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2 Element 2m / 3 Element 70cm Yagi

by ZS6TVB, published

2 Element 2m / 3 Element 70cm Yagi by ZS6TVB Apr 17, 2017
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Summary

Printing time for this project is quite extensive but you will not regret either the filament used or the time spent printing for one moment. Parts are easy to print without issues.

The end project is a professional looking antenna that looks and works well. Well worth your time spent.

I have seen many antenna designs here but none met my needs. I required a reasonably strong and light weight. The complete antenna weighs out at around 650 gram (~23 ounce) with good strength. My drawing skills are limited, hence mostly parametric parts readily available on Thingiverse were used.

This is an attempt to create an easily constructable 3D printed version of the excellent 2m/70cm 2+2/3 El antenna design by DK7ZB.
Web Page:
http://www.qsl.net/dk7zb/Duoband/duoband_2-70_2-3.htm

Should you require more bandwidth/better SWR on 70cm, you can build the antenna without the third 70cm element with a bit less gain. I suggest you read Martin, DK7ZBs page on the link above before deciding to build the antenna.

This antenna is seriously easy to build, sturdy and works as expected. It has a single feed point/driven element for both the 2m and 70cm bands. In my opinion it is worth the 3D printing time for an end product that just works and should provide many hours of pleasure afterwards.

Individual parametric parts are here:
http://www.thingiverse.com/thing:2252745
http://www.thingiverse.com/thing:2255051
http://www.thingiverse.com/thing:2252291

Tools Required:
2.5mm Drill (Drill 2 x 2.5mm holes one in each of the two driven elements for the feed point - holes can be drilled 5mm from the edge of the element)
M3 Tap (Tap the 2 x 2.5 drilled holes in the driven elements)
M5 Tap (Tap 5mm holes in the Element Holder)
M5 Die (Clean up thread on printed M5 Bolts)
Metric Allen Keys (Tighten M5 3D printed bolts (not too tight) and Stainless steel Bolts)
Soldering Iron (Solder your coax to eyelid connectors or connect directly to the driven element)

3D Printed Parts required:
1 x Yagi_El_Holder_16-55-WideWindow
4 x Yagi_El_Holder_16-55-NoWindow
10 x M5x10_Hex_Bolt
Optional 3D Pinted:
2 x Yagi end Cap 140-170-8

Other Parts Required:
15.88-16mm (1/4") x 520mm Aluminium tubing for the boom (Add 170 - 200 mm for a handle on the rear)
6mm Solid aluminium Rod (2 x 2.5m lengths were more than enough for me)
10 x M4 x 30mm Button head allen key bolts (To clamp the Boom to element brackets to the boom)
10 x M4 Nuts
2 x M3x6 Button head allen key bolts (Used to connect the coax to the driven element)

Build is quite simple. I followed the instructions as per the DK7ZB page.
The driven element of my antenna was assembled using LMR195 Coax. I drilled a 2.5mm hole 5mm from the edge of each driven element and tapped the holes to 3mm using the M3x5mm button head bolts in the tapped holes.

Should any of the info not be accurate or clear, please do not hesitate to contact me either here or by looking me up on QRZ. I will do my best at keeping this page as complete as possible and add all input received. My intention is to ensure a complete and easy to build antenna with full design instructions supplied. Please help me by contacting me should you feel that there are an additions or changes required in order to further clarify build instructions.

A simple PDF drawing of the complete Yagi has been added in the thing files for clarification purposes. Element lengths and placement positions on the boom are clearly indicated in order to assist with the build of the antenna.

73

Print Settings

Printer:

Velleman Vertex K8400

Rafts:

No

Supports:

No

Resolution:

0.1

Infill:

25% on Brackets. 100% on Bolts

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Comments deleted.

Many questions. I've printed the main parts. Went with t-glase since its relatively long lived in direct sunlight.

  1. In your pdf drawing, what's the spacing from the bottom (0mm) to the first element? (How far up?)
  2. Moderately unfamiliar with yagis, does the coax ground go on the reflectors, director, or is the driven element the only one connected?
  3. Why use 3d printed screws? My printer isn't that accurate. I assume metal screws are ok.
  4. Where did you source the rods/boom from? I'll look at the local hardware store tomorrow but they're very limited in options.
  5. What's the highest wattage you'd recommend using?
  6. Additional photos of the competed antenna, showing the way you connected the wires?
Comments deleted.

Nearly a year since I put up the design and at last someone else is building it!

Thank you!

  1. The spacing from the 0mm mark to the first element (Reflector 2m) in this case is 200mm indicated just to the left of the element (Reflector 2m) on the drawing. The length of the actual element is indicated on the right by "Length="
  2. The coax inner and outer conductors are connected to the left and right portions of the driven element which consist of 2 pieces (therefore the different bracket with a window) The ninth picture, the one just after the drawing indicates it.
  3. I tried the Yagi with real metal screws and it messed up the antenna characteristics completely. You could buy nylon/plastic screws from an electronics supplier but I really had horrible success with my first iteration of the antenna using metal screws which completely desensitised the antenna.
  4. I got the rods from my local hardware supplier in South Africa.
  5. I am not sure what wattage the antenna will be able to handle but I guess any standard mobile or handheld up to 50W should be fine maybe even double that but I can not confirm this for you.
  6. See the ninth photo as mentioned above. The 14th Picture may also help. Connect the outer shield to one side and the inner conductor to the other on the element indicated as "Radiator" on the drawing. This is the Driven Element/Radiator which consists of 2 x pieces of rod with a gap in the middle. The total length from the left to the right of the Driven Element should be 939mm including the gap in the middle as indicated on the drawing. As easy as that.

I hope the above helps you IconicJ

Added end caps for final rounding off of the boom. 2 x of these parts may be optionally printed if required.
See the pictures of the end caps for more details.

I have added a simple drawing of the complete Yagi for clarification purposes with element lengths and placement positions on the boom clearly indicated.
I hope it helps anybody interested in building the antenna!

can't see three of the images ? wrong format maybe ?

Thanks Neon22

I fixed the images and added some more. They were too large. I had to resize them.

looking good :)

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