Remote ATU v 1.0       

Below project is all about situations in HAM radio, when requirements such as "remote control of ATU", "remote control of PA", "antenna remote tuning automation" and "additional management and monitoring for ATU and PA" are in place.

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:
Video (low resolution)
(alternatively download high resolution from here)

Version 2: Relay-based T-match/L-match combo:

Final construction fit into the 350(L) x 170(Dia) pipe container:
Video (low resolution)
(alternatively download high resolution from here)

Generic diagram and description:

ATU box is mounted on mast (attaced directly to antenna input). The only wiring from the shack is RF cable and +18V (two cores unshielded cable).

Tuning power from 0.01W to 200W.
Operational power from 0.01W to 2KW constant (for varialbe coil version) and from 0.01W to 1KW (up to 5 min constant for relay version).

Transport protocol between ATUconnect and ATU box (ESP32 processor) is MQTT. MQTT server runs in background (console mode) on same PC with ESDR3.

The only transport media currently (Release v1.0) used is 2.4GHz WiFi; we have plans to add CAN-bus in future versions (however CAN will require extra 4-cores cabling, obviously).

The ESP32 Firmware code is open source and can be found via Github links.
The tuning algorithm is based on target to achieve either minimum possible or 1.001 : 1 SWR for given frequency.

For the remote control we currently use ATUconnect. However you are more than welcome to write your own control software which will suit your needs. All nessessary API are described ESP32 firmware documentation.

ATUconnect is currently maintained as closed source with access of trusted developers only; exe and dmg are available on request. The only purpose for this part of the project to remain closed is because Qt6 still in development.

Functionality brief:
   - Automated or manual tuning.
   - ATU type presets (L-match any kind) or T-match.
   - Universal FW and SW (supports either variable coil/capacitors or relay-based).
   - Unlimited Antenna presets
   - 0.01W -2000W tuning power.
   - Step values for ATU's L, C1 and C2 motors monitoring.
   - Actual values for L (in uH) and C1/C2 (in pF) monitoring.
   - ATU status display (i.e. “Ready”, “Tuned”, etc).
   - 5-12V (control) with either 19-20V (step motors) or 5-12V relays.

Fucntional differences between Variable and Relay ATU:
None of us was expecting, that fix capacitors and coils will be same selective and descrete as variable. Hence - relay-based construction performance and tuning capability is certainly less granular than variable coil remote ATU. However, T-network ATU still provides good enough tuning, while it has significantly reduced weight, power requirements and size.

Variable coil and variable capacitors ATU version
1. P-140 variable coil
2. Two variable capacitors 25-1000 pF (need to be selected to required capacity and availability)
3. Espressif ESP32-DevKit - 1 piece

This model was selected for our project due to extended WiFi range needed (provided with external antena). Any compatible ESP32-DevKit can be used, just look around Ebay to find one you like. 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 sencitivity in the given construct is 1mV with total range from 2 to 4096 mV in each A0 and A1. "Lower" 2mV is the parasitic noise with given L/C filter and shunting 100K resistors. This brings us to capability of guarranteed 1W starting measurement/tuning point. Voltage devider provides with 5mV...4V measurement range; all used ADC channels are clamped to 5V. ADS1115 has variable SPS options and tuning algorithm is using variable measured cycles before engaging next tuning step.
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.
7. TCST2103 Photo-interrupter - 3 pieces. There are also heaps of alternatives on Ebay.
8. Tandem-Match/SWR-sensor (use Tandem board only, connect controls to Motor control/ADS board described in 9 below)
9. Motor control/ADS schematics (click to enlarge). Please note that schematics cover 2-motor and 3-motor versions.

(Please contact me via EE forum if you wish to obtain KiCad sch file. Please note, that I currently do not have available printed boards, you have to order your own.)

Relay-based T-match/L-match combo ATU version

Design overview
The idea of this ATU design came out of the combination of "ATU-100 Extended board by N7DDC" and above desctibed 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 relay networks composition (or what is called "8x8x8 T-match") has the in-build on-demand L-network capability, allowing this ATU type to opecate as either version of L-match. The default operational is T-match (L-match is "called" from UI):

Features highlights

     1. Capability of T-match and 2x L-match configurations within same device. It either operates in classic T-match C1-L-C2 mode, or C1-L, or L-C2 mode. Moving from one mode to another is SW function and sully supported in remote mode. All "relay networks" can be operated in auto or manual mode.
     2. Flexible tuning options - each described above mode operates via two different tuning algorithms. Accordong to the experience, different types of portable antennas may require different kind of tuning. As an example - T-match primary algorithm when L tunes first, then hot C, then cold C; and secondary algorithm when hot C goes first, then L, then cold C.
     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 tunign time. Additionally Antenna presets is enabling next feature
     5. "Follow VFO" function is TCI-based feature, which reads current frequesncy 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 tunign power, VFO. TX, operate with PA mode and engage/disengage Tune..
     6. WiFi (as primaty communication media) and (in fiture)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. Dimentions: 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 connectos/cables).
     8. 5V operations. All relays are 5V, all components are low power consumption. Everything composed to save battery power for field operations. Very usefull for DXpeditions.

Boards schematics
C2 board schematics
C1 and L board schematics
KiCad schematics for L-C1 and C2 boards in zip file.
Gerber files: 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 (1.6 on single toroid, 3.2 - on dual and 6.4 - 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.

Main power input 12V, then reduced to 5V by DC-DC converter (one per network and one for logic) is based on LM2596S-12 stabiliser. Input voltage can be tuned between 6 and 45V if higher power source desirable. Overall device max power consumption (all relays switched on) is around 300W (12V 2.5A). In real operations used power is about 100-150W (depends on how many relays engaged).

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 relay engaging by RFI.

Bridge drivers are operated by MCP23017 GPIO expander and ESP32 GPIOs. MCP23017 is operated by ESP32 via i2C bus.

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).

For ADC the ADS1115 is used. It is 16-bit and gives good enough resolution (compared to 12-bit ESP32 in-build ADC). ADS1115 sencitivity in the given construct is 1mV with total range from 2 to 4096 mV in each A0 and A1. "Lower" 2mV is the parasitic noise with given L/C filter and shunting 100K resistors (R6 and R7 on C2 board). This brings us to capability of guarranteed 1W starting measurement/tuning point. Voltage devider provides with 5mV...4V measurement range; all used ADC channels are clamped to 5V. ADS1115 is set to 16 SPS and tuning algorithm is set to wait 8 full measured cycles before engaging next tuning step.

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 predominatly applicabe 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 comparisson: 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 datacsheet 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 sencitive. 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. As a matter of fact, 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. Hence, it is solely up to you, if you wish to use ATUconnect or create your own control application.

It 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/TX mode. In future versions the second ATU (primarily dedicated to RX mode) will be suported.

Latest UI consist of two Tabs - Dashboard and Setup:

Typical nessessary 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 powerfull mechanism to tune wide range of antennas.

ATUconnect is Qt.6 based cross-platform application. It currently can be compiled for MacOS, Linux (Ubuntu) or Win x64 10/11. Example dmg and exe are available via Github page.

Please note that this software is currently under code cleanup and optimisation, hence the acceess to code is for development team only. Additionally we are working on feature enhancements: adding new features to allow granular control of the 8x8x8 remote ATU and provide more flexibility in tuning "unknown" DXpedition's antennas.

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.