Hi,

It seems that my location boasts 60 to 110 mph winds on a regular
basis. I had put up a 1/4 wavelength 20m vertical with 1/8 wavelength
radials elevated at 7 feet, with rope guys... and the wind blew it
apart like so much tin foil!

Does anyone know of a decent commercial design for less than $1000 for
a free standing 30 to 40 foot support that can take this darn wind???

Thanks,

The Eternal Squire

It begs the question, what was it made of? It must have been very thin metal
to blow apart only 16 feet, guyed by ropes.

Please enlighten us.

wrote in message
oups.com...
Hi,

It seems that my location boasts 60 to 110 mph winds on a regular
basis. I had put up a 1/4 wavelength 20m vertical with 1/8 wavelength
radials elevated at 7 feet, with rope guys... and the wind blew it
apart like so much tin foil!

Does anyone know of a decent commercial design for less than $1000 for
a free standing 30 to 40 foot support that can take this darn wind???

Thanks,

The Eternal Squire

Ground system:

5 foot of 1 inch diameter galvanized iron pipe, halfway stuck in ground
with concrete.
1 inch diameter galvanized coupler
5 foot of 1 inch diameter galvanized pipe
1 inch to 3/4 inch copper reducer
1 foot of 3/4 inch copper pipe
4 tees: 3/4 inch thru vs 1/2 inch out, soldered lengthwise along
copper pipe.
an 8 foot length of 1/2 inch copper pipe soldered into each tee
tees are reinforced above and below radials with a hose clamp
coax shield connected to top of copper pipe

Radiator:
10 feet of 3/4 inch diameter copper pipe
9 foot carbon fiber fishing rod, handle epoxied and inserted into pipe
a wire is attached to copper pipe and run up to end of rod.
Hot end of coax connected to bottom of copper pipe

Ground system and Radiator are connected in-line with a PVC twist shaft
coupler designed for 3/4 inch pipe, weather sealed with epoxy. A gap
of 1 inch between pipes inside the coupler is filled with styrofoam to
prevent contact.

Rope guys are econnected to the top part of the shaft coupler, as the
middle of the shaft coupler is predicted to be weakest point.

Sure enough, a continuous wind in excess of 60 mph vibrated the shaft
coupler into 2 pieces despite the guys, the radiator then collided with
a radial, knocking a radial out of alignment and ripping apart a hose
clamp. I suspect the wind is going to finish the job overnight.

Sigh,

The Eternal Squire

dude it's 60-100 mph wind! You're gonna have to shell out bucks to make
anything that can stand up to that for any length of time.

wrote in message
oups.com...
Hi,

It seems that my location boasts 60 to 110 mph winds on a regular
basis. I had put up a 1/4 wavelength 20m vertical with 1/8 wavelength
radials elevated at 7 feet, with rope guys... and the wind blew it
apart like so much tin foil!

Does anyone know of a decent commercial design for less than $1000 for
a free standing 30 to 40 foot support that can take this darn wind???

Thanks,

The Eternal Squire


I use a fishing rod with a wire centre conductor for 40 metres band
(33`without guys), with a 5` mounting pole buried in the ground ....you
ought to see that mother bend ...... hasn`t fallen or blown down yet!!!

;-)

Lee.......G6ZSG.....

wrote:

Hi,

It seems that my location boasts 60 to 110 mph winds on a regular
basis. I had put up a 1/4 wavelength 20m vertical with 1/8 wavelength
radials elevated at 7 feet, with rope guys... and the wind blew it
apart like so much tin foil!

Does anyone know of a decent commercial design for less than $1000 for
a free standing 30 to 40 foot support that can take this darn wind???

Thanks,

The Eternal Squire


Maybe you should move!


Stan
AH6JR

wrote:
Hi,

It seems that my location boasts 60 to 110 mph winds on a regular
basis. I had put up a 1/4 wavelength 20m vertical with 1/8 wavelength
radials elevated at 7 feet, with rope guys... and the wind blew it
apart like so much tin foil!

Same kind of location here, wide open to the Irish Sea.... but that
wasn't a big antenna, and with the guys it certainly should have stayed
up.

You're missing something here. Typical ham antenna structures are a
mixture of over-design and weak spots, so maybe you should look at the
wreckage in more detail and try to learn something from it.

OK, I just read your second posting and pulled this back from the
outbox. From the top downwards...

* Fishing rod good. Carbon fibre not good (possibility of losses and
detuning compared with plain fibreglass; definite loss of money compared
with plain fg).

* Copper pipe not good in these long lengths. Ask yourself why everyone
else uses aluminium.

* PVC pipe coupler not good... well, that you know.

* Again, copper pipes not good for radials. Copper pipe tees not good
for supports. If the top part hadn't fallen down, those pipe tees would
probably have been next to go.

* 3/4-in copper for your main support mast is a big mistake. The heavy
radials flopping up and down create a huge leverage at this point, so
that copper will be rapidly work-hardening and well on its way to
breaking (may well have done so by your morning).

* In your wind conditions, 1-in galvanized pipe is way too small for the
lower part of your mast. The only thing that kept it from snapping is
that something else broke first.

