[Antennas] Why not twin lead?

Mon, 22 Apr 2002 16:32:43 -0400

But why not bring the twin lead down the mast, to the shack and convert to
50 Ohms at the transmitter since twin lead is lower loss?

> I once had a 10-el yagi on 2 meters with 200-300 (?) ohm impedance, fed
> with RG-58, using a 4/1 balun also made from RG-58.  See the ARRL Antenna
> Handbook for details.
> Dave          W9LYA
> What wrought doG hath?
> 
> On Mon, 22 Apr 2002 07:12:37 -0700 (PDT) Pat W <[email protected]> writes:
> >  It would be nice to be able to use twinlead, or
> > ladderline for Vhf.  THe problem is that when the Z0 of
> > the feedline does not match the Zin at the transceiver,
> > the Zload at the antenna gets transformed to something
> > other than 50 ohms.  Using 1/2 wavelength of line
> > should solve this but how to you know what is an exact
> > multiple of 1/2 wavelength ?  If you're off by a few
> > inches that could really mess up your SWR.
> >  An alternative would be to have transformers at each
> > end of the twinlead to step up/step down the load
> > impedance, but, I haven't seen anything published on
> > what materials to use at VHF.  I can build really nice
> > broadband(160m-10m) 4:1 or 9:1 transformers for HF but
> > VHF is a totally different animal.
> > 
> >  Pat W0OPW
> > 
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