Yes, The G5RV is optimized only for 20 meters, where it is a 3/2
wavelength. The 30 feet of twin lead is a matching section cut for 20
meters. At the end of the twin lead on all other bands the swr will be
high. Th secret to the wide bandwidth and low swr on all bands that
some claim is the fact that most G5RV designs specify 70 feet of coax
connected to the twin lead. The resulting high losses in the coax due to
normal loss plus high swr has the effect of smoothing out the swr.
Years ago I used a G5RV rigged as an inverted V (not the best
configuration, but the only way it would fit in the back yard). It
worked OK on 80, 40 and 20, but was terrible on 15 and 10. On 10
meters, a dipole in the attic out performed it. I took it down when I
discovered that a simple 1/4 wave inverted L was better on 80.
Check out Walt Maxwell's (W2DU) site. It has a good discussion of the
G5RV vs the merits of a dipole with twin lead, window line, or ladder
line running to the shack.
73,
Bob WB2VUF
Bob McGraw - K4TAX wrote:
Do a Google search for G5RV. You'll find a bountiful amount of info. Lots
of test data, construction techniques and design information.
From my use of a G5RV some years ago, I'd say if that's the only antenna one
can put up, it's better than no antenna at all, but not much. There are
much better antenna configurations, antennas that are more efficient, more
reliable and work quite well. All much simpler and easier to build. Try
the 135 ft center fed wire fed with a balanced feed system. And oh yes, the
balanced feed system is much much easier to install and keep in the air than
90% of the hams understand. It will always have lower loss than any coax
fed antenna too.
73
Bob, K4TAX
----- Original Message -----
From: "Verne Smith" <vernew7grn@cascadeaccess.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Thursday, January 29, 2009 8:10 PM
Subject: [TenTec] bill orr article
bill orr has a book on antennas in which he covered g5rv i believe it is
available from arrl
verne
w7grn
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|