[TowerTalk] upgrading from a G5RV

[Dennis]

Oh, by the way, the modeling I did was over real earth.


---- Dennis <radioart at charter.net> wrote: 
> Hi Chuck,
> 
> At the minimum you would want to use a high power balun to interface the unballanced coax with the ballanced 450 ohm line.  As to why type or impediance of balun, that would be determined by the impediance of the 450 ohm line at the operating frequency you intend to operate.  I ran some numbers using EZNEC +5.0 for a 135' inverted V dipole 40' high at the center and 10' high at each end.  I modeled the 90' of 450 ohm line you said you could use.  Here is what I got:
> 
> Freq.    R         J
> 3.8      46      -59
> 7.2      31      -71
> 14.2   170     +677
> 21.3    159     -486
> 28.5    130    +254
> 
> AS you can see the R ohms would work for a 1:1 balun on 80m and 40m but a 2 or 3:1 balun would work better on 20m, 15m and 10m.  The J ohms are reactance caused by the length of the antenna not being exact multipuls of the frequencies I used on my calculations.   For this reason, at home, I bring the 450 ohm line in through the window and use a Johnson KW matchbox to provide an EXACT match to the 50 ohm line at any frequency.  You could adjust the antenna length to give a lower J at the operating frequencies if you are not able to use a good ballance antennal tuner.
> 
> I do not know what stress you would place on the balun if you tried to use one size to fit all but ,what the heck, its only a hobby....
> 
> Hope this helps,
> 
> Dennis ,k0eoo
> 
>  
> 
> ---- KI9A at aol.com wrote: 
> > Gang-
> >  
> > After some serious tree trimming, I now have room to fit a full sized wire  
> > antenna where my G5RV is right now. I am thinking about a 135' open wire fed  
> > dipole, as multi bands are needed. 
> >  
> > Question is this- there is now way I can get 450 ohm feedline into the  
> > shack.  The best I can do is about 30' of RG213, then the rest 450 ohm (  maybe 
> > 90').  Is this going to be a waste of my time, or is it worth it? I'd  obviously 
> > use a balun to change over to 50 ohm feedline.
> >  
> > 73- Chuck KI9A
> > 
> > 
> > 
> > **************It's only a deal if it's where you want to go. Find your travel 
> > deal here.      
> > (http://information.travel.aol.com/deals?ncid=aoltrv00050000000047)
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