Vince Fiscus, KB7ADL wrote:

If you still want a balun, buy a one to one balun for the dipole
or just make a coax balun, coil seven to ten turns of coax six inches in
diameter.

That makes an RF choke, not a balun. There is no real advantage
for a balun on an antenna just for receiving.

Balun
 

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?

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

JJ wrote:

Vince Fiscus, KB7ADL wrote:

If you still want a balun, buy a one to one balun for the dipole
or just make a coax balun, coil seven to ten turns of coax six inches in
diameter.

That makes an RF choke, not a balun. There is no real advantage
for a balun on an antenna just for receiving.

Indeed, but Anna begins to toss and turn...

I must attend to her....

You must understand...

Mark S. Holden wrote:
"Vince Fiscus, KB7ADL" wrote:

Cut your antenna to the frequency or band of choice. Listen with the
balun in, then listen without it. I'll bet you won't be able to tell a
difference. In fact, there will even be a little loss in the balun.
The point I'm trying to make is, Cut your antenna to the frequency you
want for best performance and you won't need to waste money and time
building baluns.

KB7ADL



The typical SWL listens on several bands so they'd need more antennas.

I guestimate my cost for a 9:1 transformer at about $2. I probably spend about half an hour making and installing one.

You can't buy a remote RF switch or very much coax for $2.

Also, I find the ferrite greatly reduces RFI that is brought back to the antenna on the shield of the coax.

For receiving a balun is of little value. For a certain length of
antenna there is one wavelength that gives the ratio at which the
balun is designed for. When you go to different wavelengths then
the antenna shows a different impedance and the balun may do more
harm than good. The best bet for the SW listener who usually uses
a long wire antenna, is an antenna tuner to match the receiver to
varying impedances.

JJ wrote:

Vince Fiscus, KB7ADL wrote:

If you still want a balun, buy a one to one balun for the dipole
or just make a coax balun, coil seven to ten turns of coax six inches in
diameter.

That makes an RF choke, not a balun. There is no real advantage
for a balun on an antenna just for receiving.

It does make a balun- technically a current mode balun.
And for receiving a balun can make a BIG difference as it prevents the outer
shield of the feedline from picking up noise. As most feeds are vertical and
manmade noise at HF is primarily vertically polarized- the pick up can be
great.

Dale W4OP

Cut your antenna to the frequency or band of choice. Listen with the
balun in, then listen without it. I'll bet you won't be able to tell a
difference. In fact, there will even be a little loss in the balun.
The point I'm trying to make is, Cut your antenna to the frequency you
want for best performance and you won't need to waste money and time
building baluns.

KB7ADL


Dave wrote in news:p6olgv09n55icmuvb2b4f5hi20fbis7e88@
4ax.com:

Balderdash. A transformer that correctly drives the co-ax is a great
advantage.

On Mon, 07 Jul 2003 11:20:47 -0600, JJ
wrote:



Vince Fiscus, KB7ADL wrote:

There is no real advantage
for a balun on an antenna just for receiving.

Subject: Balun
From: "Vince Fiscus, KB7ADL"
Date: 7/8/2003 12:49 PM Central Daylight Time
Message-id:

Cut your antenna to the frequency or band of choice. Listen with the
balun in, then listen without it. I'll bet you won't be able to tell a
difference. In fact, there will even be a little loss in the balun.
The point I'm trying to make is, Cut your antenna to the frequency you
want for best performance and you won't need to waste money and time
building baluns.

KB7ADL


Dave wrote in news:p6olgv09n55icmuvb2b4f5hi20fbis7e88@
4ax.com:

Balderdash. A transformer that correctly drives the co-ax is a great
advantage.

On Mon, 07 Jul 2003 11:20:47 -0600, JJ
wrote:



Vince Fiscus, KB7ADL wrote:

There is no real advantage
for a balun on an antenna just for receiving.


Laughing..............it's obvious that you didn't read the name of the
newsgroup.
"Shortwave".........now, who in their right mind would cut 100's of pieces of
wire to the "exact frequency"

I guess that's why you guys are called "amateurs"



Les

"The two most common elements in the universe are hydrogen and stupidity"

Harlan Ellison

In article ,
"Vince Fiscus, KB7ADL" wrote:

Cut your antenna to the frequency or band of choice. Listen with the
balun in, then listen without it. I'll bet you won't be able to tell
a difference. In fact, there will even be a little loss in the
balun. The point I'm trying to make is, Cut your antenna to the
frequency you want for best performance and you won't need to waste
money and time building baluns.

I have done this and the Balun make a large difference in signal level
at the radio. There are many reasons for the improvement that a Balun
makes. Why would you think that it would not?

--
Telamon
Ventura, California

"Vince Fiscus, KB7ADL" wrote in
:

Michalkun wrote in
.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?



