I give a STRONG second to K2AV's endorsement of rotary dipoles
(for ANY band).
There's a lot to be said for having a Horizontal Antenna (4 to 6 dB
ground reflection gain), up high, in the clear, and rotating. A PAIR
of fixed dipoles at right angles is also a very good alternative.
On 40M, 70 ft is 1/2 WL high which produces a SINGLE Lobe
centered at ~30 degrees with the -3 dB points at 12 and 50
degrees and a Null from 50 through 90 degrees elevation.
This provides good coverage of the mid to upper angles
supported by the ionosphere and rejection of high angle
atmospheric noise on receive.
I worked my first 300 countries from Alabama on 40M using
a wire and bamboo rotary dipole at 80 ft. I've also worked over
300 countries with 5 watts so while 300 countries 'by itself' is
not necessarily a good endorsement for an Antenna, I believe
that experienced operators develop a 'feel' for how an antenna
plays that can come pretty close to measured results.
My 'feel' for 40M Rotary Dipoles at 80 ft is that they are
VERY GOOD DX Antennas and will allow one to work just about
everything you hear (right after the guys with the beams but
sometimes even before). In contests, you will be able to
hunt and call with ease and even generate good runs when
the band is open to Europe and JA. Of course a beam is
better, but a rotary dipole is plenty 'good enough' to provide
a lot of FUN on 40M.
On 80M, my 130 ft high dipoles 'feel' as competitive as some
of the nearby 4 squares. I got the same (579) report from A52OM
as one of my friend's received with his 4 square. I was one of the
FEW NA stations to work XU7AAV on 80M, along with a well known
W8 using a 5 element vertical array. I don't have to 'struggle' as hard
to work Asians in Zones 21, 22, 23, 24, 26 as I did with my 100 ft
high inverted vee and / or single vertical / GP.
A FLAT Horizontal Dipole is better than an an inverted vee.
Of course an inverted vee is much easier to implement,
requiring only a single high support. Pull the ends out as far
and as high as possible. With an apex angle > 120 degees,
gain approaches that of a flat dipole. (150 degees is even better).
Tom N4KG
On Mon, 8 Jul 2002 "Guy Olinger, K2AV" <k2av@contesting.com> writes:
SNIP
> Anecdotal material around here finds owners quite pleased with 40
> rotatable dipoles. Now that I think of it, can't point to anyone who
> took one down in favor of a vertical. Often find it installed off 90
> degrees instead of a 40 2 element that was trashing 15 meters on a
> co-mounted tribander.
>
> And I simply do NOT agree with the 100 times better, or even just
> better, except in extreme conditions when ONLY the very lowest angle
> is coming in. I've never found a vertical to compete with a dipole
> at height on 40. The single exception would be right at the edge of
> salt water, but only in the directions over water.
>
> On 160, and to some degree on 80, this reverses, as W8JI has proven
> (has compared a 160 dipole at height (!!) with a properly
> ground-screened full size vertical), but that is a different issue.
> Something else not well understood going on.
>
> Further, 70 feet or so up on 40 has very little high angle
> reception, if that is what one wants to do.
>
> Leave your vertical up when you put up your C4S (if that's what you
> get). Let us know how it works out.
>
> 73, Guy.
>
> ----- Original Message -----
> From: <i4jmy@iol.it>
> To: <k2av@contesting.com>
> Cc: <bruceosterberg@msn.com>; <Towertalk@contesting.com>
> Sent: Monday, July 08, 2002 9:20 AM
> Subject: Re: [Towertalk] F12 C4S
>
>
> > Transmitting is not everything and a dipole has a low rejection of
> > unwanted signals from high angles, it's F/S is quite objectionable
> to
> > be considered directivity at medium high elevations.
> > If this were not enough I didn't find any gain by a dipole (half
> WL
> > from ground or more) over a quarter wave vertical, on 40m, beyond
> 1000
> > miles hops.
> > Here in south europe, more than sometimes a vertical is quieter
> and
> > reduces broadcasting signals so allowing more reception of NA
> signals
> > above 7.1 MHz.
> > Surely, instead of an horizontal dipole I'd go for something with
> > directivity, like a two element yagi or a set of switchable
> sloping
> > dipoles/verticals.
> > The extra gain over a simple dipole or a vertical will be the
> marginal
> > issue, while reception is hundred times better.
> >
> > 73,
> > Mauri I4JMY
> >
> > > If you care about 40 meters, the C4S will walk all over the
> vertical.
> > > 52 is a wee bit low, but it is still high enough to outperform
> any
> > > single vertical. BTW, the F12 linear loaded stuff is very
> sensitive to
> > > metallic guy wires in the vicinity. If this is a self-standing
> or
> low
> > > support crankup, you will do fine.
> > >
> > > 73, Guy.
> > >
> > >
> > > ----- Original Message -----
> > > From: "Bruce Osterberg" <bruceosterberg@msn.com>
> > > To: <Towertalk@contesting.com>
> > > Sent: Sunday, July 07, 2002 5:51 PM
> > > Subject: [Towertalk] F12 C4S
> > >
> > >
> > > >
> > > > Good Afternoon:
> > > >
> > > > Well if you only had one tower and wanted a 4 band system
> would
> you
> > > go with
> > > > this antenna if your tower could handle it? I would like to
> put
> a
> > > > tri-bander at 52 feet on a Crank up tower, and was thinking
> about
> > > one that
> > > > had a 40 meter dipole as one of the elements.
> > > >
> > > > After Reading Steve Morris and H. Ward Silver, K7LXC, N0AX,
> > > tribander report
> > > > I know They likesd the C3, C4, combo. ( even though c4 was
> not
> > > tested), but
> > > > would I get any benefit on the 40 meter dipole, or should I
> stick to
> > > the
> > > > elevated 1/4 wave vertical at 20 feet with eight sloping 1/4
> wave
> > > radials?
> > > >
> > > > If I did not get this antenna I would get the C31XR.
> > > >
> > > > 73 Bruce N9BX
> >
>
>
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