Thanks for all the responses, too many to reply to individually. I haven't
decided yet which way to go for sure, but am leaning toward something like
40-50' of tower with mast 'stinger' out the top. Some of the commercial
verticals look interesting, but the tapers and number of parts make them
look too flexible.
The original question:
I am trying to decide what to use to build 4 new 80m verticals for a
4-square upgrade here. My criteria are:
1. full size 1/4 wave verticals, no top or base loading.
2. must be able to standup to new England winters at 2000' with ice and wind
3. must be new material, I don't want to go scrounging for used tower or
pipe.
4. prefer only 1 guy level, but will do 2 if necessary.
5. prefer to stand up complete, but will climb to add top section(s) if
necessary, crane or truck access will be very hard to this spot.
6. prefer something that can be delivered to here, truck delivery is not a
problem, I don't want to have to haul long stuff myself.
A couple other things I probably should have noted:
7. no concrete. Where this is going I could get a backhoe in, but probably
not a concrete truck to pour anything for self supporting verticals. I
suspect any holes in this area would fill with water pretty quick anyway.
8. I am using a raised wire array with a Comtek box now hung around a 120'
tower.
As to some of the other questions. I have had 40m and 80m 4-squares here
for years in various configurations and had time to compare them with
various beams and inverted V's... this is a quick summary:
40m:
1. halves of 40-2cd elements that broke from ice, ground mounted, lots of
radials, Wilkinson power dividers... worked, but not very good.
2. some kind of pipes, on ground, lots of radials, fed with home brew
Christman type network built with coax stubs and transformers. It was
inside an 80m 4-square and was bad.
3. rohn pipe towers, raised on pressure treated supports, 4 raised radials,
Comtek box. Works fine, still in use. This has been compared against
40-2cd at 90', 120', and 180' and now 40m4lldd's at 105' and 180'. It was
often as good or better than the 90' 40-2cd, not as good most of the time as
the one at 120', and when the 40-2cd was at 180' it was rarely any better.
We still use it for occasional quick switches to other directions or when
precipitation static is bad on the yagis.
80m:
1. 48' base loaded pipes (chain link fence top rail), lots of radials, 2
different locations, Christman type network built with coax stubs and
transformers. This was never quite good enough to be that useful, though it
was interesting at times for longer paths or to get a polarization change.
2. Raised Feedpoint wire vertical hung around 120' towers (2 different
ones), with either a single raised radial or now with the raised radial plus
150' of 2x4 fence on the ground under each one. Comtek box. This used to
work good, but had to be moved and hasn't been quite the same since. Where
it got moved to ended up too close to 180' tower guy wires I think. It is
good for changes in polarization and sometimes it runs better than 150' high
inverted v.
Why I like 4-squares.
1. polarization difference from inverted V or yagi. Sometimes we have
noticed that the arriving dx signals on 160m and 80m seem to favor one
polarization or the other. Perhaps it is related to takeoff angle also, but
switching from an inverted v to a vertical can uncover a whole new group of
stations to run that weren't there on the other antenna.
2. its nice to hear those w4's off the back of the 4-square drop way down in
qrm level while the Europeans come up or at least stay the same.
3. Sometimes they are the best listening antenna, even over the Beverages.
Seems especially true around grey line and on long path openings.
4. Zero rotation time. This can be nice to grab a south American multiplier
without turning a yagi away from Europe.
The responses, in no particular order (I will put this on my web site tech
reference section in the near future):
----------------------------------------------------------------------------
K0TV:
My 4sq here is full size 1/4 wave and is constructed from 2" pipe at the
base for the first 21 feet, 2" x 1/8 wall tubing for the next 24, and then
sufficient 6 foot telescoped .058 wall tubing for the top starting at 2 1/8"
for the first piece. The 2" pipe has an inner diameter of 2.08" and needs to
be cut at 45 degree intervals and then clamped onto the 2" tubing with SS
hose clamps. My antenna is resonant at 3550 but I have a series 1000 pf cap
in each element that can be switched in to raise the resonant point to 3750.
The guying is at two points. I use Dacron antenna rope to nearby trees. My
4sq is in the woods.
My 4sq has 24 quarter wave ground mounted radials on each element (not
interconnected) and it seems to play EXTREMELY well.
