Portable test equipment has greatly improved over the past decade, narrowing the performance gap between portable and benchtop instruments. In terms of functionality, the number of choices for portability instruments has also increased. Portable RF/microwave instruments, once relegated to voltmeters and power meters, are now available for signal generation, spectrum analysis, and even vector network analysis in lightweight housings that make it possible to bring the test bench to the job site.
The current range of portable RF/microwave test instruments is wide, from pocket-sized power meter/sensors that connect to a computer via its Universal Serial Bus (USB) port to battery-powered, multifunction instruments capable of analyzing the most complex modulated signals within their frequency ranges. In almost all cases, these portable instruments compromise little or nothing in terms of accuracy and overall performance compared to their benchtop counterparts. In addition, as these portable testers evolve, through design and improved manufacturing practices, they offer greater operating efficiency—and with it, the capability to run longer on a single battery charge.
A glance at this issue’s cover and its associated story will show some of the measurement power possible from a portable instrument. The FieldFox family of portable analyzers from Agilent Technologies, which has been on the market for some time, now features 14 new instruments with a variety of analysis capabilities through 26.5 GHz. They are designed for ease of use, long battery life, and good screen visibility even in sunlight, but they sacrifice nothing in terms of performance and accuracy. Impressive instru ments, for sure, but they are just one example of the many portable RF/microwave measurement solutions now on the market.
Of course, those needing RF/microwave measurements in the field can also count on the SiteMaster™ and VNA Master portable instruments from Anritsu Co. for different test functions. For example, the MS2028B VNA Master (Fig. 1) is a broadband, handheld solution for cable and antenna measurements in the field. It is a handheld, two-port vector network analyzer (VNA) that covers 5 kHz to 20 GHz with a 65-dB dynamic range to 20 GHz. As the name implies, this is an instrument developed for on-site testing, with a thin-film-transistor (TFT) color display that is clearly visible in daylight and a typically running time of two hours on a battery charge. It can store more than 4000 traces in memory and perform fast sweeps with a speed of 750 us/data point.
The MS2028B VNA Master features 1.5-ppm frequency accuracy and 1-kHz frequency resolution and only weighs 9.9 lbs (4.5 kg) with its rechargeable battery. It has been designed to perform as the equal of any benchtop two-port VNA covering its frequency range, and is ideal for cable loss and fault measurements at communications sites in the field. It is equipped with Ethernet and USB ports for ease of data transfer and boasts a large number of options—among them, for an internal bias tee (for active device testing), a vector voltmeter, a power monitor, and even an internal Global Positioning System (GPS) receiver for accurate identification of different test sites. It is just one of many portable instruments in Anritsu’s “Master” lines, which also include the Site Master cable-and-antenna analyzers and spectrum analyzers with frequency coverage extending to 30 GHz.
Another small RF/microwave instrument well suited for in-field measurements is the R&S® PR100 portable receiver from Rohde & Schwarz. With a frequency range of 9 kHz to 7.5 GHz, it teams with the firm’s R&S HE300 active directional antenna to form a compact receiving system for monitoring emissions, detecting interference, and locating transmitters. It is ideal (to give just one example), for detecting interference at airports and other remote locations. It weighs only 3.5 kg with its rechargeable lithium-ion battery, but is a full-featured spectrum analyzer with resolution bandwidths from 125 Hz to 100 kHz and scan speeds to 200 channels/s. Preselection can be set from 9 kHz to 30 MHz with a 30-MHz lowpass filter, from 20 MHz to 1.5 GHz with tuned bandpass filters, and from 1.5 to 7.5 GHz with highpass/lowpass filter combinations.
The R&S PR100 portable receiver runs for four hours on a single battery charge and automatically saves instrument settings when the receiver is shut off. It shows results on a bright 6.5-in. color screen and contains both 64 MB of random-access memory (RAM) and a built-in SD card for data storage. It also has an external SD card reader for moving information as needed. For in-field use, the instrument can display results on a digital map loaded within the receiver. An upgrade kit can turn the receiver into a portable direction-finding (DF) system, based on the firm’s single-channel correlative interferometer DF method.
