Radiocommunication Service Tester “RST-430” ("Repairs & Service" magazine, November 2007)

Evgeniy Kuznetsov (Ryazan)

Specialists who work in the field of radiocommunications and telecommunications and developing, testing and setting up various transmitting and receiving radio equipment have to use a great number of different measuring instruments. Most crucial amongst the devices required are high frequency (HF) and low frequency (LF) generators, modulation meters, voltmeters, power meters, frequency meters, as well as distortion factor (DF) meters and frequency and amplitude meters. Some other measuring instruments may be necessary as well.

The availability of the aforementioned measuring instruments allows different service operations and scheduled tasks to be performed, but at the same time the question arises of whether at present there exist multi-purpose measuring instruments, comprising a set of means for the debugging and tuning of communication and radio equipment, which are more affordable compared to imported devices of the 2945 type? Within the Russian market segment of measuring equipment, the Radiocommunication Service Tester RST-430 is one of the answers to the raised question.

The manufacturer was very modest when naming this device a tester, in fact it is a fully-featured service instrument, which can be used while working not only with radiocommunication equipment, but also in other fields where physical measurements are required.

The “RST-430” device is primarily intended for the complete maintenance and repair of radio stations for various purposes, and as a part of both permanently-installed and mobile service laboratories, and can be used for the tuning, monitoring, testing and calibration of radio stations of almost all types. As a functionally complete device, the instrument provides verification of the following parameters of radio stations:

  • The carrier power of a transmitter (W);
  • The transmitter distortion factor (%);
  • The deviation of frequency and amplitude modulation characteristic of a transmitter from the precorrected characteristic of 6 dB/octave (dB);
  • The maximum transmitter frequency deviation (kHz);
  • The transmitter frequency deviation (Hz) at modulating frequencies 5, 10 and 20 kHz;
  • The level of transmitter incidental frequency modulation (%);
  • The level of transmitter incidental amplitude modulation (%);
  • The transmitter frequency deviation from nominal value;
  • The receiver sensitivity at signal-to-noise ratio (SINAD) of 12 dB (μV);
  • The receiver sensitivity measurement at signal frequency deviation (dB);
  • The receiver distortion factor (%);
  • The receiver background noise level (dB);
  • The receiver frequency and amplitude deviation from the precorrected characteristic of minus 6 dB/octave (dB);

In addition, as a part of an instrument set (combined with other measuring instruments) the “RST-430” provides definition of receiver selectivity by adjacent channel (dB), receiver intermodulation selectivity (dB) and receiver protection on power circuits and control circuits (dB). The basic metrological characteristics of “RST-430” tester are shown in Table 1.

Table 1. Basic metrological characteristics of the Radiocommunication Service Tester “RST-430”

Characteristic, unit Parameter Margin of error
Range of output signal frequency forming (high frequency), MHz.
Frequency-setting increment is 1 kHz.
90…210 δrel = ± 3·10–4 (%)
Range of output voltage setting (high frequency), dB (0 dB = 1 mW).
Voltage-setting increment is 1 dB.
-60…-130 abs = ± [3 + (Uhf set/40)] (dB)
Range of signal frequency deviation setting (high frequency), kHz.
Deviation-setting increment is 0.1 kHz.
0.2…20 δrel = ± [5 + 5 (20/Dset )]* (%)
Range of output signal frequency forming (low frequency), kHz.
Frequency-setting increment is 0.1 Hz.
0.02…20 ±1 Hz
Range of output voltage setting (low frequency), V.
Voltage-setting increment is 10 mV.
0.02…2 abs = ± (0.02 + 0.05·Ulf set)* (V)
Distortion factor of output voltage (low frequency), %. ≥1
Range of signal frequency measuring (high frequency), MHz. 90…210 δrel = ±3·10–4 (%)
Range of signal frequency deviation measuring (high frequency), kHz. 0.2…20 δrel = ± [5 + 5 (20/Dmes)]* (%)
Range of output signal power measuring (high frequency), W. 0.2…20 δrel = ± [10 + (20/Pmes)]* (%)
Range of signal frequency measuring (low frequency), Hz. 20…1·105 abs = ± 1 (Hz)
Range of sinusoidal alternating voltage measuring in the frequency range of from 0.02 to 20 kHz, V. 0.02…15 δrel = ± [3 + 2 (20/Umes)]* (%)
Range of direct voltage measuring, V. 0.02…20 δrel = ± [2 + 2 (20/Umes)]* (%)
Range of alternating voltage distortion factor measuring, %. 1…100 In the range from 1 to 50%:
δrel = ± [5 + 0.5 (50/DFmes)]* (%)
In the range from 50 to 100% the distortion factor is not normalized.
Continuous operation time: 8 hours max.
Power consumption of the tester: 20 VA max.
Tester overall dimensions: 270x160x270 mm. max.
Tester weight: 8.0 kg max.
Mean time to failure: 5,000 h min.
Mean lifetime: 5 years min.
Mean time to restart tester operation after repairs: 2 h max.

* — Dset — set value of frequency deviation, kHz;
Ulf set — set value of output voltage, V;
Dmes — measured value of frequency deviation, kHz;
Pmes — measured value of output signal power, W;
Umes — measured value of direct voltage, V;
DFmes — measured value of distortion factor, %.