You don't say what kind of wire antenna you are using, but I don't
think I would worry about using a balun if you're just using the wire
antenna for receiving. If your antenna is a dipole, just connect the
wires straight to the coax. If you still want a balun, buy a one to
one balun for the dipole or just make a coax balun, coil seven to ten
turns of coax six inches in diameter. If your wire antenna is a loop
or folded dipole, you'll want a four to one balun.

And if you're reeeeally stuck on getting just the right balun, you
can find out what the impendence of your antenna is with an antenna
analyzer. MFJ make a cheap one, but I wouldn't waste the money buying
an analyzer just for a receive setup.

With the coax coiling where should I coil it, close to the antenna or close
to the radio? Do you have any idea how many coils give what ratio?

Y'all be trippin'. An MLB or a home made 9:1 UnUn does wonders for
reception across a very wide frequency range.

The device does 2 important things:

a] It prevents the source impedance from exceeding the load impedance,
(which is one rule that cannot ever be succesfully broken)

2] It places all parts of the antenna system at DC ground, preventing
static buildup and keeping the outer conductor from picking up
radiation

An antenna tuner is a big pain in the butt.

On Tue, 08 Jul 2003 06:52:59 -0600, JJ
wrote:



Mark S. Holden wrote:
"Vince Fiscus, KB7ADL" wrote:

Cut your antenna to the frequency or band of choice. Listen with the
balun in, then listen without it. I'll bet you won't be able to tell a
difference. In fact, there will even be a little loss in the balun.
The point I'm trying to make is, Cut your antenna to the frequency you
want for best performance and you won't need to waste money and time
building baluns.

KB7ADL



The typical SWL listens on several bands so they'd need more antennas.

I guestimate my cost for a 9:1 transformer at about $2. I probably spend about half an hour making and installing one.

You can't buy a remote RF switch or very much coax for $2.

Also, I find the ferrite greatly reduces RFI that is brought back to the antenna on the shield of the coax.

For receiving a balun is of little value. For a certain length of
antenna there is one wavelength that gives the ratio at which the
balun is designed for. When you go to different wavelengths then
the antenna shows a different impedance and the balun may do more
harm than good. The best bet for the SW listener who usually uses
a long wire antenna, is an antenna tuner to match the receiver to
varying impedances.

Michalkun wrote:


With the coax coiling where should I coil it, close to the antenna or close
to the radio? Do you have any idea how many coils give what ratio?

Save you time and energy, winding the coax into a few turns isn't
going to improve the reception of your antenna.

Dave wrote in message . ..
Balderdash. A transformer that correctly drives the co-ax is a great
advantage.

Depends on the radio. Very few modern radios would benefit as far as
s/n ratio.
All the transformer usually does is pump up the s meter. If when
hooking up the antenna, the noise level increases, you have enough
signal. Increasing the level does not increase the s/n ratio unless
the radio is half dead. On the lower frequencies, you have so much
signal level with any decent length wire, you could drastically reduce
it, and still have plenty.

On Mon, 07 Jul 2003 11:20:47 -0600, JJ
wrote:



Vince Fiscus, KB7ADL wrote:

There is no real advantage
for a balun on an antenna just for receiving.

Well, there is in some cases. In cases of bad shack noise, you can
drastically reduce noise ingress by adding a good balun or choke.
Also, many directional antennas like yagi's need decoupling for an
accurate pattern. Feedline radiation will skew the pattern. Also with
verticals used for VHF/UHF, decoupling is critical for good low angle
performance. Being all is reciprical, it's as important to receive as
it is to transmit. But, I do agree, as far as s/n ratio is concerned
with an HF wire antenna, a balun or transformer is not generally
needed. If adding matching actually improves the s/n ratio, you likely
have a fairly lame radio. The bigger payoff is reduced noise ingress
from the shack. That will improve the s/n ratio. If you actually have
noise that is... MK

In article ,
(Mark Keith) wrote:

Dave wrote in message
. ..
Balderdash. A transformer that correctly drives the co-ax is a
great advantage.

Depends on the radio. Very few modern radios would benefit as far as
s/n ratio. All the transformer usually does is pump up the s meter.
If when hooking up the antenna, the noise level increases, you have
enough signal. Increasing the level does not increase the s/n ratio
unless the radio is half dead. On the lower frequencies, you have so
much signal level with any decent length wire, you could drastically
reduce it, and still have plenty.

On Mon, 07 Jul 2003 11:20:47 -0600, JJ
wrote:



Vince Fiscus, KB7ADL wrote:

There is no real advantage
for a balun on an antenna just for receiving.

