Why Equipment Misbehaves - Radio World

Why Equipment Misbehaves

There are a lot of Boston Acoustics HD receivers out there now.
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There are a lot of Boston Acoustics HD receivers out there now. Cris Alexander, director of engineering for Crawford Broadcasting and a fellow RW contributor, passes on a procedure that should be useful.

(click thumbnail)Fig. 1: Inexpensive, heavy-duty, cases keep remote gear organized.
He obtained this procedure from friends at Clear Channel. It permits placing the Boston Acoustics Recepter Radio HD into the "split mode" for adjusting time-alignment of the digital and analog signals.

To get into "split mode" turn off the radio and turn it back on until the frequency is displayed.

Hold down the CLOCK button for about 5 to 10 seconds.

You will see a list of items displayed. Scroll down the list using the frequency knob on the left, until you come to SPLIT MODE. Now press the Frequency knob.

Scroll up to SPLIT MODE ON and press the knob again. A note, make sure you have the volume where you want it before going into this mode, because the volume control will be disabled.

The Digital channel should be in the LEFT channel and the Analog channel in the RIGHT channel. Of course, you'll need the optional stereo speaker in this mode, or you can use the rear-mounted stereo headphone jack.

To get out of this mode, scroll down to SPLIT MODE OFF, and press the Frequency knob again.

* * *

We exposed Entercom Scranton's Bob Drazba in the March 16 column as "King of the Remote Cases." You may recall that Bob found inexpensive yet rugged tool cases that were deep enough to hold remote gear at his local Home Depot.

Fig. 1 shows Bob's cache of color-coded cases, ready for their busy summer remote season. Thanks, Bob, for encouraging our readers to "professionalize" their departments by graduating from cardboard or plastic "postal" boxes.

Still having difficulty getting management approval? Suggest that they can charge more for a remote when the technician shows up with neat cases instead of cardboard boxes.

* * *

Speaking of cardboard boxes: We occasionally spotlight engineering ingenuity in this column, and Fig. 2 speaks volumes. No case for the monitor speaker? Why not use the box the speaker came in?

Don't you love the on/off switch and the pencil-created holes "drilled" in the cardboard grill cloth? I heard it, and it does work! But of course, no names.

* * *

I'm still getting comments about the transmitter solenoid breaker reset, originally shown in the Feb. 1 issue. Though similar breaker reset schemes have been used, here's a story with a happy ending.

(click thumbnail)Fig. 2: Speaker box?
Many years ago, Boston's Grady Moates of Loud And Clean was much further south. He had an HV breaker problem on a Collins 20V3 1kW transmitter. The breaker would trip for no apparent reason, and someone would have to drive to the transmitter site to reset it. The transmitter would work fine for a month or more, and then trip again.

The solenoid solution worked fine for the station for eight or nine years, long after Grady left the station. One day, he was contacted to come back to the station as a contractor, and one of his duties was to clean out the transmitter.

In the process of thoroughly cleaning and inspecting the rig, Grady found a dead, crystallized, carbon-traced moth, sitting on top of the G6 glass-epoxy used to hold up the RF tube plate connections to the parallel PA tubes. The moth had been there for a decade, hiding behind the threaded standoff used for the RF/DC feed, where you couldn't see it without a mirror.

Grady pulled it out, and then immediately pulled the solenoid reset, telling his client they'd not be needing it anymore. Grady muses that if he had found the moth 10 years before, the solenoid arrangement would never have been necessary.

The lesson to be learned? There's always a good reason for behavior of the equipment. We just have to be smart enough to find it.

* * *

It's rare that engineers have time to build anything any more, but when a client need arises, it has to be considered. Bill Weeks of Hungry Wolf Electronics had a client who needed a remote transmitter panel. The station was on a budget, and it just didn't make sense to purchase and install a dial-up remote control for a nearby transmitter.

(click thumbnail)Fig. 3: A simple remote transmitter meter panel.
Bill turned to www.mcmaster.com and ordered a Simpson M235 digital panel meter (McMaster part number 8339T9), 0-2VDC for $95.76; a couple of "Mighty Mite" pushbutton switches (part 5374T111 and T112 - different colors); three 10-turn 10K pots for calibration purposes (part 7436K313); and one rotary switch (part 6548K23). The rack panel and barrier strip came from Bill's junk box.

It turns out that the meter decimal point can be set with a jumper. Bill adds that if he were doing it again, he would use a multi-section rotary switch, so he could move the decimal point to the appropriate location for each switch position.

The particular DPM panel meter that Bill selected runs on 110VAC. He adds that it might be better to get a similar one that runs on something less lethal, but he couldn't find that model in the McMaster catalog, and the panel needed to be completed quickly.

The project took about three hours to build, but the construction time could have been halved if not for the close tolerance rectangular hole needed for the meter. There's no rushing that, and having it look nice.

The finished product is seen in Fig. 3.

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