To be spoilt for choice these days when it comes to ‘Antenna’ Analysers. The Mini1300 is a development of the popular open-source design by EU1KY, which was built around the STM32F7 Discovery board. It has several interesting features.
mini1300 Antenna Analyzer Review
To begin with, the many measurement parameters include: SWR, R, +Jx, -Jx, IZI, and Return Loss. The device displays these measurements graphically on the screen as a Smith Chart, a Spectrum Sweep or as numerical data.
The Mini1300 has a useful frequency range of 0.1 to 1300MHz, and there are a number of pre-set menu items covering, for example:
- Single Frequency Measurement
- Frequency Sweep / Multi-SWR
- Tune SWR / S21 Gain
- Find Frequency / Quartz Data
- TDR Mode / LC meter / DSP
Other options include Configuration, and Screen-shot management/USB Card Reader. The device also offers an RF Generator. If that was not enough, for the licensed user, the analyser incorporates a WSPR/FT8/JT65 transmitter.
It would be as well to point out that, despite the term “antenna analyser”, the Mini1300 is, in fact, another form of two port Vector Network Analyser.
As well as performing all of the functions of a conventional single-port analyser (VSWR, for example), it can also do two port through measurements for use with filters, amplifiers, attenuators, and so on.
Unboxing and Appearance
The review unit arrived, housed in a cardboard box, along with a USB power/charg-ing lead, an SMA Calibration kit consisting of a Short-Open-Load (SOL), a Type-N to SMA female adaptor, a Type-N SMA male adaptor, and a three part load kit. The latter includes three female SMC PCB sockets and three 5.1Ω, three 300Ω and three 49.9Ω SMD resistors.
These are for constructing low-impedance, high-impedance and 50Ω loads. To do this, you will need a suitable soldering iron, tweezers, and good eyesight.
A nice touch is that protective plastic caps are provided for the connectors. The analyser comes with an instruction leaflet which I can only describe as, well, ‘unique’. It is written in three languages, all at the same time, apparently randomly and combined in a garbled form of ‘Ching-Germ-lish’.
I do not think I have ever seen anything quite like it! Consequently, it is of little use.
The internet, by contrast, will be your main go-to tool for user information. However, be aware that there seem to be many variants of the EU1KY design. The Mini1300 is just one of them, and the mechanical layout and firmware versions may well vary in different designs.
The analyser itself is built into an attractive metal case, finished in black. On the top of the case, there is an SMA socket with the lettering ‘VNA’. Next to this, a socket for the TF/micro-SD card (which is included) and an N-type socket marked Test Port. You will also see the USB charge/power socket and the red power/on/off button. The unit has its own built-in Li-ion battery and charging circuit.
Underneath, there are various sockets and holes, which are not (yet) all in use. However, of those that are, one is for programming/up-dating the processor and one is for connecting to a PC to read stored files, such as images and Touchstone files from the micro-SD card. All configuration files are stored on this card, including calibration data, so it needs to be treated with care.
I did not try it, but I assume the config files could be copied to a PC and kept for backup.
The unit has a nice bright 4.3” TFT touch-screen display. The dimensions of the unit are 135Wx85Hx30D, excluding protrusions, and it weighs 550g. Overall, the Mini1300 feels well built.
Getting Started and Calibration
On switching on, the user is presented with a menu screen with 15 options, to choose from set in three rows of five. On the top row, are measurement functions; the middle row contains ‘tools’ and the bottom row ‘settings and ‘signal generator’.
Unlike the NanoVNA, where the user has to select the measurement type and assign it to the appropriate port, the Mini1300 has pre-set measurement functions. These are selected by a touch on the appropriate screen icon. The features provided are various, but the top row consists of Single Frequency Mode, Frequency Sweep, Multi-SWR, Tune SWR, and S21-Gain modes.
Like every VNA, the first thing to do is to get the unit calibrated. To do this, the user needs to navigate to the configuration menu bottom left of the screen. The first item to select is the OSL calibration menu. Here, the user has to connect the supplied S-O-L to the N-connector but in the order of Short-Load-Open.
However, before doing so, users should first check to see if the unit is asking for 0Ω Short 50 Ohm Load Infinite Open in the calibration menu, as the Mini1300 can be calibrated for systems other than 50Ω (750 is an example). It seems that calibration sweeps the whole range of the device so this can take some time. The calibration will have to be performed at the point of measurement for the best results.
As far as I can tell,16 different calibration files may be stored. For various tests I calibrated OSL A for 500, measured at the end of the N/SMA adaptor fitted directly to the instrument itself, and OSL B at the end of a 10ft length or RG58 cable with BNC plugs fitted each end.
For through-measurements (S21) the user must select [S21] Gain Calibration for VNAand connect to both the SMA and N-type connectors, to perform a through-calibration sweep.
Also on the Calibration menu is HW (Hardware) Calibration at first run. Looking online, I found that this requires jumpers to be set internally. Seeing no means by which to do this, I emailed Chris Taylor for information and was told that it was understood that this has already been done and is only required when the system is built from a kit. The only calibration required is the OSL.
Therefore, the Mini1300 comes with an HW calibration already done.