Bases are made from PVC electrical conduit mounted on a 4x4 into a mailbox
spike. I'm using the Comtek 4sq controller and at resonance I see about 5
watts into the dump load with 1500 forward into the array. The VSWR is very
close to 1:1 regardless of frequency across the band.
K4SQR:
Rohn 25G sections: many have a Delrin material machined to use as insulators
from a base section in concrete to the first stick. Then a 10' stick to a
tapered top with the locking screw = 29' of tower. Tapered aluminum from 2"
down. The locking screw permits adjustment of the stinger for resonance.
3 sections of BX/HBX tower (now made by Shelby. See www.wb0w.com click on
catalog then towers. I believe he can order the Hy-Gain insulators for the
HBX tower for you. Then a severe tapered aluminum stinger of 51 feet ala
K3LR's versions. His 2x 4-Squares on 80 do quite well NE & SW!! Then he
uses the far left array for NW and the far right array for SE so neither
fires thru the other 4-SQR. I was invited to operate CQ WW SSB 2004 and
wished I could operate 75 mtrs. it was so impressive. Being one of the 40
mtr. ops was also a big
treat for this old man, Hi. We set a new record for Multi 2 by exceeding
previous record over 6 million points.
Both of the above arrays would require one set of guys at top of tower to
withstand your New England Nor Easters in my opinion. K3LR's arrays are not
guyed.
W5LT:
Check out the Array solutions 80m vertical, AS-80V-FS. It folds over with a
removable winch arrangement for adjustments, and you can use it with one of
their phasing boxes to make a beautiful 4-square. It is made from tapering
sections of aluminum tubing. There is also one offered using sections of
Nello tower for a portion and a 'stinger' on top. Requires one level of
guying apparently. It is the AS-25N-80.
N8JV:
The way I do my 4 sq for 80 mtrs is I have a 132 ft vertical made out of 100
ft of rohn 25 and 32 ft of Alum mast and some smaller alum tubing. I have 3
guy levels with Philly an the tower sits on 3 max-gain nylon insulators.
>From the top of this tower I have 4 nylon ropes going to guy points every 90
deg. From these ropes I suspend 4 - 66 ft pieces of #10 copper wire spaced
for my 66 ft square. I
then buried abt 5 miles of radial wire to make the radial system for my 80
mtr 4-sq and my full size 160 mtr vertical. The entire system works quite
well.
If I did this again, I would put up a 200 ft tower with no insulators and I
would suspend wire 4-squares for both 80 & 160 from this support. And I
would also put a rotor and 40 mtr beam on the top of the 200 ft tower.
N5TU:
HyGain now has an 80-meter tubing vertical. They advertise it as a mast.
The model is ATM-65. Here are their specs:
The ATM-65 is an 11-section multi-purpose aluminum telescopic pole that can
be used for vertical antennas or as a mast. Length is 64 feet when fully
extended. Only 6 feet long when fully collapsed without clamps. Great for
portable or temporary and permanent use---traveling, camping, etc. Includes
one size of each of the following slotted tubing:
0.625"OD X 0.035"Wall-th X 0.555"ID
0.750"OD X 0.058"Wall-th X 0.634"ID
0.875"OD X 0.058"Wall-th X 0.759"ID
1.000"OD X 0.058"Wall-th X 0.884"ID
1.125"OD X 0.058"Wall-th X 1.009"ID
1.250"OD X 0.058"Wall-th X 1.134"ID
1.375"OD X 0.058"Wall-th X 1.259"ID
1.500"OD X 0.058"Wall-th X 1.384"ID
1.625"OD X 0.058"Wall-th X 1.509"ID
1.750"OD X 0.058"Wall-th X 1.634"ID
2.000"OD X 0.120"Wall-th X 1.760"ID
Also includes 10 hose clamps. Guying is required if the overall height is
greater than 30ft. Top section is 0.625" OD and bottom section is 2.00"OD. X
0.120" wall thickness.
Also, they have a mounting plate with a couple of insulators that they do
not advertise.
I've got some 1/2" tubing that I will use to extend this to work on the CW
portion of the band.
W1FV:
Here's a diagram of the construction of my 80m verticals:
http://i9.photobucket.com/albums/a59/jake951/Radio/80m_vertical_1.jpg?t=1166
296147.
