Portable and Rack-Mount Instruments for Base Station Monitoring
By Bill Bates, Bird Technologies
While carrier wireless systems gain the most media attention, the nation’s public safety communications networks are equally formidable and arguably at least as important. Collectively, the number of public safety sites equal or exceeds the number of commercial base stations, not even including the tens of thousands of sites operated by the US Department of Defense, Department of Homeland Security, and other government agencies.
These organizations face the same or even more stringent financial constraints as their commercial counterparts, which translates into the need to maintain their sites at the least cost with the fewest number of technicians and trips “up the mountain” by either truck or helicopter, and with the least amount of test equipment.
For much of its more than 70 years, Bird Technologies has provided test equipment designed exclusively for the needs of public safety. The company’s product portfolio, led by its SignalHawk family, is the latest example and includes portable handheld instruments as well as those designed to remotely monitor the health of systems from virtually anywhere via the Internet.
The SignalHawk Family Includes the Following Instruments:
• SH-36S-RM rack-mount SignalHawk designed to be mounted at a base station for remote monitoring and analysis of system performance.
• SH-x SignalHawk handheld, battery-operated portable instruments incorporating spectrum analysis, vector analysis, and distance-to-fault capabilities along with power measurement and other functions.
• SH-36S-PC SignalHawk combines all the capabilities of the portables but vector analysis and is designed to be used with a laptop, Windows-based tablet, or other computer.
• The measurement frequencies of the instruments are 100 kHz to 3.6 GHz (spectrum analyzer) and 1.6 MHz to 3.6 GHz (vector analysis).
Monitoring From Anywhere
While the portable SignalHawks described later have proven themselves to be able companions for field engineers, technicians, service providers, contractors, tower erectors, and military field personnel, the SH-36S-RM rack-mount SignalHawk (Figure 1) provides the ability to perform all of their functions remotely from anywhere there is an Internet connection. Consequently, they become extremely popular for monitoring installations in places that are difficult and expensive to reach, from oil rigs to utility installations, and remote base stations that are often accessible only by helicopter. The rack-mount SignalHawk makes it possible to monitor system performance and diagnose out-of-spec conditions from a Windows-based PC using Bird’s PC Tool software that emulates the user interface of all SignalHawks along with providing alarms for RF power and other critical functions.
The SH-36S-RM is housed in a 2RU enclosure measuring 19 x 10 x 3.5 in. and weighing 10 lb. and has an operating temperature of 0° to +50° C in a 95% noncondensing environment at altitudes up to 15,000 ft. It has 140 Gbytes of internal storage and connects with the outside world via 10/100 Ethernet or USB. The latter can also be used to connect peripheral devices as well as for additional storage or uploading and downloading firmware or other information.
Portable, Functional, Cost-effective
While there are a many handheld, battery-operated spectrum analyzers and other RF and microwave field service instruments, many of them provide an enormous range of capabilities, most of which are rarely if ever used by people in the field as they often require a considerable level of technical skill that is more likely to be found in a lab.
In contrast, while the SignalHawk instruments were designed to provide a broad range of spectrum analysis, power measurement, and (if so equipped) vector analysis capabilities, they are nevertheless very simple to operate as they were designed specifically for use by technicians, installers, and others whose tasks include many other things besides making RF measurements. The goal in every case is not to characterize the site but rather to ensure that it’s working properly and if not provide enough information to determine where the problem lies.
The portable instruments such as the SH-362S (Figure 2) are extremely rugged and meet drop test, explosive atmosphere, shock, and vibration requirements mandated by both U.S. and European military standards, and are sealed against exposure to the environment. They have high-resolution, 8.4-in. LCD displays that resist washout even when used in bright sunlight.
While measuring only 11.5 x 10.5 x 3.8” and weighing 7.8 lb., they nevertheless incorporate a broad array of spectrum analysis functions typical of benchtop instruments, including 1 Hz frequency resolution, display of 705 data points, sweep time of 2.2 s over full span, resolution bandwidth from 100 Hz to 1 MHz, video bandwidth of 10 Hz to 300 kHz, intermodulation-free dynamic range of 66 dB, and a noise floor of -135 dBm. Single-button presets include occupied bandwidth, channel power, field strength, ACPR, and carrier-to-interference ratio (C/I). Emissions masks include IBOC, FM, and DTV, among others.
Detection modes include peak, sample, average, and single-sweep, and external trigger modes include low and high level, rising and falling edge, and either edge (which triggers at the input goes from high to low or low to high). The gate delay function varies the time between the trigger signal and the beginning of a sweep and ranges from 100 µs to 1 s. A digitally-variable attenuator reduces RF input signal level either automatically or manually in steps of 10, 20, and 30 dB, and the variable-gain preamplifier reduces the noise floor under weak signal conditions by providing a maximum of 24 dB of amplification.
The instrument’s waterfall spectrogram provides a graphical display of spectral density with time and up to six markers that can identify various signal conditions. It has user-selectable limit lines and the ability to perform occupied bandwidth, channel power, carrier-to-interference ratio, out-of-band and in-band spurious signal, and adjacent channel power measurements. A time domain function allows the amplitude of a single frequency (rather than a complete sweep) to be measured and displayed, and the Received Signal Strength Indicator (RSSI) function provides visual and audible notification of variations in signal strength. Other features include an offset function that de-embeds the effects of attenuators, couplers, amplifiers, and other in-line components, and a frequency counter with resolution of 1 Hz.
A key function of any portable instrument for field use is its ability to make distance-to-fault measurements in order to identify discontinuities in transmission lines. SignalHawk instruments configured with two-port vector network analysis functionality cover distances up to 1488 feet with resolution of 1.6 in., making it possible to locate transmission line problems very accurately. Vector analysis capability also provides VSWR, return loss, cable loss, amplifier gain, and antenna isolation measurement capability.
All of the portable instruments operate up to 5.5 hr. on a charge of their field-replaceable battery and can offload at least 90,000 traces to a USB flash drive while storing up to 300 traces internally. Work orders can be viewed on the instrument and uploaded or downloaded via USB and results can be exported as Word, Excel, PowerPoint, PDF, and image files.
The SH-36S-PC SignalHawk (Figure 3) performs all of the above functions but is designed for use with a laptop computer rather than having in internal display. Bird PC Tool software running on the computer mimics the interface used by every instrument in the SignalHawk family, providing commonality. The unit is extremely small, measuring only 7.5 x 7 x 3 in. and weighing 4.5 lb., and operates from an internal rechargeable lithium-ion battery, or optionally via adapters for operation from a car battery or 120 VAC.
The SignalHawk family is supported by a broad range of awccessories ranging from external power sensors (wideband, directional, and terminating, for various frequencies), to adapters, vehicle and AC power supplies, field strength antennas for various frequencies, a GPS sensor, and a variety of passive components. Detailed specifications for the SignalHawk family are shown in Table 1. More information about the product line can be obtained by visiting
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