters.
Bill Traue, CSRE, 8-VSB, AMD, says he was on the receiving end of a conference call that included a station owner in Wyoming and the manager of the local airport.
“One of the owner’s FM stations had suddenly developed a problem with spurious emissions and was interfering with aircraft communications in the area,” said Traue, who runs a technical services firm in Idaho Falls, Idaho.
“The first question I asked was if the interference was being heard on 121.5 MHz, the distress frequency, and it was not. Only slightly relieved, I advised the station owner to shut down that transmitter immediately and I would come and get him back on the air, sans interference.”
Traue said he felt that the problem was with the station’s old FM transmitter. “Although a solid-state model, it occupied a full rack about a tall as Frankenstein. I hoped it wasn’t IM interference from things like rusty tower joints.”
When he arrived in town he stopped at the studio first and picked up a brand-new Bext XL3000, in its unopened box, which was awaiting another project.
He took it up the transmitter mountain and installed it as quickly as possible, moving the AC wires from the old transmitter to the new, the antenna coax with 7/8-inch flange and the composite audio from the processor to the Mux input on the rear of the transmitter. (The XL3000 can be ordered for single- or three-phase power, as can its larger brother the XL6000.)
“I prefer to operate a new transmitter into a dummy load for a week to wring out any problems and become more familiar with it. But there was no time for that since this station was off the air,” he said.
“Bext provides the transmitter documentation on a USB thumb drive, and they are also available via a front-panel USB connection even if the transmitter is not powered up.”
He resigned himself to slowing down long enough to fire up his laptop computer and read up on what this transmitter required to get it working.
“I realized after a minute that the colorful touch screen user interface on the front of the XL series transmitter was all I needed, and I put the PC away. I intuitively changed the frequency, lowered the preset power down to nothing and pushed RF ON. The cooling fans came up to full speed for a few seconds, then slowed down to just what is required to manage things thermally.”
He slowly raised power and with no reflected power, he went right up to 3000 watts. Then he called the airport manager and asked if the interference was gone. He checked around on his radios and found no trace of it.
“As I drove down the hill and around town, listening to the new transmitter, I noticed how great it sounds, a noticeable improvement from the old transmitter in the Frankenrack.” The XL3000 takes up three rack spaces, leaving lots of room for other gear.
The next morning he returned to make sure the transmitter was happy in its new home. He called up the airport manager again to verify that there was no interference with his radios and there was none. He drove the signal out as he left the area and enjoyed the improvement in sound.
“Two months later, I asked the station owner if the XL3000 had been stable so far, and it has. Several listeners have commented to him how great the station sounds and asked what they had done,” Traue wrote.
“I think the upgrade in sound is due to the direct FM at carrier frequency design. You can keep spending thousands on the latest greatest audio processing but if you don’t have the design found in this Bext XL series working for you, you are just creating louder noise.”
He said they plan to buy several more XL series transmitters.
