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Climber
Posted on Monday, December 29, 2003 - 10:52 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Hello,

Building a home-made GMRS mobile roof antenna. What is that formula to calculate antenna length when you know transmitting freq?


Thanks to them who have not yet forgotten this stuff,unlike me.

Climber
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Ca346
Posted on Tuesday, December 30, 2003 - 12:56 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

If you want the formula for a FULL WAVE length, here you go:

Full Wave Length(Feet)=983.6/Frequency

For example, x=983.6/27.385MHz
X=35.92 Feet

so, 5/8 wave length=.625x35.92 or 22.45 feet
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Ca346
Posted on Tuesday, December 30, 2003 - 12:59 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Sorry, wasn't paying attention to the actual question...

here's a better example: same formula

Full wave (feet)=983.6/146.94MHz
X=6.69 feet
1/2 of X= 3.35 feet
1/4 of X= 1.67 feet
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Barracuda
Posted on Tuesday, December 30, 2003 - 3:27 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

GMRS is in the 462 & 467 Mhz range, isn't it?
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Bruce
Posted on Wednesday, December 31, 2003 - 12:38 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

gmrs


462.550 467.550
462.575 467.575
462.600 467.600
462.625 467.625
462.650 467.650
462.675 467.675
462.700 467.700
462.725 467.725
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Viking
Posted on Friday, January 02, 2004 - 4:56 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

How about using a uhf TV antenna?
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Bruce
Posted on Friday, January 02, 2004 - 11:01 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

they are cut a tad too high but will work my antenna of choice is a gain coliner like this i have one


http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3067629614&category=4672
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Climber
Posted on Saturday, January 03, 2004 - 9:57 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

CA346, Viking, Bruce, and Barracuda,

This is the place for assistance on anything Radio, nice to know some help exists in a "what's in it for me world".

Climber
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Bruce
Posted on Sunday, January 04, 2004 - 2:11 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

thats what im here for to HELP!

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