[TowerTalk] New Tower/Antenna Installation
Guy Olinger, K2AV
k2av@contesting.com
Thu, 11 May 2000 00:47:34 -0400
Oops, left the table legend off. Please substitute:
Ht. dbi at x d takeoff
Ft. 5d 10d 15d Max @ takeoff
100 5.7 10.7 12.7 13.0 @ 18.5 d
090 4.8 10.0 12.2 12.9 @ 20.0 d
080 3.9 09.2 11.6 12.7 @ 22.5 d
070 2.8 08.2 10.7 12.4 @ 25.5 d
- - . . . . . . - - . . . . - - . . - . .
73, Guy
k2av@contesting.com
Apex, NC, USA
----- Original Message -----
From: Guy Olinger, K2AV <k2av@contesting.com>
To: Paul Christensen <paulc@mediaone.net>; <towertalk@contesting.com>
Sent: Wednesday, May 10, 2000 9:53 PM
Subject: Re: [TowerTalk] New Tower/Antenna Installation
>
> What most of them are doing is responding to figures like these for a
3
> element 40 over good flat terrain:
>
> 100 5.7 10.7 12.7 13.0 @ 18.5 d
> 090 4.8 10.0 12.2 12.9 @ 20.0 d
> 080 3.9 09.2 11.6 12.7 @ 22.5 d
> 070 2.8 08.2 10.7 12.4 @ 25.5 d
>
> The particulars for a given height and gain might change with antenna,
> but the SHAPE of these figures will remain the same. It IS true that
> there is a nasty high angle lobe at 100 feet, which can let in a lot
of
> stateside QRM, maybe 15 dB difference between 70 (least) and 100 feet
> (most local reception). But the gain at five degrees above the horizon
> changes almost a dB per 10 feet !!
>
> HOWEVER, this does NOT apply if the terrain is gently rolling down
> toward the desired direction. Such a favored location is HOT STUFF at
5
> degrees almost regardless of height, and BETTER at 70 feet overall.
>
> It's really not such a simple question. More if you are interested.
>
> - - . . . . . . - - . . . . - - . . - . .
>
> 73, Guy
> k2av@contesting.com
> Apex, NC, USA
>
> ----- Original Message -----
> From: Paul Christensen <paulc@mediaone.net>
> To: <towertalk@contesting.com>
> Sent: Wednesday, May 10, 2000 11:24 AM
> Subject: [TowerTalk] New Tower/Antenna Installation
>
>
> >
> > I am considering the purchase of a Force12 40-meter monoband MAG
340N
> and
> > multiband C-31XR antennas to be mounted on either a Tri-Ex Sky
Needle
> or
> > LM-series 70-foot tower. Apparently, the new MAG 340N is resistant
to
> > mutual coupling effects and can be mounted within a reasonably close
> > proximity to multiband Yagi antennas on a shared mast. With this in
> mind, I
> > would like to mount the MAG 340N on top of the C-31XR by a distance
of
> 15
> > feet, both pointing in the same azimuth. My question concerns the
> height of
> > the antennas and specifically, given the constraints of a single
tower
> with
> > these two antennas, is there an optimum "overall" height for the
> 40-meter
> > antenna? I want to place as much emphasis as possible on the
40-meter
> > operation. It would appear that the "optimum" height for 40-meters
is
> a
> > half-wave above ground in order to minimize the effect of high-angle
> lobes.
> > However, I see many single 40-meter monoband antennas mounted up to
> 100-feet
> > above ground. Why, if more high-angle lobes are produced? I
realize
> the
> > ideal situation is to incorporate more than one level of stacking,
but
> I
> > want to stay with one antenna at a "best overall" height. Thanks!
> >
> > -Paul, W4XR
> >
> >
> >
> > --
> > FAQ on WWW:
http://www.contesting.com/towertalkfaq.html
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> >
> >
>
>
> --
> FAQ on WWW: http://www.contesting.com/towertalkfaq.html
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
> Search: http://www.contesting.com/km9p/search.htm
>
>
--
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Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm