Topband: Wire type in two direction beverage system

[Mike Waters W0BTU]

Hello Toni,

The impedance of the two-wire line should equal the impedance of the two wires to ground. If they do not, then you need to change the ratio of the 1:1 reflection (far end) transformer.

In your case, you are proposing to use 145 ohm line, which at 6 feet above ground has a common mode (both wires to ground) impedance of about 480 ohms. You would need to change the 1:1 transformer to about 3.33 to 1 for optimum performance (F/B ratio) of your Beverage.

I fabricated my own open wire line out of plated steel electric fence wire, which is very strong. Using the known values of (1) the wire diameter and (2) the desired height above ground, I then made some plastic spacers with two holes 1.10" apart. This spacing made the common mode and differential mode (line) impedances nearly equal.

The 580' bi-directional Beverage I made from this line works absolutely fantastic.

73,
Mike Waters
W0BTU


--- On Fri, 9/4/09, Toni Lindén <oh2ua at oh2u.com> wrote:

> From: Toni Lindén <oh2ua at oh2u.com>
> Subject: Topband: Wire type in two direction beverage system
> To: topband at contesting.com
> Date: Friday, September 4, 2009, 4:43 AM
> Hi all!
> 
> 
> I'd like to know what kind of a difference the transmission
> line impedance
> makes in two way beverage system?
> 
> We have DX Engineering (W8JI design)  two way beverage
> system at CU2X. (
> http://www.dxengineering.com/pdf/RBS-1%20Rev2.pdf)
> 
> The system is designed for 450ohm ladder line, but the
> problem is that
> ladder line doesn't last in high winds up in our QTH.
> (I know, there's steel inside but even with poles about
> 15ft from each
> other, the wind load of ladder line is just too much.)
> 
> So my question is, does that two way beverage system work
> with line having
> impedance around 150 oms and if it's not working as well as
> with 450ohm
> line, how big is the difference and in what parameters
> we're loosing
> ground?
> 
> I'm planning to use the old telephone cable instead of
> ladder line.
> Detailed information about the cable can be found here:
> http://www.saunalahti.fi/hohtola/ham/killu/killu.html
> 
> 
> 73 de Toni, OH2UA
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