On Wed, 06 Apr 2005 17:15:08 GMT, Lancer wrote:


Why should I be nice? I -was- nice. We have had civil converstations,
and I even gave him enough info to install the antenna in his attic,
which apparently worked quite well. Then he stuck his finger into the
political lion cage and turned into a sniveling crybaby after getting
scratched.

As for being a general-class amateur, there are literally hundreds of
hammie websites that cover nothing but antennas, not to mention the
ARRL manual. If he's so serious about radio, why beg a CB group for
info on how to install a prefab antenna? J.H.F.C, how did he pass the
exam without knowing a few antenna fundamentals? And if part of the
hobby is to learn about radio comm, why ask a CB group for tech info
when there are countless resources available for hams? Isn't anyone
elmering the kid?




I thought your were elmering him Frank?

He really doesn't need one anyway, he buys his antennas. Even
something as simple as a dipole, or sloper...


Do you have a problem with that? Show me the rules on antenna requirements,
please.

Vinnie S.

On Wed, 06 Apr 2005 20:14:16 -0400, Vinnie S.
wrote in :

On Wed, 06 Apr 2005 17:15:08 GMT, Lancer wrote:


Why should I be nice? I -was- nice. We have had civil converstations,
and I even gave him enough info to install the antenna in his attic,
which apparently worked quite well. Then he stuck his finger into the
political lion cage and turned into a sniveling crybaby after getting
scratched.

As for being a general-class amateur, there are literally hundreds of
hammie websites that cover nothing but antennas, not to mention the
ARRL manual. If he's so serious about radio, why beg a CB group for
info on how to install a prefab antenna? J.H.F.C, how did he pass the
exam without knowing a few antenna fundamentals? And if part of the
hobby is to learn about radio comm, why ask a CB group for tech info
when there are countless resources available for hams? Isn't anyone
elmering the kid?




I thought your were elmering him Frank?

He really doesn't need one anyway, he buys his antennas. Even
something as simple as a dipole, or sloper...


Do you have a problem with that? Show me the rules on antenna requirements,
please.


Looks like Vinnie is going to be a General-class appliance operator.






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Hey Vinnie............I can help you. The formula for a 1/4 wavelength
radiator is (234 / F) whereby F is the frequency in MHz. This will give you
the length in feet. For the radials, (237 / F) will give you that length.
Always remember...multiply the radiator length by 1.05 and that is another
way of calculating the 1/4 wavelength radials.
The feedpoint impedance of a 1/4 wave ground plane is 37 ohms when you have
the radials at a 90 degree angle with respect to the radiator. If you have
the radials drooped at a 45 degree angle, the impedance rises to
approximately 50 ohms.
If you have a single radial drooped at a 180 degree angle with respect to
the radiator, the impedance rises to 75 ohms.
There was an article in RF Design magazine a few years back, explaining why
certain impedances are used in the RF industry.
72 ohms was the impedance that produced minimum cable losses...........50
ohms is a happy medium.
On a final note...........at 37 ohms, you will have a VSWR of 1.3 to
1.................at 75 ohms, you will have a VSWR of
1.5 to 1. What is the difference here? For a transmitter with a tube output
and an internal matching network, you wouldn't really see much effect. For a
typical solid state transmitter, there would be some difference between the
two antenna impedances, because the broadband solid state transmitter would
be called upon to deliver more current to the antenna. It probably wouldn't
have any effect, unless the ALC circuit was aggressive in its operation. In
this case, power foldback would occur into the 37 ohm load. Would it happen?
Probably not.
I hope this helps.

Pete

"Frank Gilliland" wrote in message
...
On Wed, 06 Apr 2005 20:14:16 -0400, Vinnie S.
wrote in :

On Wed, 06 Apr 2005 17:15:08 GMT, Lancer wrote:


Why should I be nice? I -was- nice. We have had civil converstations,
and I even gave him enough info to install the antenna in his attic,
which apparently worked quite well. Then he stuck his finger into the
political lion cage and turned into a sniveling crybaby after getting
scratched.

As for being a general-class amateur, there are literally hundreds of
hammie websites that cover nothing but antennas, not to mention the
ARRL manual. If he's so serious about radio, why beg a CB group for
info on how to install a prefab antenna? J.H.F.C, how did he pass the
exam without knowing a few antenna fundamentals? And if part of the
hobby is to learn about radio comm, why ask a CB group for tech info
when there are countless resources available for hams? Isn't anyone
elmering the kid?




I thought your were elmering him Frank?

