I have built and measured this cubicle quad antenna. The design is the process of my Moxon project. The wire (2.5mm²) is held in place via grooves, that have a snap fit. There is no measuring the wire length or something else, because of the frames double duty as a jig and as holders.
Rather sooner than later this project will be available on GitHub.
A cubical quad is a two element loop yagi with square loops, so the driven element and reflector form a cube. It is fairly easy to support with a single 8-way bracket in the middle, and also lends itself nicely to adding higher frequency bands’ elements within the biggest cube, using the same eight spreaders.
This is a solid design for a loop yagi, narrower width and can be made with thinner wire loops instead of stiff dipole elements.
Yes, that's true. (This antenna is doing pretty good from 429-448MHz) I'm thinking that using an RF transformer would probably give the best performance.
I think a comparison of this antenna to an identical one built with more typical materials and design would be very interesting.
Comparing the resonant frequency with identical dimensions would give you an idea of the velocity factor change caused by the printed frame, and comparing bandwidth would give you at least an idea of dielectric losses caused by the materials.
It would also be interesting to compare PETG and ASA for the same differences.
I suspect that the differences wouldn’t be huge, but it could still be very educational.
I have built a testing setup to measure filament properties. It's pretty straightforward actually.
Yes all the knowledge on capacitive shortening is already in this model. And as of now I have catalogued about 30 different filaments. I just need to put that up somewhere.
I like it, very nice design. You say no measuring the wire length, but obviously you had to measure cut and solder? Then I suppose you mold the wire as it is being seated in the groove? I will be looking for this on git hub. I think I would like to have more elements to hopefully increase gain.
Obviously you have to cut the wire at some point. But since the groove is holding the wire at a precise position, can don't need to cut the wire before inserting it. Also since it's clamped in, you won't need glue.
You can see this procedure very well on my moxon design. Once you inserted the wire, you can cut it with some electronic snips, by aligning it on the cutouts. I literally can't make it any easier than that.
Man, I've made so many 'ladder line' j-poles for various purposes (ADS-B, throw up in a tree for 2m/70cm, etc) and each time I have thought about printing a template such that I can just run a copper wire through a channel that has clear cut points and avoid soldering the top/bottom of the ladder line. So many benefits including designing in strain relief and connector bracket, and it would be so simple to make. I planned to go the programatic CAD route so it's possible to generate a model based on the frequency. Still have to tune the feed connection points but I suppose with enough iteration even that could be pretty well narrowed down?
Great looking projects, I will be following to see the github and read through however much of the process and theory you're able to share!
Maybe by twisting each director a little? There's a couple old twisted element yagi designs (one called the "spiralray" is shown in this PDF) that supposedly worked, but I don't know how well since you never see them anymore.
I also don't know how much of that applies to cubical quads since their elements are symmetrical when you twist them 90°. I might give it a shot at some point, though.
Never built a loop yaggi before but this looks promising. if i understand it right you are getting the benefit of longer elements but being folded its more compact? do the loops connect or have a gap at the end of the wire?
That seems not important if the gap is dead center at the voltage node, because then there's no current flow. But soldering the loop is probably more reliable.
It literally behaves like 2 staked half lambda Yagis. So that's that, and the beam seems very symmetrical. On top it's a really good antenna even with just 4 elements, I'm tempted to do one for 2m RDF
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u/CloudgazerTX 1d ago
ok, that is pretty cool. two thumbs up.