QUESTION - Does a "Non-Resonant" Dipole Antenna work better {Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
 

In article . com,
"RHF" wrote:

MW - Thank You for your Answer ~ RHF
.
But their is another work around 'trick' answer
- out there . . .

I don't care for the language of "trick answers" or "black magic" when
it comes to RF or antennas. RF and antennas behavior can be understood.
This understanding can be shallow or deep depending on what your needs
are or what you are trying to accomplish. Here in this news group where
we are interested in short wave reception we only need to understand
basic antenna and grounding behavior where simple algebraic formulas to
calculate antenna element lengths are easily found on the Internet.

Depending on your location some antennas will work better for you than
others and so is one level of investigation.

1. Determine the antenna type for your application and location.
2. Find the formula to determine the element lengths.
3. Using inexpensive wire, cable, insulators to build it.

--
Telamon
Ventura, California

QUESTION - Does a "Non-Resonant" Dipole Antenna work better {Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
 

On Tue, 25 Apr 2006 20:05:26 GMT, Telamon
wrote:

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.

300 Ohms matches better to 75 Ohm line with a 4:1 transformer.

4 X 75 = 300

4 X 50 = 200

QUESTION - Does a "Non-Resonant" Dipole Antenna work better {Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
 

In article om,
"RHF" wrote:

Telamon - The Trick is not in the Antenna but . . .
in the application and implementation of it use in
a manner for which it was not originally designed.

On its face that statement does not make a lot of sense. Engineering is
applying mathematical and scientific concepts to an application. You
could use a spoon as a shovel for digging a trench but it would not work
well. An antenna is designed for a purpose of receiving of transmitting
on some range of frequencies and it generally won't work well in other
applications.

--
Telamon
Ventura, California

QUESTION - Does a "Non-Resonant" Dipole Antenna work better {Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
 

In article .com,
"RHF" wrote:

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 . . .

Think of it as Two Horizontal Wire Antennas that are fed
with a Pair of Matched Lines {Ladder Line - Twin Lead - etc}


You have three paragraphs that appear to cover three different issues
with no attribution so I don't know how to respond to this post.

--
Telamon
Ventura, California

QUESTION - Does a "Non-Resonant" Dipole Antenna work better {Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
 

David - Now you are thinking :o) ~ RHF

QUESTION - Does a "Non-Resonant" Dipole Antenna work better {Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
 

In article . com,
"RHF" wrote:

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 . . .

Think of it as Two Horizontal Wire Antennas that are fed
with a Pair of Matched Lines {Ladder Line - Twin Lead - etc}

Second -Taking the two (a pair of) feed-in-line Wires and
Connecting them together at the "Antenna" HI-Z (500 Ohm)
{Red} Terminal of my Radio / Receiver.

Third - Then I connect my Ground Wire to the "Ground"
HI-Z (500 Ohm) {Black} Terminal of my Radio / Receiver.

The impedance does not match up that well as a 300 ohm transmission
line to 500 high impedance input on most radios but it might work well
in low noise situation. Anyone ever try this?

--
Telamon
Ventura, California

QUESTION - Does a "Non-Resonant" Dipole Antenna work better {Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
 

On Fri, 28 Apr 2006 17:03:30 GMT, Telamon
wrote:

In article . com,
"RHF" wrote:

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 . . .

Think of it as Two Horizontal Wire Antennas that are fed
with a Pair of Matched Lines {Ladder Line - Twin Lead - etc}

Second -Taking the two (a pair of) feed-in-line Wires and
Connecting them together at the "Antenna" HI-Z (500 Ohm)
{Red} Terminal of my Radio / Receiver.

Third - Then I connect my Ground Wire to the "Ground"
HI-Z (500 Ohm) {Black} Terminal of my Radio / Receiver.

The impedance does not match up that well as a 300 ohm transmission
line to 500 high impedance input on most radios but it might work well
in low noise situation. Anyone ever try this?

He's talking about shorting both legs together I think. Most Hi-Z
inputs work OK with 300 or 450 Ohm line, as well as monopole wires.

QUESTION - Does a "Non-Resonant" Dipole Antenna work better {Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
 

In article .com,
"RHF" wrote:

FWIW :

Starting with a Single Band Dipole Antenna :

First - Both the Wires of the Ladder Line / Twin Lead / Twisted Pair
are connected to "Antenna" HI-Z (500 Ohm) {Red} Terminal of the
Radio / Receiver.

