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DIY Sat Rig: Amplifier Design & Testing

Apologies for such a long gap between posts. I meant to keep up with the sat rig project more closely but work and travel are doing a good job of getting in the way. Turns out, it’s not as easy as I thought to work on a large personal project while travelling all over the country for work.

In this episode of the DIY Sat Rig saga, we’re playing with real power. Well, 10 watts at least. The boards for the first revision of my amplifier design came in, and I just couldn’t wait to start finding out if my design was going to work (or if I was poised to be letting out a lot of magic smoke.)

All wired up – check out the size of the amplifier chip compared to the SMA connectors. Tiny!
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DIY Full-Duplex? It’s easier than you think!

Well, it’s been a while. Between finishing out my EE degree, moving my life three states away, and setting up at a new job, I’ve barely had time to do anything ham related, let alone some DIY designs. Now that it’s been a few months, I’ve settled in and started busting out the Kicad skills and lab tools to get the wheels turning on a new and exciting long-term project here in the shack.

After weeks of tinkering, tuning, and troubleshooting, I’m proud to reveal the pre-alpha version of what I’ve been toiling away at during my absence from the internet: an open-source, full-duplex 15W FM satellite rig that you can build at home using nothing more than a soldering iron and a multimeter!

This post will be a very high-level overview of my current plan for the rig – how it will all work and what’s going on inside. Later posts will go into way more detail on the various systems and how they all mesh together, but I’m at a point now where I’m confident that this won’t be another one of those projects that never sees the light of day.

I give you – the AXL-2715 (2m 70cm 15-watt transceiver):

Oooh, shiny! Pay no mind to the messy bench – I’m sure yours is no better.

Panatap Update: Living in the Real World

Hi all! Just a quick update in regards to the responses I’ve received for my Panatap board.

First off, thanks to everyone who’s given me positive feedback for my design. I really appreciate everyone who has found my design useful, and I hope that future projects that I’m working on will be just as helpful.

One thing I wanted to address is a question that several people have commented or emailed me about: component values. Specifically the values of the capacitors and inductors used in the low pass filter. The values I specified in the schematic and in the board file are the raw values that came directly from the filter calculator linked in my previous post. Many of you noticed that it is neigh on impossible to get components at these values, and while I knew that as I was designing the board I never really bothered to actually update anything to reflect real-world values that could be used. As of today, I’ve updated the files on the github project to reflect the real component values that I used in the construction of my boards. In addition, I’ve added a new file with Digikey part numbers for all of the parts involved in the construction of the board. Hopefully that gives you guys a running start on constructing your own boards. I also added the LTSpice simulation file that I used for testing the original circuit for you to play around with if you’d like.

That’s all! I’m super happy that people are actually getting use from my design, and I hope that this project inspires you to dive into the world of RF PCB design for yourself.


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The Motorola Railroad Spectra – part two

So here we are again. Same radio, different day. In our last adventure, we discovered that my newly acquired Motorola Spectra Railroad Model was stuck in a boot loop with the FAIL 01/90 error code, the general hardware fault code. Unfortunately, it was not going to be as simple as program and go with this radio.