Well, there is in some cases. In cases of bad shack noise, you can
drastically reduce noise ingress by adding a good balun or choke.
Also, many directional antennas like yagi's need decoupling for an
accurate pattern. Feedline radiation will skew the pattern. Also with
verticals used for VHF/UHF, decoupling is critical for good low angle
performance. Being all is reciprical, it's as important to receive as
it is to transmit. But, I do agree, as far as s/n ratio is concerned
with an HF wire antenna, a balun or transformer is not generally
needed. If adding matching actually improves the s/n ratio, you
likely have a fairly lame radio. The bigger payoff is reduced noise
ingress from the shack. That will improve the s/n ratio. If you
actually have noise that is... MK


I don¹t understand this kind of thinking that you should not derive the
maximum benefit of an antenna that one has gone through the trouble to
put up. Your logic of all the transformer is good for is pumping up the
S meter falls flat when you don¹t have enough signal for full quieting
or whether you can make out the program material at all if the signal is
very weak. I don¹t see the need to call anyone¹s radio lame either.

Most antennas output impedance is nowhere near the typical 50-ohm coax
and a transformation can remedy that. In addition there are advantages
to preventing the coax interacting with the antenna some of which you
stated above.

Some antenna designs are better at rejecting local noise than others.
They only work if coupled properly to the coax resulting in better
signal to noise.

--
Telamon
Ventura, California

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

Telamon wrote in message


I don¹t understand this kind of thinking that you should not derive the
maximum benefit of an antenna that one has gone through the trouble to
put up. Your logic of all the transformer is good for is pumping up the
S meter falls flat when you don¹t have enough signal for full quieting
or whether you can make out the program material at all if the signal is
very weak. I don¹t see the need to call anyone¹s radio lame either.

If you are using a 70 ft random wire on HF, and you don't have enough
signal level to have a usable s/n ratio on any HF freq, you would have
a lame radio. Thats just the simple facts. Nothing personal... This is
2003. Radios are not half dead on the upper bands like to used to be
50 years ago, unless they are toys or out of alignment. There is no
"full quieting" unless you are on FM. That would generally be 10m up.
I'll repeat it again. If you hook up your antenna, and the background
noise level increases, even if just a little, you have all the s/n
ratio you need. Increasing the signal level beyond that point will not
increase the s/n ratio. It only pumps up the S meter. To see an
improvement in copy , you would need to use a directive antenna. Any
noise along with the desired signal has also increased in proportion,
so your actual s/n ratio is the same.
Sure, the signal may sound "louder" with the higher S meter reading,
but thats mainly because the level is higher, and due to the
limitations of the filter, the signal seems "wider". But the
selectivity has slightly decreased.

Most antennas output impedance is nowhere near the typical 50-ohm coax
and a transformation can remedy that.

But it doesn't matter. You don't have enough loss with the mismatch to
worry about with any decent radio. It's just not enough to knock you
out of the water. I did the math on this a few months ago, and posted
here to demonstrate this. This has been debated before many times. I
used coax feed with wild feedpoint impedances just to ensure a worst
case as far as feeder loss. It doesn't amount to enough to hurt you.
If it does, you have a lame radio. If you used a random wire direct
with no feeder, there is even less loss. For receiving, the mismatch
in that case doesn't matter enough to worry about at all.

In addition there are advantages
to preventing the coax interacting with the antenna some of which you
stated above.

Some antenna designs are better at rejecting local noise than others.
They only work if coupled properly to the coax resulting in better
signal to noise.

Sure, but that has nothing to do with the impedance tranformation. I
have no problems if people want to use transformers, I'm just saying
it's an option and should not really be needed as far as s/n ratio is
concerned. I don't use a tuner or matching on my wire antenna no
matter what freq I go to. I don't need to. I don't even come close to
needing it. I have plenty of signal level on any freq. Any doubt's and
you can pick a freq, and I'll record it and post as an mpeg.
I can dial up 28 mhz at 3 AM, and have plenty of background noise. If
I switch to the dummy load, all goes dead. Actually, I bet I could do
it at 150 mhz also...Sure, I can add my MFJ-989c tuner, and get a
perfect match as far as my radio is concerned, and maybe even pump up
the noise level an s unit or two. But it doesn't increase my s/n ratio
one whit.
BTW, any radio can be a "lame" radio, if it's not working right. I've
had a few of mine cramp up through the years. MK

In article ,
(Mark Keith) wrote:

Telamon wrote in message

I don¹t understand this kind of thinking that you should not derive the
maximum benefit of an antenna that one has gone through the trouble to
put up. Your logic of all the transformer is good for is pumping up the
S meter falls flat when you don¹t have enough signal for full quieting
or whether you can make out the program material at all if the signal is
very weak. I don¹t see the need to call anyone¹s radio lame either.