This is the old Colatchco vertical design by W1FC and W1CF from the 1980's.
They are 61 feet tall and use aluminum tubing sections, starting at 2" OD at
the bottom and tapering to 5/8" at the top. There is also a short whip
extending beyond the top section of tubing and a small wire capacitance hat
at the 48' level (part of the guying system). The tapering keeps the
vertical from becoming top-heavy and makes it very easy to erect. It's
hinged at the bottom and one person can walk the whole thing up into place.
Guys are attached at two levels (24' and 48').
I have an array of these that has survived over 20 years without failure.
N9ZV (ZeroFive-Antennas):
I make a guyed version ,It comes with a fold over ground mount and 3 guy
collars. You can guy it 2 times but 3 times is recommended.
The base mount is 4 feet long L channel aluminum that is driven in the
ground. The vertical sections are Base insulator is 2 1/2 inch OD
2 1/2 OD by .125 wall 8.5 foot long
2 1/4 OD by .125 wall 8.5 foot long
2 inch OD by .125 wall 8.5 foot long
2 1/8 OD by .058 wall 3 feet long
2 inch From 2 1/8 down is .058 3 feet long.
1 7/8
1 3/4
1 5/8
1 1/2
1 3/8
1 1/4
1 1/8
1
7/8
3/4
5/8
1/2
3/8
Guy points are 12 ,24 and 37 feet
The lower 3 big 6061T-6 sections slide into each other 6 inches and are
secured by a grade 8 through bolt The first 2 1/8 inch .058 wall section of
T-832 aircraft slides over the 2 inch top big section 10 inches and is
secured by 4 number 14 SS sheet metal screws. Then up from there each 3 foot
section is slid in 4 inches and secured with a SS hose clamp ,Then pinned
with a SS sheet metal screws.
K2KQ:
Don't overlook the value of self-supporting lightweight aluminum towers
finished off with a combination of tubing and a stainless-steel whip (such
as an old-style CB quarter wave). Of course, there's no need for the tower
to be insulated if you simply use the tower to hold a suitable wire as the
conductor. We have a Universal 30-ft aluminum tower in Grenada with a steel
tilt-over in-concrete-style base. The tower weighs about 40 pounds and is
self-supporting at 30 ft with about 4 sq ft of top load. You might have to
go to a 40-ft
tower with a tubing and whip top because of your wind and ice conditions.
http://www.universaltowers.com/catalog.htm
N2EA:
If it were me, I'd build around 25G, rather than fooling with tubing. The
Titanex and other verticals are awfully whippy. We put one up, at WJ1Z, in
VT. Thought several times that we were going to break it.
58' of 25g, tapered top, plus a 2" diameter stinger, and you would be in
business, and able to adjust the height, to tweak the drive-point impedance,
if you wanted to. Plus, the 10' sections would be easier to get onto the
site than something longer.
Used 25g is selling for..what? 35-50 bucks a section? You'd need 24
sections..so maybe 1200 bucks worth.
The other approach I'd consider is W3GM's. He used thinwall irrigation
tubing for his 80m array. Guyed it 4 ways, one guyset, and minimized
downforce. This should be considerably less expensive. I think the tubing
comes in 40' lengths, but haven't really explored it. This should be
substantially less expensive...but possibly less robust.
W4TV:
I'd suggest 38' or 48' of the tower with a shorter "whip." It still works
with a single set of guys at 30 or 35' - the whip will be stronger (two 12'
sections of tubing, double or triple walled if needed) and one can easily
get the resonant frequency down to the bottom of the band.
WC1M:
I've seen the Array Solutions verticals at NT1Y. The aluminum tube elements
are very heavy duty. I don't recall the diameter at the base, but they must
be on the order of 4"-6". In any case, they're big enough to be
freestanding. Each element has a heavy-duty base support with a manual winch
mechanism used to raise and lower the element. Undoubtedly, this is a pricey
alternative.
You should check out KT1V's full-size four square. K1RX designed it. The
elements are made of irrigation tubing. I believe several pieces are spliced
together to make each element. Each element has a simple hinged base (can't
remember exactly, but I think it's a couple of 4x4s sunk in the ground with
a long bolt between them.) A couple (?) of sections of Rohn 25 are sunk in
the ground in the middle of the array. There are pulleys on the top and
ropes running to the elements. The ropes are used to haul the elements to
the vertical.
