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[N7DC]

Guys, dont go away,  I am interested in those cage dipoles myself.  Would actually like to build a multi-element beam using bamboo as the support for the elements, with multiple wires strung along the bamboo pieces, to give better bandwidth.  The only multiple element beams I have seen described (with formulas etc.( have been for alunimum.  Has anyone attempted this before?  Thinking of 12 and 17 meters, so has anyone attempted build wire beams for those bands, 0n the same boom?  Try to get something whereby I dont have to use a tuner on them, if at all possible.  Thanks

[AF4YA]

Does anyone know where I could get some good plans to build a Multiband Cage Dipole say 10 - 80 Meters (more tuned for 10-20)? I've looked around and can't find any good descriptive plans that gives spacer diameter, wire lengths or how to actually build it . Any help would be greatly appreciated!

73s
AF4YA
Nick Mullins

[WB6BYU]

Cage dipoles are typically used when a standard wire dipole does not
have enough bandwidth to cover a given band..  For example, the
entire 500 kHz of the 80m band (where a standard wire dipole might
only cover 200 kHz or less.)  For this purpose, there was an article
in one of the early ARRL Antenna Compendiums which used just a
pair of wires spaced 4' apart.  A 6-wire cage might have 6" spacing,
but that seems a bit close for full band coverage.  (Note that a cage
dipole will be a bit shorter than one made with a single wire.)

Generally on 30 meters and up, the percentage bandwidth of each band
is small enough that a cage is not required (though it may be useful  to
cover the whole 10m band.)

Is there a specific application for which you need a multiband cage?

- Dale WB6BYU

[AF4YA]

Thanks for your reply. I have an old Yaesu FC-707 Antenna Tuner and my FT-707 is a 10 thru 80 meter rig. I would like to build an antenna that is more efficient in the 10, 15, and 20 meter bands, but would also be decent for the lower bands. I have quite a bit of cable and wire laying around that I could fashion into an antenna. Plenty of old RG-8/U, 16 or 18ga copper clad steel wire, around 40 feet of old ladder line. I thought about a double bazooka, but I'm not sure what the velocity factor is of the old RG-8/U and it is such a large heavy wire it would need lots of support. Then I began thinking of a cage dipole, seeing as I have a large spool of the copper clad steel wire. Not sure yet what I'm going to do. Just looking for something effecient in those bands and decent in the lower. I'd like something fairly easy to build. If I had plans it would be a breeze to build a cage. Just to lazy to work up the formulas;) Thanks for your help thus far!

73s
AF4YA
Nick Mullins

[WB6BYU]

Hmmm...   "More efficient" than what?

Typically when someone asks me what sort of antenna to use I ask the
following questions:

1)  What bands and modes are you most interested in?
2)  What area do you have available for it?
3)  What supports do you have available?
4)  How much are you willing to spend to improve on your present
situation?

A standard wire dipole for the higher bands should be around 90%
efficient.  Simply increasing the efficiency won't cause any noticable
difference in signal strength.   (Unless, of course, you are using lossy
cable to feed it, in which case improving your feedline can double
your radiated power.)

If you want improved performance over your current antenna, can you
put it up higher?  That usually helps.

If you just want a good all-round multiband antenna which will have
reasonable feedpoint impedances (which your tuner should handle),
I recommend a horizontal loop.  The 40m version would use 145' or so
of wire in a square/rectangle/triangle/polygon of whatever sort fits your
available supports.  If you use a 4 : 1 balun and coax feed, the SWR
should be tolerable for your tuner on 40/20/15/10.  The 80m version would
be twice the size - may be harder to fit into the lot, but worthwhile if you
have the space.  If you feed it with open wire line and a wide-range
tuner, you could use the 40m loop on 80.

For a multiband antenna which is simple to build and works well with
a limited-range tuner, I haven't found anything better than a loop.

- Dale WB6BYU

[AF4YA]

1) What bands and modes are you most interested in?
10-20 mainly, Phone.

2) What area do you have available for it?
Very hard to describe, but anything can be workable.

3) What supports do you have available?
Buildings, trees, telephone pole w/ domelight on it only.

4) How much are you willing to spend to improve on your present
situation?

Around $50 or less.



