[TowerTalk] Conclusion, G5RV vs. Dipole
Guy Olinger, K2AV
k2av@contesting.com
Mon, 16 Oct 2000 20:23:38 -0400
Well, balanced in an optimum environment.
Are both sides equally above ground, if not, a bit of imbalance. Both
sides above equally conductive ground, if not, a bit of imbalance. Does
the ground under one side or the environment near one side have
conductors, if so a bit of imbalance. Does the feedline come away at 90
(not 95 or 85) degrees, if so a bit of imbalance. A little bit, a big
bit, just depends. In most cases indiscernible at the distant end.
BTW, on the subject of dual coax for an indoor section of balanced line,
I didn't see anyone mention that tying the shields together and
grounding them one or both ends keeps it from radiating inside and being
twerped by miscellaneous nearby conductors, like the ubiquitous indoor
110 wiring, etc.
I'm going to make a run of that to the outside using parallel 5/8
hardline (handle the power), so I can tune it in the shack. I'll get to
the end of it with about six feet of RG-214 and one of those remote
baluns. That will be my E/W cloud burner for 80/40, what is it, 105 feet
center-fed? I'll look it up...
--... ...-- . ... --. .-..
Regards, Guy
k2av@contesting.com
Apex, NC
----- Original Message -----
From: <n4kg@juno.com>
To: <TOWERTALK@contesting.com>
Sent: Monday, October 16, 2000 1:20 PM
Subject: Re: [TowerTalk] Conclusion, G5RV vs. Dipole
>
> Unless I am mistaken, there is a HUGE misunderstanding
> of how the G5RV antenna works.
>
> The ONLY way it could act as a Top Loaded Vertical is for
> the currents in each side of the balanced transmission line
> to be EQUAL and flowing in the SAME direction. If that were
> the case, they could be tied together or replaced by a single
> wire and attached to the two sides of the horizontal wires at
> the top. I do NOT believe that is the case.
>
> IF the feed is indeed as a split balanced dipole of various
> electrical lengths, then the ladderline is acting as a balanced
> transmission line with EQUAL but OPPOSITE currents in
> each side and it does NOT radiate.
>
> As a balanced dipole, it acts as:
>
> 3/8 wave (short ) dipole on 80M
> 3/4 wave (long) dipole on 40M
> 2 Half Wave dipoles in phase on 30M (Voltage Node feed)
> 3 Half Wave Long Wire on 20M (current Node at feed)
> (almost) 2 Full wave LW's in phase on 17M (near voltage node)
> 9/4 wave LW on 15M (neither current nor voltage node at feed)
> 5/2 wave LW on 12M (current node at feed)
> Two 2WL LW in phase on 10M (voltage node at feed)
>
> BTW, as originally designed, the ladderline was meant as
> an impedance transformer that provided a reasonable SWR
> on SOME bands (but NOT ALL) without the need for a tuner.
>
> de Tom N4KG
>
>
>
> On Mon, 16 Oct 2000 David Jordan <wa3gin@erols.com> writes:
> > Right on Tom...
> >
> > A dipole at 1/8 wave above ground is a great NVIS antenna. Two
> > dipoles at 1/8 wave above ground spaced .67 wavelength feed with
open
> wire
> > line
> > and feed in phase from a center drop or open wire to a tuner is even
> > better. Most of the radiation goes straight up and it's omni
> > directional!
> >
> > The G5RV is a top loaded vertical on the lowest freq w/ the twin
> > lead radiating as a vertical does...a real compromise if one is
looking
>
> > for short skip high angle radiation.
> >
> > Have Fun,
> > dave
> > WA3GIN
> >
>
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