DiaLight System Wierdness

FM does it with frequency!
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DiaLight System Wierdness

Post by kkiddkkidd »

Hi all,

Anybody ever had a problem with FM RF damaging or incapacitating new Dialight LED systems?

A sometimes client has a new 3 head white LED strobe system that has lost the top beacon twice since a new Nautel GV30 HD FM TX was installed. They had been running for months on a 3kw Ecresso without a problem with the lights. The tower / building grounding is very good with the LED power cable shield grounded at both the top and bottom.

Within 2 weeks of turning up the new HD TX (22kw + HD), the top beacon (master) stopped working. About the same time, the two middle beacons started showing alarms and visibly flashing more dimly than remembered. The top beacon fixture was itself bad and was replaced. The tower crew tried installing metallic flex conduit over the LED power cable behind the antenna and well down the tower when they replaced the top beacon fixture. It worked OK for a few weeks and how has failed again. I question the effectiveness of the metallic flex for this purpose.

A few days ago, they found that the center beacons flash normally after the TX power was dropped to about 10kw. They have now moved the light controllers out of the building several feet further away from the TX thinking that it was RF leakage from the TX itself. There weren't any symptoms of excessive cabinet radiation that I saw when we fired off the tx and the move was wasted time/energy as the lights still flash dimmer than normal with the TX running over 10kw.

I haven't been involved in the lighting issues until just now, but the tower guy is very competent and has been working with Fuelgraf Electric to resolve the issues. When the new beacon arrives, they are going to try grounding the metalic flex conduit to the tower leg every few feet but I I suggested that they take the flex down and replace with well grounded rigid. I also suggested some snapon ferrites on the power wires in the flash head as well as the controllers and power inputs.

Anyone saw anything similar? Anyone have an electronic copy of the system manuals?

Kevin C. Kidd CSRE/AMD
AM Ground Systems Company
KK Broadcast Engineering

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Re: DiaLight System Wierdness

Post by NECRAT »

Yup. Happened in Boston, on a four station FM master antenna tower. Dialight Gen 5, LED on top of a 120 foot narrow pole. Light kept on having failures, on a all to common basis. One of the local tower gurus installed a special screen around the inner part of the fixture to shield the electronics, and a similar screen around the "cap" as well, and grounded them both. Light had lasted almost 4 years after that with the screens, and no issues.
He also installed a 230 Torroid Choke (31 or 61) with High Permeability on a two wire twin lead wrap of some kind.

"Arguing with an engineer is like mud wrestling with a pig. After a couple of hours, you realize the pig likes it"

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Re: DiaLight System Wierdness

Post by awsherrill »

I don't know if Rod Zeigler at KRVN Lexington NE lurks here, but he wrote about his experience with RFI into LED systems a few years ago:

https://www.thebdr.net/articles/steel/t ... ghting.pdf
and an update
https://www.thebdr.net/articles/steel/t ... isited.pdf

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