Radio Communications Test Sets

Radio communication test sets are multifunctional devices capable of performing measurements on radio systems (or communication devices) to diagnose their performance and physical condition. Often, test diagnosis is carried out by modulating and demodulating the RF (Radio Frequency) signals. However, modern radio tests sets can also modulate and demodulate CW, AM, FM, PM, and SSB signals and validate a range of Land Mobile Radio (LMR) technologies, including P25 Phase 1 and 2, DMR, NXDN, TETRA, and dPMR devices.

Test Sets – Types and Selection Criteria:

Although several test sets are available, majorly they can be classified depending on the operating principle, type of compatible devices, and the measurement technologies available.

Based on operating principle:

Test sets are classified into Analog and Digital types. As the name indicates, analog test sets contain the conventional needle system to pinpoint the reading, manually interpreting and comparing with standard measurements. The following parameters can be measured using an analog test set:

• RF Frequency
• Transmitted Power
• Modulation
• Sensitivity

A digital test set is a microprocessor-controlled, digitally synthesized, battery-operated communication service monitor, which integrates the functions of several different test instruments into a single, compact, and portable unit. The following parameters can be measured using a digital test set:

• RF Frequency
• Transmitted Power
• Symbol deviation
• Receive Bit Error Rate (Rx BER)
• Symbol clock error
• Slot Power
• Magnitude error

Digital radio test sets are the latest evolution in radio communications test equipment and are easy to use with superior service life. Advantages of a Digital Radio Test Set compared with an Analog system are as follows:

• Can save each configuration and allows for easy recollection
• Valid for all measurement types
• Frequency list can be saved for commonly tested frequencies
• Autotest feature is available with most digital test sets to test a radio system using OEM defined standard methods. This avoids manual testing and eliminates erroneous results.

Classification based on device compatibility:

A Radio test set can be used to test simplex communication systems (radios) and/or duplex communication equipment (mobile telephone systems). Simplex communicating devices can communicate only in a particular direction at any given point in time. In contrast, Duplex-operated devices can transmit on one frequency and receive on another frequency between two locations. Simplex-type systems include radios, press-to-talk operated, transmit-receive (manual or automatic) equipment. Whereas, Duplex-operated devices are cellular phones or repeaters.

Classification based on compatible technologies:

Digital radio test sets, as mentioned, are the latest evolution in radio communications test equipment and can perform digital signal processing, making them compatible with cutting-edge systems. Following are certain advanced radio systems, which can be tested with digital radio test sets:

• P25: Primary public safety radio system
• DMR: Developed with commercial communication in mind
• NXDN: Commercial communication

Radio Communication Test Sets – Maintenance and Operational guidelines:

Following are the procedures prescribed by OEMs to operate and calibrate a radio test set:

• If the cable used to connect the test kit and the radio system is changed, the measurement should follow a calibration with the new cable. Care should be calibration should be performed at the end of the new cable and not right on the SWR connector. This activity ensures that the entire length of the cable is calibrated.
• If the environmental conditions are changed since the last calibration, then another calibration should be performed before measurement.
• Digital test sets contain a screen to indicate the last calibrated time. In case if the calibration is more than 24 hours old, another cable calibration should be performed before measurement.
• Frequency Error: Error of digital signals must take into account non-symmetrical modulation. An analog frequency counter will be skewed by non-symmetrical modulation present in digital radio transmissions.
• Symbol Deviation: Symbol deviation cannot be measured with an analog FM deviation meter. It is calculated from the deviation at Symbol time. An analog FM deviation meter will display incorrect values.
• Symbol Clock Error: There is no analog meter for measuring symbol clock error. High symbol clock error can be mistaken for other issues.
• Magnitude Error: It measures the flatness of the TDMA burst. It is affected by rising or drop in power or by poor ramps at the beginning or end of a burst.

Need for Radio Communication Test Set Calibration – Why is Calibration essential?

Although modern radio test sets are rugged and portable, their accuracy is dependent on the operators’ skill and calibration frequency.

• Cable loss: Every coaxial cable has a loss associated with If extremely short, the cable loss is negligible. However, any loss that is not compensated will affect radio measurements. For example, a 4’ length of RG-58 to test a 50-watt mobile radio at 800 MHz imparts an error of approximately 0.7 dB. Although the error seems insignificant, the value is significant when converted to a percentage. A 50-watt mobile transmits almost 60 watts to the radio when calculated. Therefore, cable loss errors should be eliminated through the Cable Loss Calibration procedure.

Though radio communication test sets operation seems straightforward, the equipment needs to be calibrated and maintained following OEM operation guidelines. To comply with international standards, an annual calibration process should support the repeatability and accuracy of radio test sets.

e2b calibration offers industry-leading ISO-certified radio test set calibration services. Our labs are ISO/IEC 17025 accredited and operated by a team of qualified calibration experts to test and calibrate your test sets. Our verifiable services are unmatched in the industry. We are registered with ANAB. We are also ANSI/NCSL Z540-1-1994 certified. We have the NIST Traceable Wide scope of ISO/IEC 17025 accreditation. Contact e2b calibration for all your equipment calibration needs.