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Trends in Test Equipment
A sage, old broadcast engineer once told me that all I needed to keep a radio station going was a Simpson 260 and a three-pound soldering iron. Of course, he also said CDs wouldn't catch on, so his wisdom wasn't worth too much. I guess he wasn't so much of a sage after all. But it leads to some interesting questions:
If you had the opportunity to equip yourself anew for the year, which pieces of equipment would make your core list? How could you get the most bang for your buck? I hope to answer these questions and provide some insight into the trends in the types of test equipment that a broadcaster should have at his disposal, mainly for use at a studio location, but some of it will be of use at a transmitter site as well.
A digital multimeter (DMM) is the most basic piece of test equipment that belongs in each engineer's bag of tricks. With this meter alone you can measure battery voltages, dc power supply voltage, ac line voltages and contact resistance. With a fancier meter you can measure audio levels, frequency and current flow.
While there are many inexpensive units, my favorite DMMs are made by Fluke. If I were buying a meter today I would consider the Fluke 189, which is a hand-held DMM with a long list of features: true rms dc and ac voltage measurements; dual-display with bar graph; resistance, conductance, continuity and diode testing; temperature; ac levels displayed in dBV or dBM; a 1MHZ frequency counter; a PC interface for data exchange with a PC; and a lifetime warranty. Even as a high quality piece of equipment, the Fluke 189 is not going to break the bank. The next step allows you to verify that all the computers plugged into one outlet aren't drawing too much juice by adding the Fluke i1010 ac/dc current clamp, which connects directly to the 189. It reads from 1A to 1,000A.
Most likely you maintain and possibly install Ethernet networks in the studio facility. If you have Ethernet cables you know that it is vitally important to have some way to test them. Take, for example, another Fluke product, the Micromapper. This hand-held cable tester tests cables for opens, shorts, crossed, reversed or split pairs. It features an on-board tone generator to help trace cables in walls, under floors and above ceilings. It also provides a small remote unit that plugs into the far end of a cable under test, allowing one person to do all the testing.
Those are some basic items. The reality is that each facility has thousands of wires and dozens of voltage and current sources. Now you can test them all. But let's go to the next level.
Many one-man engineering radio shops are charged with more than just wiring the LAN. There are quite a few PC-based LAN analysis systems available. This software loads on a PC and uses that same PC's NIC to interface to the network. One that I have found is called Commview, made by Tamosoft. Commview allows the user to see what information is traveling about on the network; it allows the user to view unauthorized activity; it allows the user to identify network problems and thus facilitates more efficient data transmission; and it allows the user to test firewalls and other intrusion detection systems. The program will display vital statistics such as IP connections and it will even generate alarm flags corresponding to certain events.
Another PC-based LAN analysis system is Ethertest from Frontline Test Equipment. The idea behind it is the same: use a PC as the test equipment and the NIC as the primary interface. Like Commview, it will run on any Windows 98/2000/Me/NT/XP/2003 compatible PC and supports 10Mb/s and 100Mb/s Ethernet data rates. Commview will work up to 1,000Mb/s.
Not all (net)work
The typical day is not filled with computer work alone. The engineer's job is to make sound. The proper test equipment is needed to help with this critical task. In consideration of all the digital audio sources and destinations in a radio system, it's a good idea to have equipment that can work in the analog and digital domain. Fortunately, this isn't hard to find.
Ward-Beck Systems makes a pair of units that can hang on your belt while hanging out behind the equipment racks. The first piece is called the ABB-1 (Audio Bit-Buddy) and it provides a convenient means to receive and monitor digital and analog audio signals. The user listens to the audio (analog or decoded AES) at the headphone output while the left and right levels are displayed on LED bar graph meters. Critical signal parameters such as sampling frequency, emphasis, professional or consumer format and data errors are displayed when monitoring AES/EBU or S/PDIF signals. The digital input (via female XLR) decodes sample frequencies from 30kHz to 50kHz automatically.
The ABS-1 Audio Bit Spitter is the companion to the ABB-1. This portable, battery-powered unit generates digital and stereo analog audio test signals that can be injected into the signal path when testing device performance or signal path continuity. The ABS-1 generates an AES/EBU digital audio signal of 1kHz or 400Hz at sampling rates of 48kHz, 44.1kHz or 32kHz. The unit may also be synchronized to an external digital reference signal. Digital signal levels of -20, -12 and 0dBFS are front-panel selectable.
A similar system with more features is made by NTI and it also comes as a pair of hand-held units: the generator, called the Minirator, and the receiver, called the Minilyzer. The digital version of the Minilyzer is called the Digilyzer.
The Minirator has several output signal types and functions. It generates low-distortion sine waves that can be swept. It also generates square waves, white noise, pink noise and a polarity test signal that is recognized by the Minilyzer.
The Minirator reads all the Minilyzer test signals and has the necessary functions built in. It will measure audio levels as VU or PPM and sound pressure level. It includes a distortion analyzer (second through fifth harmonics), can determine speaker polarity in conjunction with the Minirator, can record swept-frequency tests generated by the Minirator, and has an onboard oscilloscope. With the addition of Minilink, which is a USB interface, and the Minilink PC application, data can be recorded from the Minilyzer to a PC.
Another hand-held unit that encompasses the generator and analyzer in one package, is the Terrasonde ATB-3. It has balanced XLR and ¼" TRS ins and outs with two built-in mic preamps with phantom power and a headphone out to monitor audio. The input sensitivity ranges from -120dBu to +50dBu with an output level of up to +17dBu. This kind of power in a set of hand-held devices was simply not available a few years ago.
If more power is needed, consider the Terrasonde ATB-3C (Trinity), which is a more-capable version of the ATB-3. The Trinity includes a full-complement of audio analysis tools, such as distortion analysis,
Prism Sound makes the Dscope III, which is a signal source and analyzer that works in conjunction with a user-supplied PC-via a USB connection. It uses Windows as the GUI. The Dscope III provides simultaneous AES3 and analog outputs; a user-selectable digital or analog input signal analyzer that includes what Prism calls its Continuous Time Analyzer (essentially a distortion analyzer) and an FFT analyzer that will perform a battery of tests, including user-defined ones. The Dscope also includes a battery of tests for the digital carrier itself.
Audio Precision has a 20-year history in the production of audio analyzers that work in conjunction with a user-supplied PC. The AP ATS-2 is just such a system, and includes basic tests, such as inter-channel phase response, channel separation, distortion measurement and noise measurements. Its own capability can determine whether or not the device under test (DUT) meets all digital standards and whether or not it is compatible with other digital devices. Other measurement capabilities include jitter, pulse amplitude, bit activity and word length. AP offers an upgraded measurement capability that allows the ATS-2 to make measurements on the digital carrier signal.
No matter how well versed you are in theory, and no matter how many years you've been in the business, without proper test equipment you won't be able to accomplish much. The best thing about test equipment is that it often goes beyond being simply a tool. Good test equipment can help you learn more about the equipment you work on as well. Good test equipment is worth fighting for at budget time.
A sample of manufacturers of test and measurement equipment
Conex Electro Systems
Frontline Test Equipment
Gage Applied Sciences
Narda Safety Test Solutions
NTI (Neutrik Test Instuments)
RCI Custom Products
RDL (Radio Design Labs)
Rohde & Schwarz
Irwin is director of engineering for Clear Channel Radio in Seattle.
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