[Elecraft] Balun with a G5RV?

[kc4kgu@ENTERZONE.NET]

On Sun, 21 Apr 2002, Ron D' Eau Claire wrote:

> > ...Your marginal performance on 10m is probably a result of high SWR on
> the
> > coax.  Remember: a tuner provides a 50ohm match to the RADIO.  It does
> > NOTHING to improve any mismatch you may be seeing between your antenna and
> > the tuner on the feedline.
> >
> > Last week, I converted the feed to my 80m doublet antenna from 50ohm coax
> > to TWO 50ohm coax (100ohm unbalanced-balanced)....
> > 73 de John - KC4KGU
> > K2 #2490
> 
> 
> High SWR will produce very high losses in coax. These losses increase with
> frequency as well.
> 
> Running two coaxial lines in parallel will do nothing to reduce these losses
> unless that also produces a lower SWR on the coaxial lines.

The two coax lines in parallel are being used as a balanced feed to the
antenna.  Only the center conductor is being used for the feedline.  It
acts like any other balanced feedline with the exception that you don't
have as many "gotchas" as with the "real" thing.

> The losses in the coax are a function of dielectric leakage and breakdown in
> the coaxial line at the points where the standing waves produce a high
> impedance and high voltage cross the dielectric. There are also additional
> losses at the points of high current, although the added losses at the
> current "loops" will be small provided the conductors are of adequate size.

73 de John - KC4KGU
K2 #2490