2 Rms, 20 kW, Meter Brdg Vu

If you have responsibility for multiple sites, you may find it hard to make regular visits...But summer is upon us. If it’s been a while since you paid the shack a visit, you might find the building overrun with field mice. Spring nesting season may have turned your transmitter building or AM coupling units into nurseries.
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(click thumbnail)Figure 1: These can be an engineer’s best friend in the fight against pesky mice and other intruders.If you have responsibility for multiple sites, you may find it hard to make regular visits.

But summer is upon us. If it’s been a while since you paid the shack a visit, you might find the building overrun with field mice. Spring nesting season may have turned your transmitter building or AM coupling units into nurseries.


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A case in point was one of Tim Backer’s transmitter sites in Syracuse, N.Y.

Tim is the director of engineering for the Clear Channel stations there. His post on Dave Biondi’s broadcast.net radio-tech page was humorous.

Mice found that the attic insulation made great nesting material for his FM20H3 rodent condo. Turns out that when the condo is booked with field mice "residents," they lodge in the FM1C next door – preferring the meter bridge with a view!

Dining for both consists of a smorgasbord of paper towels and manuals at the supply shelf café, or a visit to the trash barrel diner. Tim tried filling every hole, crack and crevice with expanding urethane foam, with no luck. The mice chewed right through.

It’s time for the mothballs, and as several engineers recommended, steel wool.

But before you treat the building, mow or get rid of the grass around the building. Ken Sleeman, CE for WWZZ(FM) in Washington, has a remote transmitter site in the middle of a field, just like Tim’s. The site suffered from rodents for years. Ken reduced the problem dramatically by removing the grass around the building and replacing it with crushed stone in a perimeter of about three feet. Mowing the grass regularly is an inexpensive alternative.

Mice prefer the shelter of the high grass; when it’s gone, they go elsewhere. Ken reports a similar effect with regard to insects – filters on the air intake are cleaner after going the crushed stone route.

Buy moth balls to fight the problem inside. They repel not only rodents but snakes. Throw several in the base of antenna coupling units.

(click thumbnail)Fig. 2: Arrow points to gap.
As for steel wool: plug the crevices and holes to keep rodents from turning your transmitter into a condo. In older facilities with floor trenches, I stacked the steel wool in the base of the trench, effectively blocking the use of the trenches as freeways to the condo.

Finding all the holes can be another challenge, as several engineers point out. Light the inside of your building with flood or trouble lights one evening. Walk around the outside of the building, in the dark, looking for light sources.

This also is a good way to plug all the old screw holes or misfit conduit or coax runs into AM coupling networks. Keep these network boxes insect-free to avoid a nasty sting when you surprise a nest of wasps or hornets in an effort to read a base current meter.

Inspect the entire box. Ill-fitting insulators, or output panels, as seen in Figure 2, not only permit rodents and insects but water damage, with corrosion of parts.


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Holes in the walls aren’t the only point of entry. Steve Schoon of the University of Northern Iowa stations reports that a mouse managed to squeeze through a 3/8-inch gap between the plywood wall and the floor of one of his remote transmitter sites. The mouse then decided to christen the STL receiver, taking it off the air – at 5 p.m., of course, and with a blizzard rolling in!

When Steve returned with the repaired receiver, he took some metal drywall corners. He nailed them to the corners of the plywood, covering the gaps. Then he flattened several with a hammer and nailed them along the floor.

Steve admits the solution is not the prettiest in the world, but it is effective; he hasn’t had a mouse problem at the site in five years!


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(click thumbnail)Fig. 3: Check coupling networks before the boss shows up.
So many sites, so little time. Make the time to inspect your transmitter sites.

A few years ago, we accompanied a well-known consulting engineer, the station engineer and the station owner in a pre-sale site inspection. Imagine the embarrassment of the station engineer, when the coupling network cover was removed to display a mess such as that shown in Figure 3!

The engineer thought the coupling networks were in better shape. It took some convincing that "transmitter visits" weren’t a synonym for "vacation days" – which was the owner’s impression.

The problem was that the engineer was overworked and had no assistant. He spent his time putting out bigger fires. The site inspection was a surprise to the engineer, but if it had been a due diligence inspection, this could have cost the seller plenty – and perhaps the engineer his job.

Submissions for this column are encouraged, and qualify for SBE recertification credit. Fax your submission to (703) 323-8044, or send e-mail tojbisset@harris.com

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