Don,
With respect for your wisdom and your good advice, in the UK in particular
(home of the G5RV) the 'ordinary' ham has real-estate issues, big time!
Louis Varney's garden/back yard was of average British size, which is
actually quite small when compared to 'average' gardens that I've seen in
the USA. That was his prime reason for designing a compact wire antenna.
We have other issues with planning regulations and erecting a mast or tower
over 40ft in height would probably meet with a brick-wall attitude from the
local planning authorities. Attitudes towards structures in the UK are very
different to the USA and there are many snobs who claim offense when they
see something that appears above the roof line of an average house.
My back yard is even smaller than Louis's and I just don't have space for
lengthy wires or even slopers. Even erecting tall supports is difficult as
there's limited ground to dig holes to fill with concrete supports.
Maybe in the USA, the use of G5RV antennas doesn't make too much sense, but
to us Brits, compact antennas are often the only thing we can use.
73,
Alan. G4GNX
-----Original Message-----
From: Don Wilhelm
Sent: Friday, August 05, 2016 12:41 AM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] OT:. G5RV's
Wes and all,
Yes, the G5RV, the Off-Center-Fed antennas (Carolina Windom for one
example) and the 43 foot vertical have become "magical" antennas, and I
am not certain why.
My best guess is that they are "salvation" for hams who want to operate
on multiple bands with one antenna, and they can be made to "work" in
one fashion or another.
All need a tuner of some sort, and the 43 foot vertical needs a remote
tuner at the base for efficient operation, or at least a matching
section for each band at the base for efficient operation. One could
feed that vertical with low loss open wire line and put the matching
tuner in the shack, but most choose to feed with coax along with the
attendant losses incurred if no matching is done at the vertical base.
IMHO, resonant fan dipoles are a much better solution - whether those be
constructed as inverted Vee's or whether as parallel dipoles separated
by 1 foot or more to reduce interaction.
I use resonant parallel dipoles here. The 80 and 40 inverted vee's are
supported on a 50 foot tower and the 80 meter legs are perpendicular to
the 40 meter legs, so there is no interaction.
I have another 3 band band fan dipole for 20, 15, and 10 hung as a
horizontal dipole with the radiators separated 1 foot from each other
(other than at the center point) and a similar 3 band fan dipole for 30,
17, and 12 meters.
That means 3 coax lines into the shack, or a remote antenna switch -
which I use because I have other antennas to deal with, a 60 meter
inverted vee, and a Gap Titan vertical.
As far as I am concerned, resonant dipoles are the preferred solution.
Other antennas may work, but are a compromise, and some (particularly
the OCF antennas) produce RF-in-the-Shack that can be difficult to suppress.
There is no "magic" with antennas. Some antenna designs were created
when we had PA output circuits that could handle a wide range of antenna
impedances and used low loss open wire feedlines. That is no longer the
case with the transceiver (or amplifier) that needs to operate into a 50
ohm load, and ATUs with limited matching range.
So take your pick and know the hazards and consequences of that choice.
Any antenna that you can feed power to will radiate, but some do it
better than others. My choice is to use center fed dipoles which at any
length can be easily tamed, and I shy away from the OCF antennas which
can create RF-in-the-Shack problems.
There is no "magic" with antennas, the knowledge base for radiation from
a wire (or piece of aluminum) has been around for many long years, but
the resulting feedpoint impedance is what we commonly deal with along
with all its hazards and consequences.
73,
Don W3FPR
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