Hi all, I am just about to get my Foundation licence and am contemplating a
multiband vertical. Many plan talks about "radials" being needed, now I just
happen to have a house with a nice tin roof. Can I make use of the whole
roof as a ground plain or do I need radials cut to resonance for each band?

Thank

Andre (vk3 - almost got it!!!)

"Andre & Sharon Walker" wrote in
:

Hi all, I am just about to get my Foundation licence and am
contemplating a multiband vertical. Many plan talks about "radials"
being needed, now I just happen to have a house with a nice tin roof.
Can I make use of the whole roof as a ground plain or do I need
radials cut to resonance for each band?


Do you mean a trapped vertical or the like, or are you planning to use an
unloaded vertical on multiple bands.

If it is a trapped vertical, it probably comes with instructions. For
example, http://www.dxengineering.com/pdf/hus...5btv_instl.pdf
details the installation instructions for the Huster verticals.

You could read the instructions / manual after it doesn't work properly,
or you could read them beforehand.

Not all verticals require a substantial ground system, it depends on the
design. The tin roof might well provide a sufficient counterpoise for
some trapped verticals, depending on its size and location of the
antenna.

Short verticals are invariably quite narrow band on low bands, often as
little as 20kHz on 80m.

Also, keep in mind that verticals are relatively noisy in city
environments.

You might be well served with a simple coax fed dipole for one band (40m)
initially. Gain some experience, and note how many others are using
trapped verticals or the like. Do try to resist the end fed long wire
(though it is more correctly described as an end fed random length wire)
that seems so popular with FLs.

Owen

I was hoping to get away from traps, but i dont think its possible :-(. I
only have a smallish yard, with just 30m from the chimmny (brick ) to the
back of the yard, so i think a decent wire antenna is out...but i am open to
suggestions. I guess the other considerstion is to keep "she inside" happy .

Andre
"Andre & Sharon Walker" wrote in message
...
Hi all, I am just about to get my Foundation licence and am contemplating
a multiband vertical. Many plan talks about "radials" being needed, now I
just happen to have a house with a nice tin roof. Can I make use of the
whole roof as a ground plain or do I need radials cut to resonance for
each band?

Thank

Andre (vk3 - almost got it!!!)

Owen Duffy wrote:
You might be well served with a simple coax fed dipole for one band (40m)
initially.

A similar antenna, but one step closer to multiband operation
would be a simple dipole for one band (40m) fed with a multiple
of 1/2 wavelengths of ladder-line. At the resonant frequency,
it is hard to tell from a coax-fed dipole and an antenna
tuner will allow coverage of the entire band. The bonus is
that such an antenna can be made to work well on all ham
frequencies above the design frequency. If one is willing
to vary the length of the ladder-line, one can get by
without a conventional antenna tuner. Info at:

http://www.w5dxp.com/notuner.htm
--
73, Cecil http://www.w5dxp.com

Andre & Sharon Walker wrote:
I was hoping to get away from traps, but i dont think its possible :-(. I
only have a smallish yard, with just 30m from the chimmny (brick ) to the
back of the yard, so i think a decent wire antenna is out...but i am open to
suggestions. I guess the other considerstion is to keep "she inside" happy .

A 1/2WL dipole is 20m on 40m and can be made to work on
all HF bands 40m-10m. That's probably what I would do
and then do something romantic to keep the XYL happy.
--
73, Cecil http://www.w5dxp.com

On Wed, 18 Apr 2007 09:45:39 GMT, "Andre & Sharon Walker"
wrote:

I was hoping to get away from traps, but i dont think its possible :-(. I
only have a smallish yard, with just 30m from the chimmny (brick ) to the
back of the yard, so i think a decent wire antenna is out...but i am open to
suggestions. I guess the other considerstion is to keep "she inside" happy .

Andre

You can trust Owen's advice!

Here is some recommended reading on the subject from another reliable
source:

http://www.bencher.com/pdfs/00815ZZV.pdf
http://www.bencher.com/pdfs/00816ZZV.pdf

I have found Bencher's products to be a bit pricey but they are high
quality. They do have some low cost solutions.

