Curt builds an Icom IC-705 control interface for his Elecraft T1 ATU

Many thanks to Curt (WU3U) who recently contacted me and mentioned he had built an IC-705 control interface for his Elecraft T1 ATU. This is a homebrew project based on others’ work and uses the FT-817 control port on the side of the T1 tuner.

I asked Curt if he could share a little more about his tuner to post here on QRPer:

Hi Thomas, I can’t take credit for the interface, as a guy in Japan designed it. When I built mine the entire instructions and notes for code for the PIC controller were in Japanese. I used Google translate to translate all of the information and I was able to successfully program the PIC chip and build the circuit. He has since released the details and code in English.

There are two designs: one with an on/off switch, and a newer version without an on/off switch that has auto power save. Both circuits are the same but the software for the PIC chip is different. If you build the one without the on/off switch there is a very specific sequence of connecting and disconnecting the device and it’s my opinion that the one with the on/off switch is the version that makes more sense to build. It shouldn’t matter which order you connect everything up and you simply throw the on/off switch to turn the device on and off.

Building the interface takes an understanding of a fairly simple electronic schematic and acquiring the parts. You also have to have a PIC programmer and the software to write his .hex file into the PIC controller chip.

The parts for the interface are all very common parts. The resistors are standard values. My build cost me about $30 in parts but I had to buy many of them in bulk from Amazon like the enclosures, switches and 3.5mm jacks and circuit boards to name a few. Individually the parts were $30 but my bulk order cost me much more. I also had to buy a PIC programmer for $25 and figure out what software I needed to download to program the PIC chip with the author’s code. It takes an experienced builder about two hours to build the device but it’s not out of the realm of a semi-novice as long as they can get the PIC chip programmed.

Here is the original code using the on/off switch. Everything is now in English:

Here is his newer version with the same circuit design eliminating the on/off switch by using a different PIC program allowing the interface to have auto power shutdown (low power standby) but there is a specific order for connecting and disconnecting the interface. With this version there is still drain on the battery but the designer thinks that drain is less than the normal self discharge of the battery. I feel that any discharge combined with the self discharge of the battery will be more discharge than using the design with the on/off switch.


I think this is a brilliant project and certainly one worth considering for those of us who already own an Elecraft T1 ATU and would like full control from the IC-705.

Thank you for sharing these details, Curt!


11 thoughts on “Curt builds an Icom IC-705 control interface for his Elecraft T1 ATU”

  1. Curt,

    be smart, build some more of these ATU controllers, stick your call on them and sell them, I’m sure there will be quite some guys and galls who want one. And you get rid of all those components you had to buy 🙂 🙂

    Great what you have done, congratz.

  2. Hi Frank, after building a small handful of these it’s really only a cost effective build if you can do it yourself. After building a couple more I realized that I had closer to 3 hours into the build and by the time I would sell one I’d have to sell it for $85. Once I’d ship it domestically and PayPal gets their cut and I try and recoup a few dollars on each one from buying the programmer that I didn’t already own I would make less than $13/hr.

    From the people that I’ve surveyed everyone seems to think that $85 is too much and I couldn’t get the price any lower without lowering the labor and I’m not sure I know too many people that value their time at a price that would make this more attractive to the people that wanted one. This is all while using someone else’s code that you can’t include in the price of building one for someone else so that guy has done everyone a huge favor right out of the gate. I will say it’s a good project to learn about flashing a PIC chip which I had very little experience with.

    1. I will gladly pony up for one of these. That is not too expensive. Alternately, if you sell as a kit of parts to save your labour, I bet a lot more people would jump on that.

  3. Curt,
    Sounds like a cool project!

    Could you give us more details about the chip flashing process? What programmer and programming software did you use? Any other tips and suggestions you might have would be most appreciated.

    Many thanks!

  4. Hi yes Curt if you could reference the pic programmer you purchased. Or if you would burn a pic controller chip would that be worth like $30? In this what I would simply breadboard mine and not end up with a ithe programming controller in
    My junk box. Thanks de K3GO. John

  5. Hi again Curt I purchased a DollaTek K150 for the pic programmer and software to program the PIC. Do you know If the new part being used is the same functionality and can I use the latest hex file to blast the program?

    Thanks for any help john de K3GO

  6. Hi Curt, I would be interested in one if you get around to it… I have a T1 and a 705 and it sure would make things easier… and the on-off switch makes good power saving sense to me. Price at 85 + 10% seems reasonable. So, ca. 100 shipped would be doable?

  7. Hello Curt, I’m very interested in your interface and $85 is not much. Hams are inherently cheap. Please let me know if you are willing to make me one and I will gladly pay the price.

    Rudy, W5HRH

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