He really doesn't need one anyway, he buys his antennas. Even
something as simple as a dipole, or sloper...


Do you have a problem with that? Show me the rules on antenna
requirements,
please.


Looks like Vinnie is going to be a General-class appliance operator.






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On Sun, 10 Apr 2005 19:58:28 GMT, "Pete KE9OA"
wrote in
:

Hey Vinnie............I can help you. The formula for a 1/4 wavelength
radiator is (234 / F) whereby F is the frequency in MHz. This will give you
the length in feet. For the radials, (237 / F) will give you that length.
Always remember...multiply the radiator length by 1.05 and that is another
way of calculating the 1/4 wavelength radials.


It should be noted that these formulas are only appoximations. Actual
sizes are dependent upon the conductivity and diameter of the
elements, and the quantity and angle of the radials. When building a
resonant antenna it's a good idea to make the elements a little long
and trim to resonance.


The feedpoint impedance of a 1/4 wave ground plane is 37 ohms when you have
the radials at a 90 degree angle with respect to the radiator. If you have
the radials drooped at a 45 degree angle, the impedance rises to
approximately 50 ohms.
If you have a single radial drooped at a 180 degree angle with respect to
the radiator, the impedance rises to 75 ohms.


These are impedances for antennas in free space, and are practical
only if you can mount your antenna well above the ground and away from
any tall objects.


There was an article in RF Design magazine a few years back, explaining why
certain impedances are used in the RF industry.
72 ohms was the impedance that produced minimum cable losses...........50
ohms is a happy medium.


Close. For lowest loss, the optimum characteristic impedance of coax
is 76.9 ohms. 70-73 ohm coax is used as a compromise between low loss
coax and coax optimized for minimization of flashover, the latter
having an impedance of about 60 ohms.

And while many people have many different ideas as to why 50 ohm coax
is made, it is just a compromise between low-loss/low-flashover coax
of 72 ohms and coax optimized for handling power (about 30 ohms, which
is too lossy for practical transmission lines).


On a final note...........at 37 ohms, you will have a VSWR of 1.3 to
1.................at 75 ohms, you will have a VSWR of
1.5 to 1. What is the difference here? For a transmitter with a tube output
and an internal matching network, you wouldn't really see much effect. For a
typical solid state transmitter, there would be some difference between the
two antenna impedances, because the broadband solid state transmitter would
be called upon to deliver more current to the antenna. It probably wouldn't
have any effect, unless the ALC circuit was aggressive in its operation. In
this case, power foldback would occur into the 37 ohm load. Would it happen?
Probably not.


......uh, what?

Both tubes and transistors use matching networks, so I don't know what
distinction you are trying to make there. Power will be reflected from
an antenna/coax mismatch -regardless- of whether you have a tube or
transistor final. And what does an ALC circuit have to do with
transmission line propogation?


I hope this helps.

Pete





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"Frank Gilliland" wrote in message
...
On Sun, 10 Apr 2005 19:58:28 GMT, "Pete KE9OA"
wrote in
:

Hey Vinnie............I can help you. The formula for a 1/4 wavelength
radiator is (234 / F) whereby F is the frequency in MHz. This will give
you
the length in feet. For the radials, (237 / F) will give you that length.
Always remember...multiply the radiator length by 1.05 and that is another
way of calculating the 1/4 wavelength radials.


It should be noted that these formulas are only appoximations. Actual
sizes are dependent upon the conductivity and diameter of the
elements, and the quantity and angle of the radials. When building a
resonant antenna it's a good idea to make the elements a little long
and trim to resonance.

Very true..........I use a spectrum analyzer with a directional coupler and
trim for maximum return loww.


The feedpoint impedance of a 1/4 wave ground plane is 37 ohms when you
have
the radials at a 90 degree angle with respect to the radiator. If you have
the radials drooped at a 45 degree angle, the impedance rises to
approximately 50 ohms.
If you have a single radial drooped at a 180 degree angle with respect to
the radiator, the impedance rises to 75 ohms.


These are impedances for antennas in free space, and are practical
only if you can mount your antenna well above the ground and away from
any tall objects.

Also true, but a good starting point.


There was an article in RF Design magazine a few years back, explaining
why
certain impedances are used in the RF industry.
72 ohms was the impedance that produced minimum cable losses...........50
ohms is a happy medium.


Close. For lowest loss, the optimum characteristic impedance of coax
is 76.9 ohms. 70-73 ohm coax is used as a compromise between low loss
coax and coax optimized for minimization of flashover, the latter
having an impedance of about 60 ohms.

Good memory.

