[TowerTalk] Rai Beam
i4jmy@iol.it
i4jmy@iol.it
Tue, 11 Apr 2000 10:49:12 +0200
It depends by the S/N situation, but in most cases a 3dB gain is a lot,
"to hear or not to hear".
Stated it, the gain in yagis is a direct function of boom lenght.
73,
Mauri I4JMY
> ---------- Initial message -----------
>
> From : owner-towertalk@contesting.com
> To : towertalk@contesting.com
> Cc :
> Date : Mon, 10 Apr 2000 14:05:30 -0400
> Subject : Re: [TowerTalk] Rai Beam
>
>
> Hi Joe,
> Reviewing a few known facts, i remember that the ZL Special, a dual
> driven
> phased array, has a gain of about 3 dbd. The 2 element yagi produces a
> gain
> of 4.5-5 dbd, the 2 element quad produces a gain of 5-5.5 dbd, the 3
> element
> yagi produces a gain of about 6 dbd, the 4 element yagi- about 7 dbd,
the
> 5
> element yagi- about 8 dbd, so on. Beyond about that limit, the gain
> starts to fall
> below 1 db per element.
> I don't believe for a second, that the 2 element Raibeam produces a
> gain of 8
> dbi, which translates into 5.9 dbd., but for the sake of the
arguement,
> lets assume
> that it does, for a moment. (Does anyone know how the Raibeam differs
> from
> the ZL Special?).
> First and foremost, the advantage that one enjoys with most antennas
> with
> directional characteristics, it that they are raised to a height that
> places their
> lower lobe in the range of angles of radiation that are appropriate
to a
> particular
> path. Even a dipole would perform well under such circumstances. Its
> therefore,
> not surprising that "trapped" tribanders with typical gain figures of
> 1-1/2 to 3 dbd
> would also perform well. Likewise, the ZL Special, 2 element
yagis,etc.
> The
> differences between all these antennas are only a few db. Without a
> reference
> antenna for comparison, most of us would be hard pressed to even know
> that there
> was a difference, except intellectually. A difference of 1 db is so
> insignifiicant that
> even under closely and carefully controlled conditions, most of us
could
> only just
discern that level of difference between two signals. A
difference
> of 3 db isn't
> remarkable( to quote Bill Orr), 5 db is a worthwhile difference
(again, to
> quote Orr),
> and a difference of 10 db, is a new level of performance, but still
only
> the difference
> between an s-9 signal and one 10 db above s-9, IF, the "S" meter is
> accurately
> calibrated.
> I will continue this in PART 2. 73 for now, Roy Lincoln WA4DOU
> ----------------------------------------------------------------------
---
> ----------------------------------------
>
> On Mon, 10 Apr 2000 19:14:38 -0400 Joe Reisert <jreisert@jlc.net>
writes:
> >
> > To Interested Antenna Buffs,
>
> >
> > 2. If it is true gain, we better all dump our antenna software, get
> > a
> > Raibeam and take down those big beams we are now using. Greater
than
> > 8 dBi
> > gain in "free space" on 2-element a tri-bander using only an eight
> > foot
> > (0.12 wavelength on 20-meters) boom is mighty impressive.
> > Furthermore the
> > pattern in the ad infers a F/B ratio of almost 30 dBs!
> >
> > Is this antenna patented? If so, what is the patent number so I can
> > get a
> > copy and be enlightened.
> >
> > I'm anxiously awaiting the new antenna gain theory!
> >
> > Joe, W1JR
>
>
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