In article ,
matt weber wrote:

On 23 Apr 2006 00:38:18 -0700, "RHF"
wrote:

For One and All,

Per "Telamon" - A Hertzian Antenna such as a Dipole has two elements
that develop the Voltage across the Receiver Input
- - - So an RF Ground becomes superfluous.

This Statement may be True a the specific Frequency that
the Dipole is Designed to Operate at {Resonance} .

"IS" this Statement always True at other Frequencies that
the Dipole was NOT Designed to Operate at {Non-Resonant} ?
Certainly is, the point is a dipole is a balanced antenna, i.e. a
signal impinging on the antenna will have two components that 180
degrees out of phase. Thing about which end of each half the feed
comes from. So one side will always be the opposite orientation from
the other side.

All that happens when the antenna is not resonant, is the effective
impedance changes, and will contain a reactive component. That
usually reduces the power transfered from the antenna to the front end
of the receiver.

QUESTION - Does a "Non-Resonant" Dipole Antenna work better
{Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
http://groups.yahoo.com/group/Shortw...a/message/9189

i want to know - cause iane ~ RHF
.
Shortwave Listener Antennas = http://tinyurl.com/ogvcf
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
SWL Antenna Group = http://tinyurl.com/ogvcf

Matt is explanation correct but I would like to add a little more
information on what happens on receive. If the dipole is a half
wavelength then the antenna output is at the maximum voltage point.
This a resonance point because the EM wave is 2X length of the elements
electrical length. The elements are 1/4 wavelength each.

When the EM wave is longer or shorter than the antenna's electrical
length the antenna output is not at the maximum point so the output
decreases. When you get to a frequency 2X what the 1/2 wave dipole is
cut for the antenna output point is at zero volts and the antenna will
appear to be deaf at that point.

It is easy to visualize what is happening. Draw a sine wave and below
it draw a line under the positive excursion, zero volts to max positive
and then back to zero volts. Make a break in the middle of the line.
These two break points in the middle of the line are the 1/2 wave
dipole output. Each line segment is 1/4 wave length. You can see the
voltage is at maximum in the middle of the line and zero volts at the
ends of the line.

Now do the same thing for a 1 wave length dipole. Draw a line under the
entire sine wave and make the break in the middle of the line. Each
line segment is 1/2 wave. Notice that now the antenna output is at the
zero volt point where you go from positive excursion to negative
excursion and so there is no voltage at the antenna output.

Now all you need to visualize is that going from 1/2 to 1 wave length
you go from maximum possible output to nothing. You can't see radio EM
waves but why things work as they do is not hard to visualize.

--
Telamon
Ventura, California

David :

Shortwave Listener Antennas = http://tinyurl.com/ogvcf
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
SWL Antenna Group = http://tinyurl.com/ogvcf
.
I suggest you find a nice copy of the ARRL Antenna book and put it in
your ****ter for a few months.

Painful. Is it softcover edition?

--
Bob

On Sun, 23 Apr 2006 21:31:11 GMT, Telamon
wrote:

In article ,
matt weber wrote:

On 23 Apr 2006 00:38:18 -0700, "RHF"
wrote:

For One and All,

Per "Telamon" - A Hertzian Antenna such as a Dipole has two elements
that develop the Voltage across the Receiver Input
- - - So an RF Ground becomes superfluous.

This Statement may be True a the specific Frequency that
the Dipole is Designed to Operate at {Resonance} .

"IS" this Statement always True at other Frequencies that
the Dipole was NOT Designed to Operate at {Non-Resonant} ?
Certainly is, the point is a dipole is a balanced antenna, i.e. a
signal impinging on the antenna will have two components that 180
degrees out of phase. Thing about which end of each half the feed
comes from. So one side will always be the opposite orientation from
the other side.

All that happens when the antenna is not resonant, is the effective
impedance changes, and will contain a reactive component. That
usually reduces the power transfered from the antenna to the front end
of the receiver.

