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.

The pipe thread area is a point of weakness and the overlap is way to short
to provide any strength. A better alternative is aluminum tubing with .058
wall thickness.

This allows decending sizes to fit with in one another. For example a 1"
6061 T6 10 foot long has an inside diameter of .884 and a 10 foot section of
7/8" (.875) will slide right into it. This would allow an overlap of almost
4 feet providing all the strength you need.

Good luck on your next installation.
wrote in message
oups.com...
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

My suggestion would be the following:

Cut that buried 1" pipe about a foot over the ground, to serve as a
ground support for your new antenna.

Get a heavier steel pipe (ca 1"3/4 - 2") that will fit over the 1" pipe,
and perhaps 10 foot long.

Get a cheap fiberglass (not carbon) fishing rod ca 18 feet long, (1/4
wave on 20m)

Tape a 1/4 wire radiator to the fishing rod, and feed with coax at
bottom of rod.

Attach fishing rod securely to the top of your new mast pipe.

Rise the pipe and fishing rod assembly vertically and guy at the point
where the fishing rod is attached.

Now you can run elevated wire radials along the guy ropes, and you
should probably also ground the coax shield to the mast pipe at the feed
point.

Enjoy!

73 de Hans, SM3PXG




wrote:
Ground system:

5 foot of 1 inch diameter galvanized iron pipe, halfway stuck in ground
with concrete.


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



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.



Sigh,

The Eternal Squire

Now THAT's a practical idea...

Thanks!

The Eternal Squire

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