An alternative to the G5RV for an 80 meter antenna to fit in 100 feet is the
Carolina Beam 80 which is a partly a modified G5RV and a Carolina Windom.
This antenna works more like a SCV as described by W4RNL with a figure 8
pattern broadside and a high angle oval with slight nulls off the ends.
K4UEE told me I was the loudest station in both CE0Z and easter Island on 75
and so did EM1HO. I also have good luck on VE4 and 5 plus have worked two
UA9's in Zone 18. As its broadside North and South (mounted E and W)
signals from Europe are down and its hard to work Africa in the null. You
have a choice of mounting the antenna in 84 feet or 100 feet depending on
the vertical sections you choose. I have better DX luck with a 32 foot
vertical section on the long end. Full details are in the Radio Works
catalog and their web page.
The antenna works all bands 80 to 10 and does a good job on 40 compared to
my 2 el beam (down just an S unit) and I work mults on 20 with ease. There
are parts of the bands where you will need a tuner although the built in
tuner seems to cover most instances.
I did put up a K8UR vertical dipole on 75 (A Mor-Gain 66 footer) that more
than fills in the gaps in Europe and Africa but is nowhere equal to the
Carolina 80 on short hop stateside as you would expect with a vertical.
The Carolina Beam should be mounted as close to horizontal as possible and
the higher the better. Mine is 55 feet at one end and 55 feet at the other
with the feed point being 65 feet up. It can be mounted much lower (30 foot
min) but you start to lose some of DX arrival angles.
73 Dave K4JRB