Remote ATU v 1.0
Below project is all about situations in HAM radio, when "remote control of ATU", "remote control of PA", "antenna remote tuning automation" and "additional management and monitoring for ATU and PA" are required.
There are two current and tested/working versions:
Version 1: Variable coil and variable capacitors version:Final construction fit into the 370(L) x 270(W) x 180(H)mm outdoor box:
Operations:
Video (low resolution)
(alternatively download high resolution from here)
Final construction fit into the 350(L) x 170(Dia) pipe container:
Operations: Video (low resolution)
(alternatively download high resolution from here)
Generic diagram and brief:
ATU box is mounted on mast (attached directly to the antenna input). The only wiring from the shack is RF feed cable from SunSDR2 and +18V cable (two-cores unshielded). ATU's ESP32 and operational PS can be WiFi-connected directly or via AP.
The ESP32 Firmware code is open source and can be found via Github links.
Note: Firmware is universal for all ATU versions as described the below..
Note: The tuning algorithm is based on target to achieve either minimum possible or 1.01 : 1 SWR for given frequency.
The Operational software for the remote control is the ATUconnect application (described below).
Note: This application was designed to work in pair with SunSDR2/Pro/DX models of Expert Electronics and utilises TCI protocol for communication.
Note: If you are intending to replicate this ATU design to work in pair with different transceiver type, the ATUconnect functionality will be limited due to TCI exchange absence. Alternatively, you may need to consider either use of MQTT IDE (something like "MQTT explorer" or similar) or create your own application.
Functionality brief:
Functional differences between Variable and Relay ATU:
None should be expecting, that fix capacitors and fix coils will be same selective and discrete as variable. Hence, relay-based construction performance and tuning capability is certainly less granular than variable coil one. However, relay-based T-network still provides good enough tuning, while it has significantly reduced weight, lowered power requirements and smaller size, which makes it suitable companion for field operations, when variable coil construction is more dedicated for the home QTH use cases.
Also, the relay version has the capability to switch network configurations between T-match, and two options of L-match(with C at Hot End or Cold End). When this feature allows relay version to tune very wide range of antennas, the variable coil version is discrete and selective enough to to the same in only its single T-match mode.
One more - the power consumption. In variable coil construction, once ATU is tuned, the motors are engaged into power saving more and the only power used will be ESP32 (milliwatts) in standby waiting for command. Relay versions, on opposite, will consume powers atfer tuned: due to relays will be engaged; and dependent on how many are engaged, the consumption might be anywhere between 10 and 90W. This is something you would need to consider for field operations in DXpedition.
Finally - the through power. When relay version is weight lighter and smaller, it was not design to handle contionius KW forever. In SunSDR2 the limit for continuous transmission is 5 min; and relay version is pretty match follows that: 500W within 5 min. If you are thinking about FT-8 operations on 500W with the relay version - I would say you will have to measure the coil heating over time. The variable coil versions, on opposite side, is much more tolerant for through power, it can easily handle a kilowatt over 10 min continuously.
What version to select, if you wish to replicate this construction?
Well, the answer is complex, than many may expect. But what is certain: your operational mode and targets dictates the design, not vice versa. Question number one to ask yourself - if ATU is really needed in your setup? To build this contruction - either version of it - will demand various knowledge, instruments and time. Whatever version you will build, it is highly recommended to have experience with KiCad (it is likely you may need to develop your own PCB) and 3D printing (much easier to 3D print nesessary fixings, boxes and stands these days). Additionally you will required experience with ESP32 firmware loading (pretty much same as with Arduino or similar micro controllers).
Variable coil and variable capacitors ATU version details
|
1. The physical construction consists of: - Variable coil (1 pcs) - Variable capacitors (2 pcs) - Motor control/ADS board schematics (pdf file, click to open or download) - Tandem board schematics (pdf file, click to open or download) Note: Motor control/ADS board schematics covers two ATU versios: 2-motor (both variable capacitors in sync) and 3-motor (each variable capacitor independent) versions. Note: Tandem board (aka Tandem-Match/SWR-sensor) is described in details (including specs and configuration/tuning details) within the project SWR Power Meter v1.0. 2. Motor control/ADS print board details:   PCB and Gerber files: ATU-ESP32U-P140_control_97x85mm.zip IMPORTANT: Published version is for A4988 drivers. Because DRV8825 in some instances may have different pinout, please check the pinout first, before ordering the PCB. 3. Tandem print board details:   PCB and Gerber files: ATU-ESP32U-P140_tandem_55x70mm.zip |
|---|
3 to 7 typicaly can be purchased via Ali. 1 and 2 are more the question of availability in your area. Different type of variable coil can certaily be used, but consider you have to measure its, min/max uH and uH per turn - this data will need to be respectively corrected in Firmware settings. Similar measurements need to be done with variable capacitors - min/max PF and linearity. It is highly recommended to use antenna analyser (RigExpert AA-600 or similar quality, or alternatively - oscilloscope) for such measurements.
