converting from dipole/inverted vee to beam
 

I have a wire dipole and an inverted Vee each cut to resonance on a
desired frequency. I would like to add a reflector and/or a director
(one at the time) to make each one a beam. Will adding the reflector
and/or director change the resonant frequency, or just the impedance?

Thanks
Buck
n4pgw

--
73 for now
Buck
N4PGW

converting from dipole/inverted vee to beam
 

Both, in all likelyhood.

"Buck" wrote in message
...
I have a wire dipole and an inverted Vee each cut to resonance on a
desired frequency. I would like to add a reflector and/or a director
(one at the time) to make each one a beam. Will adding the reflector
and/or director change the resonant frequency, or just the impedance?

Thanks
Buck
n4pgw

--
73 for now
Buck
N4PGW

converting from dipole/inverted vee to beam
 

On Fri, 26 May 2006 08:40:08 -0500, "hasan schiers"
wrote:

Both, in all likelyhood.

"Buck" wrote in message
.. .
I have a wire dipole and an inverted Vee each cut to resonance on a
desired frequency. I would like to add a reflector and/or a director
(one at the time) to make each one a beam. Will adding the reflector
and/or director change the resonant frequency, or just the impedance?

Thanks
Buck
n4pgw

--
73 for now
Buck
N4PGW

I guess I'll have to try it to see what happens.

Thanks

--
73 for now
Buck
N4PGW

converting from dipole/inverted vee to beam
 

"Buck" wrote in message
...
I have a wire dipole and an inverted Vee each cut to resonance on a
desired frequency. I would like to add a reflector and/or a director
(one at the time) to make each one a beam. Will adding the reflector
and/or director change the resonant frequency, or just the impedance?

Thanks
Buck
n4pgw

--
73 for now
Buck
N4PGW

Hi Buck

Isnt Resonance defined as the frequency where the Impedance has *no*
reactance? Wouldnt that imply that the resonant frequency of the antenna
will always change if its impedance changes?
Can you *ever* change one without changing the other?

Jerry

converting from dipole/inverted vee to beam
 

Jerry Martes wrote:
"Buck" wrote in message
...
I have a wire dipole and an inverted Vee each cut to resonance on a
desired frequency. I would like to add a reflector and/or a director
(one at the time) to make each one a beam. Will adding the reflector
and/or director change the resonant frequency, or just the impedance?

Thanks
Buck
n4pgw

--
73 for now
Buck
N4PGW

Hi Buck

Isnt Resonance defined as the frequency where the Impedance has *no*
reactance? Wouldnt that imply that the resonant frequency of the antenna
will always change if its impedance changes?
Can you *ever* change one without changing the other?

You're correct about the definition of resonance.

Buck's statement would have made more sense if it the last words were
"just the resistance", and that's likely what he meant.

Sure, you can change the impedance without changing the resonant
frequency -- a transformer will do that, for example. At resonance, the
resistance will simply be a different value.

But to answer Buck's question, adding another element will almost
certainly change both the resistance and reactance at the feedpoint, and
therefore the resonant frequency.

Roy Lewallen, W7EL

converting from dipole/inverted vee to beam
 

"Roy Lewallen" wrote in message
...


Jerry Martes wrote:
"Buck" wrote in message
...
I have a wire dipole and an inverted Vee each cut to resonance on a
desired frequency. I would like to add a reflector and/or a director
(one at the time) to make each one a beam. Will adding the reflector
and/or director change the resonant frequency, or just the impedance?

Thanks
Buck
n4pgw

--
73 for now
Buck
N4PGW

Hi Buck

Isnt Resonance defined as the frequency where the Impedance has *no*
reactance? Wouldnt that imply that the resonant frequency of the
antenna will always change if its impedance changes?
Can you *ever* change one without changing the other?

You're correct about the definition of resonance.

Buck's statement would have made more sense if it the last words were
"just the resistance", and that's likely what he meant.

Sure, you can change the impedance without changing the resonant
frequency -- a transformer will do that, for example. At resonance, the
resistance will simply be a different value.