Another option is to use three or four sections of Rohn 25 for each element
base, and telescoping aluminum tubing for "whips" on top of the bases. For
each element, I'd sink a section of Rohn 25 a few feet into the ground, put
insulators on top, and add three sections of Rohn 25. For the whips, I'd use
6-foot sections of telescoping aluminum tubing, e.g., 6061-T6. Simply nest
all the sections, mount to the top of the top section of Rohn 25, and extend
each section in turn, top to bottom. If you start with at least 2" diameter
tubing at the bottom, the whips will be self-supporting. I used an identical
procedure to make a 40m 4-square. BTW, the raised insulators would allow for
either elevated radials or ground-mounted radials. W4AN (SK) had an 80m
4-square built in a similar way. There's still a description of it at
http://w4an.contesting.com/80m.htm. Some of the picture links are broken,
but the text is clear. Bill used fewer tower sections and longer whips.
K3LR:
You might look at the photos on my web site http://www.k3lr.com under the
tab of 80 meter vertical project (two phased 4 squares).
I am using the HyGain Hytower as the building block for 8 verticals. They
are single band, full size (80 only) and use three Rohn BX sections (first
24 feet). The overall length is much longer (stock Hytower is 51 feet total,
mine are 75 feet). I extended the aluminum is several areas to make each
vertical resonant at 3.500 MHz (elements in a 4 square must be longer than
normal). They have survived 75 mph winds and lots of ice storms. They can be
lowered and raised by two men.
K1VR:
Despite your stated criteria, I would say used Rohn 25. On the other hand,
W1CF used 55' Army surplus push up poles, requiring two levels of guying.
The top "guys" were wire for the first 8 feet or so to make up for the lack
of height, and continued with either Kevlar rope of parachute cord. His push
up poles were in a New England swamp for 25 years.
Another approach would be 55' of Army push up poles and then 8 foot CB whips
on top. With a little machining to make the transition, that eliminates the
top loading.
W6TR:
4 homebrew HyGain Hytowers made from 3 sections of Rohn 25 and some oil
filled Nylon insulators and a 30' stinger. I can supply details if needed.
No guys required. If you don't want to build them, buy them from MFJ.
WV1K, K9CT:
http://www.zerofive-antennas.com
K1MK:
A quick round-up of the usual suspects:
* 4" (or 3") aluminum irrigation tubing is best guyed at two levels but
it can be pushed up 'Iwo Jima' style
* Rohn 25 would have to be climbed while being stacked and needs two guy
levels at 60' or 70'
* Rohn/Tubing hybrids, i.e. an extra-long 'stinger.' 30' of
self-supporting Rohn 25 has a capacity of 2.5 sq-ft at 70 mph with 1/2" ice.
37' of 3" tubing has a projected area of 9.25 sq-ft so you have to guy both
the tower and the stinger.
* Titanex verticals. These are supposedly distributed by Array Solutions
although I don't find anything on Jay's website about them.
At 615 euros per antenna these aren't cheap.
* Someone still makes BX/HBX/HDBX towers but they weren't such a great
value from what I recall
* AN Wireless or Titan self-supporting towers cost more than the Titanex
AB7E:
I used 4 inch diameter aluminum irrigation tubing to put up a 55 foot
temporary "tower" to support some wire antennas until I could get a decent
tower installed at this new QTH. I assume the stuff is available most
places around the country ... I bought mine nearby in Tucson, Arizona.
I've seen two different types, one about .050 inches thick and the other
just over .070 ... you'd definitely want the .070 stuff. It is much
stronger but still light weight. I'm not sure what the alloy is but it is
pretty stiff.
I bought a 40 foot section to go with a shorter section I already had and
spliced them with some other material I had handy to get the 55 feet. I
welded up a simple tiltover base, set it in concrete, and used a hand winch
about 7 feet off the ground to crank it up. A 40 foot length is light
enough for one person to walk up to a vertical position, though, so it
wouldn't take much to rig a temporary raising fixture for a 65 or 70 foot
section.
