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Re: [Antennaware] 160 meter 3/8 wire, steel or copper

To: "OZ1AXG Flam" <>
Subject: Re: [Antennaware] 160 meter 3/8 wire, steel or copper
From: Terry Conboy <>
Date: Wed, 24 Sep 2008 12:11:17 -0700
List-post: <">>
At 11:21 AM 2008-09-24, OZ1AXG Flam wrote:
>A question about wire ...
>I have constructed a 3/8 for 160 meter. I use the tower to support the
>antenna. It runs 22 meter vertically and then (horisontal for 24,5 meters
>(i.e. total 46.5 meter). distance from tower is 1 meter.
>A the base of the antenna it is feed with a serial capacitor of 430 pF (a
>330 in parallel with a 100pF : both door noob).
>Ground is a combination of 4 ground rods and wire (space is limited). Best
>swr @ 1860 Khz is 1:1.4. 1:2 bandwidth is app 80KHz. A noise bridse have
>shown impedans around 70+j1.
>Currently the wire is 1.5mm stainless steel wire.
>How much would the antenna be improved if i substitute the SS wire with with
>1.5mm braided copper wire?
>I guess the seial capacitor would change as well ? any idea how much ?
>Antennewire i use ( steel 40050 and copper: 40051):
>OZ1AXG Flam


I modeled this with EZNEC (without the tower) and assumed the 1.5 mm 
diameter stainless steel wire has a resistivity of 7.2 e-7 ohm-m and 
relative permeability of 1.02.  I estimated about 20 ohms of ground 
loss resistance.  Here's what happens at 1860 kHz:
Cu  G=-0.43 dBi   Z=52.6 -j 46.6   SWRmin=1.13 at 1922 kHz   BW=97 
kHz (50 ohm SWR 2:1)
SS  G=-1.48 dBi   Z=68 -j 36.2   SWRmin=1.44 at 1907 kHz   BW=90 kHz

The adjacent tower will modify these values depending on where it is 
resonant, cross section, etc.

With copper, you should get about 1 dB more signal, a better match to 
50 ohms, and resonance moved up about 15 kHz.  Adding another 27 pF 
in parallel (457 pF total) should restore the resonant point.

73, Terry N6RY

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