Now you have me second-guessing myself.
Over-simplying greatly:
If the dipoles are spaced roughly 1/2 wave apart or less, it's going to be
broadside to the axis of the elements (assuming the elements are fed in
phase, which I presume they are). That's in free-space; but here we have a
mast right in the middle of the two elements.
If the elements are spaced somewhere in the vicinity of 1/2 wave apart, that
means the mast is roughly 1/4 wave from each bay. A mast 1/4 wave behind a
dipole would normally yield a cardiod pattern, with maximum gain away from
the mast. So, two such cardiods back-to-back would yield an end-fire
"figure 8" pattern. That contradicts the first analysis (broadside).
Maybe time to model it...
I checked a Sinclair catalog (circa 1990) and, although it showed the
elliptical pattern, it didn't say how the antenna was oriented for the plot.
I don't have Comprod docs other than what's on their web site.
--- Jeff
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Paul
> Kelley N1BUG
> Sent: Wednesday, June 24, 2009 5:36 AM
> To: [email protected]
> Subject: Re: [Repeater-Builder] SRL235-2 Bi-Directional
> Antenna, which direction has gain?
>
>
>
> If the Comprod is really the equivalent of the Sinclair SRL235-2, I
> must respectfully disagree with this. The instruction sheet for the
> SRL235-2 says the opposite, that maximum radiation would be
> perpendicular to a line drawn as described. I can scan a page from
> the Sinclair instruction sheet to back up this statement.
>
> Paul N1BUG
>
> Jeff DePolo wrote:
> > If all of the elements are parallel as in your photo, then it's
> > bi-directional. If you drew a line through one element,
> through the mast,
> > and through the other element, maximum radiation would be
> along that axis.
> >
> > If the elements are staggered such that each bay pair is
> rotated 90 degrees
> > from the bay above/below it, then it's basically omnidirectional.
> >
> > --- Jeff
> >
> >> -----Original Message-----
> >> From: [email protected]
> <mailto:Repeater-Builder%40yahoogroups.com>
> >> [mailto:[email protected]
> <mailto:Repeater-Builder%40yahoogroups.com> ] On Behalf Of Jesse Lloyd
> >> Sent: Tuesday, June 23, 2009 8:28 PM
> >> To: [email protected]
> <mailto:Repeater-Builder%40yahoogroups.com>
> >> Subject: [Repeater-Builder] SRL235-2 Bi-Directional Antenna,
> >> which direction has gain?
> >>
> >>
> >>
> >> Hi all,
> >>
> >>
> >> I acquired a Comprod equivalent to the SRL235-2. Basically
> >> the same, just heavier duty and the cabling harness is in the
> >> boom. Anyway, which way is it directional? In the case of
> >> this picture of one
> >> http://www.repeater.n1bug.com/sinclairant.jpg
> <http://www.repeater.n1bug.com/sinclairant.jpg>
> >> <http://www.repeater.n1bug.com/sinclairant.jpg
> <http://www.repeater.n1bug.com/sinclairant.jpg> > is it
> >> diectional through the dipoles, or 90 degrees from them, ie
> >> in the diection of the tower (and opposite to) in that case.
> >>
> >>
> >> Thanks,
> >>
> >> Jesse
>
>
>
>
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