Here are some ideas...
I once modeled and then built a fixed bi-direction vertical vee long wave
antenna. The concept works on the same principle as a half-rhombic but
erected vertically instead of horizontally. The length of each leg of the
vee was an even multiple of 10m in length (I can't remember but I think I
used 30m legs). The top wire was supported from a tall tree (~30m) and I
pulled the wire back to the feed point with a long string fixed to the
ground behind the antenna so that the feed point was elevated to about 60%
of the height of the tree. The bottom wire was then run from the feed point
forward sloping down and anchored with another string to base of the tree so
that the end of the lower wire was about 4m off the ground. Both legs were
the same length. From the feed point I ran 450 ohm window type ladder line
at a right angle back to the shack where I fed it with a 4:1 balun and an
antenna tuner.
The antenna produced almost purely vertical bi-directional pattern.
Theoretical gain was about 10 dbi @ 5 deg wave angle on 10m down to about 7
dbi @ 35 deg wave angle on 20m with 15m somewhere in between. I recall
having to model different angle combinations to optimize a good pattern
compromise for all three bands. As with the horizontal version the idea is
to get the best angle for the steep radiation lobes radiating off each leg
to line up with each other so as to produce a combined low angle lobe on
each band. It would also be interesting to build one in a full rhombic
configuration. I would think a proper resistance value load could be placed
at the terminating end for a single-direction pattern.
Another antenna I built was a vertical version of something similar to a
spider beam. This one was for 40m band but could be scaled any band. The
radiator was simple a wire 1/4 wave ground plane hung from a tall tree with
a ground radial field. The director and reflector were vee shaped passive
dipoles of calculated resonances for directional gain. The tope were both
supported with separate strings attached to the support string for the
radiator. Middle support strings were attached to the midpoints of the
passive element and extended well forward and aft of the antenna and
anchored to the ground. The bottom of each passive element was pulled back
towards the centerline of the radiator with additional strings anchored to
the ground thus creating the vee shape.
FYI, a 6el Sterba curtain that I have used a few times also makes a strong
bi-directional pattern for a fixed antenna on a single or maybe two bands
but the polarization is horizontal. Could construct it for vertical
polarization but would need two very tall trees at the proper spacing and
would potentially present some challenge in feeding it without picking up
common mode feedback. I doubt it has enough bandwidth to cover 14-28 mhz.
Hope this gives you some ideas.
73
KM5VI
Matt
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of PY1NB
- Felipe Ceglia
Sent: Friday, June 14, 2013 6:52 PM
To: Matt
Cc: reflector -tower
Subject: Re: [TowerTalk] FW: vertical antenna advice needed
Hi Matt,
Fixed direction, low angle for DX usage.
73,
Felipe Ceglia - PY1NB
----------------------------------------------------------------------------
---------
PR1T team member /// Rio DX Group member /// Araucaria DX Group member
http://dxwatch.com /// http://reversebeacon.net /// http://riodxgroup.com
On Fri, Jun 14, 2013 at 7:31 PM, Matt <km5vi@flukey.cc> wrote:
> Do you need mention but are you looking for variable or fixed
> direction gain? Also is wave angle important - if so what angle?
>
> Matt
> KM5VI
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
> PY1NB
> - Felipe Ceglia
> Sent: Friday, June 14, 2013 7:07 AM
> To: Tower and HF antenna construction topics.
> Subject: [TowerTalk] vertical antenna advice needed
>
> Hello folks,
>
> I'd like to hear your opinions about this topic.
>
> I am looking for an antenna (or more than one) for 10/15/20m that has
> the following characteristics:
>
> - vertical polarization
> - smallest possible horizontal far field lobe
> - "good" forward gain (at least comparing to a single element
> vertical)
> - greatest possible front to back ratio
>
> I was thinking about using:
>
> - a tribander tilted 90 degrees
>
> - 2 element end phased array of:
> - vertical dipoles
> - sitting on the ground verticals (with or without radials?)
> - multiband verticals (using W9AD phasing line to switch between bands)
> - 5/8th wave verticals (at least for 10m, it would be easy to
> convert CB
> antennas)
>
> - a 4 square
>
>
> These antennas would be used for RX only.
>
> Any suggestions, anecdotal comments, field experiments?
>
> 73 and thank for your time,
>
> Felipe Ceglia - PY1NB
>
> ----------------------------------------------------------------------
> ------
> ---------
> PR1T team member /// Rio DX Group member /// Araucaria DX Group member
> http://dxwatch.com /// http://reversebeacon.net ///
> http://riodxgroup.com _______________________________________________
>
>
>
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