ATU 100 Antenna Tuner build details, tests, options, and matching capacity 

@@VA3HDL many thanks!

@@VA3HDL This link no longer works.....any better link information? Thanks for great video!!

@@eddy2561 You right. Looks like the site itself is not longer there. Check this other one I found: reflector.sota.org.uk/t/atu-100-extended-board/25135/3 It will also depend on the board you have to match the one in the picture above. 73

@@VA3HDL If you still have the link to the old one, you might be able to dig it out of the Wayback Machine...

@@oasntet I found a similar picture and saved on my website in case someone else need it... www.va3hdl.com/projects/atu-100-kit

Same! I did find the PDF manual on the GITHUB site. It is quite nicely written too.

Thanks for watching Mark! 73

Glad to hear it helped you. Thanks for watching. 73

Thank you!

Thanks for bring this up, I forgot to mention on the video. Very important before start, ensure all pre-soldering job has been done correctly.

Thank you!

Hi Ed. Thanks for watching. 73, Pablo

Thank you! 73

@@VA3HDL My pleasure as you really helped me turn the kit into a working antenna auto tuner! 73

Thanks Paul. Glad you like it! 73

Thanks for watching!

Great. Good luck with your build. 73

Now you built one you should be able to go back and fix the other two! Good luck. 73

Thank you!

Glad to hear Willie! 73

Thank you! 73

Thanks Mario. 73

Hi John, your assumption is correct, when in auto mode is enabled it kicks in when SWR goes above 1.5 - I haven't tested the attenuation in 10m band, but is a good idea, I have a nanoVNA and I can try sometime. Thanks for watching and commenting. 73

There is no quality control at all on these cheap devices. However, with a little love you can always make them work correctly. :) 73

Hi Diogenio, I never tried to run FT8 with this tuner. I only use this tuner on portable operations for POTA, Field Day, and similar with 100W SSB. I don't do FT8 while portable. On the shack I have an MFJ-939 200W SSB/CW that I used sometimes for FT8 at full 100W. I know there are 1.5 KW versions of the ATU-100 tuner. Exactly same design but with sized components accordingly to support 1.5 KW - Hope that helps. 73 and thanks for watching.

Fider - physical wiring that transmits radio signals from the transmitter to the antenna or from the antenna to the receiver, also known as the transmission line. There is more information about this parameter here: github.com/Dfinitski/N7DDC-ATU-100-mini-and-extended-boards/blob/master/README.md - This parameter is not present on my version of the firmware. I'm still running version 3.0 and the latest version is 3.2 - The fider parameter appeared on the version 3.1 - Hope this helps. 73

@@VA3HDL Thanks, I now understand. 73 PE1ATN

Hi Kevin, I didn't created them. It was given to my by the author N7DDC. I believe used a python script to create them. I cannot find the script right now. If I get it I will post the link here. 73

Is in the video minute 5:00 -- 73

@@VA3HDL the link is dead for this!

@@paul.alarner6410 I delete the comment with the dead link. Please check the pinned comment by me that has the working link. Thanks.

I'm afraid there is no manual for the ATU-100, the author website is github.com/Dfinitski/N7DDC-ATU-100-mini-and-extended-boards -- Good luck!

Hi Dean, here is the link www.amazon.ca/gp/product/B005T7T0Y6/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&th=1 I cut it to make it smaller. 73

Lyle, I had to go back and find the test board to provide you the answer. The center conductor of the coax is connected in series with the two 100 ohms in parallel resistors and the pins. The coax braid is connected directly to the other set of pins. When the inductor is connected to the pins is in series with the 50 ohms (two 100 ohms in parallel.) In reality it should not affect much if is connected in parallel or series with the 50 ohms load, since the inductor DC resistance is very low. But I haven't tested personally to confirm this theory. I hope it helps. 73.

@@VA3HDL Many thanks for this. de VE1BZE.

Gracias Sergio! Abrazo. 73, VA3HDL

Gracias Victor! 73

Hi, these are marked as RB1 and RB2 on the bottom side of the board. Take a look at this page, it is explained there radioaficion.com/news/automatic-antenna-tuner-kit/ The caps for the buttons are not on the board. Check how I mounted them around 03:17 you can see them soldered behind each button.

@@VA3HDL did you add 100nF shunt caps for those buttons? I am thinking they may already be on the board.

@@VA3HDL Hello. Is there any way to access the pad for Auto tune connector from the upper side of the card? I got a prebuilt unit with battery and much soldering is needed to get access to the underside. Jan / SM5SUH

@@janneblomquist3389 If you jump to the N7DCC circuit part on the video you will see RB1 (Auto-tune) goes to pin 22 and RB2 (Bypass) goes to pin 23 on the microcontroller. If you are brave enough you can try to solder a thin cable directly to the microcontroller pads and fix the cable to the board with some hot glue or tape. On the board I received the pads for the microcontroller are big enough to solder something else if needed. Do not forget to add the capacitor between the button pins. Hope this helps. 73.

@@VA3HDL Thank you for a quick answer, Yes, the pic is small but I think I can manage to to hit the pin 22 with a thin ground cable. If I understand it right I turn on the auto mode if I do that and it will keep it enable after that. So first I find out where the Pin 22 is than I just test with a short conecting a ground lead to se if the dot appear. After that I can figure out a place for a contact and a capacitor. 73

Hi Nem, check the pinned comment. There are links there to the pictures for these details.

Glad you liked it!

meant to say L1234 etc left to right.,hope you understand,at the moment i have the core with 8 turns L4?,in the first slot in the pcb from the left.

@@paul.alarner6410 That is correct, if you look at the schematic on the video they are positioned in the same order on the majority of the boards I've seen for this tuner. L1 is the smaller one on the far left and L7 is the larger one in the far right.

Take a look at the circuit. It seems right. 73

@@VA3HDL I had a pretty detailed look at the circuit diagram and it appears you're correct, and while I'm not an electric engineer but a dink with a soldering iron... Guess I'll plow forward and see what happens? I do still fear for my radio, using this thing.. 😳 Thanks for the video about the transformer and chokes. Your detailed instructions were excellent help on winding those. Cross your fingers and hope for the best!

As long as de driver power is not higher than 100 W then should work. I'm curious why you want to go this route. It wouldn't be simpler to build a manual matching unit? I presume once the driver is matched to the amp you do not need to change it, but I never had an amplifier so I cannot tell for sure. 73

This simple tuner doesn't have memories for previous settings on any given frequency. When in auto mode will retune automatically when SWR goes above 1.5:1 73

@@VA3HDL thanks for the reply👍👍 73's

I'm not sure. If you a referring to the picture with all the inductances, then is from VA3FUZ who provided me the picture. 73

Hi, here you a have a very good explanation for measuring coils without the resistors: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-iJ1qKE5O0bY.html Here is another one using a known capacitor value to help in the measurement of the coil: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-3LOEhvFII6c.html And finally here is another video on my channel: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Ahweiti8swk.html - Check the comments in this video, it is explained there. To be clear, the 100 ohms resistors are in parallel between them to make a 50 ohms. Because the coil resistance on itself if negligible (very low) it doesn't matter much if you put the 50 ohms in series or in parallel with the coil. If you have a coil of known value, try both and check with way gives you the closer value. 73, VA3HDL

Hello, thanks for the quick response to my query and the comprehensive answer. I will definitely use your tips. All the best to you and your loved ones.👍@@VA3HDL

Hi Paul, if you mean by "resets" it re-tunes on every keyup then that is normal for these conditions: SWR > 1.5 and mode is set to "AUTO". If SWR is < 1.5 it should not re-tune. Cheers.

Hi Horacio, is possible, it is explained here how to do it -> 19:06 - Power-On button combos for testing or manual use - 73

@@VA3HDL Thanks for your answer. I didn't realized that manual mode and test mode are the same. Thanks again.

Yes, no problem. I've used this past weekend on the contest with my g5rv and it worked better than my MFJ autotuner. 73

@@VA3HDL for g5rv to ATU-010 do need to add balun 1:1? Or just g5rv goes to this ATU-100?Thank you for your information. Sorry for my english

You need a 1:1 current BalUn with a G5RV. The BalUn goes in between your coax and the twin line of the G5RV. The reason is the twin line is Balanced (the Bal part in BalUn) and the coaxial cable is Unbalanced (the Un part in BalUn.) In this case this is exactly the purpose of the balun. The other end of the coaxial goes to your ATU-100 "antenna" port. Wikipedia quote: The ends of the symmetric feedline can be soldered directly onto a 50 Ω coax cable to the transceiver, however this is not good practice and should be avoided: It can result in high current flow on the outer surface of the coax braid, causing RF interference and degrading the polarization and gain of the antenna. A 1:1 current balun should be used between coax and ladder line. Including a balun not only prevents RF interference but reduces receive noise and increases performance. A length of at least 20 metres (66 ft) of 50 Ω cable is recommended for operation without a balun. 73

@@VA3HDL thanks, for the detailed information. 73

Hello Biagio, this text below? POWER ON BUTTON COMBOS: Special modes of operation​ The device has several special modes of operation, designed to facilitate the process of assembling, debugging or troubleshooting.​​ POWER ON + TUNE + BYPASS + AUTO​ Fast Test mode is activated. ​ In this mode, the device provides power to all relays, which allows you to quickly identify faults associated with transistor switches or soldering faults.​​ POWER ON + BYPASS + AUTO​ Simple Test Mode. ​ In this mode, you can manually, step by step, use the Bypass and Auto buttons to change the value of capacitance or inductance. ​ A long press on the Tune button allows you to select which elements will be moved at the moment, and a short press changes the point of connection of the capacitor. In this mode, it is possible to measure input power and SWR in line. ​

@@VA3HDL Thanks, very kind, bye

Hi Gaurav, No connection to the screen -> MCLR VCC = +5V GND = GND SDA = DAT SCL = CLOCK I hope that helps. 73

@@VA3HDL Thanks Indeed you made it soo simple. I have done the connections and its working now. Can you advise what is the 1st PIN MCLF is all about. ? Its just before the VCC PIN (2nd PIN in the row)

@@gaurav279 That pin is used only when you want to reprogram the unit with an updated firmware from the author GitHub site, or to make modifications to the parameters saved on EPROM, for better accuracy of the displayed measurements, power, SWR, etc. You need a "Pick" programmer to do these updates. 73

Honestly cant remember. I looked at the spares I had around in the bench that fit tight inside the binocular core. It is only the center conductor without the shield. 73

@@VA3HDL I had some RG-58, so I just used that.

I can't play with it yet. Waiting for the PIC programmer. I made this one for QRP, so need to change some parameters.

@@kq6up Correct, there are good videos explaining the entire reprogramming process. Also you can load the latest firmware. 73

@@VA3HDL yeah, got that all set after figuring out that I needed to change the default display settings. I panicked for a second.

Thanks for your feedback. I'm not sure where in the video I said I'm testing with 100 watts. While testing I clearly mention around 13:22 that the power I'm using for testing is 20 watts. Is not advisable to use more power to autotune with any automatic tuner, not just this one, due to the sparks that can produce inside the relays, burning the contacts. All radios with built-in tuners decrease their power output while autotuning automatically.

Thanks for watching Francisco! 73