If you are using a 70 ft random wire on HF, and you don't have enough
signal level to have a usable s/n ratio on any HF freq, you would
have a lame radio. Thats just the simple facts. Nothing personal...
This is 2003. Radios are not half dead on the upper bands like to
used to be 50 years ago, unless they are toys or out of alignment.
There is no "full quieting" unless you are on FM. That would
generally be 10m up. I'll repeat it again. If you hook up your
antenna, and the background noise level increases, even if just a
little, you have all the s/n ratio you need. Increasing the signal
level beyond that point will not increase the s/n ratio. It only
pumps up the S meter. To see an improvement in copy , you would need
to use a directive antenna. Any noise along with the desired signal
has also increased in proportion, so your actual s/n ratio is the
same. Sure, the signal may sound "louder" with the higher S meter
reading, but thats mainly because the level is higher, and due to the
limitations of the filter, the signal seems "wider". But the
selectivity has slightly decreased.

The signal will not sound louder with a higher S meter reading if you
are using a radio with AGC on and it¹s working right.

Sorry to use a miss leading term ³full quieting.² I did not mean to
refer to FM modulation. Let me explain that I live in town and have
local noise to compete with any signal I pick up. This noise must be
overcome so I only hear the program material of interest. In other words
the volume can be turned up so the program material is very loud without
any background noise or hiss. Antenna efficiency that generates more
signal energy overcomes the local noise sources. You must be unusually
lucky to live in a location where all you pick up is either broadcast
signal or atmospheric noise. I don¹t think most people are as fortunate.

Most antennas output impedance is nowhere near the typical 50-ohm coax
and a transformation can remedy that.

But it doesn't matter. You don't have enough loss with the mismatch to
worry about with any decent radio. It's just not enough to knock you
out of the water. I did the math on this a few months ago, and posted
here to demonstrate this. This has been debated before many times. I
used coax feed with wild feedpoint impedances just to ensure a worst
case as far as feeder loss. It doesn't amount to enough to hurt you.
If it does, you have a lame radio. If you used a random wire direct
with no feeder, there is even less loss. For receiving, the mismatch
in that case doesn't matter enough to worry about at all.

Well OK I guess my radios are lame or busted. I must be imagining things
when signals go from ³I can just make it out S1² to ³easy to listen to
S3² on the folded dipole with the transformer. My other loop antennas
must not be working right either.

In addition there are advantages to preventing the coax interacting
with the antenna some of which you stated above.

Some antenna designs are better at rejecting local noise than
others. They only work if coupled properly to the coax resulting in
better signal to noise.

Sure, but that has nothing to do with the impedance tranformation. I
have no problems if people want to use transformers, I'm just saying
it's an option and should not really be needed as far as s/n ratio is
concerned. I don't use a tuner or matching on my wire antenna no
matter what freq I go to. I don't need to. I don't even come close to
needing it. I have plenty of signal level on any freq. Any doubt's
and you can pick a freq, and I'll record it and post as an mpeg. I
can dial up 28 mhz at 3 AM, and have plenty of background noise. If I
switch to the dummy load, all goes dead. Actually, I bet I could do
it at 150 mhz also...Sure, I can add my MFJ-989c tuner, and get a
perfect match as far as my radio is concerned, and maybe even pump up
the noise level an s unit or two. But it doesn't increase my s/n
ratio one whit. BTW, any radio can be a "lame" radio, if it's not
working right. I've had a few of mine cramp up through the years.

I¹ll see about getting my radios fixed.

--
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

In article , "Dave"
wrote:

We are not concerned with the characteristic impedance of the wire
antenna. We are concerned with its RF impedance as an antenna, not a
piece of metal.

The characteristic impedance is where the center of the antenna's
impedance spiral is. That's a good choice for a matching impedance if
what you want is a broadband antenna.

See: http://www.anarc.org/naswa/badx/ante..._longwire.html

--
| John Doty "You can't confuse me, that's my job."
| Home:
| Work:

We are not concerned with the characteristic impedance of the wire
antenna. We are concerned with its RF impedance as an antenna, not a
piece of metal.

Resonance is defined as when the reactances neutralize each other, a
very frequency dependant characteristic give a fixed size conductor.

On Sat, 12 Jul 2003 20:39:45 GMT, Telamon
wrote:

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.

Telamon wrote in message ..
Let me explain that I live in town and have
local noise to compete with any signal I pick up. This noise must be
overcome so I only hear the program material of interest. In other words
the volume can be turned up so the program material is very loud without
any background noise or hiss. Antenna efficiency that generates more
signal energy overcomes the local noise sources. You must be unusually
lucky to live in a location where all you pick up is either broadcast
signal or atmospheric noise. I don¹t think most people are as fortunate.

I assume your noise must be shack generated, and is an ingress
problem. I would think anyway. If the noise was local, but picked up
from the antenna itself
along with the desired station, then adding the transformer would not
change the s/n ratio. The noise would increase along with the station
at an equal rate. Everything would "sound" the same. Only the S meter
would read higher.

