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Who wants to build a yagi beam?

M

Master Chief

Guest
Apr 5, 2005
1,312
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Hola, Patrons of WWRF!

We have talked about all kinds of antennas out here and other than Robalo, I don't know of many who are actually building and playing with them.

So I thought, why not have a little antenna building party right here on the WWRF during these next few winter months. Not only will you learn how to build your own beam, you'll learn the WHY behind the designs and WHY the elements are so long and WHY we use "x" amount of overlap, etc! I'm NOT going to spell out every little detail however; you will be required to THINK!

You can build a 3, 4 or 5 element yagi beam; I'll leave that up to you and include plans to build all three. If we do this right (and I usually do), you can start with a 3 element design (if that's all the money you have available for this project) and add directors later if you choose!

The plan will be to build this antenna with readily available parts and materials. Your antenna will NOT be some piece of crap and will most likely outperform your standard Maco. Chances are that you will have to spend a few dollars to do it right, too!

We will use the following materials and the quantity of tubes will be determined by the needs of your project.

(Boom = 6061-T6)
2" x .125"

(Elements = 6063-T832)
7/8" x .058" (for HD version)
3/4" x .058"
5/8" x .058"
1/2" x .058"

You can check with your local aluminum supplier for availability. This material is also available from Texas Towers and shipped via UPS (up to 6' lengths): http://www.texastowers.com/aluminum.htm

All aluminum will be 6' long and cut as needed. Local aluminum houses sell raw material in 12' lengths. You need to do the math if you buy lengths other than described.

We will also be buying hardware from DX Engineering and McMaster CARR. Again, if you have a local supplier, you are free to use them!

This antenna will handle an easy 5KW. Some will argue that you can buy a Maco for cheaper. They are probably right. However, you will not buy a BETTER antenna from Maco!

We'll get started shortly so start to think how many elements you want!
 
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A friends aluminum 5/8 blew down, so I recycled the aluminum ground plane into a 4-element beam for the 2-meter band. Works awesone. I used some 1.5 inch or so PVC for the boom and direct connect the dipole style driven element. I think I just need to add a 1:1 balun and it will be ToR...
 
I bought a friends Wilson Shooting Star for $35. I turned it into a 6 element beam for 6m. Fed it through a 4:1 coaxial balun with a hairpin match and it is a GREAT performer. Strong as hell too. Mother Nature won't be taking this one out. LOL
 
MC-

Good idea. Timing couldn't be better either, I'm getting ready to build a 4 element flatside to put up on my 2nd tower. Interested in seeing your construction techniques. Particularly how you're feeding it. As I recall, you're not a fan of gammas. ;)
 
what boom length will you use?
i have a cushcraft 10-d4 that has 7/8 3/4 5/8 element taper,
the boom is cut down to about 14ft i think,
i will wait to see what boom and taper schedule your gonna use then decide if im cutting up the cushcraft ;)
 
MC will you be using some software as the bases for design? If so, have you tested such a design out in the real world?

I have tried such discussions using the Internet before, just one on one and trying to stay with only one issue or design at a time. I found such discussions were not as easy to communicate as it might appear without being able to see the demeanor and/or being able to respond interactively and without time delays.

The process has to be very well thought out and some form of discipline, control, and the ability to have consensus needs to be considered, or I see a bunch of individual ideas being presented and argued all at once and confusion following. Just something to consider in planning for such an effort! I don't mean to curtail the thinking process by individuals, but in a classroom setting the instructor can at least keep the current focus on one topic or change directions with everyone present at one point in time and maintain a little continuity of effort.

I don't mean to be rushing you or make light of the idea, but have you really considered the flow of communications in this process?

How will you start off this process?
 
I just got another Cushcraft antenna today. I also have a number of Mosley beams.

My plan is to build a OWA antenna (no matching device required......50 ohm DIRECT FEED......5KW plus easy!)

The boom will be 2", length dependent on number of elements.

Boom to element clamps will be DX Engineering BEB-2:
http://www.dxengineering.com/Products.asp?ID=129&SecID=61&DeptID=33
The BEB-2 accepts 7/8" elements Bob!

This antenna will be modeled by me and people smarter than me, and tested by everyone who makes one. This is a building project and not an open debate. People will get their shopping lists and free instruction how to build their own antenna. Then it will be up to them construct and experiment as they choose. The process will be simple and people will learn a LOT!

Sorry for the delay in answering and thanks for the comments Marconi!
 
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I've purchased a Maco M103 which makes a perfect test bed for this project since most people will already have or have access to these parts. A friend has a M106 I'm trying to pick up in order to build the 4 and 5 element version.

The second option is using a random 2" boom I have here and buying the BEB-2 brackets I listed above. The Maco elements, except for the driven element, will be shorted to the boom. Using the BEB-2 brackets will insulate all the elements from the boom.

I also picked up a M2 11M5DX and will be building this up also. This is an antenna to test against and also readily available for those who want an excellent commercial built antenna. It is a bit pricey though!

I've also picked up another old Cushcraft tri-band beam for parts. I'm a little busy this month but expect to be fully involved with this project in the beginning of October. This is a winter project!

I'll use old Mosley and KLM parts for the HD version.
 
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Using the BEB-2 brackets will insulate all the elements from the boom


isn't a yagis driven elements only insulated?
why would you want to feed the others?
and if you did you know you would need such amount of spacing
between them...

The outer elements are generically called parasitic elements. One is called the Reflector and the other one is called the director element

remember just asking a question. I been keeping up with this
testing it on my spitfire 427 3 element beam. so far I don't like the whole beam grounded and using a maco 5000 watt gamma match. the antenna was designed to keep the driven elements insulated from the ground. now just trying a direct feed with 9' 4" each driven element...any help will help me :)
 
lords said:
isn't a yagis driven elements only insulated? why would you want to feed the others? and if you did you know you would need such amount of spacing between them...
Click to expand...
No, you can have them all shorted to the boom, all insulated from the boom, or a combination of both. It depends on the design of the antenna. You only feed the driven element(s).

If you short the elements to the boom, you need to make the element physically LONGER to compensate for the boom effect. Once lengthened, it will be the correct electrical length.

lords said:
The outer elements are generically called parasitic elements. One is called the Reflector and the other one is called the director element

remember just asking a question. I've been keeping up with this
testing it on my spitfire 427 3 element beam. so far I don't like the whole beam grounded and using a maco 5000 watt gamma match. the antenna was designed to keep the driven elements insulated from the ground. now just trying a direct feed with 9' 4" each driven element...any help will help me :)
Click to expand...

My new 11M5DX is DC grounded. There is nothing wrong with shorting to the boom, but you have to compensate for it. A DC grounded antenna will help dissipate any electrical build up on the elements and make the received signal quieter.

A direct feed, by my definition, means you don't need any sort of additional matching network. If you use a gamma, its NOT direct fed.
 
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