[SEDXC] Resonant Dipoles - various wavelengths

[David Johnson]

JT,

I'm sure you know that a dipole is 1/4 wave on each side of the center feed 
point and hung horizontal.  If you have the room to make it longer, you 
should make it odd multiples of a 1/4 wave on each side of the center feed 
point.  That is 3/4 or 5/4 etc.  Here's the advantage of doing that.  A flat 
horizontal dipole (as opposed to a inverted V) has a by-directional pattern 
with deep nulls off the ends.  The longer antenna ( called a center fed long 
wire) has a clover leaf pattern.  That is 4 lobes with less null between 
them. The dipole and the center fed long wire are both resonant antennas and 
require no tuner.  The center fed long wire has a slight gain over the 
dipole.  The gain increases as you go from 3/4 on each side to 5/4 etc.  The 
formula for a dipole (234/frequency for a 1/4 wave) will not work for the 
center fed long wire because of the added resistance in the wire.  I don't 
remember the formula for a center fed long wire but a 3/4 wave wire at 
14.175 is 50' 1" long.    You would need 2 of those attached to the 50 ohm 
coax so you will need 100' to put it up.

Good luck and if I can help further just let me know.

Dave - K4SSU


----- Original Message ----- 
From: "JT Croteau" <jt.w6fo at gmail.com>
To: "*SEDXC Group" <sedxc at contesting.com>
Sent: Monday, August 21, 2006 10:38 AM
Subject: [SEDXC] Resonant Dipoles - various wavelengths


> Gentlemen, OM's, OF's, et al -
>
> I don't have an antenna handbook to consult and hoping ya'll might be
> of assistance.  For resonant dipoles, it looks like the majority use
> 1/2-wave lengths.  Hung at the same height, in my case roughly 50' and
> resonance around 14.200 MHz, how much performance difference would I
> notice with either a full wavelength or a 5/8-wave instead of the
> traditional 1/2-wave?
>
> At 20M I have horizontal room for all three wavelength models, should
> I attempt a full wavelength and trim down to a shorter wavelength if
> necessary?
>
> Thanks
>
> --
>  JT Croteau - W6FO - Canton, GA
>  ARS #2,147 | NoGA-QRP | SEDXC | ARRL
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