Second - The Ground Wire is connected to the "Ground"
HI-Z (500 Ohm) {Black} Terminal of the Radio / Receiver.

For a "Receive Only" Shortwave Listening (SWL) Antenna
it works OK.

For use as a Transmitting Antenna then an Antenna Tuning
Unit (ATU) "Trans-Match" would be required.

SO... WHAT KIND OF ANTENNA IS IT ?

At the Top the Antenna has two Horizontal Arms that are
Part of the Wire Antenna Element.

The two feed-in-line Wires can be considered as simply
feed-in-line or as part of the Antenna.

David says that this is a Top Loaded Vertical.

I believe some refer to it as a Double Extended Zepp Antenna ?
http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=7682

I tent to think of it as a Twin Inverted "L" Antenna -or-
opposing classic LongWire {Random Wire} Antennas.

WHAT WOULD YOU CALL THIS MISS WIRED DIPOLE ?

Sorry I misread your previous post.

Any time you have one element for the antenna and ground for the other
side of a radio input you have a common voltage mode antenna.

There are two basic voltage antenna types Marconi and Hertzian. The
Marconi is single element and ground common mode antenna. The basic
Hertzian is two elements and balanced making it a differential mode.

Depending on dimensions of the horizontal and vertical parts your
proposed antenna could be a top loaded vertical. Change the dimensions
and it could be an inverted L. Just understand that the mode the
antenna operates in does not change. The vertical portion can connect
to the horizontal section at the end, middle, or somewhere in between
and it still is a common mode antenna whatever the resulting shape.

Call it the RHF special.

--
Telamon
Ventura, California

QUESTION - Does a "Non-Resonant" Dipole Antenna work better {Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
 

Telamon,

At least according to my reads over the years.
Amateurs have been hooking-up their Dipole
Antennas this way for decades using an ATU.

The Twin (2) feed-in-lines would effective make them
a thicker single conductor.

Assuming that the Twin (2) feed-in-line are mostly Vertical
and the Splight Top Wires (2) are mostly Horizontal

Then what you got is . . . {Marconi}
A Moderate Size Vertical Antenna with a Big Top Hat.
[ Gee isn't that what David Said ? ]

iane ~ RHF

QUESTION - Does a "Non-Resonant" Dipole Antenna work better {Benefit} when a Receiver is RF Grounded in the Shack ? ? ?
 

In article . com,
"RHF" wrote:

Telamon,

At least according to my reads over the years.
Amateurs have been hooking-up their Dipole
Antennas this way for decades using an ATU.

The Twin (2) feed-in-lines would effective make them
a thicker single conductor.

Assuming that the Twin (2) feed-in-line are mostly Vertical
and the Splight Top Wires (2) are mostly Horizontal

Then what you got is . . . {Marconi}
A Moderate Size Vertical Antenna with a Big Top Hat.
[ Gee isn't that what David Said ? ]


A tuner to fix VSWR antenna problems is not a good way to go. It is OK
to use a shack tuner for small values of VSWR so the transmitter finals
don't have to burn the added reflected power or cause instability. The
tuner in the shack does not cause the antenna to perform better.

Because hams operate on a range of frequencies in a band the strategy
is to have it resonant in the center of the band so the VSWR is about
1:1 there. Then it is about the same at the band ends say for example
1.5:1. Now the tuning unit is not needed at all in the band center and
only has to compensate small values of VSWR at the band edges. This is
an acceptable approach to using a shack tuning unit.

Now before some cleaver but silly person mentions that a certain length
of coax will cause the shack tuning unit antenna side to actually
represent the antenna impedance don't bother. While this is true it
only represents certain operating points and is not usable across a
band or bands on a multi-band antenna.

In order to get better antenna efficiency you need a tuning unit that
actually causes the antennas resonant frequency to change as opposed to
a variable impedance matching unit in the shack. This means the tuner
has to be a part of the antenna and that can't happen in the shack.

Now do you see the problem this presents for SW listening 3 to 30 MHz?

***
Yes, paralleling conductors makes them look like a bigger conductor
because RF current travels on the conductor surface. Generally you want
a better circular symmetry than two wires provide. Three would be better
as a minimum. Generally three to five is a good number. This is of
course diameter and frequency dependent number.

***
I would not know what Dave said. He is in the kill file because he keeps
going off the deep end.

Antennas operate in different modes and they can be classified in that
way. Pay attention to how they operate so you can determine what will
work for you depending on your location and needs.

--
Telamon
Ventura, California