Steve Katz <stevek@jmr.com> wrote:
>As Tom Schiller N6BT wrote in his QST article two years ago, "Everything
>Works," and he used a post-mounted light bulb as an example....
I know; I read that article, and we've all seen or heard examples,
sometimes first-hand, of contacts made with practically no antenna.
And I agree with you that it pays to have multiple antennas, and a switch.
It is silly to regard a G5RV as a "leaky dummy load," as someone else
just did on this reflector. A G5RV is very nearly (like, within 1
dB) as good as effective a full half-wavelength dipole at the same
height. A regular G5RV is a center-fed horizontal wire doublet 102
feet long, which is about 25% shorter than a full half-wavelength for
80 meters. It is resonated by what amounts to a series "loading"
inductor at its center. This inductor is not a coil, but 30 feet of
open-wire transmission line. This inductor is essentially lossless.
There is practically *no* difference in efficiency or gain or pattern
shape between a G5RV and a "full" half-wave dipole. The only
noticeable difference is that the G5RV has a lower radiation
resistance (seen at the wire feedpoint), so its Q is higher. But its
radiation resistance is not much lower (IIRC, it's around 35 ohms,
vs. maybe 72 ohms for a dipole), so there's no difficulty matching it
with a tuner.
You can see all this in a NEC-4 simulation, which I have done. But
of course the proof is on-air performance.
Although I don't have another antenna here for "A-B" comparisons, I
participate in a weekly 80-m net (the Wireless Set No. 19 Group CW
Net) that includes several other stations in my area (within 500 km);
and occasionally we get a check-in from far away (the last one was
GI3PDN, last month) who gives us all signal reports. The two
stations who get the best reports are W1NU and I. Both of us use
G5RVs. (W1NU averages about 1 S-unit better than I, which is not
surprising because his antenna is higher than mine. He is also on a
salt marsh!) The other stations use full-size dipoles, an 80/40
trapped dipole, and an 80-m Windom. We all run about the same power.
Our antenna heights average about 30 feet. W1NU's G5RV, rigged as an
inverted-V with apex at 55 ft. is the highest. Mine is rigged as an
inverted-U with its central 68 feet horizontal at 30 feet height.
I've been in this net almost every week for three years, and I always
log the signal reports. W1NU is almost always on top, and I'm almost
always runner-up. IMO, this body of evidence is about as meaningful
as "A-B" comparisons at a single station.
If I had room for a full-size dipole, I'd use one. If I had good
soil conductivity and room for the radials, I'd use a vertical. But
a G5RV, including one rigged as an inverted-V, is _not_ an
inefficient antenna, and no one should avoid using it because of
comments like "I wouldn't mount a G5RV as an inverted vee; actually a
G5RV's not much of an antenna on 80m at all, so I wouldn't bother
with it."
73 de Chuck, W1HIS
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