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

[K9AY]

Flam,

Based on your description and measurements, I am certain that proximity to 
the tower is affecting the impedance matching. I was able to obtain similar 
results modeling the tower about 30m tall. It will not have much effect on 
radiation, just matching.

With your wire length, the feed impedance would be in the 30-ohm range. 
Ground losses might add several ohms, but would not double the impedance to 
70 ohms -- that is due to the capacitance between the wire and tower.

At the present spacing, you may not be able to get a 1:1 VSWR with a single 
capacitor, because the extra "capacitor" between tower and wire is part of 
your matching system, raising the feedpoint impedance. With more spacing 
between tower and wire (1.5m or 2m), the effects will be smaller -- and the 
VSWR will not move as much in the wind!

1.  Like the other guys, I recommend using copper wire for lower loss.
2.  Add some short radials (as many you can) to reduce ground loss.
3.  If you are able, increase the spacing between antenna and tower.

73, Gary
K9AY



> Hi
>
> 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):
> http://www.wimo.de/cgi-bin/verteiler.pl?url=wireantennas_e.html
>
> --
> OZ1AXG Flam