And while many people have many different ideas as to why 50 ohm coax
is made, it is just a compromise between low-loss/low-flashover coax
of 72 ohms and coax optimized for handling power (about 30 ohms, which
is too lossy for practical transmission lines).


On a final note...........at 37 ohms, you will have a VSWR of 1.3 to
1.................at 75 ohms, you will have a VSWR of
1.5 to 1. What is the difference here? For a transmitter with a tube
output
and an internal matching network, you wouldn't really see much effect. For
a
typical solid state transmitter, there would be some difference between
the
two antenna impedances, because the broadband solid state transmitter
would
be called upon to deliver more current to the antenna. It probably
wouldn't
have any effect, unless the ALC circuit was aggressive in its operation.
In
this case, power foldback would occur into the 37 ohm load. Would it
happen?
Probably not.


.....uh, what?

Both tubes and transistors use matching networks, so I don't know what
distinction you are trying to make there. Power will be reflected from
an antenna/coax mismatch -regardless- of whether you have a tube or
transistor final. And what does an ALC circuit have to do with
transmission line propogation?

This pertains to solid state amateur transceivers that don't have an
adjustable output matching network.........most of today's units have
fixed-tuned bandpass filters after the output stage. I am not referring to
transmission line propagation; I am referring to the fact that, with a
fixed-tuned output network that expects to see a 50 ohm characteristic
impedance, the ALC can fold back the power. Usually, that doesn't occur
until a VSWR of 2 to 1 is reached. My explanation is for illustrative
purposes only.


I hope this helps.

Pete





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Oops.............that should have been maximum return loss. Touch
typing...........you know!

Pete

"Pete KE9OA" wrote in message
...

"Frank Gilliland" wrote in message
...
On Sun, 10 Apr 2005 19:58:28 GMT, "Pete KE9OA"
wrote in
:

Hey Vinnie............I can help you. The formula for a 1/4 wavelength
radiator is (234 / F) whereby F is the frequency in MHz. This will give
you
the length in feet. For the radials, (237 / F) will give you that length.
Always remember...multiply the radiator length by 1.05 and that is
another
way of calculating the 1/4 wavelength radials.


It should be noted that these formulas are only appoximations. Actual
sizes are dependent upon the conductivity and diameter of the
elements, and the quantity and angle of the radials. When building a
resonant antenna it's a good idea to make the elements a little long
and trim to resonance.

Very true..........I use a spectrum analyzer with a directional coupler
and trim for maximum return loww.


The feedpoint impedance of a 1/4 wave ground plane is 37 ohms when you
have
the radials at a 90 degree angle with respect to the radiator. If you
have
the radials drooped at a 45 degree angle, the impedance rises to
approximately 50 ohms.
If you have a single radial drooped at a 180 degree angle with respect to
the radiator, the impedance rises to 75 ohms.


These are impedances for antennas in free space, and are practical
only if you can mount your antenna well above the ground and away from
any tall objects.

Also true, but a good starting point.


There was an article in RF Design magazine a few years back, explaining
why
certain impedances are used in the RF industry.
72 ohms was the impedance that produced minimum cable losses...........50
ohms is a happy medium.


Close. For lowest loss, the optimum characteristic impedance of coax
is 76.9 ohms. 70-73 ohm coax is used as a compromise between low loss
coax and coax optimized for minimization of flashover, the latter
having an impedance of about 60 ohms.

Good memory.

And while many people have many different ideas as to why 50 ohm coax
is made, it is just a compromise between low-loss/low-flashover coax
of 72 ohms and coax optimized for handling power (about 30 ohms, which
is too lossy for practical transmission lines).


On a final note...........at 37 ohms, you will have a VSWR of 1.3 to
1.................at 75 ohms, you will have a VSWR of
1.5 to 1. What is the difference here? For a transmitter with a tube
output
and an internal matching network, you wouldn't really see much effect.
For a
typical solid state transmitter, there would be some difference between
the
two antenna impedances, because the broadband solid state transmitter
would
be called upon to deliver more current to the antenna. It probably
wouldn't
have any effect, unless the ALC circuit was aggressive in its operation.
In
this case, power foldback would occur into the 37 ohm load. Would it
happen?
Probably not.


.....uh, what?

Both tubes and transistors use matching networks, so I don't know what
distinction you are trying to make there. Power will be reflected from
an antenna/coax mismatch -regardless- of whether you have a tube or
transistor final. And what does an ALC circuit have to do with
transmission line propogation?

