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Author Topic: Build your own multi band HF yagi?  (Read 6580 times)
N3IZN
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Posts: 39




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« on: July 13, 2009, 09:33:17 AM »

Hello all, I’ve built several single band yagi with great success. Now I’m ready to take on HF. I have yagis for 50 mhz up to 1296 and I have an inverted Vee for 30, 40 and 80. Now I’m ready to take on 10 ~ 20. There are a few commercial yagis covering 10, 12, 15, 17 & 20 but they come with a price tag.
I inherited a small triband yagi,  12’ boom 3 elements. 10/15/20. Not sure of the manufacture but it appears to work OK at 15’ on temp pole.
Looking for a site or info that covers building your own. Want to keep the boom down to 25’ or so.
Thanks
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N5LRZ
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« Reply #1 on: July 13, 2009, 09:38:57 AM »

Can one be made from scratch?

Yes it is.

Is it much easier to just fork out the $$$$ and get one already designed and ready to assemble from the manufacturer?

Absolutely MUCH Better and easier.
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WA3SKN
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« Reply #2 on: July 13, 2009, 10:00:25 AM »

Before building...
Now is the time for you to invest in the ARRL Antenna Handbook, or at least the ARRL Handbook.  There is a lot of good reading there.
Size, wind loading, inter-reactions and matching are all covered there.  A good investment.
73s.

-Mike.
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N3OX
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« Reply #3 on: July 13, 2009, 02:06:14 PM »

"Looking for a site or info that covers building your own. Want to keep the boom down to 25’ or so. "

This is a pretty advanced technical project that I think few people have tackled.

There's the hexbeam of course:

http://www.karinya.net/g3txq/hexbeam/broadband/

But that's not really up the alley of converting a tribander.

I don't want to discourage you, but you might try designing and building a dual band 12m/17m to go above your tribander.

Or possibly you could use "open sleeve" elements in conjunction with the existing elements on the current antenna.

Either way, being able to use modeling software and getting a good model of your existing beam in there might be the first step.  I don't recall ever coming across a five band homebrew yagi before.



73
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
G3TXQ
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Posts: 1530




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« Reply #4 on: July 13, 2009, 02:25:01 PM »

If you liked the look of the Hexbeam option, check out K4KIO's web site. He now supplies a complete kit of parts to make my 5-band broadband version. That's a way of achieving the satisfaction of "build your own" without any of the problems of sourcing parts; you can also be guaranteed it will work Smiley

http://k4kio.com/kit.html

Steve G3TXQ
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WB5JEO
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« Reply #5 on: July 13, 2009, 03:22:13 PM »

I think anyone contemplating a multiband Yagi would do well to print out the manuals for all the commercial versions. Different makers have gone different routes over the years with such decisions as trapping reflectors and directors or using separates and improving the spacings. But the project has a lot to offer, considering the costs of new. It's certainly doable, and when you set out to do it, the doing has to be a big part of the attraction. A great deal can be done with a boom that long. I suspect a good many of your decisions will be made more on the issue of weight. I'd sure try to work up a test bed arrangement, so I could begin with one band and add bands, seeing the effects of each being added. Maybe a temporary hinged base mount for the back end of the boom, so it could be lowered and raised to add and adjust. Keep good notes, beginning with your research and impressions and continuing with development and construction. Photos, too. It's one of those great experiences that would make a good article for others thinking about such a thing.
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N3OX
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« Reply #6 on: July 13, 2009, 03:33:35 PM »

"But the project has a lot to offer, considering the costs of new. It's certainly doable, and when you set out to do it, the doing has to be a big part of the attraction."

I think the doing needs to be more of an attraction than the cost.  You can end up spending a surprising amount of money on the "minor" antenna supplies you need.

If you can do it *all* out of "junk" as your raw materials you might be able to get out the other end spending significantly less cash.  If you could buy another couple sets of traps for the same tribander on the real cheap (because the owners' tribanders have broken elements, for example), you could re-wind them to work in your new design.  

But if you start heading to DX Engineering for all those nice antenna doodads a little at a time to add elements, and you total up the bill in the end, you might wonder how you spend the cost of a 5 bander on your homebrew 5 bander :-)

That said, I'd probably rather spend X dollars and Y hours  of my time on something I built myself rather than spending X dollars and 0 hours on the commercial equivalent.

I just like building antennas, and I like using antennas I've built.

73
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
W7ETA
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Posts: 2527




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« Reply #7 on: July 13, 2009, 05:15:55 PM »

Antennas have wind load; the more wind load, and the longer the boom, the "bigger" the rotator you need.

Also, the more the wind load, the bigger the tower you need to support it.

Needing bigger means spending "BIGGER!" money.

Consider spending additional funds on getting your HF antenna higher.  Many hams cannot afford to go past 55 feet.

To get an idea of what you are in for is you want to build a 10, 12, 15, 17, and 20 meter beam, look at what people go thru building just a single quad element for for all of those bands.  then, adding just a second element will probably involve tuning each wire in the second quad, and then going back and tuning each wire in the driven element again.

Another option is to consider just building a trapped dipole for 12 and 17 meters and mounting that above your tribander.