But to answer Buck's question, adding another element will almost
certainly change both the resistance and reactance at the feedpoint, and
therefore the resonant frequency.

Roy Lewallen, W7EL

Hi Roy

I'm not qualified to enter into a theory discussion with you. But, I'd
expect the introduction of a nearly half wave long comductor into the near
vicinity of an antenna that has a purely resistive Terminal Impedance
(Resonant) will change the Terminal Impedance of the new antenna which is
the combination of the two.
I would have considered that transformer doesnt actually change the
antenna's Terminal Impedance (Resonance) the transformer converts the
antenna's impedance *at a new location*.
So, I'd expect the antenna's "resonance" to be defined by its "impedance".

I've considered that any R+/-jX can be Transformed to an impedance thats
purely resistive. But, with antennas, thats a matching situation, while
the antenna's terminal impedance remains reactive.

Jerry

converting from dipole/inverted vee to beam
 

Buck wrote:
I have a wire dipole and an inverted Vee each cut to resonance on a
desired frequency. I would like to add a reflector and/or a director
(one at the time) to make each one a beam. Will adding the reflector
and/or director change the resonant frequency, or just the impedance?

Thanks
Buck
n4pgw

--
73 for now
Buck
N4PGW

Both most likely.

Download the demo eznec and model it; www.eznec.com.

After you've used it a few times, you'll want to buy the full version.

Nope, no connection with eznec. It has saved me a lot of time, effort,
and cut up wire though.

--
Jim Pennino

Remove .spam.sux to reply.

converting from dipole/inverted vee to beam
 

"Jerry Martes" wrote
So, I'd expect the antenna's "resonance" to be defined by its
"impedance".



Antenna resonance is defined by its element's electrical properties,
"caused" by its physical properties/dimensions.
In case of 3 el "conversion" from Inv Vee, you have to picture elements as a
tuned circuits. If they are spaced within a fractions of a wavelength, they
have mutual impedance, affecting each other. As you start adding elements,
they add capacitance to the system and lower the overall resonant frequency
and impedance. Single Dipole is around 75 ohms, 3 el. Yagi around 30 ohms.
The more elements you add, the more sensitive the design is and requires
more prunning for optimum performance. So just slapping elements to Inv Vee
dipole will not produce optimized antenna. EZNEC, 4NEC2, MMANA are an
excellent tools to demonstrate that and to optimize the design, give you
dimensions and impedance and understanding behavior of antennas, give
current distribution in elements, plots of impedance, gain and other
parameters.

--
Yuri Blanarovich, K3BU, VE3BMV

converting from dipole/inverted vee to beam
 

"Yuri Blanarovich" wrote in message
...

"Jerry Martes" wrote
So, I'd expect the antenna's "resonance" to be defined by its
"impedance".



Antenna resonance is defined by its element's electrical properties,
"caused" by its physical properties/dimensions.
In case of 3 el "conversion" from Inv Vee, you have to picture elements as
a tuned circuits. If they are spaced within a fractions of a wavelength,
they have mutual impedance, affecting each other. As you start adding
elements, they add capacitance to the system and lower the overall
resonant frequency and impedance. Single Dipole is around 75 ohms, 3 el.
Yagi around 30 ohms.
The more elements you add, the more sensitive the design is and requires
more prunning for optimum performance. So just slapping elements to Inv
Vee dipole will not produce optimized antenna. EZNEC, 4NEC2, MMANA are an
excellent tools to demonstrate that and to optimize the design, give you
dimensions and impedance and understanding behavior of antennas, give
current distribution in elements, plots of impedance, gain and other
parameters.

--
Yuri Blanarovich, K3BU, VE3BMV

Hi Yuri

I thought my statement that an antenna's Resonance is defined by that
antenna having an impedance thats purely resistive, was an accurate
statement. Is than *not* accurate?? What other "electrical properties"
define an antenna's resonance??

Jerry

converting from dipole/inverted vee to beam
 

Jerry Martes wrote:

I thought my statement that an antenna's Resonance is defined by that
antenna having an impedance thats purely resistive, was an accurate
statement.
. . .

It's accurate and complete.

Roy Lewallen, W7EL