[Antennas] Wire Antenna Questions/Opinions

[Jan Reimers]

George,

	I believe you have described this before on the list.  I have done
this for about ~5 feet to get into the shack, and it works great, thanks.  I
used second hand RG58 which I can get large quantities of. Once I had it
working I asked myself "why not just run the two coax lines all the way up
the mast to the dipole, and forget about ladder line and standoffs etc."
Can we use the coax loss factors in standard tables to argue that ladder is
more efficient (when there is SWR) than paired coax?  Or are those numbers
invalid in this case?

Thanks
Jan (VA7JNR)

> -----Original Message-----
> From: George, W5YR [mailto:w5yr@att.net]
> Sent: Thursday, November 07, 2002 10:55 AM
> To: Dennis L. Wade
> Cc: antennas@mailman.qth.net
> Subject: Re: [Antennas] Wire Antenna Questions/Opinions
> 
> 
> I use a parallel-coax balanced line made of two runs of 
> RG-213. Shields are
> tied together at each end, floated at the ladderline end and 
> connected to
> the tuner chassis at the input end. Zo is 100 ohms so SWR can 
> be higher
> than ladderline SWR, of course. 
> 
> I use 213 to take advantage of its high voltage rating so that voltage
> peaks in the standing wave do not cause internal arcovers. Of 
> course, with
> 95% of my operation at 5 watts, this is not something that I 
> really worry
> over!  <:}
> 
> The only requirement on the coaxes is that they be of the 
> same length. They
> do not have to be spaced or even run together just so the shields are
> handled as described above. The line Zo does not depend upon 
> the physical
> spacing of the two coaxes, but rather is determined by the Zo 
> of each line,
> which is fixed.
> 
> My line is brought into the shack via the attic along with 
> several other
> single coaxes.
> 
> This setup is described in most ARRL Antenna Books and Handbooks.
> 
> 73/72, George    
> Amateur Radio W5YR -  the Yellow Rose of Texas
> In the 57th year and it just keeps getting better!
> Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
> K2 #489      Icom IC-765 #2349     Icom IC-756 PRO  #2121
> 
> 
> "Dennis L. Wade" wrote:
> > 
> >    I agree, that is a good rule of thumb.  However, my concern is
> > keeping the balance of the feedline through its transition into the
> > shack, and therefore keeping alot of RF out of the shack.
> > 
> >         In this case, the balun and tuner would be 
> separated by no more than
> > 20 feet of RG-8 type coax.
> > 
> >         I'd like to bring in the open wire line right to 
> the balun at the
> > tuner, so I'd like to hear suggestions about how to do that.  Note
> > that there will be actually two open wire feeders to bring in.
> >
> - - - 
> 
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