If you have a noise ingress problem, feedline decoupling is the
answer, not a better impedance match. Also,feedline decoupling, and
impedance matching, or SWR, are totally unrelated. You can have great
decoupling with an 80 to 1 mismatch. Or you can have a perfect 1:1
match with horrible decoupling. They are totally unrelated. I'm not
lucky. I live in the city of Houston amid all kinds of noise
generating crap. But due to decent feedline decoupling, any noise I
hear is picked up from the antenna. And any attempts to achieve a
better match do not increase my s/n ratio, being as I always have
enough signal level to begin with even with no matching.

Most antennas output impedance is nowhere near the typical 50-ohm coax
and a transformation can remedy that.

But it doesn't matter. You don't have enough loss with the mismatch to
worry about with any decent radio. It's just not enough to knock you
out of the water. I did the math on this a few months ago, and posted
here to demonstrate this. This has been debated before many times. I
used coax feed with wild feedpoint impedances just to ensure a worst
case as far as feeder loss. It doesn't amount to enough to hurt you.
If it does, you have a lame radio. If you used a random wire direct
with no feeder, there is even less loss. For receiving, the mismatch
in that case doesn't matter enough to worry about at all.

Well OK I guess my radios are lame or busted. I must be imagining things
when signals go from ³I can just make it out S1² to ³easy to listen to
S3² on the folded dipole with the transformer. My other loop antennas
must not be working right either.

Is the S1 with the folded dipole fed directly without the transformer,
or another antenna? It sounds like you have or had a noise ingress
problem if the noise does not increase at the same level as the signal
when the transformer is added.
If this is the case, again, this would not be a function of impedance
matching, but a function of better feedline decoupling. The decoupling
is improving the s/n ratio, not the impedance transformation. If the
signal was S1, it should have been solid copy, if it is at S3. If it
wasn't, the overriding noise was not picked up by the antenna. It was
picked up on the outer shield of the coax down in the shack, piped up
to the feedpoint, and then piped back down to the radio on the inner
part of the outer shield. "I assume you used coax"..S1 is plenty of
signal level for solid copy if no shack noise is drowning it out.
What's the problem with the loop? Lots of noise also? MK

In article , "Dave"
wrote:

Is this Smith Chart stuff? (You must forgive me, I am a primitive.)

A Smith chart is a way of graphically relating impedances to reflection
coefficients. The code that made the plots on the web page did the same
sort of calculations numerically. The plots themselves are semilog
Cartesian coordinates, not Smith charts.


On Sun, 13 Jul 2003 12:21:23 +0400, "John Doty" wrote:

In article , "Dave"
wrote:

We are not concerned with the characteristic impedance of the wire
antenna. We are concerned with its RF impedance as an antenna, not a
piece of metal.

The characteristic impedance is where the center of the antenna's
impedance spiral is. That's a good choice for a matching impedance if
what you want is a broadband antenna.

See: http://www.anarc.org/naswa/badx/ante..._longwire.html



--
| John Doty "You can't confuse me, that's my job."
| Home:
| Work:

In article ,
(Mark Keith) wrote:

Telamon wrote in message

..
Let me explain that I live in town and have
local noise to compete with any signal I pick up. This noise must be
overcome so I only hear the program material of interest. In other words
the volume can be turned up so the program material is very loud without
any background noise or hiss. Antenna efficiency that generates more
signal energy overcomes the local noise sources. You must be unusually
lucky to live in a location where all you pick up is either broadcast
signal or atmospheric noise. I don¹t think most people are as fortunate.

I assume your noise must be shack generated, and is an ingress
problem. I would think anyway. If the noise was local, but picked up
from the antenna itself
along with the desired station, then adding the transformer would not
change the s/n ratio. The noise would increase along with the station
at an equal rate. Everything would "sound" the same. Only the S meter
would read higher.

If you have a noise ingress problem, feedline decoupling is the
answer, not a better impedance match. Also,feedline decoupling, and
impedance matching, or SWR, are totally unrelated. You can have great
decoupling with an 80 to 1 mismatch. Or you can have a perfect 1:1
match with horrible decoupling. They are totally unrelated. I'm not
lucky. I live in the city of Houston amid all kinds of noise
generating crap. But due to decent feedline decoupling, any noise I
hear is picked up from the antenna. And any attempts to achieve a
better match do not increase my s/n ratio, being as I always have
enough signal level to begin with even with no matching.

Most antennas output impedance is nowhere near the typical 50-ohm coax
and a transformation can remedy that.

But it doesn't matter. You don't have enough loss with the mismatch to
worry about with any decent radio. It's just not enough to knock you
out of the water. I did the math on this a few months ago, and posted
here to demonstrate this. This has been debated before many times. I
used coax feed with wild feedpoint impedances just to ensure a worst
case as far as feeder loss. It doesn't amount to enough to hurt you.
If it does, you have a lame radio. If you used a random wire direct
with no feeder, there is even less loss. For receiving, the mismatch
in that case doesn't matter enough to worry about at all.

