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Airplane1
Senior Member
Username: Airplane1

Post Number: 1427
Registered: 5-2004


Posted on Thursday, May 06, 2010 - 8:58 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I think it would be simple to build a 6 meter 4 element yagi from an old Maco shooting star I got. All the parts are in good condition so I have what I need I think. Any help would be great on how to do it. I found some programs on the net where I just need to put the freq. in and it figures every thing out for me. I have a dumb question though, The yagis I see in the programs from the net show the driven element isilated from the boom and shield going to one side and the center conductor to the other side.

The maco shooting star I am using for this project has a gama match on the driven element and it is not isolated from the boom. I was thinking of using the gama match just like the shooting star has on my 6 meter yagi project.

Ideas? Will it work?

I am planing on stacking with a 10/11 meter 3 element yagi on the bottom, the 6 meter 4 element I build on top of that and then my A99 just above the 6 meter yagi.

Thanks,
AP
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Tech833
Intermediate Member
Username: Tech833

Post Number: 175
Registered: 12-2001
Posted on Thursday, May 06, 2010 - 2:09 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

You can feed a yagi many different ways, including gamma, beta (hairpin), balun, and direct.

By far, the most efficient method I have found to feed a 3 or more element yagi is beta, or hairpin. Next would be balun, followed closely by gamma. The least favorite way is direct (as you described). The reason is that there is no guarantee that the currents will be balanced at the feedpoint, and on a horizontal beam, that can skew the pattern to one side or the other, without and real way of measuring beforehand.

Gamma is the easiest way to feed a yagi for the lowest cost and ease of tuning. Keep in mind, by going to 6m, your existing gamma match will have to be reconfigured since the L and C will vary drastically with the frequency change. You would need closer spacing between the inner and outer rods that form the C, and a shorter gamma to decrease the L.

Regards,
833

Your radio 'Mythbuster' since 1998
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Airplane1
Senior Member
Username: Airplane1

Post Number: 1428
Registered: 5-2004


Posted on Friday, May 07, 2010 - 7:02 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Thanks 833,What is a good starting point for the spacing for inner and outer rods on C and length of gamma to decrease L?

AP
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Tech833
Intermediate Member
Username: Tech833

Post Number: 176
Registered: 12-2001
Posted on Friday, May 07, 2010 - 10:57 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Experimentation!

Best bet- Hairpin feed. No gamma required, and it also increases the power handling capability over a gamma. And, it's dirt cheap- a simple piece of wire bent in half.

Your radio 'Mythbuster' since 1998
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Funtimebob
Intermediate Member
Username: Funtimebob

Post Number: 258
Registered: 5-2002


Posted on Sunday, May 09, 2010 - 2:45 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

If you can find the ARRL antenna book disk it includes a program called yagi for windows
This post was brought to you By Umpire Cologne.
73 KD8DEY
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Tech237
Moderator
Username: Tech237

Post Number: 1336
Registered: 4-2004


Posted on Sunday, May 09, 2010 - 12:10 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I have several 6m yagi plans as PDF files if you need one..
Tech237
N7AUS

God only made some many perfect head, on the rest he put hair.
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Tech833
Intermediate Member
Username: Tech833

Post Number: 177
Registered: 12-2001
Posted on Sunday, May 09, 2010 - 2:16 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

More info on hairpin match- http://www.dxengineering.com/ShowRelatedProd.asp?PartNo=DXE-HMS-1P

Although the match shown here is for HF, you can dowsize for 6m using their info.

Your radio 'Mythbuster' since 1998
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Ferd1605
Junior Member
Username: Ferd1605

Post Number: 40
Registered: 1-2005
Posted on Sunday, June 27, 2010 - 2:10 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

hairpin match with a balun and insulated driven elemnet is how i did mine . now correct me if i am wrong , but if you use a gamma match , the driven elemnent should be shorter to bring it into resonance right ?
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Tech833
Intermediate Member
Username: Tech833

Post Number: 205
Registered: 12-2001
Posted on Monday, June 28, 2010 - 1:50 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Nope. The driven element is the same for either match.

Your radio 'Mythbuster' since 1998

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