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WP4CPR
05-20-2009, 01:19 PM
Hello fellow hamís I want to make my own 6 meter 3 or 4 element beam just to have at least one home brew antenna on my tower. All I really need is a effective way of attaching the elements to the boom:confused:. Any ideas will be appreciated if you have links or picís of your own brews please post. TX and 73ís

K9STH
05-20-2009, 03:32 PM
Those metal clamps that are used to attach conduit to walls work fine. Just go to your local home improvement center and purchase the size that fits your boom. You will have to drill holes in the elements and you have to drill one hole through the clamp into the boom to secure it so that the clamp doesn't rotate (use a sheet metal screw to secure the clamp). You can also use sheet metal screws to secure the clamp to the element or you can drill a hole all the way through and use machine screws and nuts.

I have used this method on a number of VHF antennas (and even on 10 meter and 12 meter yagis) and it works fine.

Glen, K9STH

WB3BEL
05-21-2009, 01:01 PM
This depends to some degree on the antenna design you are planning on building.

The performance of a yagi antenna relies on having the correct element lengths. The RF electrical length of the element is a function of the element to boom connection method.

Some antenna designs were made to use insulated elements some non-insulated. Some use elements through the boom or mounted on top of the boom. You must follow the design details precisely if you expect to get the best antenna performance. This may not be super critical for a short yagi on six meters. But at higher VHF and UHF frequencies this is absolutely essential.

However, if all the options are open to you, I'd recommend using insulated elements mounted on top of the boom. This kind of antenna structure is simpler to analyse using modeling software. (You dont have to include the mounting bracket into the model). For six meters where the elements are relatively short the element mounting brackets are pretty easy to make. I like to use polyethylene kitchen cutting board that you saw into smaller blocks. You can get these for less than $10 at most department stores.

For half inch diameter elements near the boom mounting plate, 4 or 5 inch long by 2.5 to 3 inch wide cutting board blocks will suffice for the parasitic elements. Drill some holes through on either side of the element and use uv stabilized zip ties to hold the element to the mounting block. Drill some holes for u-bolt sized for your boom diameter. You can use one or two per mounting block depending on how severe your weather environment is. For six meters you can get away with one if the antenna is not mounted on a high tower in a windy location.

The mounting bracket for the driven element may depend on the details of the feed structure. If it is a match that allows a continuous driven element (Gamma, Tee etc) then use the same approach as for the parasitic elements.

If the design uses a split driven element (Direct feed, Hairpin match etc) then you may need to use a little stronger mount bracket. This is because each side of the driven element will act as a lever on the mounting bracket. You can double thickness the cutting board, or use some other means to strengthen the driven element mounting bracket. You will need to use beefier method to attach the element halves to the bracket as well. This might just be more zip ties or you can use nuts and bolts.

I like the direct and hairpin feed methods as I find them to be nearly impervious to water damage. It makes the element mounting a little more complicated, but it is really a minor issue for a VHF yagi.

Hopefully this gives you some ideas.

If you don't have access to aluminum tubing and would like to build a 3 element six meter yagi out of wire and fiberglass driveway markers then take a look at this 3 element hexagonal beam on my web page.

http://wb3bel.googlepages.com/

Good luck,
Harry
WB3BEL

WA9SVD
05-21-2009, 09:21 PM
You can also use sheet metal screws to secure the clamp to the element or you can drill a hole all the way through and use machine screws and nuts.

Glen, K9STH

Either way do NOT forget the LOCKWASHERS!

In days of yore, Heath, etc. often used split ring lockwashers on the screw head, and star lockwashers under the nut. Just to be sure.

VK6MB
05-22-2009, 12:47 PM
Here is one way and some antenna designs -
http://www.g0ksc.co.uk/yagiinsulator.html

73 Mike

WP4CPR
05-22-2009, 07:17 PM
TX to all that have helped in one form or another, this is what I have up until now. I included a image of the original design and some picís of what I have done. But I still have some questions; can I leave the screws that long at the driven element so I can attach the coax wires or should I trim them down a bit? Should I attach a balun Wright at the antenna and if so should I buy one or can I make one out of Coax? The original design says to go straight to the coax. Another ting can I use Ĺ lexxon for the plate that attaches the boom to the mast? I ask this because if I do this the antenna will not be grounded by the mast. Just in case youíre wondering the screws of the driven element are not touching the boom and I have a antenna tuner and my FT-920 tunes as well. TX 73ís

W9WD
05-30-2009, 01:16 PM
I have a 4 element Yagi under construction. I chose this method

27237

That's a 2.5" square aluminum tube.
3/4" slit sleeves that will hold the 5/8" dia elements
Two Stainless clinch (pem) nuts holding the 1.5" stainless (1/4-20) set screws with stainless jam nuts.

KC8VWM
05-30-2009, 07:20 PM
Some photo's I have taken showing some contruction techniques:

http://users.belgacom.net/hamradio/schemas/69Element%20Mounting%20Method.JPG

Also, this shows how I do gamma matches:


http://users.belgacom.net/hamradio/schemas/69Gamma%20Closeup.JPG

SO-239 or N connector mounting method:

http://users.belgacom.net/hamradio/schemas/69SO%20239%20Mounting.JPG

Hope that helps.

You can build this antenna here:

http://users.belgacom.net/hamradio/schemas/yagi_vhf_antenna.htm

W4RDM
05-31-2009, 06:06 AM
A Moxon wire beam antenna is very easy to build

http://www.moxonantennaproject.com/

73,
Ron W4RDM
www.hexkit.com

W9WD
05-31-2009, 03:19 PM
A Moxon wire beam antenna is very easy to build

http://www.moxonantennaproject.com/

73,
Ron W4RDM
www.hexkit.com (http://www.hexkit.com)


Sounds like a fun project.
I like the multiband one (G0WSP)

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