🎓 Dr. Freemo 🇳🇱 @freemo@qoto.org

Now that I finally got my Electrical Engineering workbench in place I had some time to work on coding up a e-ink display. I finally got it successfully displaying images. This display is 7.5 inches and can do red black and white.

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An image showing how the protoboard I designed is laid out as well as a picture of the printed board and my Frequency Counter design soldered to it as an example. I also attached the schematic for reference.

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The first draft of the PCB protoboard I designed arrived. It is more beautiful than I could have imagined.

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The latest version of my frequency counter prototype using a Manhattan style construction.

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There is a sort of beauty in the order and chaos of a prototype design.

Just finished soldering together this frequency counter frontend.

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After several more hours of cleanup the Prototyping SMT board I've been working on is finally done. I attached both sides of the board below.

Here is a link if you want to order a few for yourself. If anyone is really interested I can even send a few out for free to try it out: http://dirtypcbs.com/store/designer/details/freemo/6230/smt-smd-prototyping-board-tssop-20-sop-20-sot-23-6

I havent decided yet if I want to make this open-source. I probably will.

It can act as a simple breakout board for either a single SSOP-20 or x2 SOT-23-6 chips. To use it as a normal breakout just use solder to bridge the 20 connectors on the right and left and sides of the board and it will be a normal breakout (which each pin on the chip going to one of the header pins directly).

Here is the full description.

However there is also a SMT grid on the front and back so you can solder a full circuit onto the chip and arbitrarily have any point in the circuit wired to the various pins. Which makes for very handle little modules you can solder up and reuse.

I also added two power rails for ground and VCC down the middle with vias to both sides of the board. I also added other connectors around the edge that add in vias and wires connections to the opposite side of the board. Should be very useful.

One other little hidden feature is the spacing. Most of the pads are the perfect size to fit most two terminal SMT components (x4 0603 components can solder onto a single pad). But because the pads down the middle are offset it is also very easy to solder on SOT-23 connectors that have 3 terminals. So you really can solder almost any sort of SMT components on here.

Next step will be to build a larger protoboard that can accept modules like this and similar to create more advanced circuits.

Attached are images of the top and back of the design.

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Cleaned up my Directional Coupler project. Labeled the ports and even added the electrical characteristics at different frequencies on the bottom. I then added a coat of lacquer resin to seal in that beautiful copper color (which otherwise would go brown as it oxidized).

The final result has a sort of beauty to it.

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If anyone is curious here are the characteristics of the Directional Coupler I just posted. The top line is the dBm on the forward port and the bottom line is the dBm on the REFL port for a 0dBm input signal. The markers for the common radio bands.

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Woot, just tested the Insertion Loss on the directional Coupler I built. It has an amazing -0.05dB IL on most frequencies except 50MHz where it is still only -0.15dB!

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I finally had the nerve to seal her up. Next I am going to clean up the outside and put a coat of laquer on her before she begins to get a patina.

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Started the final draft of the directional Coupler. Building in extra levels of shielding and a 20:1 winding ratio. I'm stoked to finally have the design locked down

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Over the past few days I built 5 different Directional couplers. Each one uses either a new design even tierly or a new winding ratio. After all the testing I've finally figured out the ideal design for the frequency range I'm targeting. Time to build the final prototype.

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It took me 3 hours but I rolled two perfect 126 turn Toroid inductors. These will be two halves of the two transformers in a Tandem Match Circuit (Directional Coupler). Should have infinitesimal insertion loss

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Decided to build another tandem match circuit based directional Coupler. This time I used a 21:1 winding ratio instead of the last one at 8:1.

It seems to have reduced unwanted coupling at lower frequencies. But more important it decreased insertion loss from about 1.15dB to only 0.03dB at 2 MHz and 0.4dB around 50MHz.

I think I prefer this particular winding ratio for my design.

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So my Directional Coupler performed fairly well. Here is the output from my spectrum analyzer. Basically one trace is for the forward port when the antenna is matched, the other is when the antenna is an open circuit. Then the other two traces are the same condition on the reflected port.

As you can see all the powers show a nice flat -20db coupling. Only exception is the one cyan trace that shows the reflected port when the antenna is matched. Since there are no reflections as expected the response is much less. It is also not linear which is to be expected.

Pretty similar results to my last attempt. Though going with fewer windings this time (8 instead of 12) seems to have results in a slight stronger coupling (-20 dBM rather than the -23 dBM I got before).

All in all I'd say its a success.

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Woot! Just finished my high power directional Coupler. She works perfectly. A day well spent.

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A sneak peek at the Schematic for Version 2.0 of the ROES meter (A SWR meter with VNA capability).

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Was running my new project in demo mode where it just continually increases the phase and magnitude of a load's complex value then plots it on a Smith chart. I was pleasantly surprised when I noticed it produced a Celtic knot pattern.

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A sneak peek at the first draft for the new UI in V2 of my ROES meter, an advanced SWR meter with VNA capabilities.

I still need to cleanup the location of the axis labels, and I want move around a few other elements. But it is coming along very nicely.

I can stare at this smith chart being generated all day long :)

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Beginning work on a version 2 of my SWR+VNA meter (ROES). Using a new much larger full color touch display. I have some debugging to do but it partly works with existing code, so yay.

I will be completely redoing the UI to add colors and various graphical representations such a Smith Chart showing the complex Reflection Coefficient (Complex SWR).

I will also be adding an extremely accurate frequency counter up to 2 GHz to improve the accuracy of the device and include a frequency readout on the display.

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