|
1. P-140 variable coil. In described construction the coil from USSR P-140 radio station is used. Note: this coil has very linear parameters per coil turn and range from 0.4 to 15 uH; hence it covers tuning at pretty much any freq from 1.8MHz to 28MHz HAM bands. |
|---|
|
2. Two variable capacitors 25-1000 pF (need to be selected to required capacity and availability). Note: The minimim recommended parameters for capacitors is 15-600 pF. Using lower max value will possibly result in under-tuning at lower HAM bands. Note: This construction assumes both variable capacitors are equal. |
3. Espressif ESP32-DevKit - 1 piece This model was selected for our project due to extended WiFi range needed (provided with external antenna). Any compatible ESP32-DevKit can be used (Aliexpress search to find one you like), just watch out available GPIO number. |
|
4.For ADC the ADS1115 is used. It is 16-bit and gives good enough resolution (compared to 12-bit ESP32 in-build ADC). ADS1115 sensitivity in the given construct is 1mV with total range from 2 to 4096 mV in each A0 and A1. |
5.
DRV8825 Stepper Motor Driver - 3 pieces Alternative is A4988 Stepper Motor Driver - 3 pieces 
|
6. Nema 17 Step Motor - 3 pieces model 17HS4401S-PG5.18 is used in our case, due to tork and gear capacity. Make sure you have tested motor model with your coil/capacitor to ensure motors are providing enough tork. Additionally, this motor comes with different gear ratio options. The one used in current construction is 5.18-1, however please note that even you will buy motor with the same gear ratio, it is still recommended to measure precisely the number of steps requied per turn and adjust the number in software settings.
|
7. TCST2103 Photo-interrupter - 3 pieces. There are also heaps of alternatives on Ebay.
|
Relay-based T-match/L-match combo ATU version details
Design overview
The idea of this ATU design came out of the combination of "ATU-100 Extended board by N7DDC" and above described variable ATU. With the requirement to meet Australian Advanced license and to ensure continuous operations for DXpeditions, the materials selected to provide x2.5 safety factor: Amidon Т130-2, 3kV+ NPO type capacitors and high voltage relays.
In general, the ATU board composed out of three "relay networks" (with 8 relays in each L, C1 and C2 network), integrated Tandem-match circuit and Control part.
The default T-match relay networks composition (called "8x8x8 T-match") has additional in-build (on-demand, called from UI) L-network capability, allowing this ATU type to operate as either version of L-match (C-L or L-C):
Features highlights
1. Capability of classic T-match (C1-L-C2) and L-match (C-L / L-C) configurations within same device in auto or manual mode.
2. Flexible tuning options - each described above mode operates with two different/concatenated tuning algorithms.
3. 0.01W (tested) to 200W (tested) tuning power and from 0.01W to 2KW operational power. Fully suitable for the range from QRP to US legal limit.
4. ATU type presets (unlimited) and Antenna presets (unlimited). Antenna presets allow to pre-calibrate antenna on band(s), which speeds up tuning time. Additionally Antenna presets is enabling next feature
5. "Follow VFO" function is TCI-based feature, which reads current frequency from SunSDR VFO and swich between antenna presets automatically.
6. Automated tuning mode and Manual tuning mode functions. In Automated mode the TCI communication is used to set SunSDR tuning power, VFO. TX, operate with PA mode and engage/disengage Tune..
6. WiFi (as primary communication media) and (in future) CAN protocol (TJA1051) (for situations where WiFi cannot be used). WiFi is simply connecting via either - access point or hotspot - to the network where ESDR PC is, For CAN there is a need of another small box, where receiving CAN board will be.
