Topband: Open wire feeder

[Donald Chester]

>I have 850 feet of open wire line to my 160 vertical.  There
>are numerous photos of it on my web site at
>http://www.n6rk.com/openwire.html.
>It is 4 AWG stranded aluminum XHHW wire, spaced 5 inches.  At
>both ends there are baluns to convert from unbalanced 50 ohms
>to balanced 50 ohms, and transformers to convert from balanced
>50 ohms to balanced 450 ohms.  The loss including the transformers
>is measured in tenths of a dB.

Another approach is to use a multi-wire open wire line, using 4 or more 
conductors.  I have heard of ones using as many as 16 wires configured in a 
matrix with a variety of patterns in which sets of wires are parallelled 
together at both ends.  Such a  configuration can drastically reduce the 
surge impedance of the line, and slightly lower the loss at a given SWR.  A 
common arrangement in older broadcast installations was to use 5 wires to 
form open wire "coax".  The pattern is a square with a wire at each corner 
and a 5th wire in the middle of the square.  The wire acts as the centre 
conductor, while the 4 outer wires forming the square are shorted together 
at each end, to act as the "shield" of the  coax.

Don k4KYV

_________________________________________________________________
The new MSN 8: smart spam protection and 2 months FREE*  
http://join.msn.com/?page=features/junkmail