QUESTION - Does a "Non-Resonant" Dipole Antenna work better
{Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
http://groups.yahoo.com/group/Shortw...a/message/9189

i want to know - cause iane ~ RHF
.
Shortwave Listener Antennas = http://tinyurl.com/ogvcf
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
SWL Antenna Group = http://tinyurl.com/ogvcf

Matt is explanation correct but I would like to add a little more
information on what happens on receive. If the dipole is a half
wavelength then the antenna output is at the maximum voltage point.
This a resonance point because the EM wave is 2X length of the elements
electrical length. The elements are 1/4 wavelength each.

When the EM wave is longer or shorter than the antenna's electrical
length the antenna output is not at the maximum point so the output
decreases. When you get to a frequency 2X what the 1/2 wave dipole is
cut for the antenna output point is at zero volts and the antenna will
appear to be deaf at that point.

It is easy to visualize what is happening. Draw a sine wave and below
it draw a line under the positive excursion, zero volts to max positive
and then back to zero volts. Make a break in the middle of the line.
These two break points in the middle of the line are the 1/2 wave
dipole output. Each line segment is 1/4 wave length. You can see the
voltage is at maximum in the middle of the line and zero volts at the
ends of the line.

Now do the same thing for a 1 wave length dipole. Draw a line under the
entire sine wave and make the break in the middle of the line. Each
line segment is 1/2 wave. Notice that now the antenna output is at the
zero volt point where you go from positive excursion to negative
excursion and so there is no voltage at the antenna output.

Now all you need to visualize is that going from 1/2 to 1 wave length
you go from maximum possible output to nothing. You can't see radio EM
waves but why things work as they do is not hard to visualize.

What about the virtual capacitor?

Bob wrote:
David :
Shortwave Listener Antennas = http://tinyurl.com/ogvcf
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
SWL Antenna Group = http://tinyurl.com/ogvcf
.
I suggest you find a nice copy of the ARRL Antenna book and put it in
your ****ter for a few months.

Painful. Is it softcover edition?

Look at it this way; you won't need TP for your bunghole.

--
All relevant people are pertinent.
All rude people are impertinent.
Therefore, no rude people are relevant.
-- Solomon W. Golomb

Telamon wrote in
:

In article , "Brian Hill" wrote:

"David" wrote in message

The Quadrifilar Helix doesn't come up
much on this group.


That's because it's a shortwave forum.

That's because they would be to big for most people to construct for
short wave and they are very directional and so they would have to be
rotated.


Oh my.

SC

FO&A - But their is another work around
'trick' answer - out there !

So I want to Rig my cut-to-order Dipole Antenna to use
for general across-the-bands Shortwave Listening.

First - Don't Think of It as a Dipole . . .

Brian,I am going to float my Sunn thingy over to you.Dontchoo worry.I
will get it to you.
cuhulin

I need to email Mary DuRose over yonder in the Sydney,OZ area.She is
originally from Kansas.I lived in Salina,Kansas in 1957.She is from the
Wichita area,or somewhere around there.My old brother in law has an Air
Force buddy in Topeka,Kansas.His buddy used to work his Farm near
Wetmore,Kansas.I am just as much Kansan as any other Kansans out there.
cuhulin

All I want to do is ''cut one''
cuhulin

In article .com,
"RHF" wrote:

FO&A - But their is another work around
'trick' answer - out there !

So I want to Rig my cut-to-order Dipole Antenna to use
for general across-the-bands Shortwave Listening.

First - Don't Think of It as a Dipole . . .

I prefer antennas for reception closer to the space impedance around it.
A ball park antenna type is a folded dipole. It can be made cheaply with
300 ohm twin lead transmission line and 4:1 BALUNs to connect it to 50
ohm coax is also cheap and common.

Another advantage is it is grounded so static charge pickup is shunted.

There is a trick to make it perform better on bands other than what it
is cut for using shorts at a specific distance from the ends depending
on the band for which it is cut.

You can use the dipole concept by using several cut for different bands
tied together at the antenna output. For this to work well the
paralleled elements need to have a relationship to each other that
prevents the energy picked up from one element flowing into another
element.

--
Telamon
Ventura, California