Even smaller, the company’s R&S CTH100A and CTH200A radio test sets measure just 4.05 x 7.95 x 1.45 in. (102.9 x 202 x 36.8 mm). The CTH100A (Fig. 2) weighs 1.17 lb (532 g) without batteries while the CTH200A is 1.19 lb (539 g) without batteries; both instruments draw power from three rechargeable or non-rechargeable 4.5-V batteries. Despite being no bigger than an old transistor radio, these devices are fully capable of receiver and transmitter testing from 30 to 512 MHz, with channel spacing of 5 MHz on the CTH100A and channel spacings of 100 kHz, 200 kHz, 500 kHz, 1 MHz, 2 MHz, and 5 MHz on the CTH200A. The CTH200A also provides frequency-modulation (FM) demodulation for FM transmitter testing, and both instruments are ideal for cable fault location. The CTH200A can measure and display the results of over-the-air (OTA) measurements (across a 60-dB dynamic range) on a bar graph on the small display screen. In addition, a cable fault locator in the CTH200A can locate faults through cables at distances to 480 m (in three different measurement ranges).
2. The R&S® CTH100A and CTH200A radio test sets are hand-held instruments that operate from 30 to 512 MHz. [Photo courtesy of Rohde & Schwarz (www.rohde-schwarz.com).]
Rohde & Schwarz also supplies instruments such as the ZVL line (Fig. 3) of VNAs, which can also be equipped with a spectrum analyzer as an option. Available in models from 9 kHz to 3.0, 6.0, and 13.6 GHz, the ZVL instruments nominally appear as benchtop instruments. But they are equipped with a carrying handle, weigh only 9 kg, and can be powered by plug-in rechargeable batteries or run from +12-VDC vehicular power supplies for remote test requirements.
3. The ZVL line of compact VNAs is available with units operating to 13.6 GHz. Although somewhat heavy at 9 kg, they can operate from battery or vehicular 12-V power. [Photo courtesy of Rohde & Schwarz (www.rohde-schwarz.com).]
The 3500A portable radio communications test set from Aeroflex, which is in the process of being replaced by the firm’s model 3550A portable test set, is designed for use from 2 MHz to 1 GHz. It is ideal for quick installed radio testing and for finding radio failures. The hand-held instrument includes a spectrum analyzer with -136 dBm noise level and a tracking signal generator with frequency range from 2 MHz to 1 GHz, power levels from 0 to -60 dBm, and 1-Hz resolution. It weighs less than 8 lbs (3.6 kg) and provides more than 5 hours on a single battery charge. The spectrum analyzer features phase noise of -80 dBc/Hz offset 20 kHz from the carrier, with harmonic levels of -30 dBc and spurious levels of -40 dBc. The 3500A offers a large number of options, including an audio frequency counter and audio oscilloscope. It can also be equipped with a received-signal-strength-indication (RSSI) meter, which indicates the RF power within the receiver’s IF bandwidth. It has a display range of -120 to +43 dBm with measurement capability of -50 to +43 dBm at the instrument’s transmit/receive (T/R) port.
Of course, not all RF/microwave instruments designed for portability are easy to transport or use while in motion. A growing number of compact instruments, such as the PWR-4RMS USB power sensor from Mini-Circuits, are designed for USB connections to a laptop or personal computer, with the computer providing control, programming, and display of results. The PWR-4RMS turns any computer running Microsoft Windows or Linux into a power meter capable of reading the power levels of modulated and continuous-wave (CW) signals. It measures just 4.89 x 1.74 x 0.95 in. and operates from 50 to 4000 MHz with a 55-dB dynamic range (-35 to +20 dBm).
In some cases, a small package size may house an instrument that can be easily carried, but may not be ideally suited for on-site or in-the-field measurements. For example, the DSA815 spectrum analyzer from Rigol Technologies, reported on in the August issue of Microwaves & RF measures just 14.2 x 7.0 x 5.0 in. and weighs 9.4 lbs. It s easy enough to move from one location to another. With a frequency range of 9 kHz to 1.5 GHz, it covers a wide range of applications. Better still, it can be supplied with a full-range tracking generator to operate in the manner of a scalar network analyzer. It features an 8-in. diagonal TFT screen with 800 x 480 pixel resolution and the ease of control that is associated with portability. It can even be equipped with a full-range tracking generator to cover its span of 9 kHz to 1.5 GHz. But it has been designed for use with AC power, rather than with batteries, so an AC power source would be required in the field for any on-site measurements.
Still, for those seeking portable RF/microwave test instruments for on-site measurements, the number of choices has never been as large, and growing constantly. A wide range of RF/microwave instruments is available for use on battery power, many units with multiple measurement functions, and many that can be upgraded at any time with additional functions.