* Were your guys helping to reduce the bending forces at the point where
the coupling snapped... or helping to concentrate them? In your
particular case, I'd bet the latter.

The big lesson is that the construction of a copper J-pole for 2m will
not scale up to 20m wavelengths... basically because copper tubing is a
poor structural material, and as the model-makers say, "You can't scale
Nature." When you increase the scale by 10x, you have to use different
structural materials and techniques.

Again, ask yourself why everyone else uses larger tubing for masts; uses
aluminium, not copper; and doesn't use small, soft plastic plumbing
fittings. Have a look at HF antenna construction in the antenna
handbooks and catalogues, and do what they do... because there's a
reason for it.


Does anyone know of a decent commercial design for less than $1000 for

Hang on now - that would be spending money to *avoid* learning
something.

a free standing 30 to 40 foot support that can take this darn wind???

One option that's surviving very strong winds here is a tapering
fibreglass pole. I'm using a Spiderbeam telescopic pole that is almost
40ft high and strongly made:
www.spiderbeam.net/english/pole.php

The pole is tied to a very solid clothes-line post at about 7ft, and
also guyed at about the 30ft level to prevent the worst of the swaying.
In very strong winds it bends into an alarming S-shape, but by the
nature of fibreglass it also springs back again.



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

I had put up a 1/4 wavelength 20m vertical with 1/8 wavelength
radials elevated at 7 feet, with rope guys... and the wind blew it
apart like so much tin foil!

It decided to blow it down so you could rebuild it with the proper
length radials... 1/8 radials won't work too well. Why would you
use those? They are fairly useless on an elevated ground plane.
The decoupling of the feedline will be poor, and probably lots
of rf in the shack. Needs 1/4 wave radials to work correctly.
As far as the wind, you need to build a little stouter... Normally, a
short 16 ft radiator should be easy to keep up, even with 60 mph
winds. Shouldn't fall down if it was guyed. My 40 m ground plane
was 32 ft tall, mounted at 36 ft. Nearly 70 ft tall at the top. Only
my mast was guyed. No guys were used on the radiator. I used
a telescoping metal mast which shrunk down to a very thin size
as it neared the top. Was quite flexible. In heavy storms, it would
nearly blow sideways, but it never hurt it, and it always popped
back up straight after the wind left. That particular antenna cost
nothing..Made from an old butchered up 5/8 wave CB antenna as
the base radiator, and then extended with extra tubing.
Was looking at your 2nd post, and notice the details. Not
exactly the recipe for a solid antenna...You would be better off
using an old butchered CB antenna, etc. The cushcraft AR-10
makes a good platform for verticals also. It's a 16-18 ft 1/2 wave
antenna for 10m. If you use only the radiator, and redesign the
feed, thats a decent quicky 20m 1/4 wave vertical. The old heavy duty
5/8 CB antennas are good to use also. They have heavy duty
bases that are often reinforced. Thats what I use for my tall 40m
antenna, and never had a problem, but I did strengthen by adding
extra tubing , inside the tubing. IE: double wall... Copper is pretty
soft, and shouldn't be used for anything that needs real strength.
MK

wrote:
It seems that my location boasts 60 to 110 mph winds on a regular
basis. I had put up a 1/4 wavelength 20m vertical with 1/8 wavelength
radials elevated at 7 feet, with rope guys... and the wind blew it
apart like so much tin foil!

I use 2x(2"x4"s) fastened together for a 4"x4" support and 1/4WL
wire radials as ground-plane/guy-wires. The vertical section is
assembled from 6' telescoping aluminum sections following the beam
element design guidelines in the ARRL Antenna Book. The top 8.5'
is a stainless steel CB whip. It has withstood wind gusts of about
100 mph. As others have said, copper is a poor choice for a 20m
vertical.
--
73, Cecil http://www.qsl.net/w5dxp

Actually, pure aluminium is even softer and far more ductile than
copper and is useless as a construction material.

But some grades of copper/aluminium alloy, known in the UK as
Duraluminum or just Dural, have properties approaching carbon steel
and are corrosion resistant. Light in weight. Easily machined and
extruded. Maintain a good appearance. High electrical conductivity.
More expensive than steel.

They are used, for example, for ladders and scaffold poles. When used
for tubular rigid dipoles and antenna masts they collapse under high
winds only because the wall thickness is too thin. Commonly used for
radio chassis and sheet metal roofs.

But NOT pure aluminium, just a few percent of copper.
----
Reg.


"Cecil Moore" wrote in message
. com...
wrote:
It seems that my location boasts 60 to 110 mph winds on a regular
basis. I had put up a 1/4 wavelength 20m vertical with 1/8
wavelength
radials elevated at 7 feet, with rope guys... and the wind blew it
apart like so much tin foil!

I use 2x(2"x4"s) fastened together for a 4"x4" support and 1/4WL
wire radials as ground-plane/guy-wires. The vertical section is
assembled from 6' telescoping aluminum sections following the beam
element design guidelines in the ARRL Antenna Book. The top 8.5'
is a stainless steel CB whip. It has withstood wind gusts of about
100 mph. As others have said, copper is a poor choice for a 20m
vertical.
--
73, Cecil http://www.qsl.net/w5dxp