I bought a RS TRC-458 Navaho base station at a garage sale this weekend
for
ten dollars and I have a twenty foot mast and I would like to build my own
antenna, to save $$$.

The pattern needs to be at least 180 degrees as I live on the coast of
Florida. I plan to run barefoot (till I can buy some power) so I need some
efficiency.

if you're interested in saving costs, antenna gain is way less expensive
than amplifier gain.

a simple dipole would be a good start, two 10' wires, and a balun.
suspend from 10' poles in the yard, and trim the wires to best match, or
best resonance, if you can borrow an analyzer.
people do it without the balun, but it's no longer a dipole, and the
radiation pattern is different.

a two element beam can be made with wire, if you don't have to turn it.
it's not too directional, but it may serve your needs.

a full wave loop is another low cost, gain antenna. a bit harder to support
though, since it's 9' on a side, and ideally should be vertical. this is
another one that wants a balun on it's feed.

Hmmm Google is one link with a four element 11 meter antenna and 300 links
to comercial sites.

br549

wrote in message
news
On Sun, 14 Sep 2003 23:37:50 GMT, "nocents" wrote:

Sorry if I am redundant, this is the fist time on this group, I am using
Central Florida Road Runner and their NG retention is about 48 hours, so
I
can't search the old posts.

Uh, Google? ...but, anyway...

I bought a RS TRC-458 Navaho base station at a garage sale this weekend
for
ten dollars and I have a twenty foot mast and I would like to build my
own
antenna, to save $$$.

Ten bucks, huh? Hmmm...

The pattern needs to be at least 180 degrees as I live on the coast of
Florida. I plan to run barefoot (till I can buy some power) so I need
some
efficiency.

Another reply was for a dipole or loop antenna (good & cheap)

How about a J-pole? This one is for 10m; you can recalculate for the
portion of 11m you want to work.

http://www.arrl.org/tis/info/pdf/5002016.pdf

Thanks,

Hey, at least you got some assembly instructions...

BR549

Thanks


wrote in message
news
On Sun, 14 Sep 2003 23:37:50 GMT, "nocents" wrote:

Sorry if I am redundant, this is the fist time on this group, I am using
Central Florida Road Runner and their NG retention is about 48 hours, so
I
can't search the old posts.

Uh, Google? ...but, anyway...

I bought a RS TRC-458 Navaho base station at a garage sale this weekend
for
ten dollars and I have a twenty foot mast and I would like to build my
own
antenna, to save $$$.

Ten bucks, huh? Hmmm...

The pattern needs to be at least 180 degrees as I live on the coast of
Florida. I plan to run barefoot (till I can buy some power) so I need
some
efficiency.

Another reply was for a dipole or loop antenna (good & cheap)

How about a J-pole? This one is for 10m; you can recalculate for the
portion of 11m you want to work.

http://www.arrl.org/tis/info/pdf/5002016.pdf

Thanks,

Hey, at least you got some assembly instructions...

BR549

Dave,
Just so you will know in the future, the dipole is
a dipole, balun or no balun. It's still a balanced
antenna, but fed with an unbalanced feed line.
Both the dipole and a vertical full wave loop will
work just fine without a balun. It does make a slight
difference in the shape of the radiation pattern but
you will never know it. Do you really mean a balun,
or do you mean a coaxial choke? At HF either will work.
'Doc

"'Doc" wrote in message ...
Dave,
Just so you will know in the future, the dipole is
a dipole, balun or no balun. It's still a balanced
antenna, but fed with an unbalanced feed line.

no, it's not.

in order to be a dipole, it has to be fed with two signals, 180 degrees out
of phase, and equal ampliude.

otherwise, it's a monopole, with a counterpoise.
do you not see the difference between a driven, and a passive element


Do you really mean a balun,
or do you mean a coaxial choke? At HF either will work.
'Doc

whichever way you do it, you need to feed it balanced.

Dave VanHorn wrote:

"'Doc" wrote in message ...
Dave,
Just so you will know in the future, the dipole is
a dipole, balun or no balun. It's still a balanced
antenna, but fed with an unbalanced feed line.

no, it's not.

in order to be a dipole, it has to be fed with two signals, 180 degrees out
of phase, and equal ampliude.

otherwise, it's a monopole, with a counterpoise.
do you not see the difference between a driven, and a passive element

---------------
Take a look at any standard text (Kraus's "Antennas" for
example) and
you will see your definition isn't correct. Among other
characteristics,
a dipole antenna (also called a doublet) has two 'elements'
which are
equal in length (and commonly accepted to be 1/2 wave length
long). Doesn't
really matter is it's horizontal, vertical, an 'L', or some
randomly shaped
thingy, it's still a dipole.
Having used dipole antennas for over 30 years, I can't think
of a single
instance when I've fed one with two signals, no matter what mode
of use. I
~have~ fed them with a single signal and each 'element' of the
antenna be
180 degrees out of phase, but that's normal with any antenna fed
in the center.
Except for commercial and military applications, I can't think
of a single
multiplex amateur or CB example (two signals to the same
antenna).



Do you really mean a balun,
or do you mean a coaxial choke? At HF either will work.
'Doc

whichever way you do it, you need to feed it balanced.
------------------
Also not true. At HF there is very little reason to worry
about using
a balun unless you have to do impedance transformations or are
feeding a
directional antenna. The primary result of an unbalanced signal
to a
balanced antenna is a very slight skewing of the radiation
pattern. Except
for directional antennas (beams) that 'skewing' of the radiation
pattern
isn't noticable (and not very noticable even with a directional
antenna).
If you will notice, I qualified all of the above to HF. At
higher frequencies
there is a more noticable change in radiation patterns because
of a balanced
to unbalanced condition. The example you furnished for baluns
is for the
VHF/UHF spectrum where pattern skewing ~is~ more noticable and
important.
Baluns are fine for when/where they are of use. At HF they are
at best
just another point of failure that isn't strictly needed.
'Doc

On Sun, 14 Sep 2003 21:00:40 -0500, "Dave VanHorn"
wrote:


"'Doc" wrote in message ...
Dave,
Just so you will know in the future, the dipole is
a dipole, balun or no balun. It's still a balanced
antenna, but fed with an unbalanced feed line.

no, it's not.