Cushcraft is my favorite supplier because for a given type of antenna
they are the lowest cost solution. You must beware when dealing with
them that they are inclined to sell what is popular rather than what
is best for a given design.

The big problem with a multi band antenna is it is like a Swiss Army
knife. You can make it work but never as well as a single purpose
device. I find twenty meters to be the most active all-around band.

BTW, I spend more time tinkering with antennas than operating.

Congratulations on the new ticket! If you don't find what you want in
Amateur Radio you are not looking in the right place...

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"

My antenna is similar to yours, but slightly longer. I have a 110 feet
dipole running between my chimney and a tree at the back of the lot. The
dipole is at a height of 30 feet and is fed with open-wire. I use an antenna
tuner and the antenna works fairly well on all bands 80 through 10 meters.

John, N9JG

"Cecil Moore" wrote in message
.. .
Andre & Sharon Walker wrote:
I was hoping to get away from traps, but i dont think its possible :-(. I
only have a smallish yard, with just 30m from the chimmny (brick ) to the
back of the yard, so i think a decent wire antenna is out...but i am open
to
suggestions. I guess the other considerstion is to keep "she inside"
happy .

A 1/2WL dipole is 20m on 40m and can be made to work on
all HF bands 40m-10m. That's probably what I would do
and then do something romantic to keep the XYL happy.
--
73, Cecil http://www.w5dxp.com

John, N9JG wrote:
My antenna is similar to yours, but slightly longer. I have a 110 feet
dipole running between my chimney and a tree at the back of the lot. The
dipole is at a height of 30 feet and is fed with open-wire. I use an antenna
tuner and the antenna works fairly well on all bands 80 through 10 meters.

Your dipole is 8 feet longer than the G5RV length which
is a positive for 80m operation. For your favorite bands,
there is probably an optimum length of feedline. EZNEC
allows one to model different lengths of feedline. I
wrote a compiled BASIC DOS program that will estimate
the optimum lengths of feedline at:

http://www.w5dxp.com/imax.exe
--
73, Cecil http://www.w5dxp.com

What do you mean by optimum length since open-wire feedline has minimal
loss? When I moved into this property last July, I just strung the longest
wire that would fit into the lot, and reeled out the amount of feedline that
would reach between the tuner and my shack on the second floor. I can not
make the feedline appreciably shorter, and if I made it longer I would have
to figure out how to support the additional feedline. I estimate the
feedline has a length of 70 feet.

John, N9JG

"Cecil Moore" wrote in message
et...
John, N9JG wrote:
My antenna is similar to yours, but slightly longer. I have a 110 feet
dipole running between my chimney and a tree at the back of the lot. The
dipole is at a height of 30 feet and is fed with open-wire. I use an
antenna tuner and the antenna works fairly well on all bands 80 through
10 meters.

Your dipole is 8 feet longer than the G5RV length which
is a positive for 80m operation. For your favorite bands,
there is probably an optimum length of feedline. EZNEC
allows one to model different lengths of feedline. I
wrote a compiled BASIC DOS program that will estimate
the optimum lengths of feedline at:

http://www.w5dxp.com/imax.exe
--
73, Cecil http://www.w5dxp.com

John, N9JG wrote:
What do you mean by optimum length since open-wire feedline has minimal
loss?

By "optimum length", I mean the length where you can
switch your antenna tuner into bypass mode and obtain
a 50 ohm SWR of less than ~1.6:1. For any dipole that
is 1/2WL on the lowest frequency of operation, that
will be at an SWR current maximum point making the
antenna plus tuned feeder system resonant without a tuner.

On 20m, for example, if one can vary the ladder-line
length by plus or minus 15 feet, one can always locate
the SWR current maximum point and usually bypass the
antenna tuner. I have a 20m 1/2WL dipole that I use
on 20m, 17m, 15m, 12m, 10m, and 6m without a conventional
antenna tuner by simply varying the length of the
300 ohm ladder-line.
--
73, Cecil http://www.w5dxp.com