Aluminum tubing for vertical antenna
Hank Zoeller
I'm contemplating putting up a vertical antenna for HF use. I'm looking
at an approximate height of 30 feet or so. I am thinking of using
aluminum tubing (0.058" wall) in a 'telescoping' manner. Here are my
questions (so far):
1) Diameter. For wind resistance, should I start with something like 1
inch diameter and work down to 3/8 inch? Would the antenna be stronger
if I started with 2 inch diameter and worked down to 1-3/8 inch?
It would seem to me that the larger diameter might be better able to
withstand wind but it would also offer more resistance to wind possibly
negating the additional strength. But, I have no experience to draw
from. So, fat or slim?
2) I am planning a set of guy ropes at about the 12 foot level, a bit
over 1/3 height. Is there a better height for guy ropes? I can put as
much concrete in the ground as I like, and a very robust mount system is
possible. Is there any way to make an unguyed 30 footer that isn't a
tower form factor? Something like making the bottom 12 feet or so from
2 inch diameter, 1/4 inch wall tubing and then light weight tubing from
there up to full height?
--
73, Hank
Cecil Moore
When I bought my aluminum tubing from Texas Towers, they had
a computer program that calculated and specified all of the above.
http://www.texastowers.com
--
73, Cecil http://www.qsl.net/w5dxp
n3ox...@gmail.com
the radius, but the stiffness of a piece of tubing is proportional to
the fourth power of radius.
So, as you make the tubing bigger, the stiffness goes up much much
faster than the windload, so bigger tubing will always be stronger
unless you make the wall very, very thin compared to that of the
smaller tubing.
Now, the weight of the piece goes up too, and the price is proportional
to the weight, so you don't see a lot of antennas made of 5 inch
aluminum tubing when they don't need to be.
For a freestanding vertical, you're going to get the best results with
a taper. It's good for the tubing to get thinner as you go up, because
the big problem with a freestanding pole is that the wind is trying to
tip it over. The mount at the base has to be strong enough to take
this torque. The wind has more leverage when it's acting on the tip of
the vertical than when it's acting further down, so having the vertical
thin at the top helps reduce the load on the base.
Cecil's suggestion about the Texas Towers calculator is a good one.
Also, after you put up a vertical you'll have more intuition about
this. I wouldn't make it a 1 inch vertical all the way up :-).
I had a 40m vertical, 4 elevated radials at 15 feet and 1 inch tubing
from that point up to about 25 feet, with smaller tapered tubing and
rod above that. It worked OK, but had to be guyed in two places! It
also snapped in half in a windstorm. Bad mechanical design, but I made
do because I had the tubing. It would have been a much nicer antenna
if I'd purchased the proper materials.
73,
Dan
n3ox...@gmail.com
tubing topped with smaller stuff... so 1 inch tubing from the 15 foot
level to the 40 foot level with respect to the ground.
The feedpoint was at the top of 15 feet of radio shack TV mast.
Flimsy bugger, anyway... pretty good antenna though!
73,
Dan
Rick
And what, if any, means are you considering to provide for tipping it
over?
I wonder if it is practical to install say, 4X4 posts in the ground
about 5 inches apart, with another 4X4 as the vertical support for
the aluminum pole. The aluminum pole bolted to the 8 foot long 4X4 at
about the 6 foot level. Would the wood detune the antenna?
Rick K2XT
Cecil Moore
I have mine with the bottom mounted at 20 ft using 2x4s.
The tubing is isolated from the 2x4s by a sleeve of PVC
pipe. There is no noticeable detuning by the wood support.
Hank Zoeller
> When I bought my aluminum tubing from Texas Towers, they had
> a computer program that calculated and specified all of the above.
>
> http://www.texastowers.com
Cool! Does it calculate the size to use based on expected wind speed?
I looked around on their web site and didn't find a calculator so it
must be something they do with you on the phone? I'll call 'em Monday
and see what they have to say.
