Search the Community
Showing results for tags 'review'.
Found 1 result
Kitdze posted a topic in Обзоры и тестыAn independent review was conducted to test two of the compact radio frequency measuring instruments developed by the company, Kroks. The devices consist of a spectrum analyzer with a built-in signal generator and a vector network analyzer (reflectometer). Both devices cover a wide frequency range from 35 (23 for reflectometer) MHz to 6.2 GHz. My objective was to determine the utility value of these meters, and to better understand the manufacturer’s comment that the device is intended for amateur radio use, since it is not a professional measuring tool. The word “amateur” hints that the devices may be closer to a display meter as opposed to a comprehensive measurement device. It should be noted that these tests were conducted as an amateur user who would lack a thorough understanding of metrological studies of measuring instruments, or the basis of the standards of the state registry and related subjects. Radio amateurs are more interested in looking at comparative measurements of devices that are often used in practice (i.e., antennas, filters, attenuators), as opposed to theoretical “abstractions” commonly explored in metrology (i.e., mismatched loads, inhomogeneous transmission lines, or short-circuit lines). To avoid the influence of interference in the comparative measurement of antennas, an anechoic chamber or open space is required. In view of the absence of the first, measurements were taken outdoors. All antennas with directional radiation patterns “looking” into the sky were mounted on a tripod to avoid displacement in space when changing instruments. Low quality, Chinese-made adapters were not used due to the frequent lack of repeatability of contact during reconnection, as well as the shedding of the subpar antioxidant coating used instead of the usual gilding ... To obtain equal comparative conditions, the instruments were calibrated with the same set of OSL calibrators before each measurement, in the same frequency band and current temperature range. OSL is “Open”, “Short”, “Load”, which is a standard set of calibration measures: “open measure”, “short circuit measure” and “matched load 50.0 Ohm”, which are usually calibrated vector network analyzers. For the SMA format, the Anritsu 22S50 calibration kit was used and normalized in the frequency range from DC to 26.5 GHz, a link to the datasheet (49 pages): https://www.testmart.com/webdata/mfr...COMPONENTS.pdf For calibration of the N type format, respectively Anritsu OSLN50-1, normalized from DC to 6 GHz. The measured resistance at the coordinated load of the calibrators was 50 ± 0.02 Ohm. The measurements were carried out with proven, precision laboratory-grade multimeters from HP and Fluke. To ensure optimal accuracy and equal conditions in comparative tests, a similar bandwidth of the IF filter was installed on the devices--the narrower the band, the higher the measurement precision and the signal-to-noise ratio. The largest number of scan points (closest to 1000) was also selected. A link to the illustrated, factory set of instructions, will help to better understand the functions of the reflectometer: http://arinst.net/files/Manual_Vector_reflectometer_Arinst_VR_23-6200_ENG.pdf Before each measurement, all mating surfaces in coaxial connectors (SMA, RP-SMA, N type) were carefully checked, since at frequencies above 2-3 GHz, the cleanliness and condition of the antioxidant surface of these contacts begins to have a rather noticeable effect on the measurement results and stability their repeatability. It is very important to keep the outer surface of the central pin clean in the coaxial connector, and the inner surface of the collet mating with it in the mating half. All the same is true for “braided” contact. Such control and necessary cleaning is usually possible under a microscope, or under a high magnification lens. It is also important to prevent the presence of crumbled metal chips on the surface of the insulators in the mating coaxial connectors, because they begin to introduce a stray capacitance, significantly interfering with the performance and signal transmission. An example of a typical metallic clogging of SMA connectors that are not visible to the naked eye: According to the factory requirements of manufacturers of microwave coaxial connectors with a threaded type of connection, when connecting, it is NOT possible to allow the central contact of the collet entering it to be turned. To do this, it is necessary to hold the axial base of the screw-on half of the connector, allowing rotation of only the nut itself, and not the entire screw-on structure. This significantly reduces