How does one can determine the impendance of a wire to get the right balun
for it, so it can be hooked up to the coaxial cable?

Michalkun wrote:

How does one can determine the impendance of a wire to get the right balun
for it, so it can be hooked up to the coaxial cable?

I give up. I surrender to the Taliban, Al Quaaaaaida, AMANDX, or whomever....

Sign me up for the retard DX'er Association...

To many here cain't read, do a Google search or just plain understand... No
wonder there are no DX'ers here...

I'm outta here... I'm leavin ya all... portable totin' lot that ya are...

Adios.....

I would also be interested in the answer.
My impression is that particular balums are used purely on a custom and
practice basis and 'suck it and see'. I have not seen any guide to measuring
the rf resistance/impedance of a throw out or long wire antenna.
If someone doesn't answer your question the chances are they don't know
either.

Lionel Carter

"Michalkun" wrote in message
.251...
How does one can determine the impendance of a wire to get the right balun
for it, so it can be hooked up to the coaxial cable?

LC,

I guess what you are inferring is that there are two approaches to
buying or building a Bal-Un (Un-Un) for an Antenna.

#1. MOST OF THE TIME: We buy or built a certain kind of antenna that
has a known XXX 'impedance' an installed it the best we can.
- - - Therefore We "ASSUME" that XXX is the antennas 'impedance' and
buy or build a Bal-Un (Un-Un) to match the antenna to the feed-line
and antenna input of the receiver.

2. SOME OF THE TIME: We buy or built a specific kind of antenna an
installed it correctly.
- - - Then We 'test' the antenna with an impedance bridge or antenna
tester and 'know' for a "Fact" the YYY 'impedance' of the antenna.
+ + + Next, knowing that YYY is the antennas 'impedance': We buy or
build a Bal-Un (Un-Un) to match the antenna to the feed-line and
antenna input of the receiver.
= = = Finally, We Re-Test the Antenna with the Bal-Un Installed to
confirm our results.


~ RHF
..
..
= = = "Lionel Carter"
= = = wrote in message ...
I would also be interested in the answer.
My impression is that particular balums are used purely on a custom and
practice basis and 'suck it and see'. I have not seen any guide to measuring
the rf resistance/impedance of a throw out or long wire antenna.
If someone doesn't answer your question the chances are they don't know
either.

Lionel Carter

"Michalkun" wrote in message
.251...
How does one can determine the impendance of a wire to get the right balun
for it, so it can be hooked up to the coaxial cable?

"Lionel Carter" wrote in message ...
I would also be interested in the answer.
My impression is that particular balums are used purely on a custom and
practice basis and 'suck it and see'. I have not seen any guide to measuring
the rf resistance/impedance of a throw out or long wire antenna.
If someone doesn't answer your question the chances are they don't know
either.

Lionel Carter

It can be modeled. Or you can use a antenna analyser, etc. Random wire
antennas feedpoint will vary radically with freq changes. So for the
most part, it is "suck it up and see". Not much you can do about it
except try a different ratio transformer. Most of the antennas I use
are not random element designs, and have a fixed pre-known feedpoint
for the bands they are designed for. IE: most coax fed dipoles will
run from appx 50-75 ohms depending on height above ground, etc. So
naturally a 1:1 is the best choice. And you will still have enough
signal on most any other band for a usable s/n ratio. The only
exception might be with short coax fed dipoles used on very low
freq's, and in that case all you need to do is just unhook the ground
shield connection from the radio and let the center pin make the only
connection. EZNEC will spit out a SWR graph of any freq range you want
to punch in. You see a green "ball" on the top of the graph line. Say
if I scan from 1 to 30 mhz. I can place the green ball on 15 mhz and
see the feedpoint data. You can do this with the EZNEC demo.

I ran a swr scan on a 65 ft random wire, end fed. 1-30 mhz, every 500
cycles.
The "ball" is on 15 mhz. The feedpoint Z is anywhere from very low on
1 mhz to high on many frequencies. In the program, you can click on
any "500 cycle" portion and see the feedpoint specs. This can be used
with any antenna you want to punch in, and you don't even have to
leave your puter. You can d/l the eznec demo on the web. MK
http://web.wt.net/~nm5k/swr.jpg

Michalkun wrote:

How does one can determine the impendance of a wire to get the right balun
for it, so it can be hooked up to the coaxial cable?