Thanks for the tip!
--
73, Hank
Hank Zoeller
> The windload on a piece of tubing of a given height is proportional to
> the radius, but the stiffness of a piece of tubing is proportional to
> the fourth power of radius.
Thanks, Dan, this is really useful info -- just what I was looking for.
What do you think of having the bottom 12 feet be 2" diameter by 0.25"
thick tubing? If I went up another say 16 feet with 0.059 thick tubing
properly telescoped do you think I'll need guy ropes?
I've been thinking of overlapping the thin tubing in such a way that
there would always be two layers of it for the entire length of the
antenna. It would seem to me it would be much stronger without
increasing the wind loading at all.
Thank you for your insights.
--
73, Hank
Hank Zoeller
> How are you planning on mounting the alum. tubing at ground level?
> And what, if any, means are you considering to provide for tipping it
> over?
I haven't yet decided how I'm going to mount this thing. Now, I'm
leaning toward (pun intended) a larger size of tubing than I initially
thought. Once I make a final determination on the tubing size then I'll
turn my attention to the mount.
Fortunately, I have a machine shop so I ought to be able to fabricate
something worthy.
As to the detuning, I'm not concerned at all about resonance as I'll
have a 1-kw antenna coupler mounted at the base of the vertical. I
would be concerned about other effects so I'll likely make the mount
with as small an electrical footprint as possible.
The fold-over idea is good. I think I'll probably make two of these
things, one about 30 feet high and another about 16 feet high for the
upper HF bands. It would be cool to be able to switch them out easily..
--
73, Hank
Roy Lewallen
in my back yard. They're free standing, no guys. They went through one
wind storm with gusts in the 80 mph range, and all other weather,
without damage. Each is made of three pieces of telescoping 6061-T6
tubing, 1-1/4, 1-1/8, and 1 inch diameter. The support is an 8 foot
chain link fence line pole (about 1-1/2 inch diameter, steel), driven 4
feet into the clay ground. The antenna element is clamped to it with
muffler clamps, insulated with a couple of slices of thick wall plastic
conduit about 1/4 inch thick.
Roy Lewallen, W7EL
Cecil Moore
> Cool! Does it calculate the size to use based on expected wind speed?
As I remember, you give them the wind speed and they give you
back the specifications. They ran the program for me while I
was standing there in the lobby wondering what size to buy.
I requested a self-supporting 33 ft monopole rated at 75 mph
but changed my mind when I found out what that required -
more than double the cost of a guyed monopole. Also building
it out of six foot sections instead of 12 foot sections reduced
the cost considerably. ME's probably understand why but, as a
EE, I was surprised.
Jozef
careful of sizes as along they fit snugly into adjacent pieces when they
were slotted. I used hose clamps. I made it 33ft and 3 inches tall (1/4
wave on 40). It has 32 radials of various lengths for the non-WARC ham
bands 40 meters and higher. 16 of them are 34 feet long for 40. SWR on 40
meters is 1.2 to 1 without any adjustment at 7100. The vertical covers the
entire band. I use a Palstar AT1500CV transmatch on other bands and run 700
watts when needed. I can work anything I can hear and I work tons of DX.
The antenna is very quiet for a vertical. The Palstar has no problem
matching this vertical on all bands 40 through 6 meters including WARC
though 12 meters is the trickiest. Works much DX on all bands whenever I
try Peter I Island, Kiribati, etc., though I use other antennas on bands
other than 40 cut appropriately. Cost of the antenna was $0.00. I used
scrap tubing, scrap #12 or thicker radial wire, leftover rope for 3 guys at
18 feet, leftover 4BTV base. This antenna has been up for months on a hill
at 1100 feet and survived 80 mph plus gusts.
"Hank Zoeller" <bogusa...@dontbothernotvalid.com> wrote in message
news:44c07393$0$10058$c3e...@news.astraweb.com...
