[Elecraft] OT:. G5RV's

[Don Wilhelm]

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

On 8/4/2016 4:41 PM, Wes Stewart wrote:
> In my 1999 paper, /"Balanced Transmission Line in Current Amateur 
> Practice"/ (http://k6mhe.com/n7ws/Ladder_Line.pdf), published in the 
> /ARRL Antenna Compendium, Volume 6, /pp 174-178, I have this 
> statement: "A popular multiband wire antenna is the so-called G5RV. 
> This antenna is rarely used as was intended by Varney, but for some 
> reason, the 102-foot length has taken on mystical properties,...."
>
> It's a pity that too many newcomers, as well as many oldsters, are 
> enamored by this piece of wire.  First, a 102' length is not resonant 
> on 20-meters, so in common jargon, it's *not* a 20-meter antenna, any 
> more than any other random length would be. Second, I understand that 
> the conventional wisdom is that it has "gain" on 20-meters.  Maybe so, 
> but the usual application has the wire strung up between available 
> supports that may, or may not, direct the "gain" in a useful 
> direction.  A coax-fed, rotatable, resonant dipole would run rings 
> around a G5RV.
>
> (While it's off-topic on this off-topic subject, the fascination with 
> the "magical" 43-foot vertical is equally bewildering to me.)
>