Well OK I guess my radios are lame or busted. I must be imagining things
when signals go from ³I can just make it out S1² to ³easy to listen to
S3² on the folded dipole with the transformer. My other loop antennas
must not be working right either.

Is the S1 with the folded dipole fed directly without the transformer,
or another antenna? It sounds like you have or had a noise ingress
problem if the noise does not increase at the same level as the signal
when the transformer is added.
If this is the case, again, this would not be a function of impedance
matching, but a function of better feedline decoupling. The decoupling
is improving the s/n ratio, not the impedance transformation. If the
signal was S1, it should have been solid copy, if it is at S3. If it
wasn't, the overriding noise was not picked up by the antenna. It was
picked up on the outer shield of the coax down in the shack, piped up
to the feedpoint, and then piped back down to the radio on the inner
part of the outer shield. "I assume you used coax"..S1 is plenty of
signal level for solid copy if no shack noise is drowning it out.
What's the problem with the loop? Lots of noise also? MK

The antenna is a folded dipole cut for 13 meters connected to the radio
with coax.

I evaluated two stations on this band. One had locally generated noise
interference and the other did not.

I tried a repeat today with switching the matching transformer in and
out of the circuit and compared it to a large ferrite toroid in its
place. The coax made one turn through the toroid. The ferrite worked as
well as the transformer on the station with the local noise on it. No
difference found on the station in the clear. In addition the
transformer did not make a difference in the S meter reading either.

It takes me several minutes to change the transformer in or out and we
had a minor geomagnetic storm yesterday so conditions changing must have
been what I saw as a performance difference.

Today conditions are more stable and I switched the transformer and / or
toroid choke in and out several times averaging the results.

So it looks like the only benefit of the transformer was isolation it
provided on the folded dipole.

--
Telamon
Ventura, California

Doesn't loose coupling pinch bandwidth? Q through the roof?

Higher Q = lower noise but not necessarily better overall voice
perfomrance, as I recall.

On 13 Jul 2003 07:40:13 -0700, (Mark Keith) wrote:

Telamon wrote in message ..
Let me explain that I live in town and have
local noise to compete with any signal I pick up. This noise must be
overcome so I only hear the program material of interest. In other words
the volume can be turned up so the program material is very loud without
any background noise or hiss. Antenna efficiency that generates more
signal energy overcomes the local noise sources. You must be unusually
lucky to live in a location where all you pick up is either broadcast
signal or atmospheric noise. I don¹t think most people are as fortunate.

I assume your noise must be shack generated, and is an ingress
problem. I would think anyway. If the noise was local, but picked up
from the antenna itself
along with the desired station, then adding the transformer would not
change the s/n ratio. The noise would increase along with the station
at an equal rate. Everything would "sound" the same. Only the S meter
would read higher.

If you have a noise ingress problem, feedline decoupling is the
answer, not a better impedance match. Also,feedline decoupling, and
impedance matching, or SWR, are totally unrelated. You can have great
decoupling with an 80 to 1 mismatch. Or you can have a perfect 1:1
match with horrible decoupling. They are totally unrelated. I'm not
lucky. I live in the city of Houston amid all kinds of noise
generating crap. But due to decent feedline decoupling, any noise I
hear is picked up from the antenna. And any attempts to achieve a
better match do not increase my s/n ratio, being as I always have
enough signal level to begin with even with no matching.

Most antennas output impedance is nowhere near the typical 50-ohm coax
and a transformation can remedy that.

But it doesn't matter. You don't have enough loss with the mismatch to
worry about with any decent radio. It's just not enough to knock you
out of the water. I did the math on this a few months ago, and posted
here to demonstrate this. This has been debated before many times. I
used coax feed with wild feedpoint impedances just to ensure a worst
case as far as feeder loss. It doesn't amount to enough to hurt you.
If it does, you have a lame radio. If you used a random wire direct
with no feeder, there is even less loss. For receiving, the mismatch
in that case doesn't matter enough to worry about at all.

Well OK I guess my radios are lame or busted. I must be imagining things
when signals go from ³I can just make it out S1² to ³easy to listen to
S3² on the folded dipole with the transformer. My other loop antennas
must not be working right either.

Is the S1 with the folded dipole fed directly without the transformer,
or another antenna? It sounds like you have or had a noise ingress
problem if the noise does not increase at the same level as the signal
when the transformer is added.
If this is the case, again, this would not be a function of impedance
matching, but a function of better feedline decoupling. The decoupling
is improving the s/n ratio, not the impedance transformation. If the
signal was S1, it should have been solid copy, if it is at S3. If it
wasn't, the overriding noise was not picked up by the antenna. It was
picked up on the outer shield of the coax down in the shack, piped up
to the feedpoint, and then piped back down to the radio on the inner
part of the outer shield. "I assume you used coax"..S1 is plenty of
signal level for solid copy if no shack noise is drowning it out.
What's the problem with the loop? Lots of noise also? MK

I used to make folded dipoles out of 300 Ohm TV Twinlead and match the
feedpoint with a TV balun driving RG-6 to the receiver. It worked
pretty well into an R-390A. Including medium wave, even.

