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I'm trying to produce a Yagi antenna for the 2.45 GHz band using a 3D dual extruder printer. The idea is to print the antenna elements using a metal filament and encasing it all in plastic.

The antenna needs to be highly directional, with 8 elements or more. Will it work?

Another option is to print the antenna plastic casing and then insert the metal rods through openings created during the printing process.

Any thoughts? Thanks

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    $\begingroup$ Hello and welcome to ham.stackexchange.com! $\endgroup$ – rclocher3 May 17 at 22:49
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    $\begingroup$ Why do you want to use a 3D printer? Since a Yagi's elements lie on a plane, have you considered a 2D printer, AKA a PCB? $\endgroup$ – Phil Frost - W8II May 19 at 17:19
  • $\begingroup$ Phil, I have done testing with some PCB antennas from multiple suppliers. There is very little information available of specs, including the smith chart. I also want them incorporated into the project enclosure. Philip YV5-KPK $\endgroup$ – PHOLAN May 20 at 20:51
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Not likely. To the best of my knowledge, any "metal filament" that's printable with a home 3D printer is PLA with 10%-50% of metal powder. This is good enough to make prints that look and feel metallic, but it's not enough for good electrical conductivity. Most likely it won't work as an antenna at all; definitely it won't have positive gain in any direction.

The idea with putting rods into a 3D-printed form is more hopeful. The low-dielectric-loss plastics you would really want to use for antennas (PTFE or polystyrene) aren't very practical to print with; PLA and ABS are very printable, but electrically they're much worse. But you might be able to get away with it if you take care to decrease the plastic coverage as much as possible.

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  • $\begingroup$ Found out that virtual foundry has a copper filament that is 90% copper. They also stated that the 10% PLA should dissolve upon melting, leaving only the metal. It's quite expensive. Current cost for 1Kg of filament is about $140. I will try the copper rods with a non conductive boom $\endgroup$ – PHOLAN May 18 at 10:23
  • $\begingroup$ @PHOLAN 90% copper might not translate to 90% of the conductivity of copper. From my past searches for copper alloys, it may be much less. If you can find what the copper is alloyed with, then a Google search might very well tell you the actual conductivity. Also, FWIW I like this answer that suggests only printing the boom with element supports. $\endgroup$ – Mike Waters May 18 at 18:23
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    $\begingroup$ Thanks Mike. That link is productive. $\endgroup$ – PHOLAN May 19 at 12:04
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Some general hints from my experience:

  1. Use wires not printed metal. You could stop the print for a while to drop in the wires, then finish it, or push them in later. For sanity's sake, design your yagi to use identical directors, and make or buy a wire cutting machine to produce lots of wires of the same length.
  1. Plastic will have an effect on tuning - the wires will need to be 10% to 20% shorter than the simulation design, and you will have to experiment to find out how much. Element spacing is not affected much, and what effect there is will be taken up by the length trimming that you do.

  2. Because you need to trim and measure many many times, you will need to print a "tuning model" antenna that can be opened and shut easily. It's nearly impossible to tune an antenna when the parts you need to adjust are sealed inside. Make sure the tuning model is representative of the plastic density of the final model.

  3. Water is a problem on tuned antennas like yagis, droplets on the elements will detune them. But if you have the elements embedded in slightly porous 3D-printed plastic, then the antenna will be completely useless if it gets wet. Printing a thin boom and letting the elements stick out will reduce the effect, but test it if it matters to you!

  4. Feed design - for 2.4 GHz, this would usually a small PCB connected to the coax, possibly with the reflector built in. See this answer for some PCB design ideas for the feed:
    PCB feed
    ( the elements are a bit truncated )

This is an ABS plastic yagi we used to make. Elements were 1.2 mm tinned steel wire. It could be tuned over 1.4 to 2.6 GHz by adjusting the length of the directors. The feed and director were on a credit-card sized PCB at the back. Two identical housing halves were glued together.
YAGI-A0005
Gain was about 12 dBi, I think the plastic cost us 2 or 3 dB in losses, it was quite thick around the elements.

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  • $\begingroup$ This is very informative and helpful. There are many things here I did not even considered. $\endgroup$ – PHOLAN May 19 at 16:58
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It's is my understanding, from my days taking the advanced radio license, is that as RF travels along the surface of the driven elements, and that the reflectors and directors should be the same diameter as the driven elements, coupled with the fact, again to my understanding, that the greater the diameter of the elements increases the bandwidth of the antenna from the cut frequency (length) of the driven element.

Even if one could print, (practically), a good quality (electrically, see previous answer) it would seem impractical. What I would suggest, and would be very useful is the 3D print a good quality sturdy boom, and element supports, (which I have always found the difficult part in antenna builds). The support structure needs to be very sturdy, UV resistant, and provide for easy attachment of the metal elements, (I have always been a fan of aluminum tubing), you could also print thin element covers with covered ends to keep the bugs out.

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    $\begingroup$ Hello and welcome to ham.stackexchange.com! $\endgroup$ – rclocher3 May 18 at 17:57
  • $\begingroup$ Yes, welcome! Upvoted and referred to this answer in a comment above. Although not necessary, you can edit your answer and insert a sketch (or two) of what you have in mind. We look forward to more answers from you on this site. :-) $\endgroup$ – Mike Waters May 18 at 18:31

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