scratching and other mechanical wear of the mating surfaces, providing better contact and extending the number of switching cycles. Unfortunately, few amateurs are aware of this procedure or the damages caused by scratching the already thin layer of the contact’s working surfaces. This is evidenced by the large number of YouTube videos from the so-called "testers" of new microwave equipment. In this test review, all the numerous connections of the coaxial connectors were made strictly in compliance with the above operational requirements. In comparative tests, several different antennas were measured to check the reflectometer readings throughout different frequency ranges. Comparison of the 7-element Uda-Yagi antenna of the 433 MHz band (LPD) Antennas of this type always have a rather pronounced back lobe, as well as several side lobes. To maintain the purity of tests, all environmental conditions of immobility were especially observed--up to locking the cat in the house—while photographing the different display modes. This will assure there is no movement that ends up in the coverage area of the black lobe, thereby introducing indignation into the graph. The figures contain photos of four modes from three devices. The top image is from the VR 23-6200, the center from the Anritsu S361E, and the bottom from the GenCom 747A. VSWR Charts: Charts of the return loss: Volpert-Smith Impedance Charts: Phase graphs: As reflected in the images, the test graphs are very similar, and the measurement values have a dispersion within 0.1% of the error. 1.2 GHz coaxial dipole comparison VSWR: Return Loss: Volpert-Smith Chart: Phase: Likewise, and according to all three devices, the measured resonance frequency of this antenna were within 0.07%. 3-6 GHz horn antenna comparison An extension cable with N-type connectors were used which slightly introduced a non-uniformity in the measurements. The task was simply to compare the devices--not the cable or antenna. If there was a problem in the path, then the devices should show it accordingly. Calibration of the measuring plane taking into account the adapter and feeder: VSWR in the band from 3 to 6 GHz: Return Loss: Volpert-Smith Chart: Phase graphs: Comparison of the circular polarization antenna of the 5.8 GHz band VSWR: Return Loss: Volpert-Smith Chart: Phase: Comparative measurement of VSWR of the Chinese LPF filter 1.4 GHz Filter appearance: VSWR Charts: Comparative feeder length measurement (DTF - Distance to fault) I decided to measure a new coaxial cable, with N type connectors: Manually measured 3 meters 5 centimeters with a mechanical meter. The devices showed: Here, as they say, comments are superfluous. Comparison of accuracy of the built-in tracking generator On this gif picture, 10 photos of the readings of the frequency meter CH3-54 are collected. The upper halves of the pictures - the readings of the test VR 23-6200. The lower halves - signals from an Anritsu reflectometer. Five frequencies were chosen for the test: 23, 50, 100, 150 and 200 MHz. If Anritsu served the frequency with zeros in the lower digits, then compact VR served with a slight excess, numerically increasing with increasing frequency: Although according to the technical characteristics of the manufacturer, this cannot be a “minus”, since it does not go beyond the declared two categories after the decimal sign. Pictures collected in a gif about the internal "decoration" of the device: Benefits: The advantages of the VR 23-6200 are its low cost, portable compactness with full autonomy which does not require an external display from a computer or smartphone, and its fairly wide frequency range displayed in the marking. This is not a scalar meter, but a fully-fledged vector meter. As demonstrated from the results of comparative measurements, VR is somewhat equivalent to the larger, reputable and expensive devices. In situations that require climbing onto the roof (or mast) to clarify the condition of the feeders and antennas, its compact size makes it preferable over a large and heavier apparatus. FPV racing equipment (radio-controlled flying multicopter and airplanes, with on-board video broadcasting to glasses or displays) using the 5.8GHz frequency bands could benefit largely from this meter for selecting the optimal antenna (from a collection) or reconfiguring (straightening and/or adjusting) an existing antenna damaged following a crash. The “pocket-sized,” meter with its low end weight (which can easily hang on a thin feeder), makes the device convenient for many field applications. Small cons are also noticeable: 1) The greatest operational drawback of the VR 23-6200 is the inability to quickly find the minimum or maximum markers on the chart, not to mention the search for the “delta”, or the auto-search for subsequent (or previous) minima / maxima. The LMag and SWR modes also lack a marker management capability that is often useful. The marker must be activated in the corresponding menu and manually moved to the minimum of the curve in order to calculate the frequency and magnitude of the SWR at that point. Perhaps the manufacturer will add this function in a subsequent firmware update. 