On Sun, 13 Jul 2003 18:49:34 GMT, Telamon
wrote:


The antenna is a folded dipole cut for 13 meters connected to the radio
with coax.

I evaluated two stations on this band. One had locally generated noise
interference and the other did not.

I tried a repeat today with switching the matching transformer in and
out of the circuit and compared it to a large ferrite toroid in its
place. The coax made one turn through the toroid. The ferrite worked as
well as the transformer on the station with the local noise on it. No
difference found on the station in the clear. In addition the
transformer did not make a difference in the S meter reading either.

It takes me several minutes to change the transformer in or out and we
had a minor geomagnetic storm yesterday so conditions changing must have
been what I saw as a performance difference.

Today conditions are more stable and I switched the transformer and / or
toroid choke in and out several times averaging the results.

So it looks like the only benefit of the transformer was isolation it
provided on the folded dipole.

Amazing.

I'm going to save this, in case it comes up at a party.

Thanks.

On Sun, 13 Jul 2003 19:58:11 +0400, "John Doty" wrote:

In article , "Dave"
wrote:

Is this Smith Chart stuff? (You must forgive me, I am a primitive.)

A Smith chart is a way of graphically relating impedances to reflection
coefficients. The code that made the plots on the web page did the same
sort of calculations numerically. The plots themselves are semilog
Cartesian coordinates, not Smith charts.


On Sun, 13 Jul 2003 12:21:23 +0400, "John Doty" wrote:

In article , "Dave"
wrote:

We are not concerned with the characteristic impedance of the wire
antenna. We are concerned with its RF impedance as an antenna, not a
piece of metal.

The characteristic impedance is where the center of the antenna's
impedance spiral is. That's a good choice for a matching impedance if
what you want is a broadband antenna.

See: http://www.anarc.org/naswa/badx/ante..._longwire.html

John,

Nice to see you back on the group. Things have been a little rough here
lately but there's still hope. I often recommend your low noise antenna
with the balun located near the ground. It worked well for me. I can
listen to shortwave now without any interference from the computer,
television and other home appliances.

How are things in the X-ray universe?

John Doty wrote:

In article , "Dave"
wrote:

Is this Smith Chart stuff? (You must forgive me, I am a primitive.)

A Smith chart is a way of graphically relating impedances to reflection
coefficients. The code that made the plots on the web page did the same
sort of calculations numerically. The plots themselves are semilog
Cartesian coordinates, not Smith charts.


On Sun, 13 Jul 2003 12:21:23 +0400, "John Doty" wrote:

In article , "Dave"
wrote:

We are not concerned with the characteristic impedance of the wire
antenna. We are concerned with its RF impedance as an antenna, not a
piece of metal.

The characteristic impedance is where the center of the antenna's
impedance spiral is. That's a good choice for a matching impedance if
what you want is a broadband antenna.

See: http://www.anarc.org/naswa/badx/ante..._longwire.html


--
| John Doty "You can't confuse me, that's my job."
| Home:
| Work:


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Telamon wrote in message ..

Isn anyone going to comment on the transformer not showing a higher S
meter reading on the radio? This sure surprised me. Maybe the two
stations I picked happened to be in a good spot where it wasn needed.

Not too surprising.. Will depend on the freq. Being your antenna is
folded, I would have to model it to see the src data for each
shortwave band. I'm guessing it would be about as for a single wire
version, except the with appx 4 X transformation of the folded
antenna. Anyway, the feed impedance will vary all over the place from
band to band. You probably have about as good a chance getting a
usable match without the transformer, as you do with it. In some
cases, the transformer could actually make the match worse. Some will
be better. Some about the same. This is a common scenario when
running an antenna like a G5RV. Most use 4:1 baluns. But really a 1:1
balun makes about as much sense being you are already using a tuner.
Of course, I don't like the feeding of the average G5RV's. I'd dump
the coax and feed straight with ladder line. I don't like mixing
feedline types and then using a balun to try to assure a good match
between lines. Usually, the match is not very good, and you have more
loss. But this is mainly a transmit issue, not receiving at HF. MK

Telamon wrote in message

I only looked at a few frequencies but those were near the frequency for
which the antenna was cut. I¹m not worried about the other bands. I want
to know why I did not get a higher S meter reading on the band the
antenna was cut for. The transformer should have made for a better match
on 13 meters and it didn¹t.

