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Various ramblings – Electronics, radio, old computers, cars & other junk…

Category Archives: Radio

PIC Development & Sublime Text 2

While working on a small PIC project as an addition to a larger project (a JUMA RX1 DDS LSB/CW receiver) I had the displeasure of using Microchip’s IDE MPLAB. MPLAB looks like it was designed in the mid-90’s, and while it does let you piece together code and compile it into PIC compatible hex, it’s not the most user friendly program.

While I was battling with MPLAB a friend re-tweeted a link about a new theme for Sublime Text 2, I had a look at the link and the editor looked pretty good! After doing a bit of reading I found out that Sublime Text has the handy ability to call user defined build systems with a hotkey, and as I read on I thought I’d have a crack at getting it working with the XC8 compiler in an attempt to ditch MPLAB.

Linked below is a small project I put together, based very heavily on a set of guides located at Gooligum Electronics. The main requirements to use Sublime to replace MPLAB are a Build System script, and a project specific build file that is launched by the Sublime build system script. This build file specifies various settings (chip type, project name, build options etc…), and is used by the XC8 compiler.

toggle-switch-led-1.0.zip – The most basic of programs, one step above a “Hello World” example. A momentary push-button is used to toggle 2 indicator LED’s along with another output pin that will be connected to the PIC chip in a JUMA RX1 radio (to switch between and display which of the two VFO’s is in use). Alongside the source files are the Sublime project files, one for Mac and one for Windows.

XC8.sublime-build – This is a multi platform version of the XC8 build-system file I am using with Sublime Text. This file will need to be loaded into the correct folder depending on your platform…
Mac: /Library/Application Support/Sublime Text 2/Packages/User/
Windows: C:\Users\<username here>\AppData\Roaming\Sublime Text 2\Packages\User\

Notes:

– The build-system above will need to be tweaked to point at your XC8 install, the project file will need to be pointed at the location of the project. Watch out for back-slashes on Windows, they need to be doubled up (escaped) to be treated as literal in the path.

– You can download the XC8 installer for various platforms here.

– This method can be used to run pretty much anything, you could substitute any build programs/scripts or even flash a microcontroller with this.

Small Wonder Labs SW-40 Kit (Part 3)

With the case finished, there was only one thing left to do… Jam the radio in the case and make it work!

The digital dial kit and main board are secured to the case using brass stand offs (used for securing motherboards in PC cases), once cleaned up they solder rather nicely to the PCB cladding. The lid is secured in the same way. The rest of the boards in the case are secured using double sided tape, they seem fairly well supported and weigh so little that they shouldn’t come free any time soon.

In the photos you can see the main board, the digital dial and a few other additions I made to the radio:

– The most visible is a small LM317 circuit used to step down the 16.5v laptop switchmode PSU. 16.5v is a little high for most of the devices in the case, 14v is just within the maximum spec (and just inside the cut-off volatge for the LM317).

– Located just below the regulator is the RIT tuning module. This is built dead-bug style, with the CMOS logic mounted in a socket which is soldered on to some veroboard up-side-down.

– The final addon board in the pictures is a failed iambic keyer I built, it’s sitting in front of the RIT board. I had a go at troubleshooting it but caved and ordered a picokeyer chip that I plan to build in shortly.

With all that done, the radio just needed a few little finishing touches and it was up and running. I am very happy with the way that it turned out, it performs well and looks great!

The SW-40 kit can be purchased from the Small Wonder Labs.

The digital dial kit can be purchased from Hendricks QRP Kits.

Small Wonder Labs SW-40 Kit (Part 2)

Being my first transceiver, I really wanted to make it my own (well, as much as I could with a kit…). I had seen many radios built into cases made from FR4 fibreglass PCB material, and thought I might have a go at doing my own.

Quite a simple process but it would have been much easier if I had access to a treadle shear. I cut the basic shapes on my table saw, allowing for a few millimeters to get the sizes accurate and remove any rough edges left by the saw. I then used wet/dry sandpaper to square up the edges and get all the sizes correct so the box fit together with no gaps.

The next step is to solder the case together. I made a jig with 3 90 degree angles in a corner shape, this helped me keep the box square as I soldered it.

Once that was done, I marked out where the holes for the screen and controls would go and I drilled/filed to shape. The final step was to clean the copper again and paint it with clear to prevent the copper from oxidising. Very happy with the results!

“100 Watt” Dummy Load

To align my SW-40 transceiver I needed to use a dummy load, something I didn’t yet have. The dummy load I bodged together in a hurry was 2 x 0.5 watt 100 ohm resistors in parallel on a BNC chasis connector. It worked, but got warm enough to discolour the resistors enough to make reading the values tricky.

I had used thick film power resistors in a previous project and thought maybe I could find something suitable for a dummy load. A quick look on RS components and I found a 100 watt 50 ohm resistor going for $20. Being thick film construction, I figured it would make a fairly good dummy load with no inductance and as a bonus it would be very easy to strap to a heatsink. A quick google confirmed this, it seems that this is a fairly popular way to build dummy loads.

Below are a few pictures of the dummy load I built. Very quick project, only took me around an hour to build. The case is recycled, in its previous life it was a VGA splitter/amplifier. I simply cut out some new end plates and bolted the heatsink on covering the holes left by the VGA connectors. The heatsink is also recycled, nabbed from an older server junked at work.

The resistor may have a high power rating, but to reach that you would need an almighty heatsink and forced cooling. The piddly heatsink I’m using might manage 20-30 watts for a fair while, more than enough for me though.

Small Wonder Labs SW-40 Kit (Part 1)

My first transceiver kit, a nice little radio with great instructions and is easy to build. I built this board over 2 nights, about 4-5 hours in total. While researching and ordering this kit I was still in the process of getting my foundation license, and not long after getting the kit in the mail I stumbled onto a small problem…

Foundation license holders are not allowed to operate homebrew transmitters…

I went ahead with the build, but until I got my standard license I was stuck using it as a receiver. All the more reason to upgrade!!