1 a) The meter appears not know how to reassign the desired display mode for markers when switching between measurement modes. For example, I switched from VSWR mode to LMag (Return Loss), and the markers still show the value of VSWR, while logically they should display the magnitude of the reflection modulus in dB, that is, what the currently selected graph shows. The same is true in all other modes. In order to read the values corresponding to the selected chart in the marker table, it is necessary to manually reassign the display mode for each of the 4 markers. It seems to be a trifle, but I would like to see some “automatism”. 1 b) In the most popular VSWR measurement mode, the amplitude scale cannot be switched to a more detailed one, less than 2.0 (for example, 1.5, or 1.3). 2) There is a small feature in inconsistent calibration as if always “open”, or in “parallel” calibration. That is, there is no sequential ability to record a calibrator measure readout, as is customary on other VNA devices. In the calibration mode the device successively prompts itself which one the (next) calibration measures should be installed and reads it out for accounting. ARINST, at the same time, grants the right to choose all three clicks of the measure record which imposes an increased requirement of attention from the operator when carrying out the next calibration stage. The need to press a button that does not correspond to the end of the currently connected calibrator may be confusing for some users and introduces the possibility of making an error. Perhaps in subsequent firmware upgrades, the creators of such an open "parallelism" of choice, "changes" the same in the "sequence", to exclude a possible error from the operator. After all, it is no accident that large instruments used precisely a clear sequence of actions for calibration measures to exclude such an error from confusion. 3) Very narrow calibration temperature range. If after calibration, Anritsu is provided with a range (for example) from +18°С to +48°С, then on Arinst it is only ±3°С from the calibration temperature, which may be small during field work (outdoors), in the sun, or in the shadows. For example: when calibrated after lunch and working with measurements until the evening, the sun has gone, the temperature has dropped and the readings are now inaccurate. A stop message should pop up stating the need to “recalibrate due to going beyond the temperature range of the previous calibration”. Instead, erroneous measurements begin with a biased zero, which significantly affects the measurement result. For comparison, here's how the Anritsu reflectometer reports this: 4) The room is normal, but for an open area a very dim display. On a sunny day, nothing is readable on the street, even if you shade the screen with your palm. Display brightness adjustment is not provided at all. 5) I have the desire to solder the hardware buttons to others, since some do not respond immediately after being pressed. 6) The touchscreen in some places is unresponsive, while in other places too sensitive. Conclusions on the VR 23-6200 Reflectometer Overlooking the few minuses when compared with other budget, portable and freely available solutions on the market (i.e., RF Explorer, N1201SA, KC901V, RigExpert, SURECOM SW-102, NanoVNA…) the Arinst VR 23-6200 appears to be the valued choice—due to the expensive pricing schemes of other devices, their non-universal and limited frequency bands, and a toy-like display screen. Despite the modesty low price, the VR 23-6200 vector reflectometer turned out to be a surprisingly decent and portable device. If the manufacturers had modified the minuses in it and slightly expanded the lower frequency edge for short-wave radio enthusiasts, this device would occupy the global sector podium and offering affordable coverage from 2 MHz for SW (160 meters) up to 5.8 GHz for FPV (5 centimeters) --preferably without gaps in the entire strip as shown in the RF Explorer example: We will most likely see cheaper solutions in the future to accommodate the wide range of frequencies. At the time of this review (July-August 2019), I believe this Arinst reflectometer to be the best portable, non-expensive, and commercially available devices in the global marketplace.