From what i have been told long wires and beverage antennas in particular can
have more than one impedance as u tune across the bands. So an antenna may be
say 200 ohms at one frequency high up but 500 ohms on a low band. Not sure why
but that was what i have been told. It was recommended I try a 8 to 1 or 9 to
1 balun for the AM band.

Some places sell a magnetic type balun that is supposed to cover all bands and
impedances but have never used one so not sure how they work. Universal Radio
had a model

--
73 and Best of DX
Shawn Axelrod

Visit the AMANDX DX site with info for the new or experienced listener:

http://www.angelfire.com/mb/amandx/index.html

REMEMBER ON A CLEAR DAY YOU CAN HEAR FOREVER

Michalkun wrote:

How does one can determine the impendance of a wire to get the right balun
for it, so it can be hooked up to the coaxial cable?

Check out the following website for how to build an 'inverted-L'
shortwave antenna with a *properly* installed balun. This design can
make a big difference in reducing local (man made) noise on your
antenna, which makes it easier to hear weak stations. I used R6U coax
which is made for satellite TV systems. It's 75-ohm (not 50-ohm) but
that's close enough for shortwave receiving antennas. I made the balun
on a T-34 ferrite core. You can get these cores from 'Amidon' or one of
their dealers.

http://www.anarc.org/naswa/badx/ante...e_antenna.html


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In article ,
Michalkun wrote:

How does one can determine the impendance of a wire to get the right balun
for it, so it can be hooked up to the coaxial cable?

The impedance of the wire will depend on:

1. The diameter of the wire. The larger the diameter (smaller AWG
number) the lower the impedance will be.

2. The height of the wire above ground. The higher the wire the higher
the impedance will be.

3. The ground conductivity. The more conductive the ground the lower
the impedance will be. Also note here that this is affected by how the
antenna is grounded. If you have just a ground stake or whether you have
radials will make a big difference on how well the wire will perform.
The poorer the ground conductivity the more how you provide grounding
will determine how well the wire will work.

Why grounding is so important is because the wire is just half the
antenna with the ground being the other half. You have to give the RF
some place to go to complete the circuit that is your antenna or it
will not work well.

The coax back to your radio can be that ground but that has the
disadvantage of mixing the antenna currents with the power line noise
at the radios location reducing the signal to noise. One reason why
people are advocates of Baluns is because the antenna can have its own
ground independent of the radio ground.

For a wire antenna one radial run directly under the antenna wire will
do the most good as a minimalist approach.

All that being said a typical wire will be something in the 400 to 600
hundreds of ohms range so the 9 to 1 type of transformer would be the
best type.

--
Telamon
Ventura, California

The diameter is usually not significantly related to the impedance, it
affects Q a lot more.

Impedance is high except at resonance, where it lowers dramatically
(e.g. 500 Ohms to 50 Ohms).

You are asking for trouble with 2 grounds. Any difference in
potential can mean noise. I ground my co-ax on the roof (the mast,
grounded at the bottom) and use the outer conductor for the radio
ground, deep in the bowells of my house.

Technically, I should use a ground lift on the IEC cord, but I don't
unlesss there's a noticeable loop.

On Fri, 11 Jul 2003 21:16:37 GMT, Telamon
wrote:

In article ,
Michalkun wrote:

How does one can determine the impendance of a wire to get the right balun
for it, so it can be hooked up to the coaxial cable?

The impedance of the wire will depend on:

1. The diameter of the wire. The larger the diameter (smaller AWG
number) the lower the impedance will be.

2. The height of the wire above ground. The higher the wire the higher
the impedance will be.

3. The ground conductivity. The more conductive the ground the lower
the impedance will be. Also note here that this is affected by how the
antenna is grounded. If you have just a ground stake or whether you have
radials will make a big difference on how well the wire will perform.
The poorer the ground conductivity the more how you provide grounding
will determine how well the wire will work.

Why grounding is so important is because the wire is just half the
antenna with the ground being the other half. You have to give the RF
some place to go to complete the circuit that is your antenna or it
will not work well.

The coax back to your radio can be that ground but that has the
disadvantage of mixing the antenna currents with the power line noise
at the radios location reducing the signal to noise. One reason why
people are advocates of Baluns is because the antenna can have its own
ground independent of the radio ground.

