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Author Topic: Vertical Fever  (Read 3598 times)
KK4AXX
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« on: August 29, 2011, 06:26:16 PM »

I have successfully built & used an 80 Meter dipole, a 2 Meter J-Pole, and a 40 Meter loop.  The 80 Meter dipole is now history, but it has made room for a new project.

I've got the vertical fever!  Not that I think it is an improvement, but that I just want to build one and experiment.

What i'm considering is building a 20 Meter vertical out of EMT to be mounted in the center of my back yard, preferably with the ability to lay it down during bad storms.  I understand that I can insert one size EMT into the next larger & clamp the two together.  Some consideration was given to roof mount, but with our high number of intense storms he lightning risk seems too high.

Please, send pointers! 
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George U. Potter Lodge, #912, F. & A. M. of Alabama
A.A.S.R., S.J. - Valley of Mobile, Orient of Alabama
Dave Langham Chapter, #536, Order of the Eastern Star
Order of DeMolay, Mobile Chapter, Adult Advisory Council
K9IUQ
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« Reply #1 on: August 29, 2011, 07:01:24 PM »

I've got the vertical fever!  Not that I think it is an improvement, but that I just want to build one and experiment.

Please, send pointers! 

Do it right and it will be an improvement.

Pointers:
Don't use EMT. Use copper or aluminum. Radials, Radials, Radials
You can buy aluminum tubing at Lowes/Home Depot or order from DX Engineering.

One of my first verticals was just a wire run up vertically next to a tree. Use imagination. Experiment. Have fun.

I presently have a 40 mtr vertical (33ft) out of fiberglass tubing with a 10 ga wire up the center of the fiberglass.

Google and read,there is a lot of info on verticals out there.

Stan K9IUQ
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WB6BYU
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« Reply #2 on: August 29, 2011, 08:08:15 PM »

You're only going up 17' for 20m (assuming a quarter wave - a good place to start.)  EMT will be heavier
than aluminum, but a couple of 10' sections should do the job.  You should be able to tilt it up into position,
especially if you use small sizes of EMT.  Put a bolt though the bottom horizontally into a wood post to form
a hinge, and use a conduit clamp (or bungee cord) to secure it upright.  You should be able to tilt it down
easily when needed.  Wood will be an adequate insulator for the base of a quarter wave vertical up to 100W
in most cases.  (Or you can use PVC pipe pieces and fittings - it's merely a matter of mechanical engineering.)
If you overlap two sizes of pipe/conduit, you can just run a couple sheet metal screws through them.   If you
are using a hose clamp to make the length adjustable, slit the top of the larger section with two hacksaw cuts
to make it easier to compress with a hose clamp.  (This will work better with aluminum, as the EMT ends will
be stiffer and not compress as easily.)

Much of the commercial aluminum tubing comes in standard diameters on 1/8" increments with 0.058" wall
thickness.  That means that a 3/8" piece just slides inside 1/2", etc.  Some of the tubing sold in home
improvement stores may be a softer type with thicker walls - you'll have to check that it nests properly.

For a 20m whip, 3 pieces of 6' aluminum tubing will be fine, and will allow you to reduce the length down
to 10m.  10' lengths of EMT won't let you get down to 10m due to the minimum length.

Feed system:  connect center conductor to the antenna (a screw or bolt with a lug is convenient.)
Radial wires go to the shield.  You can make a  ring of stiff wire 6" to 12" in diameter at the base of
the antenna, then connect the radials to the ring.  More radials are good - there are a lot of studies
out there about how to determine the optimum radial configuration to maximize the antenna efficiency
for a given length of radial wire.  But something like 16 radials each 10' long is likely to be a good start.
The radials can be any sort of wire - I use magnet wire because it is cheap.

The SWR won't be perfect unless your ground losses are somewhat high.  You can add a shunt coil
across the feedpoint and shorten the antenna element slightly to get a good match, or use any
of a number of other methods.  You can make the antenna longer than a quarter wave and put a
capacitor in series at the base, or shorter and use a coil.  In fact, any radiator length from 1/8
to 3/4 wavelengths can be pressed into service with an appropriate impedance matching network.
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W5FYI
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« Reply #3 on: August 29, 2011, 09:01:02 PM »

I read somewhere that a ham in a covenant-restricted housing development used a TV mast rotator on his vertical. No, not to "aim the beam," but to raise it from horizontal to vertical when he wanted to use it, then stow it horizontal when QRT. You can use the same method to "lay it down during bad storms" and keep yourself safely remote from lightning, and dry, too. An EMT mast might require a counterweight; aluminum tubing might not. GL
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KK4AXX
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« Reply #4 on: August 30, 2011, 08:27:53 AM »

Good stuff to work with...

I have some amount of fiberglass tent poles in the shed from an old military tent.  I may have to go see what is out there.

