Announcing The Elecraft KPOD Open Source Remote Control for Arduino and Raspberry Pi Project!

After reading the Elecraft Technical Notes on their wonderful KPOD product, I’m so confident that it would be an absolutely awesome controller for my Arduino and Raspberry Pi projects that I just ordered a second one. The first one controls my K3, the second one will be used to develop software that sends input command packets to the Arduino or Raspberry Pi and then, code will send the appropriate control commands to the output.

My first project will be to control this antenna tuner – the Palstar BT1500A. Two stepper motors will turn the L and the C controls. Here’s the script for how it will work:

  1. The rocker switch on the KPOD will select either the L or the C stepper
  2. Turning the rotary encoder will turn the selected component to control
  3. As I am tuning one or the other, I will watch the SWR meter in my Expert 1.3K FA amplifier

This is the exact same way that I would tune an antenna tuner in the shack. But my “Modified Bobtail” with its open feed works very well with this tuner remotely and at the base of the antenna. Because I am transmitting with 1500 watts I am not at all comfortable with trying to use a fully automatic remote tuner – as I have heard too many stories of people blowing up MFJ remote tuners at the base of their verticals. I am sure they were trying to use a shortened vertical on bands that caused excessive voltage at the base of their antenna, and that they never looked into N6BV’s TLW program that comes with the ARRL Antenna Book.

When I was using the Elecraft KPA-500 and KAT-500 in the shack I was basically “lazy” and just let it do its thing. It wasn’t very efficient, but I could be lazy. At 500 watts, you don’t see nearly the issues you do at 1500 watts. This is where QRO teaches lessons that QRP can’t.

I find because of the high voltages that can happen with 1500 watts at the base of a vertical – or vertical array – that I would rather take a few minutes to manually tune and then know there will be no arcing or sparking, and most importantly a nasty amplifier fault.

I have support from Elecraft, and will seek support from Adafruit – run by “Lady Ada” Limor Fried, AC2SN, and will get a proof of concept working and publish this in QST. Then I will open the project as an Open Source project.

If you are interested sooner than when the POC proves success – please let me know – I’d love to have contributors and collaborators!

12 Comments on “Announcing The Elecraft KPOD Open Source Remote Control for Arduino and Raspberry Pi Project!

  1. So your project will just be to retrofit an existing tuner, not a soup-to-nuts fully automatic antenna tuner from scratch? Now that would be interesting, but maybe too big in scope?

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    • I initially thought fully automatic, but then realized that I’m ok with that up to 500 watts, but uncomfortable at 1500 watts.

      When I learned that the KPOD uses the standard HID USB command set and protocol, it hit me like a ton of bricks.

      Use the KPOD to retrofit ANY tuner that has 1-3 components that can be tuned via Steppers.

      It’s not meant to be an end to end product or project, but one that gives you at a minimum what I want, but which could then be taken and extended.

      It’s like building Core that then can be extended.

      Selfishly, it fills 100% of what I need.

      R

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      • Well if you do it properly, it could also be used to make old tube amps remote-controllable. I have an old Ten-Tec Centaur that I thought would be fun to remote-control, but in the end I just bought a KPA-500 instead. But the exact same circuitry could be used to twist just about any knob.

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      • Yes, that’s exactly the value of this. Imagine how cool it would be to front end older technology this way, digitally.

        That old equipment will become so cheap that putting in a basement or out shack and remote controlling it via WiFI with stepper motors creates a whole new interesting market

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      • Finally, I want to build the Core. Then others extend it. There will be Ten Tec extensions, Collins extensions, etc.

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  2. Well in that case, this should be super easy. You can use a Raspberry Pi to host the kpod, since it requires USB and the HID driver. Use ethernet or WiFi to connect to the remote end, have an Arduino there that drives the stepper motors. If you want to do it with style, use PoE and then you just need a single inexpensive line for both control signals and power. The hardest part will be the physical build out. The software you can knock out in a day or two, it should be that easy.

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    • You speak like a pro. I just got the code to do the Raspberry Pi code from the developer at Elecraft. Its best on RasPi. It’s “close” to what I need. The Arduino code at the stepper has been done many times over. Yay!

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      • To be fair, the Raspberry Pi is not even strictly required. There’s no reason you couldn’t host the kpod code on a PC, Mac, or Linux desktop that you probably already have in your shack. At that point, the Arduino bit is purely an IP device with any number of possible control points. Heck, you could even build a little web server in. It’s all a question of style at that point, and how far you want to take it. But the Arduino+stepper motors are the only indispensable part. Everything else is polish.

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      • Agreed. I think I’ve been so “smitten” with the Raspberry Pi that I’ve wanted to use it for the cool factor.

        But my laptop is always on in the shack, so….

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      • If it were me, I’d design it so the Arduino exposes a very simple API over ethernet. Could be as simple as two methods, one to query the rotor position, one to set it. Then you can create any number of clients to suit your fancy. Control it with kpod, control it with a web interface, control it with a “fat client,” whatever you like. The Arduino side can be very thin and stupid.

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