7. Dimensions: At this stage the construction fits it into 150mm diameter and 320mm length PVC pipe, mountable on antenna mast. Fully assembled boards total weight is 1150 gr. Add extra weight for enclosure (for example pipe, as described above, is about 1.5 kg extra with both sides caps and RF connectors/cables).
8. 5V operations. All relays are 5V, all components are low power consumption. Everything composed to save battery power for field operations. Very useful for DXpeditions.
Boards schematics
C2 board schematics
C1 and L board schematics
KiCad schematics for L-C1 and C2 boards in zip file. Note: update Library Path in KiCad 'Preferences-Manage Symbol libraries-Project Specific Libraries' and 'Preferences-Manage Footprint libraries-Project Specific Libraries' to reflect your project folder location.
Gerber files (Please note that those Gerber files have some significant errors, so provided for you reference only. It is better you to create own PCB and Gerber from provided schematics.): L-C1 board, C2 board, Power Supply board
The photos
below are real boards pictures (FR4 / TG150, 1.6mm, 1oz, dual layer):
L/C1 board 320mm x 150mm (click on pic to see full size in new window):
C2 board 320mm x 60mm:
Power board front 89mm x 86mm:
To the 8x8x8 construction details:
C1 network and C2 network
5pF / 10pF / 20pF / 40pF / 80pF / 160 pF / 320pF / 640pF.
total 1304pF with 255 step tuning combinations and 5pF/step for each network
Measured parasitic capacitance of assembled boards is about 35-40pF.
Parameters and datasheets:
5pf combined out of 2x10pF in series. 40, 80, 160, 320 and 640 capacitors are combined from 2-4 in parallel and measured to be as close as possible to indicated nominals.
Capacitors are the combination of Murata Electronics MLCC C0G(NP0) and AVX MLCC C0G(NP0) 3kVDC with 5% tolerance.
Coil wire is Single Core 2.03mm (14 SWG) Copper Wire.
L network
0.05uH / 0.1uH / 0.2uH / 0.4uH / 0.8uH / 1.6uH / 3.2uH / 6.4uH
total 12.75uH with 255 step tuning combinations and 0.05uH/step
0.05uH, 0.1uH, 0.2uH, 0.4uH and 0.8uH coils are frameless inductors, made from above wire. Remaining coils are wired with same wire on Amidon T130-2 (1.6uH on single T130-2, 3.2uH - on 2xT130-2 and 6.4uH - on 3xT130-2).
Relays are Omron Electronics G2R-1-E-DC5. Using 5V relays makes crucial difference in power requirements and overall device power consumption. Relay switching is performed on positive wire (this gives fair enough RFI protection, compared to ground wire switching). HW version 2 uses SN754410 Quad Half-H bridge drivers to operate the relays. When relay is off, the "positive" is connected by bridge to the ground, preventing unwanted relay engaging by the RFI. Bridge drivers are operated by MCP23017 GPIO expander (i2C bus) and ESP32 GPIOs.
Main power input 12V, then reduced to 5V by DC-DC converter (one per each 'network' and one for the 'logic' board) is based on LM2596S-12 stabiliser. Input voltage can be tuned between 6 and 45V if higher power source desirable. Overall relay network max power consumption (all relays switched on) is around 30W (12V 2.5A). In real operations overall device used power is about 90-110W (depends on how many relays engaged and how effective used buck converters).
ESP32-WROOM32U with external WiFi antenna should provide up to 50-60meters (open space) signal distance coverage with acceptable signal level. For situations where WiFi is not an option, the future designs will be provided with CAN bus module. (However there is the feedback for using CAN media: additional (receiver) device is needed. This can be based on any Arduino (like Nano), or on ESP32D. I have working/tested device in hand, will add construction and code details later).
The ADC the ADS1115 is used. It is 16-bit and gives good enough resolution (compared to 12-bit ESP32 in-build ADC). ADS1115 sensitivity in the given construct is 1mV with total range from 2 to 4096 mV in each A0 and A1.
Tandem-match is based on BN43-3312 (20:1, -26dB) combined with Pi-att (-25dB) of 56 Ohm-442 Ohm-56 Ohm and two AD8310 log amplifiers. This solution allows to perform tuning even on values 1uW above AD8310 intercept level. For performance reasons the values set to perform tuning within the range from 0.01W to 200W PEP.