Yes it is.

A dipole antenna is a straight electrical conductor measuring 1/2
wavelength from end to end and connected at the center to a
radio-frequency (RF) feed line. This antenna, also called a doublet,
is one of the simplest types of antenna, and constitutes the main RF
radiating and receiving element in various sophisticated types of
antennas. The dipole is inherently a balanced antenna, because it is
bilaterally symmetrical.

Ideally, a dipole antenna is fed with a balanced, parallel-wire RF
transmission line. However, this type of line is not common. An
unbalanced feed line, such as coaxial cable, can be used, but to
ensure optimum RF current distribution on the antenna element and in
the feed line, an RF transformer called a balun (contraction of the
words "balanced" and "unbalanced") should be inserted in the system at
the point where the feed line joins the antenna.

in order to be a dipole, it has to be fed with two signals, 180 degrees out
of phase, and equal ampliude.

otherwise, it's a monopole, with a counterpoise.

So I can feed my Ground plane or quad with a balun, then its a
dipole?

do you not see the difference between a driven, and a passive element

You think the end thats fed with the shield of the coax is passive?
Come on over and grab the end of my dipole, (fed with coax and no
balun), when I have 1Kw running to it. You will change your mind
about it being passive.



Do you really mean a balun,
or do you mean a coaxial choke? At HF either will work.
'Doc

whichever way you do it, you need to feed it balanced.


You will notice very little, or more likey no difference between a
dipole fed with or without a Balun.

So I can feed my Ground plane or quad with a balun, then its a dipole?

no, it's not. be careful, you're making my case.

for a pair of quarter-wavelength wires to act as a dipole, several things
must be true.
physical arraingement, and feed are both important. your broken dipole is
somewhere between a real dipole, and the ground plane. basically, a
monopole, with a counterpoise.

if you significantly bend the wires, or re-arrainge them physically, then it
is no longer a dipole.

if we remove three radials from your ground plane, /i'm assuming it's fed
with unbalanced line directly, as it should be/ and straighten out the
remaining radial relative to the driven element, then we have your broken
dipole again.

there's another class of antenna, called a bicone, that has significantly
different charachteristics, but is conceptually very close to the dipole.
it's got broader bandwidth, and is commonly used in part 15 testing for that
reason. the discone is another very close relation, somewhere between the
bicone, ground plane, and a feedhorn.

this stuff does matter. when you make changes, they have effects, even if
your particular arrangement is too sloppy to notice them. when you make a
change that should have an effect, and it dosent, this is telling you that
you have other problems.

do you not see the difference between a driven, and a passive element

You think the end thats fed with the shield of the coax is passive?
Come on over and grab the end of my dipole, (fed with coax and no
balun), when I have 1Kw running to it. You will change your mind
about it being passive.

no, i won't. where did you get the idea that passive elements wouldn't have
current flowing in them. and where pray tell, is that current coming from

grab the director on a beam, and see what you get. that's a simple wire
sitting in space, with no connection to the coax at all.. is it a passive
element, absolutely.. has it got rf current flowing in it, you'd better
believe it.

your two wires fed in the middle with coax, are not a dipole.
the best name i can give it, is a monopole with counterpoise.
throw it into mininec, and see if you get the same results as a properly
constructed dipole.
that's freeware, a little limited, but it can do simple antennas like
dipoles with no problems.

you've also got a lot of rf current on your shield, which is making the
shield an active part of the antenna. you didn't think that this current on
your non-driven element magically stopped at the connector, did you.. why
would it stop there.. there is one possibility, that your feedline is an odd
number of quarter wavelengths long, so that this pont is high impedance. but
that only works at particular frequencies. in this case, it's still not a
dipole, /half the antenna isn't driven/ but it will work better than an
identical antenna with feedline an even number of quarter wavelengths long.

You will notice very little, or more likey no difference between a
dipole fed with or without a Balun.

like i said, errors in one area can obscure results in another area.

almost any damn thing will radiate and be tuneable.
a quick look at the antenna wall in the local truck stop will tell you that.

a proper dipole is resonant, given a balanced feed, and therefore does not
put significant signal onto the coax shield. /or it's fed with ladder line,
from a balun in your tuner/

Dave,
There is a big difference between the current flowing on
the inside of the shield of coax and any current flowing on
the outside of the shield. The current flowing on the inside
of the coax shield is the same current that flows in the
center conductor (not the same polarity/phase). Ideally, there
will be no current flowing on the outside of the coax shield,
but you very seldom ever run across the 'ideal' situation. The
current flowing on the outside of the shield is what makes the
feed line radiate.
'Doc

Dave,
Keep at it, you'll figure it out eventually. Jerry and
I don't agree on several things, which is neither here nor
there. And a lot of his research is useless, for any practical
use. Ask him, he'll tell you the same thing.
There is a big difference between what is done in a lab for
testing or research purposes and what is done in the 'real'
world. Most, or at least some of the things done in the lab
are just not needed with 'practical' antennas and radio
stations.
I'm afraid you will have to pass your certifications by your
self. I quit taking them a long time ago...
'Doc