[Elecraft] G5RV
Ron D'Eau Claire
[email protected]
Thu Apr 1 12:59:02 2004
Antennas evolve and, sometimes, the work of the inventor gets buried in =
the
changes others make. The original G5RV published back in 1946 was =
designed
for 20 meters using a 1.5 wavelength radiator at 14.14 MHz (102 feet or =
37.2
meters long), center fed by a 34-foot (10.36 meter) matching section of =
open
wire line that would provide a non-reactive impedance of 75 ohms. On 20
meters it provided a decent match to rigs without an ATU.
That was Varney's (G5RV) original design objective.=20
Hams quickly discovered that it would work on other bands as well and =
began
all manner of tweaking of the matching sections to provide "multi-band"
coverage. Varney himself published an update in the RSGB journal in 1984
discussing the use of the antenna as an "all band" design. He =
recommended
using a good ATU with it in that case.=20
Of course, it's a 102-foot center fed doublet with open wire line. In =
that,
there's nothing at all different about it compared to any center-fed =
doublet
using open wire line and it works like any such antenna. It's quite good =
for
DX if it's at least 1/2 wave length above the ground on the lowest
frequency. It's a good local short-skip antenna on any band down to =
where
it's about 0.2 wavelength above the ground if DX isn't needed on the =
lower
frequency bands.
Its drawback usually appears on the higher bands. Because of its length,
very strong nearly-vertical lobes can appear up on 10 and 12 meters,
reducing its efficiency for DX. That's why Moxon recommends that a =
doublet
that will be used as a multi-band antenna including 10 meters be limited =
to
42 feet. At that length it's an "extended double Zepp" on 10 - very
efficient for low angle DX with some gain over a half wave - and still =
quite
efficient up through 40 meters.=20
On 80 and 160 meters its efficiency suffers from being too short.=20
Ron AC7AC
-----Original Message-----
In a message dated 3/31/04 3:34:35 PM Eastern Standard Time,=20
[email protected] writes:
> A thing to keep in mind about the G5RV is that it was intended for 20m
> optimally. Later authors, in as stretch, tried to make it something =
else
> on many more bands.
Not quite!...
73 de Jim, N2EY