What's the difference between an end-fed dipole and a random wire?

Is an end-fed dipole really 'balanced'? If so, how is this balance
achieved, and does the balanced nature of an end-fed dipole mean it
doesn't require an rf ground the way a random wire would?

Thank you for your time.

In article . com,
" wrote:

What's the difference between an end-fed dipole and a random wire?

Is an end-fed dipole really 'balanced'? If so, how is this balance
achieved, and does the balanced nature of an end-fed dipole mean it
doesn't require an rf ground the way a random wire would?

Thank you for your time.

The "di" in Dipole means two as in elements. A dipole has two 1/4 wave
elements where a passing EM wave induces an opposing voltage or
potential at its output terminals where the two elements meet.

The way an random wire works with a output terminal on one end of a (1)
wire element is that it has to work against a counter poise or ground.
As such the best potential at its output terminal is when it is a 1/4
wave electrically to a passing EM wave where the dipole would be
electrically at 1/2 wave.

Now that you understand this you can understand that 1/2 wave random
wire is a waste of time and that a end-fed dipole random wire makes no
sense. Yes you can find it out there on the web. Plenty of confused
people in the world.

--
Telamon
Ventura, California

Exactly why is this a "waste of time": Now that you understand this you
can understand that 1/2 wave random
wire is a waste of time.

Rank

Telamon wrote:
In article . com,
" wrote:

What's the difference between an end-fed dipole and a random wire?

Is an end-fed dipole really 'balanced'? If so, how is this balance
achieved, and does the balanced nature of an end-fed dipole mean it
doesn't require an rf ground the way a random wire would?

Thank you for your time.

The "di" in Dipole means two as in elements. A dipole has two 1/4 wave
elements where a passing EM wave induces an opposing voltage or
potential at its output terminals where the two elements meet.

The way an random wire works with a output terminal on one end of a (1)
wire element is that it has to work against a counter poise or ground.
As such the best potential at its output terminal is when it is a 1/4
wave electrically to a passing EM wave where the dipole would be
electrically at 1/2 wave.

Now that you understand this you can understand that 1/2 wave random
wire is a waste of time and that a end-fed dipole random wire makes no
sense. Yes you can find it out there on the web. Plenty of confused
people in the world.

--
Telamon
Ventura, California

Telamon wrote:
The "di" in Dipole means two as in elements. A dipole has two 1/4 wave
elements where a passing EM wave induces an opposing voltage or
potential at its output terminals where the two elements meet.

The way an random wire works with a output terminal on one end of a (1)
wire element is that it has to work against a counter poise or ground.
As such the best potential at its output terminal is when it is a 1/4
wave electrically to a passing EM wave where the dipole would be
electrically at 1/2 wave.

Now that you understand this you can understand that 1/2 wave random
wire is a waste of time and that a end-fed dipole random wire makes no
sense. Yes you can find it out there on the web. Plenty of confused
people in the world.

--
Telamon
Ventura, California

Let us take a look at the 2M 1/4 vertical on my car roof.
It is end fed, and while it is only half of the antenna, the metal
roof is the other "half".

A vertical HF antenna can be built with, dah, a vertical electrical 1/4
wave over
either very conductive, think salt water marsh, or an array of raidals.
The more the
better up to around 190 or so, Contrary to popular ham myth 16 radials
is barely
enough. 32 is better with 64 and moer starting to get there.

Of course it is posible to cheat and use an antenna tuner or "match
box" and
load nearly anthing. Of course just because you managed to get a 1.5:1
doesn't mean
you RF is really going anywhere.

For field day, an anual event held every June where hams take to the
field and pretend
it is an emregency and operate from improvised (and other) antennas. I
used to be
very active with 80M and 40M CW QRP and found out real fast that end
fed dipoles,
or end fed anythings worked much worse then true dipoles.

However I did operate with a 20M 1/4 wave vertical mounted on a large
metal roof that
was simply killer.

An end fed horizontal single side of a dipole will be, generally, way
less effecient
then a true dipole. By runing a counterpoise below the half of the
dipole can, but not
always, improve performance.

