Building an ATU-100 (N7DDC)

  

I won't make a full report of my build , since all information on this autotuner is available online.
This is the github page where you can find it all.
Some nice descriptions can be found by Googling ATU-100.

And visit these pages by R0AEK with some very helpful information (in Russian, but Google does a decent translation). There are 4 parts.

So here just some pictures of what I did, from the package arriving from China (in 11 day's, that was quick !), to the final result.

The parts arrived in a nice plastic box, and then in some plastic bags.

The SMD's all pre-soldered.

The SWR bridge

All coils ready, with some other components.

Adding the 15 relay's.

Winding the tandem match was the hardest part. TIP : I removed a few strands from the RG58 center conductor to make it fit the holes in the PCB.

All parts of the case ready to assemble.

Detail of the front panel

Back panel

Back panel inside.

Boxed it !

Making the connections to the board is not complicated, see markings on the main PCB.

GND and + is for the 12V DC power supply or battery. 

GND and B is for the big TUNE button

On the 5 pin connector, only 4 pins are used to connect the OLED display:

VCC  goes to VCC on the display

GND              GND

DAT               SDA

CLK               SCL

Finally there are two optional buttons, they connect to two pads on the underside of the PCB, the other side of the buttons goes to GND of course.
B1 is the AUTO button (it shows as a DOT on the display).
B2 is the BYPASS button (it shows as an UNDERSCORE on the display).

 

This pictures show clearly where those pads are, but be careful with static when soldering, the pads are directly connected to two CPU pins. It is advised to put a 100 nF capacitor over each of those buttons, to avoid RF getting directly into the CPU. 

Almost finished

The last step was making a nice cover. I used the top cover from an old Macbook Pro laptop, and was able to save the "Apple" ... hi.

Adding a high brightness LED, using only an extra 5 mA to light the Apple logo, this is the result !

I only did a short test on my home antenna, and all seemed to work ok. 

More extensive testing to follow during my SOTA or other /P activities ...

73,

Luc - ON7DQ