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Re: [TowerTalk] real world formula for the length of a quarter wave tran

To: towertalk@contesting.com
Subject: Re: [TowerTalk] real world formula for the length of a quarter wave transmission line
From: Jim Lux <jimlux@earthlink.net>
Date: Wed, 13 Feb 2013 21:07:22 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On 2/13/13 11:39 AM, n2mm@comcast.net wrote:


Help,



I lost my antenna handbook. Does anyone know the formula that is
fairly accurate for a 75ohm quarter wave tranformer for my 80m quad.
is it 234xVF     or 246 x VF


3e8 m/sec free space speed of light

300m/microsecond

80m is 3.75 MHz

80meters*VF gives you one wavelength

that's 80*3.28 ft = 262.4 ft

so a 1/4 wavelength is going to be 262.4/4*VF ft or 64.6*VF feet
for 3.5 MHz -> lambda = 300/3.5 = 85.7 meters = 281 ft
for 4.0 MHz -> lambda = 300/4 = 75 meters = 246 ft

So, for a top of 75meters 1/4 wave, it would be 246*VF/4 or 61.5*VF
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