This pertains to solid state amateur transceivers that don't have an
adjustable output matching network.........most of today's units have
fixed-tuned bandpass filters after the output stage. I am not referring to
transmission line propagation; I am referring to the fact that, with a
fixed-tuned output network that expects to see a 50 ohm characteristic
impedance, the ALC can fold back the power. Usually, that doesn't occur
until a VSWR of 2 to 1 is reached. My explanation is for illustrative
purposes only.


I hope this helps.

Pete





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On Mon, 11 Apr 2005 08:03:21 GMT, "Pete KE9OA"
wrote in
:

snip
On a final note...........at 37 ohms, you will have a VSWR of 1.3 to
1.................at 75 ohms, you will have a VSWR of
1.5 to 1. What is the difference here? For a transmitter with a tube
output
and an internal matching network, you wouldn't really see much effect. For
a
typical solid state transmitter, there would be some difference between
the
two antenna impedances, because the broadband solid state transmitter
would
be called upon to deliver more current to the antenna. It probably
wouldn't
have any effect, unless the ALC circuit was aggressive in its operation.
In
this case, power foldback would occur into the 37 ohm load. Would it
happen?
Probably not.


.....uh, what?

Both tubes and transistors use matching networks, so I don't know what
distinction you are trying to make there. Power will be reflected from
an antenna/coax mismatch -regardless- of whether you have a tube or
transistor final. And what does an ALC circuit have to do with
transmission line propogation?

This pertains to solid state amateur transceivers that don't have an
adjustable output matching network.........most of today's units have
fixed-tuned bandpass filters after the output stage. I am not referring to
transmission line propagation; I am referring to the fact that, with a
fixed-tuned output network that expects to see a 50 ohm characteristic
impedance, the ALC can fold back the power. Usually, that doesn't occur
until a VSWR of 2 to 1 is reached. My explanation is for illustrative
purposes only.


I understood that much. My point was that whenever an antenna/coax
mismatch occurs, tuning the output tank (as with a tube final) doesn't
cure the mismatch or the resulting signal loss. All it does is protect
the final from the reflected power. The output tank should be matched
to the characteristic impedance of the coax whether the final is a
tube or a transistor. If the coax shows standing waves, the mismatch
should be fixed at the point of mismatch, not at the radio. I realize
that this is not always practical, but people should know that such a
conjugate match just dissipates that reflected power somewhere else,
usually from the outside of the coax or the radio.

As for ALC, I thought you were referring to a different type of
limiting. My bad.





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On Mon, 11 Apr 2005 08:03:21 GMT, "Pete KE9OA"
wrote:

It should be noted that these formulas are only appoximations. Actual
sizes are dependent upon the conductivity and diameter of the
elements, and the quantity and angle of the radials. When building a
resonant antenna it's a good idea to make the elements a little long
and trim to resonance.

Very true..........I use a spectrum analyzer with a directional coupler and
trim for maximum return loww.

So do I. It gives a much better picture than a simple SWR bridge.


The feedpoint impedance of a 1/4 wave ground plane is 37 ohms when you
have
the radials at a 90 degree angle with respect to the radiator. If you have
the radials drooped at a 45 degree angle, the impedance rises to
approximately 50 ohms.
If you have a single radial drooped at a 180 degree angle with respect to
the radiator, the impedance rises to 75 ohms.


These are impedances for antennas in free space, and are practical
only if you can mount your antenna well above the ground and away from
any tall objects.

Also true, but a good starting point.

Some people like to make the subtle conditions into much greater
points than they need to be.



.....uh, what?

Both tubes and transistors use matching networks, so I don't know what
distinction you are trying to make there. Power will be reflected from
an antenna/coax mismatch -regardless- of whether you have a tube or
transistor final. And what does an ALC circuit have to do with
transmission line propogation?

This pertains to solid state amateur transceivers that don't have an
adjustable output matching network.........most of today's units have
fixed-tuned bandpass filters after the output stage. I am not referring to
transmission line propagation; I am referring to the fact that, with a
fixed-tuned output network that expects to see a 50 ohm characteristic
impedance, the ALC can fold back the power. Usually, that doesn't occur
until a VSWR of 2 to 1 is reached. My explanation is for illustrative
purposes only.

Not only that, but the bandpass filter characteristics of the output
stages can change if the load impedance changes significantly,
increasing loss and broadening the cutoff points.