Jozef
http://www.metaphoria.us/hamradio/40monoband.htm for the 40 meter
monobander vertical
http://www.metaphoria.us/hamradio/4BTV.htm for the base with radials. The
radials are now covered by grass that I mow with a hand manual non-powered
Scott's push mower.
73, Jozef WB2MIC
"Hank Zoeller" <bogusa...@dontbothernotvalid.com> wrote in message
news:44c07393$0$10058$c3e...@news.astraweb.com...
Cecil Moore
> I took scrap pieces of aluminum tubing lying around, not being particularly
> careful of sizes as along they fit snugly into adjacent pieces when they
> were slotted. I used hose clamps. I made it 33ft and 3 inches tall (1/4
> matching this vertical on all bands 40 through 6 meters including WARC
> though 12 meters is the trickiest.
That antenna is 5/8 wavelength on ~17.5 MHz. Above 21 MHz,
most of the radiation is lost at a high elevation angle.
Such an antenna is a poor performer on 15m, 12m, 10m, and
6m. Matching doesn't mean much for a monopole appreciably
longer than 5/8 wavelength.
ji...@specsol.spam.sux.com
I have an almost identical vertical with a relay controlled loading
coil I switch in for 160 and 80M and a SGC tuner.
Works great 160 to 30M.
Marginal at 20M and goes to poor from there up.
--
Jim Pennino
Remove .spam.sux to reply.
Jozef
try Peter I Island, Kiribati, etc., though I use other antennas on bands
granted, you're also make a case against success. It works. Though as you
suggest, with handicaps.
"Cecil Moore" <myc...@hotmail.com> wrote in message
news:Ebqwg.133521$dW3....@newssvr21.news.prodigy.com...
Hank Zoeller
> For about 20 - 25 years I've had four verticals of about 33 foot height
> in my back yard. They're free standing, no guys. They went through one
> wind storm with gusts in the 80 mph range, and all other weather,
> without damage. Each is made of three pieces of telescoping 6061-T6
> tubing, 1-1/4, 1-1/8, and 1 inch diameter.
[trimmed]
Roy,
Thank you very much. There's nothing like tapping the experience of
others. I'm really happy to hear I can build a freestanding vertical!
(But, I'll buy some spare aluminum anyway..)
--
73, Hank
Hank Zoeller
> I neglected to provide the following links:
>
> http://www.metaphoria.us/hamradio/40monoband.htm for the 40 meter
> monobander vertical
> http://www.metaphoria.us/hamradio/4BTV.htm for the base with radials. The
> radials are now covered by grass that I mow with a hand manual non-powered
> Scott's push mower.
Jozef,
What did you use for staples for the radials?
Thanks,
--
73, Hank
n3ox...@gmail.com
Just wanted to add that you don't need 1/4 inch wall stuff anywhere in
a 33 foot vertical.
If you have it lying around you could use it, but the extra weight
really isn't worth it. Same for reinforcing by thickening the tubing
on the inside.
A hollow tube 2" in diameter with 0.058" walls is about 3 times stiffer
than a SOLID 1" rod.
Now, strength and stiffness are two different things, but you're better
taking the aluminum and making a fairly thin wall tube of large
diameter if you're trying to make a strong, stiff element.
For the price of one 12 foot 1/4" wall 2" tube you can buy the whole
vertical in 2" 0.058 wall tubing and the next telescoping size for
joints.
1/4" wall would be good if you're going to guy it and put a tribander
on top!
I'd go with Roy's vertical design, in fact. My antenna was a mess of
found aluminum, tent poles, etc. Might have even been 7/8" now that I
think of it.
This means that Roy's bottom section, if 0.058 wall 1.25" diameter 6061
was at LEAST 3 times as stiff as my 7/8" OD 3/4" ID 1/16" wall stuff,
and that's assuming I was using a good, stiff grade of aluminum, which
I wasn't.
