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Author Topic: Equations for a Yagi  (Read 664 times)
KG4DED
Member

Posts: 17




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« on: December 05, 2000, 06:02:34 PM »

I have been looking for the equations that govern the element spacing and length for a Yagi antenna.  I have seen a bunch of cook book antenna designs that say, “Cut to this length, position element here………”.  I want to run the equations my self.  Can anyone point me at a web site that has this info.

Thanks
Steven
KG4DED@hotmail.com
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KC0IMF
Member

Posts: 10




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« Reply #1 on: December 05, 2000, 08:07:21 PM »

what i learned in the construction of my five element yagi for 2 m the equasion i was givin by a ham friend that biulds them for a living or at least mopre of a living.he told me depending on the amount of elements used you simply divide the number of elements by the wavlenth then divide by the frequencie or is the backwards im not sure but you can play with that and try it to my best recolection that is true. if im wrong im sorry but thats how i did mine and i ended with a 1.5:1 match  
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WB6BYU
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Posts: 13342




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« Reply #2 on: December 07, 2000, 04:32:56 PM »

There is not single set of dimensions for Yagi-Uda antennas.
Your best bet is to get an antenna modeling program to try
out the different designs.  There are lots of possible variations,
many will give low SWR, some will work better than others.

An alternative is to get Dr. Lawson's book on HF Yagi Antenna
Design.  He has pages of tables and graphs for different element
diameters, lengths, spacings, etc.  This is an excellent book, and
I have used it to design several HF and VHF antennas.  (His work
also appeared in a series of articles in the old hamradio magazine
around 1984.)

The book is great.  The software is faster.  Take your pick.

Good luck!     - Dale WB6BYU
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N6QTH
Member

Posts: 42




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« Reply #3 on: December 08, 2000, 12:05:09 AM »

Your question was, simply: "Can anyone point me at a web site that has this info."
You might try:  http://www.cebik.com/taper.html  for starters...
Good luck.  Serious Yagi design is not for the faint of heart (or for the couch potato)
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WT8Y
Member

Posts: 65




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« Reply #4 on: March 12, 2001, 08:12:28 AM »

I have built a number of yagi antenna's and have used the following numbers with good results. I have used .15 wl spacing between elements on all of the antenna's. I use 497/freq for ref, 473/freq for driven/and 457/freq for directors. These numbers have worked very well with a number of great performing 20/15 and 10 meter beams. If you have ever modeled yagi's at VHF and looked at spacing and tuning real time (REAL ANTENNA'S) and not a program you will see and be surprised at how broad a yagi can be tuned and produce good gain and FB. It's not the ROCKET science
we are led to believe.
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