My initial measurements confirmed that the unit was reading correctly.
mini1300 Antenna Analyzer in Use
All user interactions are using the touchscreen display. The keypad-screen is typically used for frequency entry, which I found well laid out and intuitive. Many of the features may be run as a single scan or in continuous mode. Source impedance can be changed in the Configuration Editor (for example, to 750, see under ‘Calibration’, above. In what follows, I shall outline the main functions of this unit.
Single Frequency Measurement
In single frequency mode, the analyser continually sweeps a narrow bandwidth and returns figures for SWR, Impedance and Reactance. It also displays results on a Smith Chart. The frequency for the measurement can be set from the keypad menu screen in the usual way. It can be incremented/ decremented ‘on the fly’, by +/- 10, 100 and 500kHz steps, while probing to find the required measurement point.
In this mode, the analyser sweeps a frequency range entered by the user (this can be to the full extent of the unit’s frequency coverage). Frequency values are set as the minimum frequency + the required sweep. There are several options, available from the menu bar at bottom of the screen. The results are displayed panoramically as VSWR, Real Impedance, Reactance, S11 or Smith Chart. A moveable cursor may be placed at any point on the screen to read off details
The Multi SWR Function
Five user-defined bands can be swept simultaneously, with the unit displaying SWR, Impedance and Reactance. This is great for users with multiband aerials, such as the recently-reviewed Vine 404 OCFD, because it can be seen whether or not adjustments on one band are affecting other bands.
The Tune SWR Function
This feature uses a horizontal bar graph and audible tone (which can be turned off) that changes in the note as the SWR alters. The lower the SWR, the lower the tone and bar graph level will be. This will be found of much use when performing adjustments to aerials where the analyser is located away from the adjustment point.
This is used for through-measurement. It performs a panoramic scan of the user-selected frequency range. This function may be used for reading loss or gain of amplifiers and attenuators, and for measuring the parameters of filters, and so on.
The L/C Meter
With capacitance selected, the Mini1300 measures down to around 3pf and up to about 15nf, although a 15nf capacitor measuring correctly on my Peak Atlas LCR meter and VNWA read 18nf on the Mini1300.
Switching to reading inductance a 0.470uh inductor read 0.560uh and a 4.7uh read 5.1uh. It appears that components can be measured at frequencies of 100kHz, and 5, 10, 15, 20, and 25MHz . There is a provision to perform an SOL calibration, which I assumed needed to be carried out and saved before any measurements were taken.
Time Domain Reflectometry Mode
One of the inbuilt measurement features located on the second row is the Time Domain Reflectometry (TDR) mode. This is useful for determining the length of a cable, and, in particular, a coaxial cable.
With this mode selected, the cable is connected to the test-port, preferably fitted with a suitable connector. A value of either 10, 50, 150 or 300 metres is then selected, based on an estimate of the cable length. This selection is not critical; once a run is made, the length of the cable and cable impedance is displayed, no matter what range the analyser is on. However, the graphical representation on the screen of the cut-off point may be out of range.
The sweep runs automatically if the cable length is changed, or the Scan icon pressed.
For this to work correctly, the Velocity Factor (Vf) of the cable must be known and entered into the unit. The unit is preset with a value of 0.66 (such as for RG58). This may be altered and stored, either temporarily or permanently. I found this feature accurate although; with some cables, the analyser presented some odd impedance values directly at the cut-off point.
The Vf of an unknown cable can be found by measuring a known length of the cable and altering the Vf on the analyser until it reads the correct cable length.
With amateurs now having to conform to RF exposure limits, the Mini1300 is an ideal tool to accurately measure feeder length (especially in existing installations) and this data can then be entered into the EMF calculator.
An RF Generator
The analyser incorporates a basic signal generator, capable of outputting a fixed-level signal on any frequency within its range. There is also a basic facility for either FM or AM modulating of the signal.
The modulating frequency is 500Hz. On the review model, I did notice a frequency error that increased as the generator was tuned higher in frequency. At 10MHz, I measured it at a negligible 0.6kHz high, by 144MHz it was 8kHz high, and by 1 GHz it was 52kHz high. I found that this error also applied to SWR measurements.
It may be that this can be trimmed out in the Configuration Menu but as this was a review model I did not attempt this. However, it does mean there may well be a frequency error of a few kHz with measurements made at the higher frequencies. Not having the correct USB lead I was unable to test the USB/ Reader PC connection.
In this brief look, I found that the Mini1300 provided a complete “all in one box take anywhere” tool for the testing and adjustment of aerials. It performs all of the usual S11 SWR, Impedance, TDR, Return Loss functions that most traditional analysers do. Also, it can perform S21 through-tests.
The unit also benefits from a signal generator that can typically be used for relative field strength measurements on a receiver connected to the aerial under test. With WSPR/FT8/FT4/JT65 capability, you can even use it to try your aerials out on-air and see how they perform.
The metal case is sturdy and well finished. The touchscreen is easy to manipulate clear, bright and colourful; it provides plenty of information. It is easy to recall images to view on the device or upload to a PC.
When images are saved, Touchstone files are generated at the same time, and these can be uploaded into other applications for analysis.
© 2021 Keith Rawlings