I guyed the pole with one set of dacron ropes at the 40 foot point and it
hasn't budged even with the horrific spring wind gusts we get down here in
southern Arizona, and I have three wire dipoles with coax all hanging from
the top. I'm sure you could get by with one set of four orthogonal guys at
the 50 foot level. The tubing is really stiff and won't bend.
The tubing can be bought in lengths up to 60 feet, but if I were you I'd buy
some 40 foot sections and some 30 foot sections and fabricate your own "boom
splices" ... I'm sure you'd know how to do that better than I.
It's not cheap (I think I paid about $8 per foot) but you could easily carry
the pieces by hand to a spot with difficult access. The tubing also comes
in 3 inch diameter and would be cheaper, but I don't have much experience
with it.
KB1H:
I went through about 5 designs (failures) before we arrived at a design that
has been up here for probably 8-10 years.
I should take some pictures but anyway...
The full size 1/4 wave is made up of 2" aluminum conduit. Using couples,
bolting and lots of NoAlox, there are self standing but guyed at two points,
four times (90 degrees between anchor pins for guy ropes)
The pipe is mounted on a pressure treated 4 X 4 and that board is mounted
between two 2 X 6 planks. The beam is bolted with carriage bolts near the
top and bottom. The top is left out because when you rotate the whole
assembly up you pivot from the low point.
The bottom of the pipe is 9' off the ground with 4 raised radials each.
Measured power dump into the dummy load is usually around 5%. I guess it
could be made better but with this 2" pipe the system needs no tuning
through the whole band.
If you are a purist and not as pragmatic as I, then I am sure some
additional tuning can optimize the system more.
When I finally got these up, I began to collect Rohn 25 to replace them if
they came down. Well, 8 years later the tower sections are still being
stored. I hope I never have to use them.
BTW, the mechanical failure of earlier designs all happened at about the 33%
point up the pipes. I think if you talk to a mechanical engineer they will
tell you that is the weakest point in the structure. That is why I believe
the Hoover dam has its thickness concrete at the 1/3 point from the bottom.
What the heck, I build bridges with diodes (BSEE) not with steel girders! I
think I proved that point about 5 times!
I also found most of the 2" conduit in a salvage yard.
W9GE:
In descending order:
1. Rohn 45 or equivalent, guyed at 40 feet, insulated from base and guys
2. Rohn 25 or equivalent, guyed at 30 and 60 feet, insulated from base
and guys
3. Zero Five antenna 80 meter verticals Expensive but nicely made.
Two guy points might be a bit thin.
4. Heights or Universal aluminum towers, self supporting and fed with
gamma matching. Its tough to make all four the same with a gamma but it
can be done.
5. Hy Gain Hy towers.
K8DO:
My first thought is 3 sections of 20G tower guyed at the top and setting on
UHMW pads. Then 3 sections of 10 foot long schedule 40 aluminum pipe in
decreasing diameters... You will need to shim them to fit together with ~1/2
foot overlap and have them MIG welded into a single 29 foot piece... If you
make the two step down diameters far enough apart you can have a machine
shop bore a sleeve to join each section properly without fiddling with thin
sheets of flashing, etc., or with bending thicker pieces for shims.. Say 3"
to 2" to 1"... I'll let you look up the sizes and play with the ratios...
There are other ways to shim without machining, using rectangular tabs with
bored holes and welding through the holes... Homebuilt aircraft fabricators
will know how or you can call me and I'll explain...
Here is one source for pipe schedules:
http://www.easternmetal.com/products/pdfs/standards/aluminum-pipe-extrusions
.pdf
Anyway, this will leave you roughly 58"-4" tall and shy of resonant and a
0.5" tip extension and/or capacity hat will walk them on to frequency...
K1IR:
The K1EA design might be for you. Check with Ken. Lower part is tower
upper is tubing and I think its all self supporting.
GW3NJW:
Take a look at
http://www.spiderbeam.net/sb/product_info.php?XTCsid=8b0a7bd877a80638cc284c4
da4a9ad8f&info=p71_Spiderbeam%2018m%20fiberglass%20pole.html
S57ND:
How about DXE (if I recall correctly) freestanding verticals and/or Titanex
V80HD?