How close to the ground? 6 inches?  Also, it seems odd that simple magnet wire would work as radials. But what do I know?  Huh  Seems that if any wire would work that a mat of wire, like chicken wire, would make for a more solid ground - even better if it were of some less prone to rust material.

If I do this, the vertical will be dead center of my back yard & therefore dead center of my Loop.  Would there be any interference from the 143 feet of 14 gauge Copperweld?  There would be about ten feet of air between the top of the vertical & the nearest part of the loop.
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George U. Potter Lodge, #912, F. & A. M. of Alabama
A.A.S.R., S.J. - Valley of Mobile, Orient of Alabama
Dave Langham Chapter, #536, Order of the Eastern Star
Order of DeMolay, Mobile Chapter, Adult Advisory Council
WB6BYU
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Posts: 13458




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« Reply #5 on: August 30, 2011, 08:48:34 AM »

There may be some interaction - such things can be difficult to predict without knowing the exact
configuration when the antennas are in the near field.  But because the loop is horizontally polarized
the interaction with the vertical should be small.

I've picked up a couple bundles of aluminum tent poles at thrift shops that work well for portable
masts and/or vertical antennas.  Sometimes it takes a bit of creativity to splice them together
if they aren't all designed to go together into a single unit.
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WB8YYY
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« Reply #6 on: August 30, 2011, 06:48:36 PM »

verticals are generally useful when you cannot get your horizontal antenna high enough for low angle radiation.  for many of us a vertical is highly beneficial on 80m and 160m.  on 20m you may do as well or better with a dipole if you can get it up a bit.  but its an easier band to make a vertical for, and you already have plenty of good suggestions. 

i don't sense there is a magic formula for radial wire type.  i obtain a spool of something like #20 aluminum wire with insulation cheaply at a hamfest, so this is what i have down.  a commercial vertical i have came with heavy duty magnetic wire for radial use - maybe its something like #16.  ease of getting it down and attached to the ground is more important, but I suggest staying with aluminum or copper.  as you have probably read, ground mounted radials do not have to be a resonant length.  my field is 30 radials that vary in length from 30 to 50 feet.  another hint is that you may end up using a field of radials for several different antennas - in fact I use these radials at the same time now for 2 different verticals, and they were previously used with a vertical i no longer have. 

once i thought this was a waste of good wire - but now I have discovered these are real cool antennas for the lower HF spectrum especially.  do consider what your present antennas do well in terms of adding your next antenna.  i sense you are well positioned on 15 and perhaps 40m, so perhaps 20 and 80m can be your next objectives. 

73 curt
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KJ4ADN
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« Reply #7 on: September 03, 2011, 02:38:09 PM »

We have all sorts of Verticals, and love them (we're a family of 8 HAMs). 

The biggest performers, and most versatile for us is the OMTA - it covers 40, 20, 17 & 15m (an insertable tuning stub switches from 15m to 17m).  A little more work to build, but it's strong and have held up well.  We have 3 of these, separated about 400' apart and we can all work the same bands to within 5kz of each other before we start to "hear" the other radio.

I've got 6 fiberglass 40m poles, 32.5' with wire inside them, and a connector on top for "fine tuning", add a short piece of wire via connector...   Also have 2 80m spider-beam poles with wire inside - co-phasing these for a figure 8 pattern or endfire, and WOW!  what a great DXer!

We have a pair of aluminum 80m 65' telescoping sched 40 pipes, still by far the best performing DX antenna... and hardest to keep up!  (they're on the ground, repairs complete, and ready to be re-deployed).

Our latest project is building a 7 or 9 element 40m array....  working on that, the front yard is full of pipe.

The bottom line is - WHAT's your GROUND like.
In our case, we've got lots of IRON  and it's rather conductive, wet or dry.  So, we take advantage of our QTH and switched from dipoles to verticals for "primary" antennas.  What works for "me" might not work for "you" and vice versa.

Whenever we set up somewhere else....  We always take the 40m fiberglass verticals, with our radials....   CAT-5 cable, 34' long, with a ring terminal tying one end together, which attaches to the base of the antenna mount.  Pound in a cut off fence post, snap the fiberglass antenna to it, spread the 4 pairs of conductors out on the ground, and hook up the coax - my boys can set up 2 of these in less than 15min.  Co-phased, they're

For 20m, we took 3/8" aluminum tubing, cut it into 30" lengths, and crimped 1/4" solid aluminum rod into one end of each section.  The top section has a sliding 1/4" rod for "fine tuning".  This antenna is no-tune for 20m, 17m, 15m, 12m, 10m - you just adjust the length to the band you want... again, uses cat-5 cable for the radials, and it's backpack portable!

I would stay away from any vertical antenna that "requires a tuner".  This stuff is simple to build.

KJ4ADN - Bill
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