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CRAZY IDEA

AE5RD

AE5RD

Reformed CB'er
May 4, 2005
136
1
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I was looking at my tower when I got a crazy notion. Why couldnt I extend the elements on my Maco 5 element beam and make it into a 20 meter beam? I was thinking if I could add the missing length with a one piece aluminum tube in the middle of each element. Could that be possible. I mean I allready have a 5 element beam. I could just make it bigger. Also I have 30 more ft of boom the same that is on my Maco. Any thoughts? Ideas?
Or maybe i'm way off track here.
 

Just depends I guess. A driven element of around 32-33 feet for 20 meters, unless you load it in some way. And then extending the boom, something like twice it's present length, at least? It's certainly possible, but not sure how practical. Lot of tubing there! Hope your tower/pole will support it, and the rotor turn it. Hmm... wanna re-think that, maybe?
- 'Doc

Wouldn't exactly call it 'crazy... sort of...
 
The boom for a 20m beam should be a lot bigger and stronger than one for an 11m beam. Also the elements should be a lot bigger. The middle section of my beam has heavy walled1 1/8 inch tubing. The smallest tubing at the very end is heavy walled 1/2 inch. getting it up is one thing. Keeping it there is another.
 
You may be about to find that dimensional modeling on paper is often significantly easier than doing it in three dimensions....

The difference between a full-size 3 element yagi for 146 MHz and a full-size 3 element yagi for 14 MHz is boom length, element length and spacing. Period. The difficulty comes along when you take the paper and turn it into aluminum. Or steel.

It might be worth looking at this antenna and getting some of his ideas. This yagi is for 80 meters, so he took your idea a step or two further:

http://www.smeter.net/7j4aal/antennas.php

But still, the only differences between this and a five-element two meter yagi are boom length, element length, and spacing.
 
Beetle said:
You may be about to find that dimensional modeling on paper is often significantly easier than doing it in three dimensions....

The difference between a full-size 3 element yagi for 146 MHz and a full-size 3 element yagi for 14 MHz is boom length, element length and spacing. Period. The difficulty comes along when you take the paper and turn it into aluminum. Or steel.

It might be worth looking at this antenna and getting some of his ideas. This yagi is for 80 meters, so he took your idea a step or two further:

http://www.smeter.net/7j4aal/antennas.php

But still, the only differences between this and a five-element two meter yagi are boom length, element length, and spacing.
Click to expand...

Don't forget diameters and thickness as well.

BTW thanks Pat for the link to 7J4AAL. I was looking for that antenna and forgot who had it. (y)
 
QRN said:
Don't forget diameters and thickness as well.

BTW thanks Pat for the link to 7J4AAL. I was looking for that antenna and forgot who had it. (y)
Click to expand...

The "diameters and thickness" are part of the translation from two dimensions (on paper) to three dimensions (real world). It's up to the translator to make the final product sturdy enough for the application.

And I just googled "80 meter yagi" ;)
 
Beetle said:
The "diameters and thickness" are part of the translation from two dimensions (on paper) to three dimensions (real world). It's up to the translator to make the final product sturdy enough for the application.
Click to expand...

I just wanted to reinforce that fact. You would not believe what I have had some guys ask me if I thought would work. A 20m dipole made out of 1/2 inch copper pipe with no stays was one .Sure it will work but only until it breaks under it's own weight in the first breeze,or the lengthening of elements on an 11m yagi to make a 20m beam using just 3/8 tubing extensions. Some people either forget all about physics or just plain have no clue in the first place about mechanical forces. :confused:
 
I had one guy get all mad at me because I didn't tell him that his very thin-walled copper pipe beam wouldn't work. I had pointed out the salient points about length, wall thickness, moments of leverage and so forth, and gave him some reading material. He said that reading was too much trouble and I was a terrible person for not helping him.

Boo hoo. :bored:

If Marconi had had the Internet, he'd never have invented radio because of guys like me. :glare:
 
Can't win can you Pat? Some people would complain if you built them the best beam they could afford but left it up to them to reach out and operate the rotator to turn it. :D
 
QRN/Beetle...So TRUE

I was able to get a downloaded PDF file of the ARRL antenna book chapter 11 on YAGI design...it contains the info for 20m/2 through 6 element info and construction setup...should help with your project...and help you decide on material/boom length and feedpoint coupling...it is about 4Mb long so I need a AD that will accept this info...let me know...without knowing the material(tubing size)...matching network...etc/ it is not as simple as wanting to build for MAX Gain...but I have used EMT conduit/Alm tubing/wire etc., on my projects and been able to get good results every time...
All the Best
BJ
Click to expand...

I offered this post above on the thread started on the basic same subject...but never hear a reply.
I guess I should have drafted the plans...wrote the construction details and supplied materials and labor...silly me for forgetting to fill in all the blanks and dotting all the I's...my bad!
What's the old saying about leading a horse to water?(y)
All the Best
BJ:D
 
Wow I was gone awhile and imagine my surprise to see the direction this thread has taken. Not only are most of you mistaken but I didn't expect to see the thread turned into one that made it sound like I was a dumbass who couldnt read and was too lazy to learn the physics of antenna building. I bet you guys resent the fact that code is gone.
Shame! Not supposed to be that way. I however have done my research and have my answers. I appreciate everyones help and suggestions. BJ sorry I didn't acknowlege your help. Don't build anything for me. My internet was down for awhile and I couldnt post so I read the ARRL hanbook for antennas. My Bad. Hell I tried to sell a perfectly good pair of bird meters and sections in the swap section and they didn't sell. I didnt get an attitude about it. I mean I didn't let that sarcasm sink in. The sarcasm I saw in some posts. I thought I was at another forum I used to know. A CB forum. I've got a bad taste now. I'll see what happens.
 
Hey 161, I don't think anyone was directing their comments at YOU,at least I wasn't, but rather at how SOME people view things. All info presented was good and factual and was meant to INFORM you so you would not make a greivous error in construction.Beetle and I were simply relating a couple of true experiances WE had with OTHER people,and yes it was a bit off topic, but those comments were not directed at YOU in any way.
 
I,m over it. I don't stay upset too long. I went out in the backyard and built an 80 meter dipole. Nothing like doing what you love. You have to understand. I get fixated on the hobby and I am still relatively a newbie. I have come along way. I just don't like the intellectual smuggness that people sometimes exibit. Especially when I am indirectly concerned. I sometimes play the intellectual games with my co-workers where they don't know that they have been insulted because they just don't operate on the same wavelength. I just feel that this forum is an easy place for that kind of sport. Very hard to prove yet it is done all the time. Certain members have come to the front and have a certain level of knowledge, a certain number of posts, some sort of credibility. They are in fact part of the click of the fiber of this forum. Others must be content to only read
and have to swallow whats handed down. (the dumb CBers) or the guys that are learning as they go. After reading those last posts I felt dumb. My problem is that I am too smart for my own good. In my exuberance I share my ideas in my posts before thinking about them and doing my homework so I must look just like the guys that were referred to in the posts. MY BAD... Bye the way my 80 meter dipole works great.
 

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