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XR6 still On-Air after Direct Hit

The morning of Friday, 13 August 2010 began with the expectation of thunderstorms in our region. Shortly after arriving at our main location, I received a remote control alarm from our WLBL – AM site about 45 minutes away. A listen on my car radio confirmed that the station was off the air. When I got close to the transmitter site near Auburndale, Wisconsin, however, the station appeared to be back on the air.

“What was amazing is that the Nautel XR6 transmitter continued to stay on the air at very low power in spite of the collapsed coils. This is why I thought it had come back on air by itself as I got near to the station!” – Mark Hoenecke, Assistant CE

Once at the transmitter, it was apparent that something was very wrong. Our Nautel XR6 had switched to its backup PA module, and was operating at very low power, showing a shut back condition. The back-up Ampfet 5 also would not come up in power and alarmed from high reflected power. After finding nothing amiss in the RF system in the transmitter building, I took a hike out to the tuning house and immediately discovered the problem upon opening the door. Both the series and shunt coils in the tuning network were collapsed!

Collapsed coils before and after reforming; with plastic tie-wraps holding them in place.

An associate, who is a veteran engineer with many more years experience than I, said that no doubt the tower took a direct lightening hit. With the transmitters off and the tower base shorted to ground for safety, I reformed the damaged coils as best as possible to get us back on the air, utilizing plastic tie-wraps to hold the turns in place.

Some of the copper had hardened to the point where it took hand tools to bend it; other parts of the copper were soft and easily formed by hand. Once back in the transmitter building, the XR6 was turned back on – first at low power, then slowly ramping up to full power while watching the reflected power. We operated like this on PA Module B until repairs were made to PA Module A.

Nautel’s 24/7 Technical Support confirmed diagnosis of the PA Module as having two failed RF Amps (out of eight). We elected to order two replacement RF Amps and repair the PA Module ourselves rather than send it in to the Nautel factory for repair. These days we are on a tight budget. The parts arrived and after installation, the repaired PA Module A was returned to the transmitter, where it has been working without further problem since.

What was amazing is that the Nautel XR6 transmitter continued to stay on the air at very low power in spite of the collapsed coils. This is why I thought it had come back on air by itself as I got near to the station!

Our thanks to Nautel’s Terry Crouse who initially commissioned the XR6 in January 2009 – as part of a planned replacement of our 20+ year-old Ampfet 5, now in standby service – during some cold and windy weather, and who also has provided technical help with it. It was the long-term reliability of the Ampfet 5 and other unique Nautel features that led us to select the Nautel XR6.

Mark Hoenecke
Assistant CE
WLBL-AM