And unless one is only interested in receiving one frequency, located
in one direction,
such as WWV on say 10MHz, any sort of dipole is very likely to be way
less then
ideal for general SWL work. In my life I have installed several
dedicated WWV, WWVB systems, this was befroe GPS became as common and
cheap as it now is, and while
logic suggested a dipole would have been a good idea, the fact that I
was trying to
receive 2.5, 5, 10, 15, and once 20MHz meant a dipole's pattern would
fragment,
for lack of a more discriptive word. To do the job right required
mulitple dipoles,
and I found there was no easy way to combine dipoles without the
varrious odd patterns combining for some really odd peaks and nulls.
this required switches to choose between the 4 dipoles and 4 feedlines.
In the last situaiton I ended up going with an active (single ended)
antenna. If I had to do it again I would almost certainly go with a
active dipole.
Other SWLs have found loops to be an effective choice.

I think every new SWL gets hung up on dipoles, failing to grasp that
for 99% of their
listening, dipoles would not be a good choice. Think about it. A
dipoles best stength
is it biggest weakness. The built in peak and null. Peak broadside to
the dipole,
null off the ends. But how do you rotate a true 80M dipole? So do you
errect one for each
target station? That peak in one direction will be a null in another
and just as likely to
be a null for the direction you want as a peak. In my situation I jump
from frequency to
frequency, And the targets wil be at nearly all points of the compass.
Very hard to
build a steerable, broad band dipole. A horizontal active dipole can be
rotated, or a
pair of vertical dipoles can be combined in a Phaser to create an
synthetic rotatable
antenna that gives the ability to peak and null. But we are getting
very complex here,
and quite a leap from any "reasonable" antenna. While quite a leap, it
is what I plan
to have completed by Thanksgiving.

The average SWL will be well served with an antenna like the one DxAce
uses.

http://www.iserv.net/~n8kdv/pics.htm

Simple, inexpensive and will last for years. As their skill sets and
needs evolve, then
it would be reasonable to ponder more complex antenna. It is way too
easy to get lost
in searching for the "perfect" antenna before gaining enough experience
to understand
why perfection isn't needed.

Terry

Bart Bailey wrote:
In ps.com
posted on 14 Nov 2006 04:37:18 -0800, wrote:
Begin

A vertical HF antenna can be built with, dah, a vertical electrical 1/4
wave over
either very conductive, think salt water marsh, or an array of raidals.
The more the
better up to around 190 or so, Contrary to popular ham myth 16 radials
is barely
enough. 32 is better with 64 and moer starting to get there.

I have a Butternut HF2V with 0 (zero) radials, but a fairly good ground,
no salt marsh, just two stakes three feet apart driven into the ground
in an inner city neighborhood in San Diego, and I typically propagate on
80m better than the guy who gave it to me that uses the same model, but
with an ideal radial pattern. We run similar power levels so am thinking
I might be getting some parasitic excitation of very close power lines
that he doesn't have, nor the accompanying noise either. Those power
lines are a 138kv tie line, a 12kv distribution line and a 4kv
distribution line, all less than 100 feet from the antenna. Another
possibility is that since everything in the shack is very well bonded
and grounded, that at RF maybe I'm getting some counterpoise effect on
the entire city wide grid, now that's a long wire!

--

Bart

When it comes to radiation patterns it is hard to calculate what is
really gonig on ,
and even harder to make meaningful measurements. Ground reflection,
amoung
many other things, makes a lot difference. Whne I was much yougner, and
I
expected to be able to make meaningfull measurements, I wasted several
weekends
by trying to measure the real pattern from a 20M dipole at about 30'
elevation and
a 20M vertical on a large grounded metal roof. I nver got results that
made any sense.


Your observation about power lines is correct. "Nearby" wires can
produce
pattern distortion beyond the abiltiy to calculate. One nice thing
about 6M
and up is the ease with which you can make readings that knid of relate
to
reality.


