Topband: Open wire line vs. Paralleled coaxials.

[David J. Sourdis]

Hello,

The Antenna Book says is not as good as ladder line regarding losses. The impression I had when I read it, is that it was better than coax anyway, and not for the doubled power rating. There is even a suggestion of using four coaxials to get a balanced line with the same impedance of one of the single, unbalanced, coaxials.

I have used this type of line several times and  not with unsatisfactory results, feeding 80m delta loops on resonant and higher frequencies, long dipoles, verticals. QRO. Maybe I've been lucky with the lenghts of antennas and these TX lines.

David  
HK1KXA
EC5KXA




> Date: Thu, 5 Nov 2009 19:18:09 -0800
> From: richard at karlquist.com
> To: r_bakalov at yahoo.com
> CC: topband at contesting.com
> Subject: Re: Topband: Open wire line vs. Paralleled coaxials.
> 
> Rudy Bakalov wrote:
> 
> > the impedance of a single cable of the same type. However, the power
> > rating will be about the same as for a single cable, since the current-
> > carrying ability of the center conductors has not changed. However, in
> 
> No.  The power handling capability is doubled.  The insertion loss
> is unchanged.
> 
> > The losses on a coax are because of dielectric losses. But here you are
> 
> Dielectric losses in coax are neglgible on 160 meters.  Nearly all
> loss is conductor loss.
> 
> > not using the shield as RF conductor, so the PE of foam dielectric is
> > working in a different manner.  The return goes on the other center
> > conductor and not the shield. Loss figures are between those of coax and
> > those of "real" open wire lines; they are closer to the open wire and not
> 
> Again, the dB/100 ft loss of two coax lines in a balanced configuration
> is exactly the same as one coax line in an unbalanced configuration,
> assuming the shields are tied together, and assuming a matched load.
> If unmatched, losses in general tend to go up.
> 
> >
> > Rudy N2WQ
> 
> Rick N6RK
> 
> _______________________________________________
> 160 meters is a serious band, it should be treated with respect. - TF4M
 		 	   		  
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