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Smart Automatic Antenna Tuner for portable QRV

New elements LC for expand band of tune ... see further below



 A lot of designs of the external automatic antenna tuners (AT) is developed today, the part is made of them by HAMs , the most part is made by factories (LDG, ICOM and others). The best place for the AT installation - in a point of a antennas food, without feedline. This reduces or eliminates SWR losses in the coax transmission line, what is very important for save good efficiency of antennas !
 If you want QRV from field conditions and you use narrow-band antennas - you will be have problem with high SWR, because narrow band antennas in field conditions with non-optimal height need compensation of reactance.

 Let me introduce my new design ! This is Smart Automatic Antenna Tuner has been designed at 2012 year.

 Some Specifications of this Smart Automatic Antenna Tuner

Inductance range: 0-3,75 µH in 16 steps (0-7,75 µH with additional LC elements)
Capacitance range: 0-310 pF in 64 steps (0-630 pF with additional LC elements)
Network: Series L, shunt C (all switchable) - 2048 steps
Tuning times (typical): 12-15 seconds for tuning; 1 seconds to re-tune from memory
Max power: 100 W peak, 10 W in time of tuning
Frequency range: 3,5* to 30 MHz (*- 3,5 MHz with pre-tune antenna)
Supply voltage and current drain: via RF feed line (injector) 11 to 14 VDC , current drain (only in time of tuning) - to 100mA (peak 2A average 1mcek), latching relays consume no current after tuning

 The actual tuning operation is controlled by detectors (VD1,VD2 and VD3) at the measuring bridge to the matching network. These detectors provide information of the condition SWR to Microcontroller (Atmega 16), which adjusts the L-matching-network constants to achieve the required match. To conserve primary power (important for portable operations) , latching relays are used throughout the tuner for L-matching-network.

 DC injector is necessary for inject DC onto the coax between tranceiver and automatic tuner.

 Only this AT saves low SWR for your TX in all automatic tuning cycles!

 The Microcontroller sets up successive L/C combinations in accordance with a matching algorithm, without measure frequency of the RF signal applied to the input bridge. Finding lowest SWR. Microcontroller not have any information from CAT system and is absolute independent. This AT has five (8 in new AT)"antenna-memory" bank and matching time - about 10-15 sec. AT tunes in CW mode .

 Tuning cycle is very fast if configuration is stored in EEPROM memory of microcontroller. First time microcontroller will be "learn" for new antenna in every band.

 The AT has been enclosed in a weatherproof, high-impact plastic housing for installation to the antenna feedpoint.
This reduces or eliminates SWR losses in the coax transmission line, what is very important for save good efficiency of antennas !

 If you need capacitors for L-matching-network with value 1:2:4:8 (10pf 20pf 40pf…) - you can made its very easy. You must take high frequency laminates with dielectric constant above 7-8 (better 10, from Rogers corp. or other ) and make small size capacitors.
 If you want use this AT for balance antennas - it is strongly recommended a 1:1 CURRENT balun is included to INPUT of AT ( between AT and Antenna).

Current balun

Home made capasitor ...... for example

Click for full size image

Modification circuit of Injector for use with ALC and PTT remoute :


Click for download AutoTuner description (russian)


Inside Box

Top of Tuner`s PCB


Bottom of Tuner`s PCB

MCU Atmega 16

Bottom of PCB

Top of PCB MCU Atmega 16


PCB file (Layout 5 format)


Sound indicator with high SWR (SWR >3)

HEX file for Flash and EEPROM memory of Atmega16

(ver 7) 5 memory, sound indicator "S" in CW code with SWR>3, fix some little bug

Fuses and Lock bits settings for Khazama AVR Programmer

Frequently Asked Question(s) :

1. How can i check circuit of tuner ? Here many wires, relay ... That easy ! Here you are - HEX file for test circuit

After start - all capasitors and inductor will be turned on .


New elements LC for expand band of tune for 3,5 MHz and 7 Mhz

 You can easy add new LC elements. You need only inductance 4 uH and capacitor 320 pF. Inductance must have good quality and capacitor must have enough reactive power. I used ferrite toroid (m=50) and old mica capacitor.

 Anyway, you also must add 4 keys by BC546 for pin # 7,6,5,4 of port Atmega16.

 Will be good if you use ferrite beads or tubes, which employ for the dissipation of high frequency currents in wire from keys.




New elements has been added from above on Top of Tuner`s PCB


Keys has been added from above on Bottom of PCB



HEX file v 8 for Flash and EEPROM memory of Atmega16

(ver 8) 8 memory bank, sound indicator "S" in CW code with SWR>3 , support new elements

Inductance range: 0-7,75 µH in 16 steps + additional few steps for new L element
Capacitance range: 0-630 pF in 64 steps + additional few steps for new C element