On Lord Howe Island last summer, on 160M, we deployed a Spiderbeam 18M
fiberglass telescopic pole with a 1/4 wave wire taped to it.
The excess wire came off the top like an inverted L and was tied to a
convenient fence.
There were two sets of 4 light synthetic rope guys to ground stakes.
We had a bunch of radials made of electric fence wire on the ground and
a small matching network at the base.
Light, easy to erect, shippable, not too expensive and worked very well.
I believe we will have the same antenna on Campbell Island in November.
No engineering required except for the matching network.
Les W2LK
On 7/30/2012 8:32 PM, bills stuff wrote:
> The plan is to develop a simple, relatively inexpensive, relatively
> light weight and shippable/airline transportable 160 antenna kit for one
> man quick deployment for modest DXpeditions or contributed for use by
> resident hams in rare-ish (for 160 m) locations.The ability to make
> adjustments to actual deployments to provide matching is important since
> such antennas are famously variable due to soil and local obstruction
> environment and there should not be a need for antenna matching
> hardware, especially at the planned higher powers.
>
> First cut electrical design:Inverted L using telescoping aluminum tubes,
> two elevated radials and "hairpin" matching.
>
> Mechanical features of a prototype that was deployed:
>
> 9 Alum tubes 6', .058" walls, 2" diameter through 1" diameter -- this
> gives a 50' or 15.3 m mast (it can be pulled upright by 1 person, or
> probably telescoped up also)
>
> #14 wire ~ 28 m for top wire and 2X ~34 m radials (values after some
> adjustment, not unique, some tradeoff between the top and radials)
>
> Base - 2 thicknesses of Walmart (cheap 8X11") ¼" plastic cutting board
> resting on ground with a ~ 1.5" wood cylinder bolted in the
> center.SO-239 connector screwed to the board.
>
> Guys -- 4X 3/32" dacron rope attached at 7 tube height, angled at ~ 45deg
>
> Guys held down by sandbags (very effective and moveable)
>
> Inv L top wire end was at ~ 2.5 m height with a support of opportunity
> (e.g., a tree) ~ 25 m from base
>
> Radials have their closest support near the base from plastic rings
> looped through each of an opposite pair of the guys at ~ 6 m high and 6
> m from the mast.The radials therefore go from the base to the rings at
> about a 45 degree angle.(Elevating the base and everything else, by a
> meter did not seem to affect the impedance.Beyond that, supports of
> opportunity were used - above neck height is always nice.
>
> This produces, with some fiddling with wire lengths, an impedance around
> 20 -- j20 which can be matched using a practical "hairpin" coil shunt of
> inductive reactance ~ 45 ohms ( 4 microHenrys, say 5 turns 4" dia).
>
> More details of the test case including the EZNEC example are shown on
> my website.There are obviously a number of ways this design could be
> modified/improved, several discussed on the website.However, the
> tradeoffs with size, weight and complexity must be considered in the
> light of the mission here which includes transportability and ease of
> deployment.
>
> I am looking for collaborators to contribute ideas to help improve, and
> potentially, test design issues.Check out the website at
> http://n6mw.ehpes.com <http://n6mw.ehpes.com/> for the Itinerant 160 m
> antenna project expanded discussion toward the bottom.
>
> The immediate target is designing and assembling a respectable 160 m
> antenna that might go to KH8 on a DXpedition.
>
> Bill, N6MW
>
> billsstuff(at)gotsky.com
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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