Sounds like a plan with a loop, or just a regular dipole. Be better than fooling with a double bazooka or a cage dipole. Sounds simpler and more what I'm looking for. I'll just need to get a good Balun I suppose. I appreciate all the information you've given me. I haven't done to much HF work. Just now getting set up with this new rig and needed help figuring out what would be best antenna wise.  Thanks again!

73s
AF4YA
Nick Mullins

[WB6BYU]

The traditional cage dipoles are broad-band antennas, but not typically
multi-band antennas.  Thay were mostly used to cover the complete
80m band (3.5 - 4 MHz, the largest percentage bandwidth of any of
our HF bands) where a single wire dipole can only cover 100 - 200 kHz
of bandwidth at a reasonable SWR.

The double-bazooka is also designed for the same purpose - to provide
a match across a wide band, instead of across multiple bands.  This
would not be suitable for multi-band use, even with a tuner.

However, there are antennnas which will cover a bandwidth of better than
2 : 1, such as 14 - 30 MHz, with a low SWR.  And some of these may
resemble a cage.  Three such designs are the biconical vertical or
dipole, the discone, and the fan dipole.

But, before we get into those, I suggest that you consider a simpler wire
antenna fed with twinlead or ladder line and using a tuner in the shack.
If you build a dipole with an overall length of 40' or so and feed it with
balanced, low-loss line, it should work as well on 10 m through 30m
as any of the more complicated designs.  The length of the dipole isn't
critical - longer wires will work better on the lower bands, at the expense
of a multi-lobed pattern on 10m.

Note:  lengths of over, say, 100' will work best on the high bands if they
are installed horizontally, instead of in an inverted vee configuration.

That said, here are some ideas for experimentation with wide-band
antennas to cover 14 - 30 MHz...

A biconical antenna is comprised of two cones - imagine two ice cream
cones with the openings placed together.  This is often build as a vertical
fed against a ground plane.  The angle at the feedpoint determines the
impedance, and the bandwidth is related to the "fatness".  I think the
feepoint angle is 40 to 60 degrees for a 50 ohm impedance, but you can
experiment with this and see.  The total length of the wires from the
feedpoint to the top is around a quarter wave on the lowest frequency.
As a starting point for experimentation, cut a number of 18' wires and
connect them in parallel at both ends.  Hoist one end in the air using
a pulley or tree branch perhaps 20' up.  Go down in your basement and
find an old "Hula Hoop":  use it to spreader about 4' from the bottom
of the antenna.  Experiment with the size of the hoop, location along
the wires, number of wires, etc.

A biconical dipole is just two of these elements arranged as a dipole.
Because an end angle of close to 90 degrees is requried to make a
wide-band 50 ohm match, they are often designed for 100 ohms each
(200 ohms overall) and used with a 4 : 1 balun.

A discone is a vertical radiator which can cover a 10 : 1 frequency range
if carefully built.  (They are often sold for scanner antennas.)  It looks
like a cone pointing up, with a disc sitting on top (hence the name.)
The center of the coax is connected to the center of the disc, and the
shield is connected to the top of the cone.  You can try 18'  to 20' wires
for the cone, perhaps a dozen of them connected at the top.  The disc
can be 4 to 8 spokes, possibly with a wire run around the tips of them.
Starting size for the disc would be about 10' to 12'.  The cone wires
should slope down about 30 degrees from vertical (so the distance across
the bottom of the cone is about the same as the length of the wires.)

A fan dipole is similar to a cone, but compressed in one plane, so is often
more practical.  If you have been trying all of these designs, you already
have a bunch of wires cut around 18', so we will use them again.
Connect 6 wires together at one end, and spread the other ends evenly
to a total width of 10' or so (using strings or by tying them off to a piece
of PVC pipe.)  Do the same to another set of 6 wires.  Connect your
feedline to the points where the wires come together, and hoist the whole
mess in the air (so it looks like a bow tie, or a butterfly with skinny wings.)
Depending on the angle of the wires, the feedpoint impedance may be
closer to 200 or 300 ohms, so you can use a 4 : 1 balun and try 50 or
75 ohm cable. (You can also use 300 ohm twinlead to a remote balun,
so the antenna doesn't have to support the weight of the balun.)

Sorry I don't have my reference books handy to give you exact numbers
and angles, but there should be plenty of opportunities to experiment
with these antennas.

Have fun!       - Dale WB6BYU