Cross yagi dimensions

Hello, can you provide dimensions and description how is dipole phased for UHF cross yagi from GITHub ??

Thank you very much.

Regards, Ondra

Hey @ok1cdj !

This was an initial and not-tested design of an UHF cross yagi. Maybe @Acinonyx can chime in with more details on dimensions.

Dear ok1cdj,

The dipole is phased by positioning the two dipoles λ/4 distance apart.

I made one similar to what is used elsewhere but with modified element mounts, and using an LY3H design for measurements here:

Pic of the antenna in testing (perfect RX of SO-50)

I threaded the driven elements and used terminals and nuts to secure the coax and matching section using another modified element holder from the original satnogs design:

I got it all together and realized that I had compensated for the offset of the rods away from the mast on all of the non-driven elements, yet spacing the driven elements out evenly from the center of where they meet in the holder meant that nothing matched up. I didn’t want to re-do the driven elements, so I adjusted the rest of them accordingly and surprisingly got that 1.2 SWR at 435mhz while the cross does not line up to a perfect + (offset is about 12mm X, 12mm Z).

Great, i made some improvement of your element holders and working on some yagis on 25 mm PVC pipe and from 3.2mm welding rods . I’m using mainly DK7ZB designs…
Will post some pictures soon.

73 Ondra OK1CDJ

Hello Everyone,

Where are the files for Imperial dimensions? Also, is there a design for yagi using PVC rather than aluminium tube? I’m ready to start building!

–greg K5GSL

Hey Greg,

I made some imperial sized element and radiator holders at the link below (the files used for the pics above). See the link above for the element spacings and measurements. I used 1/2" PVC and 5/32" aluminum TIG rods. That can be a difficult size to find, call your local welding supply company to see if they have it in stock. Amazon sells them in 10lb boxes which is enough to start mass production of antennas…

** if you read the commits I mention a #10-24 die on the radiating elements, I ended up going with #8-32 instead.

** I had to grind a bit out of the PVC for the nuts to fit inside the radiator holder:

** As mentioned above in this thread, I lined all of the elements up to be centered in the holders themselves - meaning that it is not a perfect cross and has some offset due to the pvc. Still tested out fine so I didn’t bother fixing this (would need a bit of redesign in the radiator holder)

** I used the same radiator holders and PVC to make a 2m yagi (you can see the full setup in the gallery or hamvention threads). In this setup the TIG rods had to be extended just a bit longer than they are made, I used hollow aluminum tube to join tig extensions. This all works and has a decent SWR, but the 1/2" PVC sags a bit with the weight. Works well for the 440 though. I would like re-do the 2m with aluminum square tubing as the mast, leading to my last point,

** the cross yagi with the aluminum mast and larger, hollow elements that the team from Athens has made is epic. After seeing that through hamvention I am sold on replacing my PVC yagi with it. Commercial grade quality! I’ve got a couple of the pieces resized for imperial aluminum but not everything yet. Here’s the issue though - cost increases considerably. By poking around some sites online the aluminum alone would be in the $80 range. (a comparable commercial antenna goes for about $200) So, do make the PVC cross yagi, just realize it is a gateway drug! :smile:

Files are here: GitHub - cshields/3d-misc: Misc 3d stuff

You can see more pics of the pvc and aluminum mast antennas in this thread: SatNOGS at Hamvention 2015 - #8 by cshields

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