What is the difference between AD8310 and "classic" diode detector based Tandem? What is predominantly applicable to this project case:
- diode detector is cheap, simple and does not require any calibration
- at the same time, diode detector is non-linear and typically affected by distorsion and interference.
Diode detector was tested during this project and we found that it does not work well specifically on the values close to diode's forward voltage minimums.
Of course, there are techniques, making possible overriding diode detector's issues on low bias. However, those techniques have their own "buts" and "ifs". And even then - practically, it is very hard to create the diode-based construction which will cover range even from 10W to 1000W. It is most likely the range from 50W to 1000W can be covered. But when it comes to extend it to 2000W, the issue appears again.
- Log amplifiers (like AD9307/AD8310) are much more expensive. Of course we should speak about "expensive" in context and comparison: it is $0.10 for diode vs $10 for log amp. Rounded, using log amps instead of diodes will make whole project cost $20 more.
- log amps are better to be calibrated. Sure, it is possible to just use datasheet and base the code purely on theoretical supply - however this approach may introduce significant risk going "out of band" for measurements. Calibration process is not really complex and once completed, it will give very precise slope and intercept values per log amp chip.
- massive advantage of log amplifiers - those are very linear and extremely sensitive. There is no issue to detect RF Power values within range from 1mW to 10KW in steps of 0.1mW (or less).
ATUconnect application
ATUconnect is one of the UI control options, currently maintained as closed source and available upon request. The only purpose for application to remain 'closed source' at this point of time: is because it is in development and changes can be done to the software without any notice. It is Qt.6 based cross-platform application, can be compiled for MacOS, Linux (Ubuntu) or Win x64 10/11. As a matter of fact, current ESP32 firmware can be operated directly from MQTT command line or from any other application, which is capable to send JSON-based and TCI commands (can be found in TCI protocol manual and ESP32 firmware documentation).
ATUconnect was developed with entire and sole purpose to fit VK6NX's common IOTA Dxpedition laptop environment. It fits my needs and screen resolution, which does not automatically mean it will fit your purposes. Hence, it is solely up to you, if you wish to use ATUconnect or create your own control application.
ATUconnect is integrated with ESDR3 via TCI and provides core User Interface functions, i.e. ATU profiling, Antenna's profiling, ATU initialisation and ATU operations. Current SW version supports single ATU in TX/RX mode. In future versions the second ATU (primarily dedicated to RX mode) will be supported.
Latest UI consist of two Tabs - Dashboard and Setup:
Typical necessary setup would include MQTT:
ATU profile:
and Antenna profile:
At glance - the combination of user-selectable starting tuning C1/C2/L values, starting step size and direction and selection of particular tuning algorithm (L first or C first) - provide quite powerful mechanism to tune wide range of antennas.
If your target is to build ATU to work in pair with the transceiver model different than SunSDR2/Pro/DX range, then please note limited fucntionality with ATUconnect. The reason is because application was build to utilise TCI protocol capabilities, which is in-build with SunSDR's.
So, what will not work, if your transceiver has no TCI? First and most important, the single button push automated tuning will have limited functionality. The "Tune" button in ATUconnect at push sends the command ESP32 to engage tuning and at the same time sends the command to transceiver (via TCI) to enter into Tune mode.
What real options do you have?
Option one: Well, the "TCI" part will not work in case of there is no TCI, hence you have to push your transceiver manually. Also at the end of tuning, when minimum SWR reached, ATUconnect sends the command to transceiver (via TCI) to exit Tune mode - this part you also have to engage manually.
How hard to add your transceiver into support? The answer can vary from "easy" (if you know the command protocol of your transceiver and it does support remote in/out Tune mode) to "impossible" (if you transceiver does not support remote operations). In addition to "easy" you would need to be familliar with C++ programming and Qt6 - then you can add nesessary modifications to ATUconnect.
The other option (which might be more feasible for most people with TX differerend from SunSDR2) is to pre-configure ATU with full automatic tuning mode. In that case the ATU will enter into tuning mode as soon as two conditions are met: there is power and SWR is different from 1:1.01.
In that option all you would need to do is to engage Tune mode on your transcever and ATUconnect can be used as the "indicator" only, to confirm when minimum available SWR is reached.
Team:
VK6NX overall concept, physical construct, initial programming, testing - and using :)
VK3FDMI SW concept, programming, customisation and optimisation.
Warm thanks to Dmitry RV9CX and Serge RA9DM for their support and suggestions.