The design of the “RST-430” tester is shown in the figure.

The operating principle of the tester is as a digital measuring and computing device. It is evident that measurements based on algorithms of digital signal processing allow the accuracy to be improved, compared to the use of an analogue instrument set. A number of modifications allow the tester to be connected to a PC via a RS-232 serial interface (ETX socket). This is an additional advantage of the “RST-430”, since it provides the user with additional functions for receiving, storing and processing of obtained metrological data. One more fact that is positive is that the instrument works directly with radio stations having an output voltage of 20 W (up to 50 W as an option) without connecting an external attenuator, a feature that not many devices of similar profile can boast of. When compared with devices similar in purpose, the advantages of “RST-430” are obvious, which shown both in the superior technical characteristics of the meter as well as by the enhancement of its functionality and by its more convenient, ergonomic and improved control and peripherals.

On the web-site of the manufacturing company, in addition to reference data and guidelines on tester usage one can download an operations emulator for the Radiocommunication Service Tester “RST-430”, which allows a prospective user to closely examine the controls and main peculiarities of this measuring instrument functioning in different operation modes.

The manufacturer claims the operational lifetime of the device to be 5 years minimum. It is not longer, because the device was initially planned as a portable instrument weighing up to 8 kg (including its specialized case) that enables it to be used easily when going out for scheduled works. This device is a “workhorse” for active operation in field conditions, and for this purpose the instrument can be additionally complemented with an external power source, providing at least 4 hours of autonomous work in its active mode, something which is hardly possible with other larger and more expensive devices.

The advantages of the instrument as a model include the fact that it is flexible: the device can be customized with individual functions and can increase its accuracy when using a reference generator up to 10-7, and much more. The device is certified, and has a clear calibration procedure. Table 2 describes measuring instruments for device calibration.

Table 2. Measuring instruments and auxiliary equipment

Designation, type, brand of a reference measuring instrument or auxiliary equipment Basic technical and/or metrological characteristics
Spectrum analyzer “С4-74” Frequency measuring range from 300 Hz to 300 MHz.
abs = ±(1·10–7·fc + 1/tread), Hz.
Voltage level measurement range from 300 nV to 3 V.
Selective micro-voltmeter SMV8.5 Frequency range from 26 Hz to 1000 MHz.
Calibration error is 0.8 dB.
Additional error in the frequency range from 26 to 300 MHz is 0.4 dB.
Amplifier “У3-33”
Calculating modulation meter “СК3-45”
Selective micro-voltmeter SMV8.5
Amplification of 25 dB, gain flatness <2.2 dB.
Frequency range from 0.1 Hz to 400 MHz.
Limits of peak deviation values measurement -0.1÷1000 kHz.
abs = ±(0.02⊗f + 0.02), kHz.
Electronic calculating frequency meter “Ч3-54” Limits of frequency measurement from 0.1 Hz to 120 MHz.
δrel = ±{5·10–7 + 1/(fmes · tread)}%
Universal digital voltmeter В7-34
Distortion factor meter “С6-12”
Range of sinusoidal voltage measuring up to 500 V in the frequency range from 20 Hz to 100 kHz.
δrel = ±{0.15+0.05[(Ukx/Ux)–1]}%
Distortion factor measurement range is 0.03÷100 %.
abs = ± (0.05 Кread + 0.02) %, where Кread equals the readings of the instrument.
Programmable high frequency signal generator “Г4-164”
Power amplifier УМ100-400
Frequency range from 0.1 Hz to 639.999 MHz.
Output voltage range from 0.032·10–6 to 2 V. ⊗abs = 2…2.5 dB.
Output power up to 20 W in the frequency range from 90 to 400 MHz. Amplification up to 30dB.
Programmable high frequency signal generator “Г4-164”
Power amplifier “УМ100-400”
Calculating modulation meter “СК3-45”
Consumed power watt-meter “М3-56”
Power amplifier ““УМ100-400”
Programmable high frequency signal generator “Г4-164”
Power measuring range 0÷20 W in the frequency range up to 17.85 GHz.
δrel = ±{4 + 0,1[(Pк/Pх)–1]}, %
Low frequency signal generator “Г3-112/1”
Electronic calculating frequency meter “Ч3-54”
Output voltage: 0÷25 V.
Frequency range from 10 Hz to 1 MHz. δrel = ±6%
Low frequency signal generator “Г3-112/1”
Universal voltmeter “В7-34”
Distortion factor meter “С6-12”
Low frequency signal generator “Г3-112/1” (2 pcs.)
Distortion factor measuring range is 0.03÷100%.
abs = ± (0.05 Кread + 0.02) %, where Кread equals the readings of the instrument, %


In conclusion it must be noted that the use of the “RST-430” device by a company for the self-maintenance of communication means is economically reasonable if its fleet of radio stations include 40 or more devices.

With regard to the fact that the fleet of radio-measuring equipment in many companies is rather out-of-date, the purchase of a “RST-430” tester will significantly facilitate the work of specialists in communication divisions.

 

PDF version