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Message |
    
Airplane1
Senior Member
Username: Airplane1
Post Number: 1427
Registered: 5-2004
| | Posted on Thursday, May 06, 2010 - 8:58 am: | 
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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 |
Tech833
Intermediate Member
Username: Tech833
Post Number: 175
Registered: 12-2001
| | Posted on Thursday, May 06, 2010 - 2:09 pm: |
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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: |
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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 |
Tech833
Intermediate Member
Username: Tech833
Post Number: 176
Registered: 12-2001
| | Posted on Friday, May 07, 2010 - 10:57 am: |
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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: |
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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: |
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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: |
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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: |
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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 ? |
Tech833
Intermediate Member
Username: Tech833
Post Number: 205
Registered: 12-2001
| | Posted on Monday, June 28, 2010 - 1:50 am: |
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Nope. The driven element is the same for either match.
Your radio 'Mythbuster' since 1998
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