Incidentally, Cecil, I think the 12 footers are more expensive because
you can UPS ship 6 footers anywhere and can't do that with 12
footers... it may be that it's just cheaper to keep the 6 footers in
stock because the market is bigger. Could also be that it's cheaper
for TX Towers to get them in .... dunno. It's too bad though, 12 foot
continuous sections would be good for this sort of thing.
73,
Dan
Hank Zoeller
> Hank,
>
> Just wanted to add that you don't need 1/4 inch wall stuff anywhere in
> a 33 foot vertical.
Thanks, Dan. I see that now and I think I'll start with 2" diameter
tubing in 6' lengths and taper down accordingly. I do get some serious
wind here from time to time.
Thanks to all who responded; I'm moving forward with considerably more
confidence in the outcome..
--
73, Hank
Sal M. Onella
"Hank Zoeller" <bogusa...@dontbothernotvalid.com> wrote in message
news:44c07393$0$10058$c3e...@news.astraweb.com...
http://www.valcom.ca/Guelph/products/highfreq/as3772b-u_photo.html This is
built for navy shipboard use so it may be "scary expensive." These are
virtually indestructible. You have to hit one with a crane boom to break
it. It is exactly what you described in your last paragraph. This size
whip covers 2 - 30 MHz with a tuner.
The Navy has used many 35-foot whips over the years. There were
five-section versions, but any you found now would probably be too corroded
to be of use.
Hank Zoeller
> http://www.valcom.ca/Guelph/products/highfreq/as3772b-u_photo.html This is
> built for navy shipboard use so it may be "scary expensive." These are
> virtually indestructible. You have to hit one with a crane boom to break
> it. It is exactly what you described in your last paragraph. This size
> whip covers 2 - 30 MHz with a tuner.
>
> The Navy has used many 35-foot whips over the years. There were
> five-section versions, but any you found now would probably be too corroded
> to be of use.
Actually, I *did* find one of those things!
http://www.american-milspec.com/p961.html
Alas, it's a bit too tall for my use. I'm thinking of using a 26' whip
with a remote coupler (Harris RF-601) for operating from 40 through 15
meters. Or, I might go to a 30' whip for ops on 60 through 18 meters.
I haven't made up my mind yet although I'm leaning toward the 26' version.
If I go that route I might pick up a commercial, little brother of that
massive Navy style whip - the Shakespeare 5300. It's sold as a 28' whip
but it's actually 26' as they use the bottom two feet for a mounting
sleeve. It's made for shipboard use but is substantially lighter than
the Navy 35' whip. It's only 2-3/8" in diameter, for example..
Time is a precious commodity, at the moment, but I still might roll my
own from Texas Towers Aluminum.
73,
--
HZ
Bitz
self supporting and have a wind rating of 90mph. In a vertical
configuration with guys they would never blow down in a 100 years.
Dont forget the Navy Whips by valcom etc were designed to take a take
from a wave etc. Tons of water would bend any noodle. They really a
overkill. Some were also designed to take shock blasts from canons etc
and fatigue from 20,000 rounds weakening the metal.
Theres a lot of Yagi element stress element software around, i would use
it and design it to your spec. I would make sure you use 6061 which is
the most corrosion resistant and has the most strength. Array Solutions
sells element stress software from some Ham Kurt Andress or something
like that. ON4un also has some free software with his latest book.
How you gonna tune this beast on all bands? Would be interested to hear
how you going about this.
Pat
Hank Zoeller
> How you gonna tune this beast on all bands? Would be interested to hear
> how you going about this.
Same way the Navy does it! With a Harris RF-601 remote antenna coupler.
Only way to go in my view..
But, for the record, I'm not planning on using it on all bands -- only
on the bands where it has some chance of being an effective radiator.
That's why I'm thinking of either 30' (60 thru 17 meters) or 26' (40
thru 15 meters).
73,
--
HZ