I think mainly because the antenna is "folded". I tried modeling a
folded 40m dipole last night just to look at a few bands. At it's
design freq, the feed impedance is pretty low. You might need to
reverse the transformer to get a better match on that band if it was
set up to match mainly Hi-Z loads. If you want a good match to coax on
one particular band , I'd go to a straight dipole, not folded. I've
never used folded dipoles, so I'm not sure of any quirks they may have
as a multiband antenna. But really no matter...It sounds like you have
enough signal level no matter what route you take.
MK

Telamon wrote in message
I only looked at a few frequencies but those were near the frequency for
which the antenna was cut. I¹m not worried about the other bands. I want
to know why I did not get a higher S meter reading on the band the
antenna was cut for. The transformer should have made for a better match
on 13 meters and it didn¹t.

I mentioned in an earlier post that the folded dipole I modeled showed
a low Z. But after thinking about it, that didn't seem right. I had
always assumed most folded dipoles with two wires had about a 300 ohm
feedpoint. And double checking in a book, that seems to be the case. I
don't know why the antenna I modeled showed that, but I'll have to
look into it. But anyway, if you had a 300 ohm feedpoint, and used a
9:1 balun, you would end up quite low in Z to the radio.
A 4:1 would put you in the ballpark. But, I'd still prefer to use a
single wire dipole fed with coax for a single band dipole. No
transformer needed. Only a balun, and that can be a choke wound from
the coax. But again, as far as s/n ratio, not counting noise ingress
problems, any of them should work. MK

Mark Keith wrote:

Telamon wrote in message
I only looked at a few frequencies but those were near the frequency for
which the antenna was cut. I¹m not worried about the other bands. I want
to know why I did not get a higher S meter reading on the band the
antenna was cut for. The transformer should have made for a better match
on 13 meters and it didn¹t.

I mentioned in an earlier post that the folded dipole I modeled showed
a low Z. But after thinking about it, that didn't seem right. I had
always assumed most folded dipoles with two wires had about a 300 ohm
feedpoint. And double checking in a book, that seems to be the case. I
don't know why the antenna I modeled showed that, but I'll have to
look into it. But anyway, if you had a 300 ohm feedpoint, and used a
9:1 balun, you would end up quite low in Z to the radio.
A 4:1 would put you in the ballpark. But, I'd still prefer to use a
single wire dipole fed with coax for a single band dipole. No
transformer needed. Only a balun, and that can be a choke wound from
the coax. But again, as far as s/n ratio, not counting noise ingress
problems, any of them should work. MK

Hi Mark,
What software are you using for modeling? NEC engines do not like close wires
(perhaps NEC4 has dealt with this).
EZNEC or AO should handle the problem better.

Dale W4OP
for PAR Electronics, Inc.

Michalkun wrote:
Is it true that if you feed a dipole in the middle you don't need a balun?

Depends on how you feed it, and what with.

--
The function of an asshole is to emit quantities of crap. Spammers do
a very good job of that. However, I do object to my inbox being a
spammer's toilet bowl. -- Walter Dnes

Michalkun,

If you are going to 'use' a "Balanced FeedLine" (300 Ohm Twin Lead or
450 Ohm Ladder Line) and connect this FeedLine directly into the
radio/receivers HI-Z Terminals then you do not need a BalUn.

However, if you wish to use Coax Cable as a 'feedline' from the
antenna to the radio's LO-Z Antenna Connector; then some form of
matching transformer should be used to get the best results from your
dipole antenna.


~ RHF
..
..
= = = Michalkun
= = = wrote in message 2.251...
Is it true that if you feed a dipole in the middle you don't need a balun?

RHF wrote:

Michalkun,

If you are going to 'use' a "Balanced FeedLine" (300 Ohm Twin Lead or
450 Ohm Ladder Line) and connect this FeedLine directly into the
radio/receivers HI-Z Terminals then you do not need a BalUn.

However, if you wish to use Coax Cable as a 'feedline' from the
antenna to the radio's LO-Z Antenna Connector; then some form of
matching transformer should be used to get the best results from your
dipole antenna.

A typical half-wave dipole fed with 50 ohm, or even say 75 ohm coax should feed nicely
right into the Lo-Z input on a receiver without a balun of any kind.

Purists may wish to put a 1:1 balun at the feedpoint though.

Steve
Holland, MI

Drake R7, R8 and R8B

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?

Dale Parfitt wrote in message

Hi Mark,
What software are you using for modeling? NEC engines do not like close wires
(perhaps NEC4 has dealt with this).
EZNEC or AO should handle the problem better.

Dale W4OP
for PAR Electronics, Inc.

It was MMANA "freeware" which uses the mininec engine. I finally got
it to work.
I wanted to try some other programs also. The first version I made
placed the wires at only .3m apart. "40m antenna" When I tried .5m, it
clicked in and started showing believable results. Around 300 ohms,
plus or minus depending if high or low from the design point. When I
tuned that particular antenna so I had nearly no reactance, I got
284.617-j0.444 . Thats probably fairly close. MK