73
Bob
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KC2VKD
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Posts: 10




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« Reply #8 on: July 14, 2009, 08:58:37 PM »

"Is it much easier to just fork out the $$$$ and get one already designed and ready to assemble from the manufacturer? "

But whats the fun in that. i like to build 'stuff'

i also like to take apart 'stuff' (my mother did not like it when i was a teenager and took apart the vacuum to prove how it works to her)

right now i am building some HF dipoles/ inverted-vee's and i will try to modify them.

i am also working on building a cross polarized dual-band (2m/70cm) yagi to try to work some satellites (if only home depot had the parts i needed) i have the rough draft on paper (and in my head)
now i just need to see if i can find a cheap antenna analyzer

Michael
KC2VKD
grid(fn30)
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K8POS
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« Reply #9 on: July 21, 2009, 02:53:50 PM »

Michael,
Never give up, never stop trying.
I have built all of my own VHF antennas.  Yes they are easier than HF due to size.  My 9 element yagi for 2 meter only cost me $6.00 for some hardware.  I built it all from old TV antennas.  I do not have the tower to put up a HF tri-bander.  I am sure if you hit some of the local (if you have them) metal salvage yards you could find much of the material you need.  I built my own cross beam for the satellites on 1/2" PVC. I built them as separate antennas then glued the two booms together. Works pretty good.
Keep in mind everyone here is trying to help you get the best bang for your buck.  However, you would be surprised what you can do with some left over household wire and duct tape.

Bob
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KC8VWM
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Posts: 3121




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« Reply #10 on: July 21, 2009, 09:34:40 PM »

I have found when homebrewing HF antennas you are far better off and less cost is typically invloved with constructing antenna's like wire quads, hexbeam (G3TXQ hexbeam design),bruce arrays, lazy H's, rhombics etc. instead of traditional yagi designs.

They all have considerable gain over a dipole and many of these design exhibit similar characterists to Yagi's.

As Bob pointed out earlier, more alumimum in the air means extra weight, bigger rotors, bigger towers, bigger bank accounts etc.

I can already hear the cash register chinging away.

New $600 antenna rotor - ca ching!

Tower capable of adequately supporting the heavy yagi antenna. - ca ching!

Pouring concrete to hold the new tower up in the air - ca ching!

Renting crane to install new heavy duty tower - ca ching!

Replacing the twisted, broken and bent aluminum Yagi elements after the antenna comes crashing down on the ground during the ice storm. -ca ching!

Yeah...

I'll just stick with the lighter wire antenna designs for those reasons.

My Best,

Charles - KC8VWM
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N3IZN
Member

Posts: 39




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« Reply #11 on: July 22, 2009, 11:11:26 AM »

Thanks for all the replies. I think just about every angle was covered.
I just want to stress the point to any casual reader about building your own yagis. It’s not hard, plenty of sites to get ideas and go from there. In my case the gamma match was the thing scarring me away. Once I figured that out it was easy. I also have a local metal salvage yard that has aluminum tubing available and bought by the pound. The biggest expense on my yagis was the stainless steel hardware. But that is for single band yagis.
I have 20’ booms on 50, 144 and 220. Proportionately smaller on 432 and 1296. I have to admit the 1296 was Mastercarded.  With over 120 elements in the air and Andrews hardline feeding it all I have an above average VHF/UHF station. Performance is comparable to other stations in the area with their name brand yagis. I’m betting my feedline loss is helping me, with the exception of 1296, I have less than 1.5 db of feedline loss on all bands. While other are using some variation of RG8. I’m lucky to be in the telecom industry and have access to hardline.
The original intent of the request was to find info on building a multiband yagi for HF. I can’t use a quad because of space. A yagi is probably too close to the other yagis as is, but I see lots of people doing it and it seems to work. I don’t have time or patience to learn a software program and design one and couldn’t find any article on building one. I don’t think it is hard, and if had the time could reverse engineer a trap design and build one. I enjoyed the building and tuning of my VHF/UHF stuff, but I enjoy operating more. So I think I’m going to spend the $$$ and buy one.
So my plan for now is to put up the tri-bander I have, with its measly 12’ boom and starting working some HF. I see 5 and 7 band yagis go up for sale occasionally; I’ll keep my eye out for one of those. I have a manufacture in mind but the cost of new is sobering. If I can find a 10 ~ 20 yagi maybe a 30/40 hexa beam drooping down underneath it?
Thanks for all the replies and ideas.
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N3OX
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« Reply #12 on: July 22, 2009, 04:24:39 PM »

"don’t have time or patience to learn a software program and design one and couldn’t find any article on building one. I don’t think it is hard, and if had the time could reverse engineer a trap design and build one"

I think that people who spend a lot of time designing antennas for the homebrewer tend to lean toward wire antennas, and it seems that they do it with interlaced elements.

I think a trap antenna of aluminum might be an easier construction project overall and not necessarily *harder* to design than an interlaced wire type antenna, though just as hard.

"maybe a 30/40 hexa beam drooping down underneath it? "

Something that works well on "paper" is a 40m Moxon  with an L network and reflector capacitor switched in on 30m as the 40/30 version of this antenna:

http://www.n3ox.net/projects/2017moxon

Here's an old post about it:

http://lists.contesting.com/archives//html/Towertalk/2008-03/msg00202.html

Of course, I haven't tried it because I've got nowhere to put a 40m Moxon in the first place ;-)

73
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
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