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CB Radio Forum - Discussions regarding Citizens Band Radio (CB)

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Old 07-07-2018, 6:34 PM
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Default antenna boom question

For my 3 element aluminum CB antenna. - Must the boom be aluminum ? Are at least is it the best ?
Also what is the best wire to connect 1 to 1 balun to the elements ? Thanks to all the help you expert guys, are giving me.
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Old 07-07-2018, 7:47 PM
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Is this for a commercially made antenna or something you are making?


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Originally Posted by arkieguide View Post
For my 3 element aluminum CB antenna. - Must the boom be aluminum ? Are at least is it the best ?
Also what is the best wire to connect 1 to 1 balun to the elements ? Thanks to all the help you expert guys, are giving me.
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Old 07-08-2018, 6:48 AM
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Hello A+9: Aluminum Tubing such as 6061 T6 will work very well for a Boom on a small short antenna as a 3 element Yagi Beam Antenna. I would use 1 1/2 inch to 2 inch diameter with a .058 inch wall thickness or heavier.

https://www.dxengineering.com/

The wiring from the Balun to the elements I would use part number 544 or 545, FLEXWEAVE™ 14 AWG with Black, Army Green, or Clear ultra violet resistant, very flexible PVC jacket. Break strength 143 lbs.

https://thewireman.com/antennap.html

Click the description under "Antenna Materials".

Good Luck.

Jay in the Great Mojave Desert
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Old 07-08-2018, 8:57 AM
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PRC guy - It is an antenna I am building. 3 elements of aluminum, 10' boom, 40' mast of galv. pipe,
JayMojave - thanks
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Old 07-08-2018, 9:33 AM
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Ok, aluminum as mentioned is typical and DX Engineering is one of the better places to get it if you don't have a local supplier. Boom material also depends on how you are making the Yagi and if the elements will be insulated from the boom, grounded to it, etc. For a short boom you can use a length of Unistrut or whatever you want but if the elements ground or pass through a metal boom or are insulated from the boom, the element lengths will be a little different for each type.

10ft is a pretty short boom for a 3 element Yagi at 27MHz. The gain of a Yagi is not how many elements it has but how long the boom is with the right amount and properly spaced elements for that particular boom length. Are you copying another antenna design or using a Yagi calculator program?



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Originally Posted by arkieguide View Post
PRC guy - It is an antenna I am building. 3 elements of aluminum, 10' boom, 40' mast of galv. pipe,
JayMojave - thanks
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Old 07-08-2018, 4:45 PM
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It is a design I found on the web - however it is very close to what the yagi calculator comes up with.
R = 18.333 - DE = 16' - D + 15' and boom = 10'
calculator has R= 18.888 - DE = 17.40 - D= 15.74

Thanks for your help/
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Old 07-08-2018, 5:12 PM
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Is that for all elements attached and grounded to the boom or insulated? How are you going to match the driven element? I find one of the best and easier ways to match the driven element is insulate it into two halves then feed it with a 1:1 choke balun and use a hairpin match across the feedpoint. Its quick easy and will handle almost unlimited power.

Quote:
Originally Posted by arkieguide View Post
It is a design I found on the web - however it is very close to what the yagi calculator comes up with.
R = 18.333 - DE = 16' - D + 15' and boom = 10'
calculator has R= 18.888 - DE = 17.40 - D= 15.74

Thanks for your help/
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Old 07-08-2018, 5:27 PM
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. prcguy
elements attached to the boom - DE split with a 2" space between them using a fiberglass rod - connected to co-ax with a 1-1 balun - bought.on line.
Question ? should the DE both ends be attached to the boom ? are would that do away with the 2 " separation? I had planned to attached the DE by UBOLT at the fiberglass separation. Thanks.
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