My 1/4 has a 6dB lobe toward the front because I drive a hatch back
Civic
and ther is moer surface metal toward the front. Of course the lobe
isn't
exactly straight ahead, but canted about 15 degrees to the right for an

unknow reason. The NEC modeling program prediction and measurements
in an open field agree to a impressive degree. And by using the remote
S-meter
in a local repeater and having it repeat the level as I drive a tight
circle confirmed
the theory and my measurements. But I still can't explain the lobe's
offset. The
antenna is centered to within a few mm. I thoguht maybe wiper blades so
I removed
them, then I thought BCB radio antenna so I removed it. No change.


Sadly at HF reality and theory have almost nothing in common. The nice
peaks
and nulls of a 10MHz horizontal dipole are seldom as distinct as the
graphs
shown in text books.


If it works then it is good regradless of what theory might say. Some
of my
first DX HAM contacts were on really bad, not effeceint, random
antennas,
When I started using "correct" antennas, dipoles for the most part, my
ratio
of heard and worked versus heard and not worked increased dramaticaly.
But
I still have a wide range match box with my QRP rig just in case I
can't errect
a real antenna. I once worked Scotland runing 5W CW on 80M into a
random,
~~100', wire wraped along a rail fence.

Terry

On Tue, 14 Nov 2006 03:56:08 GMT, Telamon
wrote:

In article . com,
" wrote:

What's the difference between an end-fed dipole and a random wire?

Is an end-fed dipole really 'balanced'? If so, how is this balance
achieved, and does the balanced nature of an end-fed dipole mean it
doesn't require an rf ground the way a random wire would?

Thank you for your time.

The "di" in Dipole means two as in elements. A dipole has two 1/4 wave
elements where a passing EM wave induces an opposing voltage or
potential at its output terminals where the two elements meet.

The way an random wire works with a output terminal on one end of a (1)
wire element is that it has to work against a counter poise or ground.
As such the best potential at its output terminal is when it is a 1/4
wave electrically to a passing EM wave where the dipole would be
electrically at 1/2 wave.

Now that you understand this you can understand that 1/2 wave random
wire is a waste of time and that a end-fed dipole random wire makes no
sense. Yes you can find it out there on the web. Plenty of confused
people in the world.

Speak for yourself. Make sure you don't have a Marconi antenna
confused with your random wire.

On 13 Nov 2006 12:20:16 -0800, "
wrote:

What's the difference between an end-fed dipole and a random wire?

Is an end-fed dipole really 'balanced'? If so, how is this balance
achieved, and does the balanced nature of an end-fed dipole mean it
doesn't require an rf ground the way a random wire would?

Thank you for your time.

There is such a thing as an end-fed Zepp; it's a half-wave wire with a
balanced feedline like 300 or 450-ohm ladderline.

These end fed Zepps were popular with the old Zeppelin airship radio
operators. Only one side of the balanced feedline is connected to the
antenna.

Look around the web for a diagram of one.

They don't require a ground, and an antenna tuner can be used for a
wider range of frequencies.

A random wire does require a counterpoise or ground if you're
transmitting, but when I had one up, it didn't seem to have much
effect on reception.

bob
k5qwg

In article .com,
wrote:

Telamon wrote:
In article . com,
" wrote:

What's the difference between an end-fed dipole and a random wire?

Is an end-fed dipole really 'balanced'? If so, how is this balance
achieved, and does the balanced nature of an end-fed dipole mean it
doesn't require an rf ground the way a random wire would?

Thank you for your time.

The "di" in Dipole means two as in elements. A dipole has two 1/4 wave
elements where a passing EM wave induces an opposing voltage or
potential at its output terminals where the two elements meet.

The way an random wire works with a output terminal on one end of a (1)
wire element is that it has to work against a counter poise or ground.
As such the best potential at its output terminal is when it is a 1/4
wave electrically to a passing EM wave where the dipole would be
electrically at 1/2 wave.

Now that you understand this you can understand that 1/2 wave random
wire is a waste of time and that a end-fed dipole random wire makes no
sense. Yes you can find it out there on the web. Plenty of confused
people in the world.

Exactly why is this a "waste of time": Now that you understand this
you can understand that 1/2 wave random wire is a waste of time.

The voltage is maximum at the center of a half wave dipole and zero at
the end. Is this enough of a further explanation for you?

--
Telamon
Ventura, California