Doc,
You will find a good selection of plans for wire verticals on my web site.
http://www.dj0ip.de/vertical-antennas/
All of these antennas have been built and used by one or more of the
Spiderbeam team members.
They are all field proven and many DX-peditions use them. I know that for a
fact because I sponsor them and they send me pictures.
These are quick and easy antennas to build. Of course the purest might want
to optimize the feedpoint impedance to get a lower indication the SWR
bridge, but that doesn't bring anything in performance. Performance is a
function of two factors: 1) the height of the vertical radiator (radiation
resistance) and 2) the efficiency of the ground network (radials) under it.
Many of these antennas have an SWR of 2:1 or higher and they work just fine
like that.
A couple of rules to remember when working with fiberglass poles:
1) NEVER drill holes in a thin wall telescoping fiberglass pole; that's
the best way to break them.
2) Best practice is to mount the retracted pole securely to something
(i.e., long wooden ground stake), attach the wire to the top segment of the
pole, and then push (telescope) the segments up, one after another. If you
mount everything to the fully extended pole when it is laying on the ground,
then try to pivot it up, it may break.
3) Guy lines should be thin rope and kept light (2mm Kevlar is perfect);
they should always have a little slack in them, not be pulled tight.
4) Spiral the wire around the pole on its way to the ground, with about one
turn every 2 to 3 ft. This reduces flopping in the wind.
5) When pressed tightly against the pole, it tends to reduce the velocity
factor of the wire by about 0.01. Example, if the vf of the wire is
normally 0.98, then it will be about 0.97 when snug against the pole. So
your radiator will be a little shorter. Regardless, start with full size
and trim to resonance.
6) A quarter wavelength 80m vertical, 67' long, fits easily onto the 60'
Spiderbeam pole, due to the reduced vf and the spiraling of the wire. Start
with the normal full length of wire (according to the formula) then as you
approach the bottom of the pole, wind the wire a bit closer together (2
turns per ft. for the bottom 5 ft.). The antenna will be resonant too low.
Unwind a little wire, space the turns a little farther and trim off a little
to raise resonance.
7) Though traditionally we have used 1/4 wavelength radials, they may be
shorter (as short as 1/8 wavelength) and though it is better to have them
all the same length, that is not absolutely necessary. 24x 1/8 wavelength
radials will give you better performance than 12x 1/4 wavelength radials and
uses the same amount of wire.
8) If you use elevated radials, you will find it works "OK" with just one
radial, better with two, a little better with 3 but more than 4 doesn't buy
much more gain. Each elevated radial is usually as good as 6 ground mounted
radials (YMMV). However these radials must all be the exact same length and
resonant 1/4 wavelength long.
Rumor has it that with each fiberglass pole, Scott is throwing in a bag of
sunspots... though I haven't confirmed this.
Check here: http://www.spiderbeam.us/index.php?cat=c2
73 - Rick, DJ0IP
(Nr. Frankfurt, Germany)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Doc
Sent: Saturday, November 05, 2016 9:27 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Fiberglass poles?
Barry, thanks a lot for this feedback re Spiderbeam. I have had some
questions about the cost, which seem too low for such length.
PS Could you send me the formula for making up some wire verticals?
73,
Doc/K0EVZ
On Nov 5, 2016 1:46 PM, "Barry N1EU" <barry.n1eu@gmail.com> wrote:
> The Spiderbeam poles are also worth considering. Our good friends
> W4PA and DJ0IP are intimately involved.
>
> 73, Barry N1EU
>
> On Sat, Nov 5, 2016 at 3:20 PM, Doc <k0evzdoc@gmail.com> wrote:
>
> > What has been your experience with the MFJ or Jackite collapsible
> > fibreglass poles, either 33' or 43' in length? I have been
> > considering a purchase in order to construct a wire vertical.
> >
> > Would really appreciate hearing from you, please.
> >
> > GL in the SS!
> >
> > 73,
> > --Doc/K0EVZ
> > _______________________________________________
> > TenTec mailing list
> > TenTec@contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
> >
> _______________________________________________
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