For a wire antenna one radial run directly under the antenna wire will
do the most good as a minimalist approach.

All that being said a typical wire will be something in the 400 to 600
hundreds of ohms range so the 9 to 1 type of transformer would be the
best type.

In article ,
Dave wrote:

On Fri, 11 Jul 2003 21:16:37 GMT, Telamon
wrote:

In article ,
Michalkun wrote:

How does one can determine the impendance of a wire to get the right balun
for it, so it can be hooked up to the coaxial cable?

The impedance of the wire will depend on:

1. The diameter of the wire. The larger the diameter (smaller AWG
number) the lower the impedance will be.

2. The height of the wire above ground. The higher the wire the higher
the impedance will be.

3. The ground conductivity. The more conductive the ground the lower
the impedance will be. Also note here that this is affected by how the
antenna is grounded. If you have just a ground stake or whether you have
radials will make a big difference on how well the wire will perform.
The poorer the ground conductivity the more how you provide grounding
will determine how well the wire will work.

Why grounding is so important is because the wire is just half the
antenna with the ground being the other half. You have to give the RF
some place to go to complete the circuit that is your antenna or it
will not work well.

The coax back to your radio can be that ground but that has the
disadvantage of mixing the antenna currents with the power line noise
at the radios location reducing the signal to noise. One reason why
people are advocates of Baluns is because the antenna can have its own
ground independent of the radio ground.

For a wire antenna one radial run directly under the antenna wire will
do the most good as a minimalist approach.

All that being said a typical wire will be something in the 400 to 600
hundreds of ohms range so the 9 to 1 type of transformer would be the
best type.

The diameter is usually not significantly related to the impedance, it
affects Q a lot more.

Two AWG wire sizes will change the impedance about 6%. I was trying to
give a sense of how all the parameters of the wire affect the impedance.
The Q of the wire is a complex thing and fairly advanced concept
compared to its impedance. Increasing the wire diameter will reduce the
DC resistance of the wire increasing the Q. Typically this also infers a
narrowing of a resonant peak but other factors conspire to broaden the
peak in this case. Are you concerned with this? I think this is a
non-issue for most receiving antennas.

Impedance is high except at resonance, where it lowers dramatically
(e.g. 500 Ohms to 50 Ohms).

You are confusing the wires intrinsic impedance to its reactance to some
specific frequency of signal energy. This is a common mistake.

You are asking for trouble with 2 grounds. Any difference in
potential can mean noise. I ground my co-ax on the roof (the mast,
grounded at the bottom) and use the outer conductor for the radio
ground, deep in the bowells of my house.

There are two possibilities he

1. You operate the radio on batteries and there is no power line noise
to contend with. From the signal to noise standpoint one or two grounds
are a non-issue.

2. You operate the radio from a AC supply. Here two grounds will reduce
the possibility of power line noise being conducted common mode to the
antenna and then into the radio input. With one ground signal to noise
will be worse if there is any noise on the power line and there always
is some there.

Technically, I should use a ground lift on the IEC cord, but I don't
unlesss there's a noticeable loop.

This is a quick and dirty way to solve a problem. It can be dangerous
and is not recommended. This can also make things worse instead of
better because power supplies in most devices generate some AC noise
currents on the device ground.

Ground loops can cause problems in measurements systems by creating
error voltages and should be avoided. If you don't use two grounds here
a ground loop is formed so noise from the power line, which powers the
radio is added to the measurement and connecting the measurement device
provides the other half of the antenna changing the measurement. Looking
at it this way the radio input is a voltage or power measurement device
that is not floating, which we use to measure the voltage or power from
the antenna. For a single random / long wire antenna the wire is just
half the antenna. The other half is its ground. You don't want your
measurement device ground to influence the measurement so a separate
antenna ground is required. The measurement is the potential difference
between the random wire and its ground terminated in its characteristic
impedance. You then measure the voltage or power across the termination.
The antenna output is some distance from the radio (measurement device)
use coax to convey the signal to it. Here the coax impedance should be
at the antenna output impedance and also the receivers input impedance.
If the antennas output impedance is different then use a transformation
device at the antenna output to change it.

In this way you will get a similar result of signal level whether the
radio is powered from batteries or the AC mains. You can see that if the
antenna does not have its own ground that how the radio is powered will
make a big difference on received signal strength and signal to noise.

--
Telamon
Ventura, California