Dave
"Sandbagger"
http://home.ptd.net/~n3cvj

On Sun, 10 Apr 2005 19:58:28 GMT, "Pete KE9OA"
wrote:

Hey Vinnie............I can help you. The formula for a 1/4 wavelength
radiator is (234 / F) whereby F is the frequency in MHz. This will give you
the length in feet. For the radials, (237 / F) will give you that length.
Always remember...multiply the radiator length by 1.05 and that is another
way of calculating the 1/4 wavelength radials.
The feedpoint impedance of a 1/4 wave ground plane is 37 ohms when you have
the radials at a 90 degree angle with respect to the radiator. If you have
the radials drooped at a 45 degree angle, the impedance rises to
approximately 50 ohms.

So far, that is what I have read. What I am going to do is this. I am going to
add the 45 angled GP, simply because it is fairly cheap, and because it will be
much easier to put it up now, than later. The formula you gave indicates that
radials should be about 8.8 feet at 27 MHz. If these radials fair poorly, I will
take Lancer's advice and build my own. For some reason, the radials are 6 feet.
I don't know if they ran 9 feet of wire in there, or what.


If you have a single radial drooped at a 180 degree angle with respect to
the radiator, the impedance rises to 75 ohms.

I won't do this.

There was an article in RF Design magazine a few years back, explaining why
certain impedances are used in the RF industry.
72 ohms was the impedance that produced minimum cable losses...........50
ohms is a happy medium.
On a final note...........at 37 ohms, you will have a VSWR of 1.3 to
1.................at 75 ohms, you will have a VSWR of
1.5 to 1. What is the difference here? For a transmitter with a tube output
and an internal matching network, you wouldn't really see much effect. For a
typical solid state transmitter, there would be some difference between the
two antenna impedances, because the broadband solid state transmitter would
be called upon to deliver more current to the antenna. It probably wouldn't
have any effect, unless the ALC circuit was aggressive in its operation. In
this case, power foldback would occur into the 37 ohm load. Would it happen?
Probably not.
I hope this helps.

Pete


It's does help, Thanks ! I am borrowing an Autek RF analyzer to check the
antenna while I am up in the tree. Most people that have purchase this antenna,
say that it is tuned very well to 27.205. I should be flat up and down in CB and
10 meters for about 1 MHZ.

I will follow up.

Vinnie S.

Sounds good, Vinnie....................feel free to e-mail me directly if
you have any questions.

Pete

"Vinnie S." wrote in message
...
On Sun, 10 Apr 2005 19:58:28 GMT, "Pete KE9OA"

wrote:

Hey Vinnie............I can help you. The formula for a 1/4 wavelength
radiator is (234 / F) whereby F is the frequency in MHz. This will give
you
the length in feet. For the radials, (237 / F) will give you that length.
Always remember...multiply the radiator length by 1.05 and that is another
way of calculating the 1/4 wavelength radials.
The feedpoint impedance of a 1/4 wave ground plane is 37 ohms when you
have
the radials at a 90 degree angle with respect to the radiator. If you have
the radials drooped at a 45 degree angle, the impedance rises to
approximately 50 ohms.

So far, that is what I have read. What I am going to do is this. I am
going to
add the 45 angled GP, simply because it is fairly cheap, and because it
will be
much easier to put it up now, than later. The formula you gave indicates
that
radials should be about 8.8 feet at 27 MHz. If these radials fair poorly,
I will
take Lancer's advice and build my own. For some reason, the radials are 6
feet.
I don't know if they ran 9 feet of wire in there, or what.


If you have a single radial drooped at a 180 degree angle with respect to
the radiator, the impedance rises to 75 ohms.

I won't do this.

There was an article in RF Design magazine a few years back, explaining
why
certain impedances are used in the RF industry.
72 ohms was the impedance that produced minimum cable losses...........50
ohms is a happy medium.
On a final note...........at 37 ohms, you will have a VSWR of 1.3 to
1.................at 75 ohms, you will have a VSWR of
1.5 to 1. What is the difference here? For a transmitter with a tube
output
and an internal matching network, you wouldn't really see much effect. For
a
typical solid state transmitter, there would be some difference between
the
two antenna impedances, because the broadband solid state transmitter
would
be called upon to deliver more current to the antenna. It probably
wouldn't
have any effect, unless the ALC circuit was aggressive in its operation.
In
this case, power foldback would occur into the 37 ohm load. Would it
happen?
Probably not.
I hope this helps.

Pete


It's does help, Thanks ! I am borrowing an Autek RF analyzer to check the
antenna while I am up in the tree. Most people that have purchase this
antenna,
say that it is tuned very well to 27.205. I should be flat up and down in
CB and
10 meters for about 1 MHZ.

I will follow up.

Vinnie S.