Dipole Beam Antenna

[riverrat373]

I have thought about building a dipole antenna like the one Riverman71 displayed in the dxGallery. Instead of using a couple short loaded fiberglass mobile antennas like he did, I would use two 102" stainless whips with guys to keep them from sagging. Then I would add a director and reflector, mounting the whole shebang on a 8' piece of .75" conduit. Any thoughts?

 

[KC9Q]

Why not go to DX Engineering and build it from aluminum tubing? No sagging and it will not rust like conduit will in a while, plus it will weight a lot less.

 

[midnight special]

and with tubing it will be better broad banded

 

[riverrat373]

I was thinking of using 102" whips for the driven element because I already have a couple of them. I had planned on using pvc electrical pipe (.75") for the director and reflector with 10 gauge wire (already have) attached to conduit. I guess I could use some aluminum tubing for the mount. I want to try and keep the cost down to a bare minimum otherwise I would just buy a Sirio 3-element beam for $140.

 

[Robb]

There are a few Yagi beam calculators on the web that should guide you to getting the dimensions right. Materials can be costly, as compared to a pre-made commercially built unit. But there is also nothing like the satisfaction of a DIY job. So long that it works.

I personally use the Sirio SY27-4 because it was inexpensive, complete, light, and used good instructions. There are better ones; but not at that price point. It is lightweight and cannot handle heavy snow or ice. The Maco antennas are more costly but use a thicker gauge of materials that would probably stand a better chance against ice. The Sirio did better in high winds than I anticipated; but nothing is going to stand up to hurricane force winds either - of course.

Your call . . .

 

[riverrat373]

Robb, I've built more than a few antennas myself, mostly for shortwave listening so I know what you mean about the satisfaction gained from DIY! I like to experiment with antennas and although sometimes my ideas don't work, it's still great fun.

 

[wavrider]

Build it!!!
I use 1/2 EMT conduit for most of my home brew ground planes AND yagis, bit on the heavy side but they work well and cost pennies on the $$ compared to aluminum tubing.

And I can get the EMT conduit at the local big box stores.

As for those who say it will rust, yes it will but the so 239 and coax may fail long before the galvanized emt conduit does.

Use what you have on hand, so many arm chair perfectionists with keyboards now a days.

Build it have fun and make some contacts.

IF you are going to make a three element you may need a matching device at feed point, either gamma, or t match or hairpin match etc etc, to bring up the impedance to 50 ohms.
Or the spacing of the elements will also change the impedance of the yagi.

 

[BJ radionut]

http://diana.bib.uniurb.it/antweb/arrl/yagi.htm
1 1/2" -2" diameter Boom for 3 or 4 elements...If you use EMT, your dipole lengths will have to slightly less...smallest tubing for std. EMT is 7/8th" diameter.
https://mapleleafcom.com/calculator_3element_yagi.shtml
http://www.gb3pi.org.uk/hf.html

There are a ton of calculators on-line and designs...just use the one that best fits your location, needs and skill
All the Best
Gary
https://www.dxengineering.com/searc...t&SortOrder=Ascending&N=4294953330+4294951539

https://www.dxengineering.com/searc...toview=SKU&sortby=Default&sortorder=Ascending

 

[binrat]

Why not just an inverted V wire yagi?? I recently made a 2 element for portable work.

 

[HomerBB]

There is always the simple Moxon.
I've had good results from them. And aluminum is as simple as a thrift store. Used an old walker for the last two I made.