[Elecraft] Balun with a G5RV?
Ron D' Eau Claire
[email protected]
Sun Apr 21 19:45:01 2002
> ...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 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.
The same dielectric losses are what make common "twin lead" or even "ladder
line" a poor choice when the SWR on the line is high. Good open wire line
uses a LOT of air insulation and a minimum of very high quality solid
dielectric to hold the lines parallel with the proper spacing.
Ron AC7AC
K2 # 1289