Todd Dixon is the market engineer for Crawford Broadcasting in Birmingham, Ala. In the company’s Local Oscillator engineering newsletter, Todd recently related a story that I want to share with Workbench readers.
Crawford’s tower site for 50 kW AM station WXJC is in Tarrant, broadcasting on 850 kHz. A power module failed in its Nautel NX50. Todd noticed that the B+ voltage was missing for one module, and the NX50 diagnostics identified the third module as the problem.
Todd had worked previously with a friend to replace an automotive engine and recalled that his pal owned a borescope, a tool that can help you conduct remote visual inspections in areas that are hard to reach. The instrument has a camera connected to a flexible articulating cable, with the image shown on a high-resolution tablet screen. It permits viewing in low light as well as places where a human eye or cellphone camera can’t see.
Engine mechanics use borescopes to check engine cylinder walls, inspecting for major evidence of scarring. His friend’s borescope was a nice Xtool model, with a large 10-inch tablet screen and a lighted HD camera at the end of the articulating head.
Housed on the backplane of the NX50 transmitter are some 20A cartridge fuses for each module B+. The backplane conveniently is placed over the transmitter’s power transformer.
After opening the transmitter AC circuit breakers and discharging everything, Todd covered the power transformer, and proceeded to pull the fuses from their holders, hoping they would drop onto the covered power transformer.
As Todd’s luck would have it, this was an upper power module, so the fuses didn’t fall to the transmitter’s cabinet below; they got stuck. To make matters worse, they fell to a spot that Todd couldn’t see.
Nautel’s support team suggested that the side of the transmitter could be removed, then the entire backplane removed, and the fuses could be extracted from their positions.
But first Todd considered trying to fish the fuses out with a bendable tool with a sticky substance on the end, possibly also using a mirror.
Then he remembered his friend’s borescope. He borrowed the instrument along with a claw grabber.
He said it took about an hour to figure out the best way to manipulate everything to pull the fuses from their positions, but that the borescope and grabber worked exceptionally well. Todd figures he saved 10 hours of work removing the side and backplane.
Todd hadn’t considered a borescope before, but this experience has him thinking differently.
Articulating borescopes can run from $400 to $600 for high-end models. The tool Todd used was extremely high resolution, and its accompanying tablet included accessories to function as an automotive on-board diagnostics reader.
But less expensive borescopes with lower resolution and fewer features can be found for under $100. And as we have mentioned here previously, Amazon sells a lighted “Endoscope Camera” that includes a 16-foot semi-rigid cord for under $20. It plugs into your smartphone, which serves as the display screen. See some options here.
Under pressure
Steve Tuzeneu, KZ4DF, is chief engineer for Hall Communications in Lakeland, Fla. He recently purchased a regulator for a nitrogen tank from a local company.
After installing it, Steve noticed that the pressure tended to drift up or down from where he had set it. Steve found himself traveling to the transmitter site several times a week to readjust the pressure.
He asked around, and a fellow engineer suggested a PneumaticPlus Miniature Air Pressure Regulator. Steve added one to his system and the nitrogen levels are now stable.
This mini-regulator costs about $30. Buy PneumaticPlus products via online retailers or visit the company’s website.
Log it
Larry Wilkins, technology director for the Alabama Broadcasters Association and a recipient of the Radio World Excellence in Engineering Award, recently touched on the important — yet often overlooked — topic of transmitter site visits and maintenance logs.
Section 73.1580 of the FCC rules and regulations states that “Each AM, FM, TV and Class A TV station licensee or permittee must conduct periodic complete inspections of the transmitting system and all required monitors to ensure proper station operation.”
And despite the proliferation of sophisticated facility management systems, I think we can agree that it’s still hard to perform a complete inspection unless you visit the site!
Section 73.1350 states that “Each licensee is responsible for maintaining and operating its broadcast station in a manner which complies with the technical rules set forth elsewhere in this part and in accordance with the terms of the station authorization.”
It further states, “The licensee must establish monitoring procedures and schedules for the station and the indicating instruments employed must comply with §73.1215.”
Beyond these protocols, it is essential for station personnel to maintain clear and up-to- date maintenance logs. Such records not only provide a historical account of equipment performance and any corrective actions taken, but also serve as documentation of compliance in the event of an FCC inquiry or technical audit.
Even if a written log is not explicitly required, it is implied. How else would you prove compliance?
Properly kept logs should include the date and time of each inspection, a description of any deficiencies noted, the steps taken to remedy issues, and verification that all parameters meet established standards.
Consistent attention to these details helps ensure the station’s ongoing reliability and legal operation, safeguarding both its technical integrity and its standing with regulatory authorities.
Maintenance logs foster a culture of diligence and accountability, especially in the face of an FCC inspection. When broadcasters respond proactively to any concerns and demonstrate their commitment to responsible stewardship of the public airwaves, everyone wins.
Looking for a sample maintenance log? Larry can send you a sample. Email him at [email protected].
Workbench submissions are encouraged and qualify for SBE recertification credit. Email [email protected].