----------------------------------------------------------------------------
-----------------------
Related parts and stuff
K1VR:
Rohn 25 Tower Leg insulators see http://www.k0xg.com/products/product20.html
----------------------------------------------------------------------------
-----------------------
Ones not so much to the point:
W6RMK
A couple things to think about, and a few questions..
What are you going to use as a feed network? A Comtek box, A Lewallen
current forcing, Full on Gehrke networks? Are you operating over the entire
3.5-4 MHz? Or just over a small slice?
In any phased array the mutual impedances make it so that "resonance" is
sort of poorly defined. When the array is driven, none of the
elements are going to be a nice 50+j0 ohms, so obssessing about the length
may not be worthwhile. The vertical radiation pattern of a
single element doesn't change much with, say, a 10% length change one way or
another, so you can choose a height that is convenient mechanically.
If you want a particular impedance at the feedpoint for individual elements,
some lumped components at the feed point would probably
meet the need quite nicely. A big inductor with low loss might be easier to
build than a low loss capacitor, so cutting the element "short" might be a
plan. On the other hand, vacuum variable caps show up surplus all the time,
and you're going to be investing several thousand dollars in the rest of the
array, so a few hundred bucks for some caps might not be a problem. And,
this gets back to my question about how you intend to feed the array. Some
feed methods (e.g. "current forcing") aren't all that picky about feedpoint
impedances, although, if you get too far away, the losses in the element
feedline *might* become significant (you'd have to calculate and see..)
On one hand, it might seem that making large diameter elements for broadband
is useful. On the other hand, the spacing isn't a fixed fraction of a
wavelength as frequency varies, either, so it's not clear that a real
broadband element is needed. Either you tune for a particular frequency
(including spacing and relative electrical phasing) and accept less
performance at other frequencies or you use multiple networks and customize.
Given all the practical uncertainties in things like ground radials, soil
properties, local environment, etc, I think that one's best bet is to design
for mechanical considerations, and then fool with the electrical issues
second. You want something in the quarter of a wavelength area (unless
you're going to do a vertical dipole array), so you need something that's
reasonably structural for a 60-70 ft
length. I think that tubing, in some form or another is probably the best
deal overall. Thin wall irrigation tubing in the 3-4" diameter range, with
guys, can easily do those heights, and it's inexpensive (especially if you
buy it used) and easy to handle. You could step the diameter down as you go
up to make it lighter and easier. If you want free standing, then maybe
something like a flagpole is the way to go. (or, since you won't have the
wind load of the flag, you can use dimensions from commercial flagpoles, and
build it lighter). 60-70 ft flagpoles are about a foot in diameter at the
bottom.
While I know you don't want to go scrounging used tubing, if you call the
places that sell the new stuff, they'll usually also have a line on used
stuff. Or, if you call a place like "Rain for Rent" which does irrigation
stuff in general, they'll have tubing that can't be rented out any more (too
many dings and/or pin holes.
Do they have 4" irrigation tubing in New England? It's one thing where
you've got miles of flat ground to irrigate like in California's central
valley or around here in the Oxnard plain.. totally another in rolling hills
with more natural rain where it
might not be the usual thing.
N8RA:
Admittedly a contrarian response, but have you considered making just 2 of
those verticals out of Rohn 45 and then stacking them on top of each other
to make another 150' tower (we can always use another one of those, can't
we?) sited such to make a nice triangle with two of the other tall towers
that you already have. Then string an array of wire full size half wave
verticals between them, perhaps with the ends bent horizontally a bit as
need be, and work out a phasing scheme between these.
I am not a fan of 4 squares inland on rocky terrain if you have tall towers
available. EZNEC shows a 4SQ gain at 20 deg to be about 9 dBi if over salt
water. This drops to about 5 dBi over rocky soil, and the low angles are
sucked out too of course, maybe the biggest sadness. A single vertical
dipole shows about 0 dBi at 20 deg. My guess an array could get that up a
few dB, perhaps approaching the 4 SQ over rocky.
(A model of my single half wave center fed sloper on 80M shows a gain of
about 2 dBi at 20 deg, with a bit of F/B, because of the tower from which it
slopes.)
If you could not get the desired F/B receiving performance of the 4-square
with the proposed wire array, then perhaps an easier to build receive 4SQ
could supply that.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
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