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Author Topic: Spiderpole (Fiberglass) antenna ideas that have worked?  (Read 2367 times)
AD0AE
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Posts: 76




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« on: January 11, 2013, 07:00:21 AM »

All-

I have been trying to conjure up some ideas that would employ using a fiberglass rod?  Dipoles, multiple-band dipole, a vertical, an elevated ground plane vertical? 

There are two things I am especially curious about.

1. How do you secure the pole into the ground?  Do you just use a big stake?  Or some sort of holder that is guyed down?  Maybe attaching it to a tripod?

2. If I put a dipole, wouldn't feeding it at the peak of the pole end up causing the pole to bend?  While this may not be a big deal, I would see it being an issue if it was done enough.


I would just like to see or hear about ideas that have worked.

Thanks all!

AD0AE
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WB6BYU
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Posts: 12983




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« Reply #1 on: January 11, 2013, 08:11:32 AM »

I've seen a number of designs that use a 20' telescoping fiberglass fishing pole.
The tip section is too flimsy to support a dipole, and is usually removed.  Using
RG-174 coax  with light wire (such as #22 stranded, insulated hook up wire) puts
less stress on the rest of the pole.  I've helped several hams put together such
a system with good results.  The center insulator can be attached to the pole
using some sort of bracket with a hole in it that fits the taper (I've seen a solder
lug used, with an added grommet if needed), or a big rubber band, or clamp of
some sort (such as a hose clamp or cable clamp.)  If you have removed the top
section you can use some sort of hook of stiff wire that fits inside the opening
in the top section.

One approach that avoids the weight of the coax on the top section of
the mast is to make a loop antenna, with the mast holding the top of the
loop and the corners tied off to stakes.  Ideally this would use a mast taller
than 20' for 20m, but if fed for vertical polarization it can work well at low
heights.  This isn't entirely self supporting, of course, as it requires that
the loop corners be tied off somewhere, but the same is true of an inverted vee.

The mast can be supported by securing it to a sign post or other upright
object with bungee cords.  For a stand-alone mount, a piece of plastic pipe
that just fits around the mast should do the job - this can be attached to
a tripod, a stake in the ground, a drive-on wooden mount that goes under
one wheel of your vehicle, attached to the bumper, etc.  One option that
provides good security is to use a horizontal brace of some sort coming
off a roof rack to hold it above ground level, along with a stake, drive-on
mount, or large brick to keep the base from moving sideways.  Details
depend to a large extent on the circumstances in which you plan to
operate.

For a vertical, some hams have glued one end of a wire inside the top section
and let it hang down inside the mast.  This could then be used with a tuner
at the base:  20' is a bit short for good efficiency on 40m perhaps, but would
at least be usable, and will work well up through 10m.  If you are going to be
sitting close to the antenna, or don't change bands very often, you can build
a set of fixed-tuned matching networks for each band and connect them to a
big switch rather than having to fiddle with the tuner knobs each time you
change bands.

A common design for 80m transmitter hunting competitions is to run a wire
up the mast and wind a loading coil around the bottom section to make a
self-contained vertical.

Another approach is to run a 1/4 wave wire up the mast for each band you
want to operate (perhaps with a loading coil to provide 40m and/or 30m
operation where the fishing rod isn't long enough.)  This might work better
with some sort of light spreader installed near the middle to separate the
wires somewhat, then they can run back together at the top.

A trap vertical could use pieces of thin PVC pipe for the trap formers, large
enough to slip over the bottom section of the mast.  That would allow
them to remain around the mast when it was telescoped down.

Any such vertical could be fed against a car body, elevated radials, or
some sort of earth ground (preferably with ground radials).  Elevated
radials should be cut to 1/4 wave for each band of operation, though
there are ways to get around this with some design.

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N3OX
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Posts: 8852


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« Reply #2 on: January 11, 2013, 08:58:34 AM »

1. How do you secure the pole into the ground?  Do you just use a big stake?  Or some sort of holder that is guyed down?  Maybe attaching it to a tripod?

Steve,

The 40 foot Spiderbeam pole works well as a vertical with just three guy ropes on the bottom section held by some orange 12 inch tie down stakes from Home Depot and a slight pocket dug in firm soil for the pole base... I've had it up in up to 40MPH winds or so without trouble.

With guys on only the bottom section, it's easy to telescope up and put down if there's stormy WX expected.

http://n3ox.net/projects/lowbandvert/

Quote
2. If I put a dipole, wouldn't feeding it at the peak of the pole end up causing the pole to bend?  While this may not be a big deal, I would see it being an issue if it was done enough.

Best to use light wire or remove some sections. If you're going to put a dipole at the top of the pole and it's not very lightweight wire, you will probably want to use clamps on the sections.

