Ed Dulaney is the market engineer for Crawford Broadcasting’s Denver cluster. He writes that for several months he’s had some old 2.4 GHz Wireless Access Points (WAPs) lying around in storage. From all outside indications they seemed to be functioning perfectly.
When plugged in, Ed saw the “blinking lights” on the front and was able to log into the Web interfaces with a computer connected to the Ethernet port. However, no matter which way he set up the wireless configuration, he couldn’t see the access points with a WiFi card in his PC. It just seemed that the units weren’t radiating any RF.
Being an industrious sort, Ed decided to see if he could measure the RF output of the units with a “Microwave Leakage Detector.” These are the units sold by almost every department store — RadioShack too — and are used to check a microwave oven for excess radiation.
Since microwave ovens operate at 2.45 GHz, Ed figured that these detectors would be able to pick up the 2.4 GHz signals from his WAPs. Sure enough, when he put one of them next to a working antenna, it read the approximate power density of the access point.
(click thumbnail)Fig. 1: Using a microwave oven leakage detector to verify wireless access operation.Seen in Fig. 1, the D-Link wireless access point is radiating 2.40 milliwatts per cubic centimeter, proving that the device is indeed putting out a signal
Ed found that the levels will bounce around wildly, as a wireless access point utilizes spread-spectrum modulation. Readings varied between 0.1 and 3.1 mW on the Microwave Leakage Meter.
He tested the units in storage, and found some that never gave any reading, proving without a doubt that the RF section was toasted!
Sure, you could drag out the spectrum analyzer and check the levels that way. But for $20 at your local department store you can have a portable WAP tester.
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Jim Swartos owns the tallest communications tower in northwest Washington state.
The last time he had to call in a NOTAM on a tower lighting issue, he was on hold for over three hours. While waiting, he was thinking, “There must be some serious storm problems over a large part of the country!”
When he finally got through (it was after midnight and thus the next day) the person taking his call said, “No, we haven’t been that busy, the phone system must have a glitch in it. I’ll tell tech support to take a look at it.”
What this really meant was Jim was on “Ignore” for that time period. Needless to say, Jim feels that this recent consolidation (using Lockheed Martin) has a few issues to be ironed out.
Jim further advises anyone who calls and is placed on hold for more than a few minutes, to hang up and call again.
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(click thumbnail)Fig. 2: A simple carpet strip helps deaden hall noise in this simple sound lock.
Adapting studios to existing buildings isn’t always the easiest job. Especially where long halls are involved, dampening the hall noise can be a problem.
Joe Jarjoara, chief engineer for Qantum Communications of Cape Cod, Mass., sent in an effective sound lock seen in Fig. 2.
His first step was adding a second door to make the sound lock. Joe obtained additional deadening by adding the carpeted strip inside the frame of the two doors, as pictured. Not fancy, not costly and it works.
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Energy Transformation Systems builds a variety of problem solutions supporting data, voice and multimedia.
The California company has introduced a product called InstaSnake that consists of two small boxes with four XLR microphone inputs and a shielded RJ-45 jack on one box, and corresponding outputs on the other.
You can find out more about the product by heading to the company’s Web site; see www.etslan.com.
The InstaSnake is a passive unit so you do not need power. The device accepts mic, line, analog or digital audio and supports phantom power. The interconnect between the two boxes is Cat-5 cable.
In-house testing using a low-Z Shure microphone showed that Cat-5 could be used to distances of nearly 2,000 feet with no diminution in the quality of sound. The advantage, especially for remotes, is that you can get four channels of analog or digital audio signal from one place to another on one run of Cat-5 or better cable
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(click thumbnail)Fig. 3: A sling added to the engine hoist keeps the Phasemaster from tipping as it’s moved.Engineers who maintain mountaintop transmitter sites are familiar with the Phasemaster.
In places where it’s costly to run three-phase electric service, the rotary phase converter generates three-phase AC out of single phase. Usually very reliable, they sometimes need to be moved or replaced when larger capacity is needed. That’s when you find out how heavy these devices are!
Nassau Broadcasting Maine Market Engineer Bill Ryall had to swap out and move Phasemasters at one of his sites last summer. Not only are the devices heavy, but their physical construction makes them awkward to move.
Although there are two motor eye hooks, when lifted from these hooks the Phasemaster tips back toward the rear terminal box. If you’re not careful, the device can be damaged as it’s lifted.
Seen in Fig. 3, Bill’s solution was to build some lifting slings to use in conjunction with his engine hoist. The hooks fit into the eyes, and the rear bracket holds the terminal box level, preventing the Phasemaster from tipping.
This setup will allow one person to easily pick up and move a Phasemaster single-handed, though I don’t recommend that. Have a partner at hand.
