Trees Don’t Improve AM Propagation - Radio World

Trees Don’t Improve AM Propagation

An important reminder to have the transmitter field mowed regularly. Even if this area were cleared, a new ground system probably is warranted because the shrub and tree roots could not be removed without destroying the buried ground radials.
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(click thumbnail)Avoid a fine and improve your signal. Keep tower base growth to a minimum.Yes, there’s actually a tower amidst the trees in Fig. 1 — a transmitter building too.

An important reminder to have the transmitter field mowed regularly. Even if this area were cleared, a new ground system probably is warranted because the shrub and tree roots could not be removed without destroying the buried ground radials.

It’s amazing how quickly small saplings grow. Maybe it’s the RF!

Schedule bushhogging now, at the end of summer season. Black landscape plastic or fabric under crushed rock at the base of each tower will reduce growth and protect your ground system.

Thanks to Bill Weeks of Hungry Wolf Electronics for his mowing and tower base suggestion.

* * *

When was the last time you walked your tower site? Are guy anchor points fenced in? If not, are they weed-proofed with crushed stone, as seen in Fig. 2?

Most important are the turnbuckles. Looping and securing guy wire strands through the turnbuckles may not eliminate vandalism altogether but it certainly discourages the act. Add a yellow shell around one of the guys, as seen in the photo, to help identify it in the middle of a field if there is no fence protection.

* * *

Fig. 3 shows a Knox-Box used by Paul Shulins of Greater Media’s Boston cluster. Since 1975, Knox, an Arizona company, has provided rapid entry systems used by thousands of fire, emergency and government agencies.

The box can be opened by the emergency responder, who doesn’t have to wait for the property owner or break down the door in the event of a fire or other emergency. The Knox-Box padlocks and vaults come in a variety of sizes — big enough to hold building plans, if needed.


(click thumbnail)Pay close attention to guy anchor turnbuckles.If your local fire department does not use Knox-Boxes, the company can help get the program implemented. Paul uses the Knox-Box at his transmitter sites. More information can be found at the company’s site, www.knoxbox.com.

* * *

Necessity is the mother of invention, ’tis said. How true this is among broadcast engineers.

Loud and Clean Broadcast Engineer Grady Moates was on one of those rare vacations, not far from a client site, and got a call. He found himself troubleshooting a “missing audio” problem. He had no butt-set, no little battery-operated $12 amplified speaker from the Shack, so he felt handicapped.

Then he remembered the Bose QuietComfort 2 noise-canceling headset he’d brought along on the flight. He ran to his suitcase and pulled them out. Approaching the male XLR with trepidation (will this really work?), Grady turned the QC2 power switch on and stuck the mini plug in the open end of the connector between Pins 2 and 3.

He heard clear, clean audio at a comfortable level. Tracing back through 66 blocks was a breeze, too, because the little mini plug fits between the punch-pins nicely.

Grady found the problem quickly and looked like he knew what he was doing (always a plus).

Now he keeps a pair of QCIIs in his tool kit. They clip onto his head (nothing to keep a hand busy, no need to look for a place to hang); the little slide switch on the removable audio cable has a “hi-lo” switch that sets input sensitivity for +4 (low gain) or –10 (high).

These headphones cancel out the low-frequency noises you get in rack rooms and transmitter sites, and sound pretty good, he tells us. You’ll also find the QCIIs light, comfortable and small. They come with their own little carrying case, with room in a zipper pouch for a clip-lead adapter and a 110 block adapter that Grady made.


(click thumbnail)Use the Knox-Box to provide site access for emergency crews.One of the best features, though, is they don’t appear to load pro audio circuits at all.

* * *

Here’s a tribute to a piece of equipment that seems to have at least nine lives.

Mark Ward with WTSN(AM) and WBYY(FM) in Dover, N.H., writes that there is a Hughey & Phillips motorized tower light controller at the FM site. The device uses a clock motor to drive a cam wheel that operates the beacon flasher; the wheel rocks a mercury switch, turning the beacon on and off.

It’s very old technology but it works just fine until the clock motor dies.

Hughey & Phillips was acquired some years ago by Honeywell Inc., which eventually quoted Mark a price of just under $500 for a new motor. This struck Mark as a tad expensive.

Digging further, he found that the original motor had been manufactured by Synchron, which is still in business. They referred Mark to Essex Product Group/Industrial Timer Corp., which sent an exact replacement for less than $100 including shipping. The clock motor was replaced and the tower light flasher is back in business.

I serviced a station in my contract engineer days that had a problem with this type of older flasher. In my case, the mechanical linkage that connected the motor to the rocking mercury switch simply had worn out. When you replace a defective motor, check also to see that the mechanical linkage isn’t worn, and that the electrical leads from the mercury switches aren’t rubbing the inside of the box.

On the subject of tower lights, Mark suggests that readers check the validity of the telephone number for their nearest FAA Flight Service Station. The local FSS in his region changed its number (and procedures) awhile back; it took quite an effort to get hold of them when this beacon flasher went out. To make matters worse, a local airport gave him the outdated number!

Mark’s advice: Check the number now before you need it in a real tower lighting emergency.

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