The Spiderbeam poles won't break even if this is happening:

http://w9oy.painloss.com/SSvert/40mph.htm

But I guess if you put a G5RV on it and Hurricane Sandy hits Brooklyn, it does break, no surprise:

http://instagram.com/p/ToSlg0ACoi/

(that's Bre Pettis, CEO of Makerbot and K2BRE's  antenna setup)

Might have even broken if used as a vertical... don't know the details.

 
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
AD0AE
Member

Posts: 76




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« Reply #3 on: January 11, 2013, 09:02:21 AM »

Dan, thank you for the response.  I have definitely checked out your website for ideas. I like your spiderpole vertical idea.  I know you put the matching right at the bottom of the antenna in a little dog house type thing, but would an autotuner work?  I have an idea for a possible dual 40/20m groundplane vertical which I may draw up and post.

Also, it was very good to chat with Ethan and you at AGU this year!  Frankly, that was one of the most enjoyable conversations I had all week! 
« Last Edit: January 11, 2013, 09:05:55 AM by AD0AE » Logged
N4JTE
Member

Posts: 1147




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« Reply #4 on: January 11, 2013, 03:04:14 PM »

I have been using spider type fiberglass poles for years. Best of coarse is when used as verticals and some insuled wire tie wrapped to the pole for a monoband vertical.
Your point about the bend moment when the coax is fed to the top for a dipole or inverted vee configuration is valid.
However the wire elements will act as guy supports and so far I have never busted one. Definetly useless if you plan on using them as the end supports, They won't break but you will be around 20 feet high with the resulting bend !
Also, I put a 4x4 into a post holed hole around 2 ft deep and tamp rocks and soil while plumbing the remaining 6ft of pole.
Some C type screw on pipe clamps are used to attach to the post.
Bob
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VA7CPC
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Posts: 2354




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« Reply #5 on: January 11, 2013, 10:40:40 PM »

I built a 20m dipole (full-size, 33' long) out of 20 gauge copper wire, with loading coils at the center of each element, sized for resonance on 40m.  For 20m operation, short out the coils with short pieces of wire ending in alligator clips.  Coax feed in the center.

I tied it to a 31' windsock pole (similar to Spiderpole, but lighter construction).  That gave me a vertical dipole, usable on both bands.  With a tuner, usable on 30m on everything else.

It's a perfect "picnic-table portable" antenna, because you can tie the base to a picnic table and use it un-guyed.  Results were very good on 20m, and tolerable on 40m.

.          Charles
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N3OX
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Posts: 8852


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« Reply #6 on: January 12, 2013, 09:14:43 AM »

I know you put the matching right at the bottom of the antenna in a little dog house type thing, but would an autotuner work? 

Yeah, absolutely. I put something together out of stuff I had around because I have a lot of stuff around, and I when I built that antenna I was just starting to use some tools to calculate matching networks and stuff.

Quote
Also, it was very good to chat with Ethan and you at AGU this year!  

You too! Hope things are going well there...

CU
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
G4AON
Member

Posts: 512




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« Reply #7 on: January 15, 2013, 07:50:40 AM »

See my web page at: http://www.astromag.co.uk/vertical/

Just a few ideas put on a page to help other antenna builders.

73 Dave
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W6EM
Member

Posts: 697




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« Reply #8 on: January 16, 2013, 05:17:32 PM »

The best source I know of for fiberglass tubing sections is Max-Gain Systems of Marrietta, GA.  www.mgs4u.com  Sold in 8 foot sections of everything from 1/4 inch on up.  They have tables at most of the larger hamfests in the Southeast.  Round and square tubing.

One can make a great VHF/UHF multisection collinear using alternating 1/2 wave sections of smaller coax inside the tubing.

My mental cobwebs seem to recall that an antenna called the "StationMaster," commercially made by Phelps Dodge many years back, used beeswax to support the coax sections inside a tapered fiberglass rod.  The melting temperature of beeswax is higher than that of parrafin wax.  

« Last Edit: January 16, 2013, 05:37:47 PM by W6EM » Logged
N3LCW
Member

Posts: 133




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« Reply #9 on: March 24, 2014, 12:06:54 PM »

I know this is dated but here goes anyway.

No one mentioned an Inverted L with a remote auto tuner at the feed point.  Using two 31 foot poles as supports makes a very highly effective antenna for 10-80M, even with a modest amount of counterpoise wires, either buried or elevated.  Light weight #22  wire could be easily supported.  A 30 foot vertical length with a 60 foot horizontal length will work great even on 80M.  No guys would be needed if the poles are carefully mounted.  I've found those 4ft or 5ft green chicken wire fence posts driven into the ground a very stable mount for these poles.  Throw a 4ft long, 1.75" sch 40 PVC tube over the fence posts, strap the pole to the PVC with bungee cords, and your set.

Andy
N3LCW
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